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311 Cards in this Set

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Definition: medial
Closer to the midline of the body
Anything closer to the sternum
Definition: lateral
Farther from the midline of the body
Oblique muscles would very lateral
Define: Anterior vs. Posterior
Front vs. Behind
Define: Superior vs. Inferior
Closer to top of head vs. closer to the feet
Define: Cranial vs. Caudal
Closer to top of head vs. closer to bottom of trunk
**Only used to describe the trunk
Define: Proximal vs. Distal
Closer to the attachment of a limb vs. Further from a limb's attachment
Define: Internal/deep vs. external vs. superficial
Away from body's surface vs. close to body's surface
What is the sagittal plane? About which axis do movements in this plane occur?
The vertical plane dividing the body into right and left halves. Movements in this plane occur around transverse axis.
Left and right
What is the transverse/horizontal plane? About which axis do movements in this plane occur?
The plane that divides body into superior and inferior halves. Movements in this plane occur on a vertical axis.
Top and bottom
What is the frontal/coronal plane? About which axis do movements in this plane occur?
The vertical plane dividing the body into ventral and dorsal portions. Movements in this plane occur in the anteroposterior axis.
Chest and back
What is kyphosis?
An increased thoracic curvature from the curvature normally seen.
What is lordosis?
An increased lumbar or cervical curvature from the curvature that is normally seen. Cervical lordosis can be induced by kyphosis in the thoracic region.
Lower back and upper back
What is scoliosis?
A lateral curvature of the spine. A completely abnormal curvature of the spine.
Do you really need a hint?
Describe gametogenesis.
The halving of the amount of DNA that will be in the gamete through the process of meiosis. It also involves the development of structures that will aid the gametes (like flagellation of sperm) and embryo (like the rich cytoplasm of the oocyte) during the processes of fertilization and early development. The process produces 4 sperm in males and 1 oocyte and 3 polar bodies in females, where meiosis remains incomplete until fertilization. All resulting cells are haploid.
Production of gametes.
Definition: zona pellucida
The thin membrane that surrounds the primary oocyte that protects it before and after fertilization. It is surrounded by follicular cells directly after ovulation.
Layer that protects an unfertilized egg
Where does fertilization occur?
At the ovarian end of the fallopian tube, near the fimbriated end (the ampulla). The oocyte produces another polar body that remains inside the zona pellucida once it completes meiosis II (after fertilization). The process takes about 24 hours to occur.
It involves a tube.
What is a morula?
The solid ball of 12-16 cells produced after fertilization and mitosis occur.
Forms after several cell divisions, but before a blastocyst forms
Which part of the blastocyst develops into the embryo? What are the other cells called and what do they become?
The inner cell mass becomes the embryo. The trophoblasts are feeder cells that eventually become the placenta and extraembryonic membranes.
During the first 8 weeks of development, a child is known as a(n) _____ and the rest of the term it is known as a(n) _____.
Embryo and fetus.
Zygote is not one of the blanks.
Name the three layers of the developing embryo and what structures they become.
1. Ectoderm- superficial layer of skin, nervous tissue
2. Endoderm- epithelium of the gut, derivatives of the gut tube
3. Mesoderm- muscle, bone, connective tissue, circulatory system
Ecto, meso, endo
What are the two layers of the inner cell mass that form after 7 days? (right after implantation) What tissues will these become in the developing embryo?
Epiblast and hypoblast. They will form the bilaminar disk (when each layer cavitates) as the layers will remain connected, which will become you someday.
Epi- hypo-
Definition: syncytiotrophoblast
A fusion of the cytotrophoblast that becomes the majority of the placenta.
Derived from the trophoblast cells
From where is extraembryonic mesoderm derived?
Cytotrophoblast cells. These cells will eventually line the inside of the trophoblast and the outside of the yolk sac and amnion. These cells will also become the connecting stalk that links the trophoblast to the yolk sac/amnion within. This structure will eventually become the umbilical cord.
Describe the process of gastrulation.
It begins with a thickening of the primitive streak and the migration of epiblast cells to a depression called the primitive groove. These cells then detach and move between the epiblast and hypoblast to form a trilaminar disc. The three distinct tissue types of the embryo have now been formed. Mesoderm, as it is now called, migrates further between the plates. Some of it will form the notochord. The only place where ectoderm and endoderm do not become separated by mesoderm is at the oral and cloacal plates.
The movement of tissues within an embryo
What is the notochord?
A condensed mass of mesoderm that run cranially to caudally and directs neural tube formation during the process of neurulation.
It isn't ectoderm or endoderm
The primitive yolk sac develops from the ____ and the primitive amniotic cavity develops from the _____.
Hypoblast, epiblast.
The yolk sac is on the side furthest from the syncytium.
What are the two types of mesoderm before and during gastrulation and from where to they arise?
Extraembryonic mesoderm (from cytotrophoblast migration to the bilaminar disc) and intraembryonic mesoderm (from epiblast cell migration into primitive groove).
Extra-, intra-
The _______ and ______ are formed when cells migrate from the epiblast of an embryo at about days 14 to 19.
intraembryonic mesoderm and endoderm
Neither of the blanks is ectoderm
Describe the process of neurulation.
The initial sign is a thickening of the ectoderm directly above the notochord to form the neural plate. This then proceeds to fold inward (ventrally) to form the neural groove and then the neural tube. Neural crest cells that begin on the edges of the neural plate fold together and are the last parts to touch when the neural tube is formed. An intermediate zone of neural crest cells is formed directly above (dorsal to) the neural tube. (Later these cells migrate ventrally) The initial fusion of the neural folds is about midway along the length of the neural plate and proceeds in both directions (cranially and caudally), leaving two pores- the cranial neuropore and the caudal neuropore.
It starts by folding the embryo like a little Taco Bell chalupa.
All the neurons of the central nervous system develop from the _____.
Neural tube
It's a tube.
The cranial portion of the neural tube has three enlargements that become different parts of the brain. What are they called and what structures do they give rise to?
1. Prosencephalon--> forebrain
2. Mesencephalon--> midbrain
3. Rhombencephalon--> hindbrain
for-, mid-, hind-
How do neural crest cells form?
The edges of the neural plate eventually become the neural crest cells. As the neural folding fuse to form the neural tube, the intermediate form of neural crest cells form dorsally to the neural tube. These cells separate in half so that there are two columns of cells that flank the neural tube dorsolaterally. The columns divide into separate blocks. Each block has a twin on the opposite side. These cells migrate ventrally and proceed to differentiate into a variety of cell types (the majority of which are associated with the spinal cord and peripheral nervous system).
Differentiation of the neural crest cells depends on what major factor?
The distance they migrate from the neural tube. Example, proximal neural crest cells develop into dorsal root ganglion while the neural crest cells that are the next level ventrally become chain ganglion.
Distance from what?
The neural crest cells that migrate dorsally of the dorsal root ganglion but above the terminal ganglion become several different types of nerves that fall under a specific category. What is this category and what are the structures?
They form sympathetic neurons. The structures they form can be chain ganglion, pre-aortic ganglion, secretory cells of the adrenal medulla.
What nerves connect to the lateral horn of the cortex of the spinal cord?
What happens to the neural crest cells that migrate most ventrally, away from the neural tube?
They enter the wall of the gut and become terminal ganglia, parasympathetic neurons of the gut.
A specific part of the autonomic nervous system that is NOT part of the sympathetic nervous system.
Name the sensory ganglia that develop from the neural crest cells and where these are located.
1. Dorsal root ganglia- ganglia of the trunk
2. Cranial ganglia- 4 pairs are formed and they are in the head
These four pairs are: trigeminal, facial, glossopharyngeal, and vagal.
There are two major types, one of which is subdivided into four other types.
What types of neurons come from the alar plate of the neural tube hold?
Sensory. These nerves are on the dorsal half of the neural tube.
Top of the neural tube.
What types of neurons come from the basal plate of the neural tube?
Motor, skeletal specifically. These nerves are on the ventral half of the neural tube.
Bottom of the neural tube.
Definition: axial skeleton
Bones of the head and trunk (skull, vertebral column, ribs, sternum)
Upper part of body
Definition: appendicular skeleton
Bones of the limbs (limb girdles, bones within free limbs)
Things appended to the body
How does the intraembryonic mesoderm differentiate during embryonic development?
It develops into three types of mesoderm. The paraxial mesoderm lies closest to the notochord. The intermediate mesoderm lies laterally to the paraxial (will form the kidney and gonads). The lateral mesoderm lies the furthest from the notochord (will form the celomic sacs).
Three different tissues form
How do somites form?
Paraxial mesoderm next to the notochord segments that divides the continuous column of mesoderm into 44 pairs of blocks that flank the neural tube.
Each somite is divided into three morphologically and developmentally distinct regions. What are they?
Starting closest to the neural tube and moving laterally
1. Sclerotome
2. Myotome
3. Dermatome
Describe sclerotome development. What structures does the sclerotome contribute to?
The sclerotome forms the vertebrae and intervertebral discs. In the thoracic region, the contribute to the formation of ribs.
Sclerotome cells migrate ventromedially and aggregate around notochord. There, they condense to form the presumptive vertebral body. The processes of this structure grow dorsally to totally surround the developing neural tube and associated structures. This premature structure is the primordia of the neural arch.
How does spinal bifida occur? What structure fails to develop?
Spinal bifida occurs when the the dorsal migration of the sclerotome fails to occur and the spinal cord is incompletely closed. The neural arch is incompletely developed.
Failed fusion of what tissue?
How do intervertebral discs develop?
The sclerotomes that migrate into regions where the vertebral bodies are less dense develop into the intervertebral discs.
Similar to vertebral development
What happens to the notochord during vertebral development?
In regions that become ossified, the notochord becomes ossified as well and gets incorporated into the bone. In the intervertebral discs and spaces where it is not ossified, the notochord hydrates becomes the nucleus pulposus.
It stays in the backbone, but its local environment determines what it becomes.
Describe the development of dermatomes from their somites.
The middle layer of the paraxial layer of mesoderm is called the dermatome. These cells migrate outward (laterally) directly from their somite block to form the dermis and subcutaneous tissue of the skin. These cells have receptors for neurons from the dorsal root ganglion at the same level of the spinal cord.
Parts of the skin
"Dermatome" has two meanings. What are they?
1. Dermatome refers to the PART of the paraxial mesoderm that develops into the dermis and subcutaenous tissue of the skin.
2. It also refers to the AREA of the body that derives its sensory innervation from a single dorsal root ganglion at the same level.
One refers to a set of cells, the other refers to an area in adults.
Describe the development of the myotome and the structures that result.
Almost all skeletal muscle is derived from the myotome. It coalesces into two masses: the epimere and hypomere. The epimere is more dorsal and forms the paravertebral extensor muscles. The more ventral hypomere forms the body wall (intercostal, abdominal) and limb musculature.
Myo implies muscle
Name the types of vertebra and how many there are in each category.
Cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused)
There are 5 types
Define the curves of the adult spine. How many are there and what do the look like? When do they develop?
The two primary curves are in the thoracic (curves anteriorly) and sacral (curves anteriorly) areas. These curves develop in the fetus.
The two secondary curvatures are in the cervical (curves posteriorly) and lumbar regions (curves posteriorly). These develop after birth.
There are 4 curvatures
What is the most common form of scoliosis?
Right thoracic/left lumbar (curve is directed to the right in the lumbar region and to the left in the lumbar region)
What is the most common directionality of the lateral curvatures?
Definition: vertebral body
Weight-bearing, anterior portion of the vertebra. Increase in size from cervical to lumbar.
Largest part of the vertebra
Definition: vertebral arch
The posterior portion of the vertebra. It is composed of two pedicles and two lamina.
Posterior region of the vertebra
What are the parts of the vertebra that align with the notches of the adjacent vertebra superiorly and inferiorly called?
Superior and inferior vertebral notches
These are the parts that form the joints between vertebra
Definition: intervertebral foramen
The hole formed where the inferior notch of one vertebra aligns with the superior notch of the one underneath. This is also the place where the spinal nerves exit from the spinal column.
Lateral hole
Definition: vertebral canal. Which structures form this?
This is the tube where the spinal cord runs. The body and arch of each vertebra forms a vertebral foramen. The vertebrae then align and the canal is formed.
Spinal column
Where are the spinous process, transverse processes, and superior and inferior articular processes on a vertebra?
Spinous proces- where the two meet. This projects posteriorly and is the attachment place for ligaments and muscles
Transverse processes- the two places (one on either side) where the pedicle and lamina meet. They project obliquely.
Superior and inferior articular processes- form the zygapophyseal joints above and below each vertebra.
There are three different types of projections from the vertebra
The cervical vertebrae are characterized by...
A small body, articular processes in the horizontal plant, and a transverse foramen in each transverse process.
There are three main characteristics
Definition: atlas
The first cervical vertebra. It lacks both a spinous process and a body.
Vertebra closest to the base of the skull
Definition: axis
The second cervical vertebra. It has a large vertical projection called the odontoid process (aka dens) where the atlas rotates. This altlantoaxial joint is called the "no" joint.
Thoracic vertebrae are characterized by...
Inferiorly pointing spinous processes, articular processes in the coronal plane, and facets on the transverse processes for ribs.
There are three characteristics
Lumbar vertebrae are characterized by...
Large bodies, articular processes in the sagittal planes, and large, square spinal processes.
There are three characteristics
Describe the movements of the joints of the vertebrae. What movements do these allow?
The range of motion decreases as you go down the spine. Range depends on the thickness of the intervertebral disks, position and orientation of the vertebral joints, and the looseness of the joint capsule. The cervical region can move in three planes (lateral, rotation, flexion/extension). The thoracic region can move in two (lateral, rotation). The lumber region can move in one (flexion/extension). 3-2-1
Think of the ranges of motion allowed in cervical, thoracic, and lumbar regions
The atlantooccipital joint is specialized for what type of movement?
Flexion/extension. The "yes" joint
The atlantoaxial joint is specialized for what type of movement?
Rotation. The "no" joint
Describe the position and function of the anterior longitudinal ligament.
It covers the anterior 1/3 of each vertebral body and extends all the way down the column. It is a strong ligament that prevents hyperextension and reinforces the annulus fibrosus.
Anterior to the vertebral column
Describe the position and function of the posterior longitundinal ligament. How does it differ from its counterpart on the anterior side? What consequences does this have for the body?
It extends the length of the spine, covering the posterior side of each vertebral body. It is narrower and weaker than the anterior ligament, which means that the annulus fibrosus breaks more often here and you get more herniations of the disk.
Weaker than the anterior ligament
Describe the position and function of the ligamentum flavum
A ligament that links the lamina of adjacent vertebrae on the posterior wall of the vertebral canal. There is a LOT of yellow elastic tissue and therefore stretches like a rubber band.
Rubber band of the backbone
What are the supra and interspinous ligaments? How do they protect the vertebral column?
They attach to the spinous processes of adjacent vertebra. They prevent hyperflexion and are weak in humans.
Most posterior on the vertebral column
Describe the intervertebral disk.
It is made up of an outer ring of fibrocartilage called the anulus fibrosis and an inner gelatinous core called the nucleus pulposus (acts as a shock absorber). The thickness of this disk determines the amount of movement between the two disks. Thicker disk=more movement.
Two parts
When an intervertebral disk herniates posteriorly, which nerve is compressed?
When a disk in the thoracic or lumbar region herniates, the nucleus pulposus pushes on the nerve of the lower of the vertebrae. (Ex. in an L4-L5 herniation, the impinged nerve is 5) However, in cervical herniations, the herniation pushes on the nerve of the higher numbered vertebra. (Ex. C3-C4 herniation pushes on C3) Lumber herniations are the most common.
It varies depending on the region where the herniation takes place.
Which nerves innervate the deep back muscles?
The dorsal rami of spinal nerves.
Describe the layers of deep muscles of the back. Where do they attach?
Most superficial layer passes obliquely from medial to lateral and superiorly from its origin to its insertion. (ex. splenius capitis muscle)
The middle layer passes vertically between attachments. (ex. erector spinae muscles)
The deepest layer passes from lateral to medial as it passes superiorly from its origin to its insertion. (ex. transversospinae muscles which includes semispinalis capitis muscle.
There are three layers, two of which look like V's (but one is up-side-down)
What happens during embryonic development and the formation of the head and tail folds?
The neural tube begins to grow faster than the rest of the embryo (after neural tube formation) and both ends of the embryo begin to fold down beneath it on their respective ends. The cardiogenic mass folds beneath the embryo and moves caudally relative to the buccopharyngeal mass. The cloacal end does the same at the caudal end of the embryo. The amniotic cavity expands around the embryo as it rises up from where it began at the embryonic disk.
Things fold under
What are the three main parts of the neuron?
1. Axon
2. Dendrite
3. Cell body
Describe the cellular features of a neuron cell body.
They can vary in size and have prominent nuclei and nucleoli. (This is due to the cell body being the nutritional, or trophic, center of the neuron and the high volume of transcription there) There are clumps of ribosomes called Nissl bodies arranged in a large aggregate of RER and free polysomes. A Golgi, who job is to maintain the plasmalemma and to create synaptic vesicles, wraps around the nucleus like a shell. Other features include SER, lysosomes, MANY mitochondria, neurotubules (microtubules), and neurofilaments (intermediate filaments). Lipofuscin, a type of pigment inclusion, are also present. The axon hillock is the part of the cell body where the axon branches from and contains many neurotubules and neurofilaments but lacks Nissl bodies. This area appears clear.
RER, SER, Golgi, etc.
Dendrites always conduct nerve impulses _____ the cell body and respond in a _____ fashion.
toward, graded. The dendrite responds with a graded potential- the greater the stimulus, the greater the response.
What are the Nodes of Ranvier?
The gaps in the myelinated segments of the axon of a neuron. These are used to transmit electic impulses more quickly.
Axons conduct nerve impulses ____ from cell bodies and while graded potentials can occur, axons exhibit an ____ response.
away, all-or-nothing. (The SENSORY nerves of the PNS is the exception to the rule that nerves carry impulses away from the cell body.)
What is the initial segment of the axon?
This is the short segment where the axon originates from the axon hillock. This is length of axon that is just before myelination begins.
Close to the cell body
What are axon collaterals in nerve cells?
They are branch points from the axon (that occur at the Nodes of Ranvier in myelinated axons).
Branches from...
Dendrite NEVER contain which two organelles?
Nucleus and Golgi body. Dendrites contain mitochondria, Nissl bodies, SER, lysosomes, neurotubules, neurofilaments, and pigment inclusions.
Axons NEVER contain these organelles.
Golgi, RER, ribosomes, or nuclei. All nutrients and proteins needed by the axon must be transported there.
Retrograde transport is...
transport from the axon terminal TOWARD the cell body. Retrograde transport returns materials to the cell and functions at a similar speed as fast anterograde transport.
TOWARD cell body
Anterograde transport is...
transport FROM the cell body toward the axon terminal. This can take place at two speeds, slow and fast. The slow transports proteins while the fast flow transports synaptic vesicles, mitochondria, sugars, amino acids, and calcium.
AWAY from cell body
What is a multipolar neuron?
The most common type of neuron that has two or more dendrites that conduct nerve impulses toward the cell body. The impulse then passes through the cell, then the axon transmits the signal away from the cell body.
The usual type of axon
What is a bipolar neuron?
These neurons have one dendrite and one axon. This single, more pronounced and extended dendrite conducts a nerve impulse toward the cell body, and then it travels down the axon and away from the cell body. These nerves are often seen in special senses like taste, sight, smell, etc.).
Longer dendrite, cell body in the middle.
What is a unipolar neuron?
These are found in dorsal root ganglia and sensory ganglia of cranial nerves. There is a short dendrite associated with an axon, which passes the nerve impulse to the inital axon (that is myelinated). This action potential then BYPASSES the cell body and travels along the central process of the rest of the axon to the terminal at the end.
Impulse skips the cell body!
Define synapse.
Synapse is the FUNCTIONAL connection between one neuron and the next.
What are the three most common types of axons and what do they connect?
1. Axodendritic- connect axons and dendrites
2. Axosomatic- connect axons and cell bodies
3. Axoaxonic- connects axons to other axons
Named by the two structures they connect
A synapse must be capable of ____ transmission of nerve impulses. The _____ membrane delivers the action potential to the synapse while the ____ membrane responds to that action potential. The ____ ____ is the space between these two membanes.
1. Unidirectional
2. Presynaptic
3. Postsynaptic
4. Synaptic cleft
Chemical synapses can be either _____ or _____.
Excitatory or inhibitory. BOTH function by changing the resting potential of the cell (normally -70mV).
Define membrane depolarization versus hyperpolarization in terms of nerve impulses.
Depolarization is a reduces the resting membrane potential, so the inside of the cell becomes less negative. This shift is usually from -70mV to -50mV Hyperpolarization is an increase in the resting membrane potential. This is usually a shift from -70mV to -90mV.
What happens during an excitatory chemical impulse?
The membrane depolarizes to threshold value of -50mV which causes the generation of an action potential, if it is in an axon. If the postsynaptic membrane is a dendrite or nerve cell body, the changes in polarity cause a graded response (not an action potential). An action potential may be generated if the change in dendridic polarization is sufficient.
What happens during an inhibitory chemical impulse?
The membrane hyperpolarizes (or repolarizes) and there is no transmission of an action potential.
What two structures are always found in the presynaptic terminal of the chemical synapse?
Synaptic vesicles (containing neurotransmitter) and mitochondria. Both arrive from the cell body via anterograde transport.
Energy and neurotransmitters come from where?
What are the defining features of a chemical synapse in the electron microscope?
Dense cytoplasmic material on the inner surfaces of the pre- and postsynaptic membranes as well as synaptic vesicles
Densities and vesicles
What are some of the qualities of a chemical synapse of a neuron?
They contain a specific amount (quantum) of neurotransmitter and contain a single type of neurotransmitter. They can vary in shape and the appearance of their contents depending on their function.
An electrical synapse is ALWAYS _____.
Excitatory (as opposed to chemical, which can be both excitatory and inhibitory)
What are the features that define an electrical synapse? Where are these synapses useful?
Electrical synapses are found in places where speed is at a premium (like in auditory regions of the brain). The impulses are VERY fast due to the fact that the pre- and post- synaptic membranes are connected via gap junctions, which allow ions to pass directly from one cytoplasm to the next. Action potentials here always cause depolarization of the postsynaptic membrane. There is NO synaptic delay and NO synaptic cleft.
No synaptic delay. Why?
Name the six types of support cells in the nervous system and whether they are found in the CNS or PNS.
1. Astrocytes- CNS
2. Oligodendrocytes- CNS
3. Microglia- CNS
4. Ependymal cells- CNS
5. Schwann cells- PNS
6. Satellite cells- PNS
Which three types of neural support cells in the CNS fall under the category of neuroglia ("nerve glue")?
Astrocytes, oligodendrocytes, and microglia
What are astrocytes?
Support cells around neurons of the CNS that have many cellular processes that are supported by intermediate filaments. Their processes (astrocyte endfeet) adhere to capillaries or neurons. These are the most abundant glial cells in the CNS. These cells are responsible for removing excess potassium and play a role in homeostasis in the CNS.
The continuous layer of astrocytes called subpial glia make up the external surface of the CNS and they produce the basal lamina. Large blood vessels enter their surface.
What are oligodendrocytes?
Glia support cells in the CNS that produce myelin. They have fewer processes than astrocytes.
Myelination in CNS
What are microglia?
Glia support cells in the CNS. They are small cells that are scattered throughout CNS and are phagocytic- cleaning up cell debris and damaged myelin after injury. They have dense oval nuclei, little cytoplasm, and short processes.
Phagocytes in CNS
What are ependymal cells?
These cells line the ventricles of the brain and central canal of the spinal column. This simple epithelium help forms the choroid plexus (a core of connective tissue/capillaries surrounded by ependymal cells) and they produce cerebrospinal fluid.
Cerebrospinal fluid (CNS)
What are Schwann cells and satellite neuronal support cells?
Schwann cells are flattened cells that produce myelin around the axons of the PNS. Satellite cells surround the nerve cell body and dendrites in the PNS.
These are support cells of the PNS
How does the excitatory action potential in an axon work?
Start with an adequate stimulus that begins the response. This causes sodium channels to open in the axon. The positive charge rushes into the negatively charged interior of the axon (that is at resting potential). The local depolarization reaches a threshold potential (-50mV) that causes more Na+ channels to open. The depolarization continues to a voltage of +30mV (the reverse of the resting potential), when the Na+ channels close and the membrane can return to its resting potential (by pumping potassium out of the axon). This action potential is carried down the axon by successive openings and closings of sodium channels. The potential is carried along the axon WITHOUT decreasing in magnitude, hence the all-or-nothing response.
How does a saltatory conduction of an action potential along a neuron work?
Ion exchange on myelinated axons cannot occur except at the nodes of Ranvier. The action potential seems to leap from one node to the next, significantly increasing the speed of potential conduction.
Myelination of axons is important.
How do oligodendrocytes myelinate axons in the CNS?
Oligodendrocytes myelinate axons greater than 1um in diameter by wrapping plasmalemma (of the oligodendrocyte) around the axon many times in tight spirals. The closely packed adherent layers of oligodendrocyte plasmalemma.
Two oligodendrocytes meet at the Nodes of Ranvier, but there are no junctions between adjacent oligodendrocytes at nodes, so there is free access for ion exchange between extracellular space and axon cytoplasm.
Wrapping around axon...
How are neurons myelinated in the PNS?
Small neurons (<1uM) are unmyelinated, but exist in bundles that are protected in troughs of Schwann cells that run with them. The plasmalemma of these neurons is exposed to the surrounding environment and the conduction of signals is significantly slower than with saltatory conduction. There is NO myelin present in this system.
Neurons >1uM in diameter are myelinated by Schwann cells, that produce myelin from their plasmalemmas. ONE Schwann cell myelinates ONE axon (unlike the CNS where one oligodendrocyte can myelinate multiple axons).
1<uM are unmyelinated but still protected
Name the meninges of the spinal cord from the outermost to the innermost.
Dura mater, arachnoid, pia mater
There are three layers
Describe the features of the dura mater.
The dura mater is a tough layer made of a dense feltwork of connective tissue that is the outermost layer of the spinal cord. The space that separates the dura mater from the vertebral column is the epidural space, which contains a thin layer of veins, loose connective tissue and fat that allow movement. The dura mater rests atop the arachnoid, with a small space in between called the subdural space.
Outermost spinal cord layer
Describe the features of the arachnoid layer of the spinal cord.
The middle layer is called the arachnoid. It sits close to the dura mater (above it). It is a delicate layer of flat cells bound with tight junctions, since this layer acts as a selective barrier.
The arachnoid connects to the pia mater with a system of trabecule that look like a spider's web. The subarachnoid space is filled with cerebrospinal fluid (produced from the ventricles of the brain and choroid plexus). The trabeculae attach to the pai mater. Blood vessels pass through this subarachnoid space that the trabeculae support.
Middle spinal cord layer
Describe the pia mater.
This innermost meningeal layer of vascular loose connective tissue adheres to the spinal cord. This does NOT function as a barrier.
Over the brain, the layer is delicate, but is thick over the spinal cord. This tissue forms denticulate ligaments that anchor to the dura mater and this runs between the dorsal and ventral nerve rootlets that come off of the spinal cord. The pia mater extends past the spinal cord and into the cauda equina in a structure called the filum terminale.
Innermost spinal cord layer
What is white matter?
The axons, supporting cells, and capillaries of the nervous system. The myelination of the axons give it the white color. It contains NO nerve cells bodies.
In the spinal cord, the white matter surrounds the gray matter, but in the brain, the gray matter surrounds the white matter.
Not myelinated
What is gray matter?
It is nervous tissue that is composed of cell bodies as well as axons, dendrites, axon terminals, astrocytes, oligodendrocytes, microglia, and capillaries. Neuronal cell bodies + neuropil (everything else)= gray matter.
Gray matter is beneath the white matter in the spinal cord, but it surrounds the white matter in the brain.
Nuclei are collections of nerve cell bodies deep in the brain that have common functions.
There is no _____ _____ or other structural boundaries between the cellular elements of the gray and white matter. The only connective tissue element present are the ____ ____ of blood vessels.
External laminae, basement membranes. All of the specialized cells have a very thick epithelium, but not connective tissue.
Parts of connective tissue
How are the spinal nerves numbered along the spinal cord?
Those that exit in the cervical vertebra are named for the vertebra BELOW their intervertebral forament exit point. (there is a C8 spinal nerve, but NOT a C8 vertebra!) All others are named for the vertebra ABOVE their exit point.
Since the spinal cord is shorter than the vertebral column, any segments below vertebra L2 do not correspond to adjacent vertebral bodies.
Above vs. Below
Below the L2 vertebral segment, the collection of descending spinal cord rootlets are called the...
Cauda equina. The rootlets that form the spinal nerves below L2 must descend from the spinal cord to the appropriate vertebral level where they exit the intervertebral foramen.
Horse's tail
What is the clinical significance of the organization of spinal nerves?
Damage to the spinal cord (ex. in the cervical region) can disrupt neural signals to all spinal nerves below the point of injury. However, if you damage the spinal cord below L2 (ex. in the sacral region), you would only damage the exiting nerves of the cauda equina.
How can you damage the spinal cord and how does the injury vary depending on the region?
What are the five components of the spinal nerve and their cell body location?
1. General sensory (dorsal root ganglia)
2. Somatomotor (ventral horn of gray matter in spinal cord)
3. Preganglionic symapthetic (lateral horn of gray matter, T1-L2)
4. Postganglionic sympathetic (sympathetic chain ganglion lateral to vertebral column)
5. Preganglionic parasymathetic (lateral horn of gray matter S2-S4)
Lateral horn, ventral horn, dorsal horn of spinal cord gray matter
Definition: dorsal rami
The division of the spinal nerve that goes posteriorly and innervates the skin and intrinsic muscles of the back.
Contains: general sensory, somatomotor, and sympathetic axons
Posterior innervation
Definition: ventral rami
The division of the spinal nerve that goes anteriorly to innervate the skeletal muscles of the thoracic and abdominal walls and the skin of the lateral and anterior body walls. Contains: general sensory, somatomotor, and sympathetic axons.
Anterior body wall innervation
What are the layers that surround peripheral nerves and what do they consist of?
1. Endoneurium- innermost sheath made of loose connective tissue (collagen fibrils, fibroblasts, macrophages, capillaries) Schwann cells secrete external laminae to separate axon/Schwann cells from endoneurium.
2. Perineurium- middle layer. Binds bundles of nerve fibers. Extremely flat cells with no extracellular space, connected by tight juntions. Is a seletive barrier to large molecules, but transports useful substances in their cytoplasm via transcytosis.
3. Epineurium- outermost wrapping composed of dense connective tissue (large collagen fibers, few fibroblasts). This layer protect the nerves from physical damage.
There are 3, very similar to skeletal muscle
What are ganglion?
Collections of nerve cell bodies in the peripheral nervous system. (similar to gray matter of CNS)
Like gray matter in CNS
How are ganglion wrapped?
Exactly like peripheral nerves- epineurium, perineurium, endoneurium. Except here, satellite cells surround the nerve bodies (not Schwann cells like with axons) and secrete the external lamina barrier against the endoneurium.
Just like peripheral nerves
What are the two types of ganglion in the PNS?
1. Sensory ganglion (which consists of dorsal root ganglion and sensory ganglia of cranial nerves)
2. Autonomic (motor) ganglion
Sensory and voluntary motor
What is the structure of most sensory nerves? How do they carry impulses to the CNS?
They are unipolar neurons with dendrites located in remote receptors. Dendrites respond to stimuli with a graded potential that passes to the axon, where it becomes an action potential. The action potential bypasses the cell body and continues along the central process of the axon to the axon terminal in the CNS
Unipolar neurons
Define autonomic ganglia.
Motor ganglia for the sympathetic and parasympathetic divisions of the autonomic nervous system. The are multipolar neurons, have synapses, and are found in multiple locations throughout the body (sympathetic trunk, prevertebral ganglia, digestive tract)
Parasympathetic sympathetic
What is a dermatome (in terms of locations on the body) and how do they work?
A dermatome is a strip of skin extending from the dorsal midline to the ventral midline innervated by spinal nerves. They overlap to some degree and you have to remove a few of the spinal nerves to completely de-innervate an area.
Strip of skin
Sensory receptors are classified into two types based on structure. These are...
1. Free nerve endings- dendrites that branch and end freely. They respond in a graded fashion to stimuli.
2. Encapsulated nerve endings- have dendrites surrounded by a capsule of connective tissue.
Covered and uncovered
Between which vertebrae do you perform a lumbar puncture? What is the order of the layers that you will penetrate to get there?
Go midline between L3 and L4 or L4 and L5.
The needle passes through the skin-> supraspinous ligament-> interspinous ligament-> ligamentum flavum-> epidural space-> dura mater-> subdural space-> arachnoid space-> subarachnoid space (location of the cerebrospinal fluid)
Anesthetics may be introduced into the epidural space (where it can diffuse through the connective tissue) in order to effect the lower nerve roots. This is called the caudal block.
You're looking for the cauda equina
What are the three muscles that span the intercostal space? What is their function?
External, internal, and innermost. These muscles serve to stabilize the thoracic wall and prevent the intercostal spaces from enlarging.
How do the intercostals receive innervation and blood?
VAN-vein, artery, neuron. These run below each rib in between the internal and innermost intercostal muscles. The innervation derives from the ventral rami while the blood supply is from the posterior intercostal branches from the aorta and the anterior intercostal branches from the internal thoracic artery.
Each intercostal nerve is ____ to the intercostal muscles, ____ to the overlying skin, and ____ to the parietal pleura lining the inside of the ribs.
Motor, sensory, sensory. Each nerve is numbered for the rib that lies above it.
Where is the neurovascular bundle? What is it and why is it clinically important?
The vein, artery, and nerve running along the rib, right below it. There is a slight depression in the upper rib where this runs and the vessels and nerves run on the upper side of the lower rib.
This is clinically important because you want to avoid the neurovascular bundle when you are performing thoracocentesis.
Define: anastamose
Two arteries or veins that run into each other (ex. anterior and posterior intercostal arteries and veins)
Coming together of...
Definition: aponeurosis
Fibrous or membranous sheet connecting a muscle and the part it moves
Thoracolumbar aponeurosis is a good example of this
The posterior intercostal vessels are segmental branches from the ____ ____.
Thoracic aorta
The anterior intercostal arteries are segmental branches from the ____ ____ ____, which are branches of the ____ ____.
Internal thoracic arteries, subclavian arteries
Internal thoracic...
What is considered deep fascia?
All fascia deep to the subcutaenous tissue.
Define investing fascia
The complete fascial investment covering the underlying muscles and bones.
Any nerve that is superficial to the investing fascia will contain only ____ and ____ nerve fibers.
Sensory and autonomic fibers. No skeletal muscle is superficial to the investing fascia.
No need for skeletal motor fibers here!
Define intermuscular septa
Extensions of the investing fascia that pass inward to bones and divide the muscles into groups.
A weak spot or tear in the ____ may result in a herniation of the muscle tissue during a contraction.
Why is the linea alba a good place to enter for abdominal surgery?
Because here there aren't nerves to sever and this area of dense connective tissue at the midline is relatively nonvascular.
No nerves, no vessels
What is the rectus sheath? Describe its organization.
The rectus sheath is the sleeve of connective tissue that surrounds the rectus abdominus muscle. It is made of the aponeuroses of the lateral abdominal muscles. It has both an anterior and posterior sheath, but once it reaches the level under the umbilicus, there is only an anterior layer.
What are the layers of muscle in the lateral abdominal wall? Where to they attach?
1. External abdominal oblique- fleshy portion attached to the bottom 7 ribs and iliac crest; the midline is an aponeurosis that connects to the superficial part of the rectus sheath
2. internal abdominal oblique- originate from several ribs, the thoracolumbar aponeurosis, and the iliac crest and attach into the lower ribs and the rectus sheath
3. the transversus abdominus- originate in several ribs, the thoracolumbar aponeurosis, and the iliac crest and attaches to the rectus sheath
What are the three surgical approaches to the abdominal wall?
Midline approach (at the linea alba), Paramedial (in rectus sheath), Gridiron approach (direction of the muscles taken into consideration)
Describe the movements the muscles of the abdomen around each axis of motion.
External oblique- flexion on transverse axis, bend to same side on anteroposterior axis, rotate to opposite side on vertical axis
Internal oblique- flexion around transverse axis, bend to same side on A/P axis, rotate to same side on vertical axis
Rectus abdominus only does flexion around transverse axis
Flexion/extension is around transverse axis, lateral bending is around A/P axis, and rotation is around vertical axis
For all muscles of the vertebral column, the ____ attachments of the muscles will move while the _____ attachments will remain fixed.
Superior, inferior
What is the guarding response of the abdominus muscle?
It is the reflexive spasm of the abdominal musculature is response to being pushed on.
What are the three general layers of the largest blood vessels?
1. Tunica intima (a layer of endothelium that lines the lumen of the blood vessel and loose connective tissue)
2. Tunica media (a layer of multiunit smooth muscle fibers, circularly arranged that may contain elastin secreted by the muscle. The elastic sheets are fenestrated)
3. Tunica adventitia (outermost layer of loose connetive tissue, supplied with blood by the vaso vasorum)
Where to the autonomic nerve fibers pass through to reach the tunica media?
Tunica adventitia
How are the three layers of tunic composed in arteries?
There is an internal elastic membrane between the endothelium and loose CT of the tunica intima from the smooth muscle in the tunica media. Tunica media is ALWAYS the thickest tunic and has varying amounts of elastic membranes and type III collagen.
Lots of elastin
What are the two types of arteries?
Elastic arteries and muscular arteries
Describe the makeup of an elastic artery. Where are they found?
They are the largest and closest to the heart. They are in the aorta, pulmonary trunk, pulmonary arteries, brachiocephalic trunk, common carotid, subclavian, and common iliac arteries.
In elastic arteries, there is abundant elastic laminae in the tunica media. The smooth muscles of the tunica media are responsible for secreting this (and aren't really used for muscular control) The elastic sheets stretch during systolic contractions of the ventricles and provide pressure during diastole by recoiling. The elastic membrane are essential in maintaining blood pressue.
How do you maintain blood pressure
Describe the makeup of muscular arteries. Where are these found?
Muscular arteries are found everywhere that elastic arteries are not. They are very useful in controlling blood flow.
The smooth muscle controls the lumen of the artery to a much greater degree than in elastic arteries. There is an external elastic lamina that separates the tunica media from the tunica adventitia.
What is the key characteristic that differentiates a vein from an artery?
The artery has an internal elastic membrane between the tunica intima and tunica media.
Name two types of arterial disease and what causes them.
1. Hypertension- vasoconstriction in the arterioles that increases the systemic blood pressure
2. Atherosclerosis- thickening of the tunica intima and general obstruction of the artery's lumen. This is due to arterial damage. Monocytes and LDL-cholestrol move into the tunica intima and a plaque forms. This calcifies over time and causes three serious problems: a clot may develop within the plaque, necrotic plaque can fragment, or the vessel wall may weaken and cause and aneurysm.
High blood pressure and hard arteries
What is the structure and diameter of a capillary?
A capillary is only a single layer- the tunica intima. This includes the endothelium and its basement membrane. This allows for the maximum exchange. The diameter is 7-9 uM.
What are the three types of blood-carrying capillaries and how do they differ structurally?
1. Continuous capillaries (high degree of control)- endothelial cells are joined by tight junctions, exchange must occur between cells, across tight junctions, or through endothelial cells via transcytosis
2. Fenestrated capillaries (intermediate control)-endothelial cells controlled by tight junctions but there are perforations where basal lamina and luminal plasmalemma meet, the holes may contain diaphragms that regulate passage of substances
3. Discontinous capillaries- (minimal control) lack junctional complexes and basement membranes, making discontinuities between endothelial cells. The spaces are called sinusoids in some tissues.
Describe the structure of lymphatic capillaries.
Lymphatic capillaries carry lymph, which is recovered extracellular fluid and proteins that have leaked out of the capillaries. They are strucurally similar to discontinuous capillaries. Lymphatic vessels contain valves that prevent back flow. They combine to form larger and larger vessels, which will ultimately drain into the right and thoracic lymphatic ducts. (These will drain into the subclavian and jugular veins at the base of the neck)
Name the 5 routes of transport across endothelial cells in the capillary beds.
1. Diffusion (small, lipid soluble substances like oxygen)
2. Vesicular transport
3. Fenestrae (small "windows" that allow passage of materials)
4. Paracellular pathway (if occluding junctions are leaky, things pass between cells)
5. Endothelial discontinuities
No endothelial cells use all 5 types of transport
What is the diameter at which you can differentiate a venule from a capillary?
Diameters exceeding 10uM are considered venules
What do the walls of venules consist of?
Endothelial cells and their basement membranes
During an immune reaction, the histamine secreted from mast cells causes what to happen to venules and capillaries?
The tight junctions of venules and capillaries become more permeable
The three layers of a vein appear when it reaches what diameter?
200uM. At 50 uM smooth muscle cells and fibroblasts appear outside the endothelium.
Arteries have ____ or more layers of smooth muscle, arterioles have ________.
Five; one to four
How do arterioles control the blood flow to capillary beds?
Precapillary sphincters which are smooth muscles that can constrict to stop blood flow and dialate to allow it. Neural or hormonal influences stimulation can cause the contraction.
How do arterioles differ from arteries?
Arterioles usually don't have an external elastic lamina (and most don't have an internal one either)
What is the rule when determining whether you have a vein or a venule?
It is a vein if it runs with an artery and a venule if it runs with an arteriole.
What is the structure of a vein?
Veins have a tunica intima composed of endothelium with a basement membrane beneath it. There is no internal elastic membrane. The tunica media (smooth muscle) is thinner than the tunica adventitia (loose CT).
No internal elastic membrane
What is a mechanism that drives blood back to the heart from the capillary beds?
Valves. Veins with diameters greater than 2mm have valves that prevent back flow. The semilunar valves are inpockets of the tunica intima with edges directed toward the heart. They are most prominent in the extremities and absent in the head, neck, and trunk. (no valves means you can have collateral circulation)
What are the distinguishing characteristics when deciding whether something is an artery/vein or arteriole/venule?
1. Lumen of a vein is larger than its accompanying artery
2. Arteries almost always have internal elastic lamina, but not veins
3. The tunica media is thickest in arteries while the tunica adventitia is thickest in veins.
4. Only veins have valves
What are arteriovenous anastomoses?
Also known as AV-shunts that convey blood directly from the arterial system to the venous system, bypassing the capillary bed. They are used to control body temperature. Opening a shunt decreases flow to the capillaries, decreasing heat dissapation.
They are found in the soles of feet, palms of hands, skin of fingertips, nose, lips and erectile tissue.
A-V shunt
What is angiogenesis? How does angiogenesis work?
Angiogenesis is the development of new blood vessels from existing ones. New vessels originate as capillaries from small venules or other capillaries. There are five stages in angiogenesis: endothelial cells dissolve basil lamina, cells actively migrate, cells secrete new basal lamina, the endothelial cells align to form a solid sprout, they proliferate, the sprout hollows, then it anastamoses with another vessel to complete the loop.
Essential in tumor development
What is collateral circulation? Give an example.
More than one route for delivering blood to some part of the body. Blood vessels anastamose with each other so that blood can be shunted around a blockage.
Examples include the internal thoracic artery and the superior and inferior epigastric arteries.
Shunting blood around
Where are the landmark dermatomes and which ventral rami are they associated with?
T4 at the level of the nipple. T10 at the level of the umbilicus. T12 at the suprapubic region
Name the 4 celomic sacs present in the adult.
Two pleural sacs surrounding the lungs, a pericardial sac surrounding the heart, and the peritoneal sac surrounding the abdomnial visceral organs.
Lungs, heart, viscera
The body cavities are derived from ____ ____ in the embryo, which forms from lateral plate mesoderm and a portion of the cardiogenic mass.
Intraembryonic mesoderm
Describe the formation of the intraembryonic celomic tubes that flank the gut tube as the embryo folds.
The lateral plate mesoderm splits into two layers with an intervening space. The layer associated with the roof of the yolk sac is called splanchnic mesoderm and the layer associated with the body wall is called somatic mesoderm. The space in between them is the intraembryonic celom. A portion of the intraembryonic celom incorporated into the body of the embryo. This occurs on both sides of the embryo and forms a cylindrical tube on intraembryonic celom on either side of the gut tube. The connections that remain on the dorsal and ventral sides of the gut tube are called mesenteries. The cardiogenic mass cavitates and joins the celomic tubes on either side of the gut tube by a strip that runs ventrally, in front of the gut tube.
How does the pericardial sac form?
The pleuropericardial folds grow to separate the pericardial cavity from the celomic tubes. These folds form where the celom (derived from lateral plate mesoderm) and the cardiogenic mass fused. The part in contact with the heart is the visceral pericardium he space between the two is the pericardial cavity.
How do the lungs and pleural sacs form?
The lungs develop as outgrowths from the foregut. They bud, bifurcate, then invaginate the celomic tubes to form the pleural cavities. The part in contact with the lungs becomes visceral pleura and the part in contact with the body wall is the parietal pleura. Pleuropericardial folds keep the pleural sacs separated from the pericardial sac. Pleuroperitoneal folds separate the pleural portions of the celomic tubes from the caudal ends that will form the peritoneal cavity.
What elements contribute to the formation of the diaphragm?
Pleuroperitoneal folds, portion of body wall, tissues associated with the esophagus, and the septum transversum (from the cardiogenic mass)
Portions of the intraembryonic celom that flank the gut tract caudal to the pleuroperitoneal folds will form the ____ ____.
Peritoneal sac
What happens to the ventral and dorsal mesenteries in the developing embryo?
The dorsal mesentery persists and forms blood vessels and nerves that feed the peritoneal cavity and its viscera. The abdominal portion of the ventral mesentery persists because it develops blood vessels that feed the liver. Any ventral mesentery below that, though, degenerates because it is functionless.
Name the regions of the parietal pleura as well as the recess where it contacts the visceral pleura.
Diaphragmatic pleura, costal pleura, mediastinal pleura. The recesses are the costodiaphragmatic recess (at the inferior edge) and the costomedialstinal recess at the pericardial edge. The recesses are almost fully occupied during inspiration.
Along the ribs, next to the heart, etc.
What is an accumulation of fluid or blood in the pleural cavity called?
Hemothorax or hydrothorax
What are the fissures of the lungs called? Where are they?
The left lung is divided by only the oblique fissure, which divides it into lower and upper lobes.
The right lobe is divided by a long oblique fissure and another horizontal fissure. This divides the lung into upper, middle and lower lobes.
There are 2 lobes on the left and 3 on the right.
Where are the surface projections of the lungs on the body?
During expiration the oblique fissures fall in the 5th intercostal space. In the right lung, the horizontal fissure runs from the right 4th costochondrial junction to the right 5th intercostal space (beneath the 4th rib).
The inferior margins of the pleura are at rib levels 8, 10, and 12. The inferior margins of the lungs are at rib levels 6, 8, and 10.
Where would you insert a needle to remove fluid from the pleura cavity in the midaxillary line?
Between the 8th or 9th intercostal space, just above the lower rib
How is pain sensation in the pleura innervated?
By the intercostal (costal pleura) and phrenic (mediastinal and diaphragmatic) nerves. There is no sensory innervation to the visceral pleura
How and why is the procedure of thoracentesis performed?
Thoracentesis is used to aspirate fluid or air from the chest cavity. If fluid is in the pleural sac, the needle is inserted one or two intercostal spaces below the fluid level, 5-10 cm lateral of the spine on the back of a patient. If removing air, the needle is inserted into the second or third intercostal space in the midclavicular line on the patient's chest. Either way, it must be ABOVE the diaphragm.
Asprirate fluid or air
How is a chest tube inserted?
A chest tube drains the fluid, blood or air from the chest cavity. A common site is between the 5th or 6th intercostal space at the midaxillary line. Make a short incision over the 6th rib, the tunnel over the rib. Puncture the parietal pleura with a hemostat. Insert the chest tube into the opening then tie it into place using a purse string suture.
Where is the trachea located? Where does it bifurcate?
In the neck, at the inferior margin of the larynx and lies anterior to the esophagus. The arch of the aorta crosses the trachea anteriorly. The trachea bifurcates at the level of T5. (the location of the carina)
How do the right and left bronchus differ? How does this difference cause problems?
The right bronhus is shorter, wider, and oriented more vertically than the left. this means that object get aspirated more easily into the right bronchus.
What kinds of nerve fibers does the cardiopulmonary plexus contain? Where is the cardiopulmonary plexus located?
Sympathetic, parasympathetic, and sensory nerve fibers. It is located anterior to the trachea, at the level of the bifurcation of the trachea called the carina.
No somatomotor fibers needed here!
Name the structures at the hilus of the lung.
Bronchi, pulmonary arteries, pulmonary veins, bronchial arteries and veins, lymphatic vessels (hilar nodes), branches of pulmonary plexus.
What is the purpose of the bronchial arteries and veins? Where do the arteries originate and the veins drain?
Their purpose is to nourish the bronchial tree and the veins drain it. The bronchial arteries originate from the aorta and the veins drain to the azygos vein.
What feeds the lung tissue?
Describe the positions of the pulmonary arteries relative to the bronchus.
RALS= right anterior, left superior. The right pulmonary artery is anterior to the bronchus, the left pulmonary artery is superior to the bronchus.
Bronchi have the ____ walls of the structures at the hilus of the lung.
Pulmonary veins have the ____ walls and are usually the most ____ and ____ vessels.
Thinnest, anterior and inferior
What are bronchopulmonary segments?
A bronchopulmonary segment is the region of the lung aerated by a tertiary bronchus.
Each tertiary bronchus branches from the secondary at a very specific and predictable angle.
How do the pulmonary arteries and veins run within the lungs?
The pulmonary arteries run alongside and branch with the primary, secondary, and tertiary bronchi. The arteries are consider INTRAsegmental.
Pulmonary veins run separately at the interfaces of the bronchopulmonary segments. The veins are considered INTERsegmental.
How does the lymphatic system run within the lung?
They have a rich lymphatic system that follows the pulmonary and bronchial segments run through a series of pulmonary lymph nodes to the bronchopulmonary nodes at the hilus. The lymph travels superiorly along the trachea to the left and right lymphatic ducts.
What are sentinel nodes?
They are the supraclavicular lymph nodes that enlarge when there is disease in the lungs.
Name the parts of the conducting portion of the respiratory system.
vestibules of the nose, nasal cavities, pharynx, larynx, trachea, right and left primary bronchi, intrapulmonary bronchi, bronchioles.
These are the parts that are responsible for cleaning, warming, and humidifying the incoming air and bringing it to the lungs)
Name the parts of the respiratory portion of the respiratory system.
Alveolar ducts, alveoli. These parts are specialized for gas exchange.
Proper functioning of respiratory system depends on its ____, which is continuous with several regional differences.
Epithelia. The walls of the conducting system become thinner as the air proceeds to the alveoli.
Respiratory epithelia is what kind of tissue? What function do the structures have?
Pseudostratified columnar epithelia with cilia and goblet cells. The goblet cells secrete mucus that humidifies the air and traps particulates. The cilia moves mucus away from the lungs, so that the incoming air will be as clean as possible.
What cells and structures make up the trachea?
Respiratory epithelium, lamina propria containing seromucous glands and elastic fibers, cartilaginous and muscular layers. There are 18 C-shaped hyaline cartilage rings that prevent it from collapsing. The gap is filled in with smooth muscle called trachealis muscle, which becomes more prominent as you proceed down the trachea.
The trachea bifurcates into two ____ ____.
Primary bronchi. They have the same structure of cartilage rings as the trachea.
How do secondary bronchi differ from primary bronchi?
Secondary bronchi are intrapulmonary segments that have irregular (discontinuous) plates of cartilage and a more prominent layer of smooth muscle. These layers are more easily modified than the previous layers. As you proceed down the bronchus, the amount of cartilage becomes reduced.
When cartilage in the bronchi has disappeared completely, we are at the level of a ____.
Bronchiole. Bronchioles have a diameter of <1mm and each branches to form 5-7 terminal bronchioles. They lack hyaline cartilage and glands in the lamina propria, but do have a lot of smooth muscle and elastic epithelium.
How is the respiratory epithelium different in the bronchioles?
The layer must be thinner because the diameter of the passageway is smaller and you need to transition from the thicker epithelium in previous layers to the thin layer of alveolar epithelium. Terminal bronchioles are lined with simple columnar epithelium with cilia and Clara cells. (NOT goblet cells)
What are Clara cells?
Clara cells are non-ciliated, dome-shaped apical surfaces that are filled with secretory granules. They secrete a surfactant-like substance that prevents collapse of the bronchioles.
Prevent collapse of bronchioles by secreting something
How is the smooth muscle in the bronchi and bronchioles innervated?
By the autonomic nervous system. The sympathetic nerves cause the diameter of the bronchioles and bronchi to increase.
Describe the respiratory portion (cells) of the respiratory system.
The bronchiole splits into 2-4 alveolar ducts, that have alveoli in their walls as well as isolated regions of simple cuboidal epithelium with cilia and Clara cells. There are now more Clara cells than ciliated ones. The lamina propria and alveolar ducts contain a layer of discontinous smooth muscle.
What is an alveolus?
The cellular unit of gas exchange between air and blood in the lungs. They are cup-shaped strucures about .2mm in diameter.
Describe the alveolar septum.
The wall of the alveolus that are lined with simple squamous epithelium that contains many capillaries. 95% are type I alveolar cells, 5% are type II.
What is the difference between type I and type II alveoli?
Type I= the business end, involved in gas exchange. These flattened cells have organelles that are packed around a flattened nucleus and are so thin that their apical and basal plasmalemma almost touch each other. They are bound to each other by tight junctions.
Type II= secrete pulmonary surfactant, which reduces surface tension. They are usually cuboidal and bulge into lumen of alveolus.
Describe how gas is exchanged occurs across the air-blood barrier.
It must go across a layer of surfactant, a type I alveolar cell, a fused basal lamina, and an endothelial cell to reach the blood.
What is the function of the thicker parts of the alveolar septum?
No gas exchange occurs. These area contain elastic fibers, collagen fibers, Type II alveolar cells, fibroblasts, macrophages, and lymphatic vessels.
What causes emphysema?
The destruction of the elastic fibers in the alveolar septum so that air can no longer be forced out of the lungs as easily.
What causes respiratory distress syndrome in infants?
The Type II alveolar cells do not produce adequate pulmonary surfactant, so their alveoli collapse.
What is the function of the alveolar macrophage?
They are the last line of defense between the air and the blood. They remove what the conducting system could not and are coughed up or swallowed with their cytoplasmic debris. They can move about the alveolar lumen, but usually reside in the septa.
What is the mediastinum and what are its boundaries?
It is the region between the pleura sacs. The superior boundary is the thoracic inlet (T2). The anterior boundary is the sternum. The inferior boundary is the diaphragm (T9). The posterior boundary is the vertebral column and laterally it is the mediastinal pleura.
There is a plane at the T4-5 vertebra that separates the superior mediastinum from the inferior mediatstinum (where the trachea bifurcates). The middle mediastinum is the pericardium and its contents, the posterior mediastinum is anything behind the pericardium to the vertebral column and the anterior mediastinum is anything in front of it to the sternum.
Describe the path of the left vagus nerve.
It enters the superior mediastinum, passes anterior to the aortic arch, and gives off the left recurrent laryngeal nerve (that passes under the aortic arch, inferior to the ligametum arteriorsum). The left vagus nerve continues to reach the anterior surface of the esophagus, where it contributes to the esophageal plexus along with the right vagus nerve.
What is contained in the anterior mediastinum?
Fat, lymph nodes, branches of the internal thoracic artery, retrosternal lymph nodes (along the internal thoracic vessels)
What is contained in the posterior mediastinum?
The descending aorta, thoracic duct, azygos vein, hemiazyos vein, esophagus, vagus nerves, sympathetic trunks
Describe the development of the heart tube from the cardiogenic mass in the developing embryo.
After the cardiogenic mass tucks underneath the embryo, it cavitates to form two parallel vessels that fuse to form a single heart tube, surrounded by developing a pericardial cavity.
Blood flows into the venous end of this tube (caudal) and out the arterial (cranial) end. The structures of the heart tube (from top to bottom) are: the aortic arches, bulbus cordis, ventricle, and atrium.
How does the heart tube fold to form the heart loop in the developing embryo? What is the pathway of blood flow after it is done folding?
Because the heart tube is restricted to the pericardial sac and it continues to grow, it will fold up within the sac. The kink always bends to the right to form a bulboventricular sulcus. The atrium and ventricle don't grow as quickly as in diameter causing constrictions to form in these regions. The atrium and the sinus venosus (connected to it inferiorly) move posteriorly and cranially.
The bulbus cordis grows so that it is subdivided into a right ventricle and outflow tracts (conus cordis and truncus arteriosis) The atrium and ventricle are common, but constrictions exist to show where they will be subdivided. (interventricular sulcus for ventricles and truncus arteriosis for the atria)
Throughout this process, blood flow through the heart tube is relatively simple: common atrium-> artioventricular canal-> left ventricle-> narrow interventricular canal-> right ventricle-> conus cordis-> trunus arteriosis
How are the atrium and ventricles separated in the developing embryo?
The atrioventricular canal separates the atrium from the ventricle. It lies just above where the interventricular septum will be. It becomes H-shaped as the superior and inferior endocardial cushions grow toward each other and subdivide the canal into right and left A-V canals.
Describe the septation of the common atrium in the heart of the developing embryo. How does this structure allow for fetal circulation?
The septum primum descends from the roof of the atrium toward the endocardial cushions, leaving an ostium primum open as it grows downward to allow for right to left circulation of blood. When the septum primum meets the endocardial cushion, the ostium primum disappears and the ostium secundum opens up on the upper portion of the septum. (Right and left atrium can communicate at all times)
Then a thicker septum secundum forms on the right side of the septum primum and grows inferiorly. It remains open at a hole called the foramen ovale (right next to the inferior vena cava). This allows for a right to left atrial shunt to remain open for fetal ciculation. The high pressure in the right atrium forces the blood into the left atrium via the foramen ovale and ostium secundum. If the pressure is reverse, the septum primum is pushed against the septum secudum and it closes.
How are the ventricles of the heart divided during embryological development?
The ventricles are already partially separated by the muscular interventricular septum. They are separated completely when the membranous portion of the septum forms in conjunction with the partitioning of the truncus arteriosis. The spiral septum that forms from the truncus arteriosis division fuses with the muscular portion of the interventricular septum. The fusion of the spiral septum, interventricular septum and endocardial cushion completes the ventricle separation.
How is the outflow tract of the developing heart divided into the pulmonary trunk and the aorta?
The truncus arteriosis is divided into the pulmonary trunk and aorta by right and left trunconal ridges. These two flaps on either side of the tube grow together and spiral up the tube, fusing together at the midline. The spiral forms the aorticopulmonary/spiral septum.
In the end, the pulmonary trunk emerges from the right ventricle and the aorta from the left. The spiral septum grows down to meet the muscular part of the interventricular septum.
The complete interventricular septum is made from four parts. What are they?
The right and left trunconal ridges, the muscular part of the interventricular septum, and the inferior portion of the endocardial cushion. The trunconal ridges form the membranous part of the septum, since it is devoid of muscular tissue. This is a common place for congenital defects, since so many structures must come together to form this.
Describe the pathway of fetal circulation once the septa of the heart have been formed. (Both major and minor)
Major circulation: placenta-> umbilical vein->through liver via ductus venosus->inferior vena cava->right atrium->left atrium->left ventricle->aorta->systemic circulation (head and neck receive most oxygenated blood)->umbilical artery-> placenta
Minor circulation: Blood from the right atrium goes to the right ventricle and into the lungs (where it will then return to the left atrium) or into the aorta via the ductus arteriosis (connection between the left pulmonary artery and the aorta). Blood from the superior vena cava comes to the right atrium then goes to the right ventricle.
What are the five elements of fetal circulation that are nonfunctional in the adult? What are their functions in fetal circulation?
1. umbilical vein (placenta->liver)
2. ductus venosus (bypass liver, goes to inferior vena cava)
3. foramen ovale (right->left atrial shunt)
4. ductus arteriosus (connects left pulmonary artery to aorta, shunting most of blood from pulmonary trunk to aorta)
5. umbilical arteries (carry blood from the iliac arteries to the placenta)
What are the difference between fetal and maternal hemoglobin?
Fetal hemoglobin carries about 20-30% more oxygen and is 50% more concentrated than maternal hemoglobin. Oxygen saturation in fetal tissues is always sufficient.
Why do the head, neck, and upper limbs receive blood with higher oxygen content?
Because the first branches off the aortic arch go to the head, neck, and upper body and carry the most oxygenated blood there. This blood will drain to the superior vena cava. Also, the ductus arteriosis shunts blood from pulmonary circulation to the aorta, but further along than where the first branches of the aorta come off.
Describe the changes that occur to go from fetal to adult blood circulation.
The foramen ovale closes and the septum primum and septum secundum become fused together. This happens because the pressure gradient is higher in the left atrium than the right because there is no more placental blood flow and the capillary beds open when the lungs begin to function.
The ductus arteriosus deteriorates. This is because blood pressure decreases in the pulmonary arteries after birth and blood starts to flow in the opposite direction (into the pulmonary artery). Oxygen level increase and a drop in the prostaglandin levels cause the smooth muscle of the ductus arteriosus to contract and finally close.
The ductus venosus and umbilical vein have blood flow through them eliminated when the umbilical cord is clamped. Falling prostaglandin levels cause the ducts to contract and finally close.
What are the residual structures of the elements of fetal circulation that are nonfucntional?
Ductus venosus-> ligamentum venosum
Umbilical vein-> ligamentum teres
Foramen ovale-> fossa ovalis
Ductus arteriosus-> ligamentum arteriosum
Umbilical artery-> branch of the internal iliac artery
What are the three categories of congenital malformations? Name examples of each.
Obstructive lesions- aortic stenosis, pulmonary stenosis, coarctation of the aorta
Non-cyanotic malformations (left to right shunt)- ventricular septal defects, atrial septal defects, patent ductus arteriosus
Cyanotic malformations (right to left shunt)- transposition of the great vessels (aorta exits right ventricle, pulmonary trunk exits left), persistent truncus arteriosus (trunconal ridges fail to fuse), tetralogy of Fallot (ventricular septal defects, overriding aorta, pulmonary stenosis, right ventricular hypertrophy)
Describe the surface projections of the heart.
The superior margin of the heart runs from the left 2nd intercostal space to the right 3rd costal cartilage.
The right border of the heart runs from the right 3rd costal cartilage to the right 6th costal cartilage, right along the sternum.
The inferior margin of the heart runs from the right 6th costal cartilage to the left fifth intercostal space, 3.5 inches from the sternum.
The right border of the heart is formed entirely by the right atrium, while the left atrium forms the posterior border of the heart. The left ventricle forms the left border and the diaphragmatic surface of the heart and the right ventricle forms the anterior border of the heart.
The left border of the heart runs from the left 5th to 2nd intercostal space, 2-3 inches from the left of the sternum.
What is pericardiocentesis? How is it performed?
Pericardiocentesis is the removal of excess fluid from the pericardial sac. The pericardium is unable to distend, so any fluid puts increased pressure on the heart.
Palpate the xiphoid process and the left costal margin. Insert the needle between the two in a superior/posterior direction, angled toward the left shoulder. Push the needle though the chest wall, penetrating the central tendon of the diaphragm. Another placement of the needle can be between the 4th intercostal space. Use an ECG lead to determine how close you are to the heart since you DO NOT want to puncture the myocardium.
Where do the phrenic nerves arise and where do they run?
Cervical spinal nerves C3, C4, and C5. "345 keep the diaphragm alive). They enter the superior mediastinum between the subclavian artery and the brachiocephalic veins. The right phrenic nerve is on the right side of the right brachiocephalic vein, the superior vena cava and the right atrium, lying between the mediastinal pleura and the pericardium. The left phrenic nerve crosses the arch of the aorta, then runs along the pericardial surface of the left atrium and left ventricle. BOTH phrenic nerves run anterior to the hilus of the lungs.
Which nerve fibers are found in the phrenic nerve?
Sensory (running to the diaphragm, mediastinal pleura, pericardium), somatomotor, sympathetic???. Since the sensory nerve fibers run to the same place as the upper limbs, pain in the diaphragm can often be felt in the upper limbs (referred pain).
Describe the features of the cardiac skeleton. What is the function of the cardiac skeleton?
There are four interconnected rings of dense connective tissue called annuli fibrosi. They are located between the openings of the atria and ventricles (atrioventricular valves) and at the base of the pulmonary trunk and aorta (semilunar valves).
The dense CT has many collagen fibers, some adipocytes and elastic fibers but NO cardiac myocytes.
The cardiac skeleton is an attachment site for cardio myocytes and valves. It also electrically insulates the atria from the ventricles, so they can contract at different locations at different times.
Where is the atrioventricular bundle run? What is its function?
The atrioventricular bundle transverses the cardiac skeleton in the middle of the mitral valve, the tricuspid valve and the aortic valve. This bundle serves to carry the electical impulse from the atria to the ventricles, carrying it to the apex of the heart before spreading it to both ventricles. This allows for the contraction to begin at the apex of the heart, so the blood can be pushed out of the ventricles.
Name the valves of the heart and their location.
The tricuspid valve between the right atrium and the right ventricle. The bicuspid valve is between the left atrium and the left ventricle. The semilunar valves are between the ventricles and their respective great vessels (the right and the pulmonary trunk, the left and the aorta).
What is the makeup of the cusp of the cardiac valves?
It is composed of dense connective tissue that is continuous with the cardiac skeleton. The atrioventricular valves are attached to chordae tendineae and papillary muscles (within the ventricles)
ALL valve cusps, chordae tendinae, and papillary muscles are lined with endothelium because they directly contact blood.
Describe how papillary muscles in the heart work.
The papillary muscles contract when the ventricles contract and keep the valve cusps from inverting into the atria. They are attached to the chordae tendineae to prevent the valve cusps from inverting into the atria. They are ONLY associated with the atrioventricular valves, not the semilunar.
Describe the semilunar valves of the heart.
They are semilunar flaps of tissue that protrude into the lumen of the aorta and the pulmonary trunk. They function WITHOUT the help of the chordae tendinae and papillary muscles.
What is mitral valve stenosis?
A narrowing of the mitral valve seen in patients with rheumatic fever. The leaflets of the valve inflame initally, then scar- thickening and distorting the leaflets as well as the chordae tendinae. This disrupts the range of motion in the valve, leading to mitral valve insufficiency. The aortic and tricuspid valves may also have this damage, but the pulmonary valve has the least chance of being damaged.
Where are the sounds of the heart best heard?
Aortic valve- right 2nd intercostal space
Pulmonic valve- left 2nd intercostal space
Tricuspid valve- 5th costal cartilage
Mitral valve- apex of the heart (5th intercostal space 2 inches to left of the sternum)
What are the layers of the wall of the heart?
The outermost is the epicardium (same as the visceral pericardium), the middle layer is the myocardium, and the innermost layer is the endocardium.
Describe the endocardial layer of the heart.
The endocardium has an inner layer of endothelium and an outer layer of loose connective tissue. The endothelium is simple squamous epithelium connected by tight junctions. This endothelium is continuous with the lining of the veins and arteries that enter and leave the heart. The loose CT connect to the myocardium.
Describe the myocardial layer of the heart.
This is the thickest layer of the heart that consists of bundles of cardiac myocytes that attach to the cardiac skeleton. The atrial myocardium is much less thick than the ventricular myocardium. The thickest myocardium is in the left ventricle. The spiral orientation of the myocytes squeezes blood out of the heart effectively.
Describe the epicardial layer of the heart.
This layer is composed of mesothelium. A subadjacent layer of fat and loose CT connects the epicardium to the underlying myocardium. This layer produces serous fluid that fills the pericardial cavity and lubricates it to minimize friction with the parietal pericardium. Coronary arteries and cardiac veins travel through the pericardium CT to reach the myocardium.
What is the makeup of cardiac myocytes?
Individual, mononucleated cells that have centrally placed, euchromatic nuclei in the shape of a rectangle. (Larger myocytes can be binucleated because they have replicated their DNA but not divided) The ends are branches to contact 3-5 other myocytes. LOTS of capillaries run throughout the myocardium!
Describe the fine structure of a myocyte.
It is striated muscle with intercalated disks that run through the myocytes within the same fasicle. The sarcomeres have bands that are named the same as those in skeletal muscle. The intercalated discs occur at the Z line. An intermediate filament called desmin attaches the edges of adjacent Z bands. T-tubules form diads with a single sarcoplasmic reticulum cistern at the Z-line. T-tubules allow the sarcomere to contract in synchrony by carrying the action potential all myocytes. Cadiac myocytes use connective tissue as an attachment point (cardiac skeleton)
What are intercalated discs in cardiac myocytes? What makes them up?
Intercalated discs are where myocytes are attached to the fasicle. They are staggered. They contain gap junctions (for establishing electrical continuity with the fasicles), macula adherens (spot desomsomes that are associated with intermediate filaments), and fascia adherens (attach the terminal sarcomeres to the myocyte membrane).
Cardiac muscles use ____ ____ for contraction.
Extracellular calcium. During excitation, calcium channels open in the sarcolemma. This activates calcium-sensitive channels in the sarcoplasmic reticulum and initiate a contraction.
What are the different myocyte types?
Atrial myocytes- smaller
Ventricular myocytes- larger
Cells of the sinoatrial node, atrioventricular node, and Purkinje fibers
What is the function of atrial natriuretic factor/protein (ANF) and where does it come from?
Atrial myocytes release ANF into the bloodstream to reduce blood pressure.
Can cardiac myocytes regenerate?
Yes, to a point. There are adult stem cells that allow replacement of myocytes. But if the insult on the myocyte population is too large, myocytes are replaced with scar tissue that will not contract.
How does the conduction system of the heart work?
The signal for a contraction is initiated at the sinoatrial node, at the junction of the superior vena cava and the right atrium. This sends fibers out in three directions: the right atrium, the left atrium, and to the atrioventricular node that lies in the interatrial septum. The AV node provides a momentary hesitation between the contraction of the atria and the contraction of the ventricles. The AV bundle descends through the membranous portion of the interventricular septum and divides into two branches (crura). The left crus forms branches that reach the ventricular wall along trabeculae carnae. The right crus goes to the ventricular wall via the septomarginal band at the apex of the right ventricle. Both crura end as Purkinje fibers that stimulate the contraction of ventricular monocytes.
The entire conduction system can be modified by the autonomic nervous system.
SA node-> AV node
How does the motor innervation to the heart run?
The SA and AV nodes are heavily innervated by parasympathetic and sympathetic fibers that can change the rate of contraction.
Vagal efferent fibers synapse in ganglia of the cardiopulmonary plexus or in the walls of the atria. They decrease the heart rate and constrict the coronary arteries.
Sympathetic efferent fibers are postganglionic nerves from the cervical and upper thoracic ganglia of the sympathetic trunk. They increase the heart rate.
Cardiac myocytes don't have neuromuscular junctions, since they aren't individually extrinsicially innervated by the nervous system. Instead, axons lie in the endomysium among myocytes and the axons have periodic dialations containing neurotransmitter that serve many myocytes.
How does sensory information get relayed from the heart?
Afferent sensory information travels with the sympathetic and parasympathetic nerves to reach the CNS. Vagal afferent carry information on reflex actions, blood pressure, and oxygen/carbon dioxide content in the blood. Sympathetic afferents contain pain fibers that travel back to the CNS. Therefore, you get referred pain about the heart at the skin of the upper limbs because the afferent information from the heart converges on the same dorsal horn as the afferent information from the skin.
Parasympathetic-status info
Sympathetic- pain
Describe a contraction of cardiac muscle.
It is very similar to skeletal muscle. The sarcolemma becomes depolarized by an action potential and extracellular calcium enters the sarcoplasm. T-tubules carry the action potential to deepest sarcomeres. Calcium is released from the sarcoplasmic reticulum at proceeds to bind troponin, which removed tropomyosin from the myosin-binding sites on actin. The myosin/actin interaction occurs and the myocyte contracts.
In the absence of extracellular calcium, skeletal muscle myofibers will continue to contract, but cardiac myocytes will stop contractin immediately. True or false?
True- the action potential in caridac myocytes triggers extracellular calcium to enter the sarcoplasm. Calcium triggers the release of calcium that causes a contraction in cardiac muscle. Skeletal muscle needs sodium to cause the release of calcium from the sarcoplasmic reticulum.
Describe the arterial coronary circulation.
The are two major coronary arteries: the right and the left. They both branch from the aorta.
The left coronary artery arises from the left side of the aorta, passes between the pulmonary trunk and left auricle to reach the coronary sulcus. Then it splits into the anterior interventricular (supplies the right and left ventricles and anterior part of the interventricular septum) and circumflex (supplies the left atrium and left ventricle; runs along the posterior side of the heart) arteries.
The right coronary artery arises from the right side of the aorta and lies in the coronary sulcus. It divdes into the sinoatrial artery (supplies SA node), the right marginal artery (supplies right ventricle), and the posterior interventricular artery (supplies right and left ventricles and the posterior portion of the interventricular septum).
Any variations that occur in circulation are usually at the back of the heart.
Describe venous cardiac circulation.
A cardiac vein accompanies each of the coronary arteries. The great cardiac vein is the largest and accompanies the left coronary artery, anterior interventricular artery, and circumflex artery. The middle cardiac vein travels with the posterior interventricular artery. The small cardiac vein travels with the right marginal artery.
All major cardiac veins drain to the coronary sinus, which delivers blood to the right atrium. Anterior cardiac veins empty into the right atrium and the smallest cardiac veins empty directly into openings in the heart chambers.
What is a myocardial infarction?
A coronary artery that is obstructed rapidly causes myocytes to die quickly, causing a heart attack. Although there is collateral circulation in the heart, any stoppage that is too quick can cause this.
If it is left heart failure, you get dilation of the left ventricle, incomplete emptying of the ventricle during systole and hypertrophy in the surviving ventricular tissue. Left ventricular diastolic pressure increases.
If there is right heart failure, you get the same types of symptoms- systemic congestions, increased venous pressure, edema in the ankles.
What is the autonomic nervous system?
A system of nerves that are purely motor in function. They are not voluntary. The autonomic nervous system can be divided into parasympathetic and sympathetic. It innvervates smooth muscle, cardiac muscle, and glands.
The most important distinguishing feature is that two neurons are needed to transmit an impulse from the CNS to the target. (Skeletal muscle needs only one) The first cell body lies within the CNS (preganglionic or presynaptic neuron). The second lies in the autonomic ganglion, and this postganglionic/postsynaptic neuron sends an axon to the target tissue.
Where are preganglionic cell bodies located?
ALL preganglionic sympathetic nerve cell bodies are located in the lateral horn of the spinal cord, levels T1-L2.
What is the sympathetic trunk?
The sympathetic trunk or chain ganglia contain postganglionic sympathetic cell bodies. (These are the autonomic ganglion that the first neuron in the sympathetic system must synapse with before reaching its target.) There is one on each side of the vertebral column, from the cervical to the lowest sacral level. The presynaptic axons from T1-L2 the lateral horn must synapse somewhere within the chain ganglion (C1-S5). Some nerves synapse at the same level where the nerves exit the spinal cord, others travel up the chain to synapse at another level.
Describe communicating rami in the autonomic nervous system.
They are part of the sympathetic nervous system that bridge the ventral ramus to the sympathetic chain. Sympathetic nerves leave the lateral horn and join the ventral root leaving the spinal cord, travel with the ventral ramus a little, then branch off to their respective chain ganglion via a white (myelinated, preganglionic) communicating rami. After synapsing at a particular chain ganglion, they exit via a gray (unmyelinated, postganglionic) communicating ramus to join the ventral ramus again and travel to their target destination.
White communicating rami from the sympathetic nervous system connect the ventral rami of the spinal nerves and sympathetic chain ganglia ONLY from ____ to ____.
T1-L2. This is because all sympathetic nerves must first go through the chain ganglion and the only sources of preganglionic sympathetic nerves are T1-L2.
Where do sympathetic nerves originate?
What are gray communicating rami?
They contain postganglionic nerve fibers that come from the sympathetic chain to join with the ventral and dorsal rami to reach their peripheral targets.
What are the targets of the axons leaving the gray communicating rami?
Body wall and extremities
What are sympathetic splanchnic nerves?
Branches from the sympathetic splanchnic nerves to the viscera.
Targets in the heart, lungs and thorax contain postganglionic fibers(that synapse in the chain), while splanchnic nerves going to the abdominal and pelvic viscera contain preganglionic fibers that will synapse nearer to their targets in the collateral ganglia.
Sympathetic splanchnic nerves are named to the level of the splanchnic trunk from which they originate.
What are collateral (prevertebral) ganglia?
Sympathetic ganglia anterior to the abdominal aorta (and the vertebral column) at the sites where major arteries branch from the aorta to supply internal organs. Preganglionic fibers synapse here and then their postganglionic fibers innervate the abdominal organs and pelvic viscera.
What is an autonomic plexus? Give one example.
An autonomic plexus is a mixture of sympathetic, sensory, and parasympathetic fibers that may or may not have small ganglia within them.
The cardiopulmonary plexus is one such collection of nerves. It receives sympathetic fibers from the sympathetic trunk (postganglionic) and parasympathetic fibers (preganglionic) from the vagus nerve. The parasympathetic fibers will synapse with ganglia in the cardiopulmonary plexus or in the walls of the heart.
Describe vagus nerves and their function.
They are parasympathetic nerves that arise from the brainstem (hence they are cranial). They go to all of the viscera of the thorax and a portion of the viscera of the abdomen.
What is the esophageal plexus?
It a plexus of nerves formed from the convergence of the right and left vagal nerves on the esophagus. It contains primarily preganglionic parasympathetic fibers. The mixing ensures that target organs aren't solely innervated by the right or left vagal nerve.
Describe parasympathetic splanchnic nerves. How are they formed? What is their function?
They are formed by the sacral portion of the parasympathetic nervous system. They arise from spinal cord levels S2-4 and exit with these spinal nerves. They branch off in the pelvis to reach abdominal and pelvic targets, hence they are called pelvic splanchnic nerves.
What are parasympathetic ganglia and how do they differ from symapthetic ganglia?
They are part of the autonomic nervous system where preganglionic parasympathetic fibers must synapse before innervating their targets. They are located very close to the organs that they innvervate. They are widely scattered and usually very small.
What is the thoracolumbar system?
Another name for the sympathetic nervous system. This is because all preganglionic sympathetic fibers arise from the T1-L2 spinal nerves.
In the sympathetic nervous system, a neuron can terminate in either a _____ _____ or the _____ _____.
Chain ganglion (of the sympathetic trunk) or the collateral ganglion
Where do the sympathetic neurons that innervate the trunk and extremities synapse? What structures do they innervate?
The sympathetic chain ganglia. They join with the spinal nerve at that level using a gray communicating ramus and distribute on the dorsal and ventral rami of that spinal nerve.
These sympathetic fibers innervate sweat glands, smooth muscle (think erector pili muscles), and blood vessels.
How are targets in the head innervated by sympathetic nerves?
There are no sympathetic ganglia in the head, so preganglionic sympathetic fibers with targets in the head must synapse in the cervical region. (Superior cervical ganglion) This is usually at a fusion of the upper four cervical ganglia and they travel with the internal carotid artery.
How do sympathetic neurons that innervate the thoracic viscera work?
Thoracic viscera receive preganglionic sympathetic innervation from the upper thoracic spinal cord levels. They enter the sympathetic chain and ascend to ganglia in the cervical region. They leave the synaptic chain as superior, middle, and inferior cardiac nerves, then the postganglionic fibers go to the cardiopulmonary plexus. These fibers go to the coronary arteries, the SA node of the heart, and the bronchi and arteries of the lung.
How are the abdominal and pelvic viscera innervated by sympathetic nerves?
Preganglionic sympathetic fibers form splanchnic nerves that travel to collateral ganglia where they synapse. These thoracic splanchnic nerves form greater (T5-9), lesser (T9-10) and least (T12) thoracic splanchnic nerves. They pass through the diaphragm and enter the abdominal cavity. They synapse in the collateral ganglia then travel to their target via their respective arteries.
Some collateral ganglia don't receive innervation from thoracic splanchnic nerves. They receive their preganglionic splanchnic nerves from the sympathetic trunk of the lumbar and sacral regions. (Hence they are called lumbar or sacral splanchnic nerves)
How does the parasympathetic nervous system work?
The preganglionic cell bodies are located in the brainstem for cranial nerves (III, VII, IX, X) and spinal cord for sacral nerves (2, 3, 4). The preganglionic fibers leave the CNS as a cranial nerve or a ventral root of a sacral nerve.
Their targets are structures in the head or viscera of the trunk. The body wall and extremities don't receive parasympathetic innervation.
Parasympathetic nerves synapse near their target organs.
How are thoracic viscera parasympathetically innervated?
The vagus nerve. The preganglionic right and left vagus nerves descend from the neck and give off branches to the cardiopulmonary pleuxus, which innervate the heart and lungs. The vagus nerves descend further to the esophagus where they break up to form the esophageal plexus, which innervate the esophagus. They then combine again to form anterior and posterior vagal trunks that go to the abdomen.
Describe how the abdominal viscera are parasympathetically innervated.
The vagal trunks innervate the intestinal tract and colons. The sacral portions of the parasympathetic system innervate part of the colon, and pelvic viscera.
What are pelvic splanchnic nerves?
Preganglionic parasympathetic fibers that branch from the S2-S4 spinal nerves to reach visceral targets.
What are the sympathetic and parasympathetic nervous systems for? How do they differ?
Sympathetic nervous system provides the fight-or-flight response. Parasympathetic nervous system is a homeostatic system. The sympathetic nerves innervate all structures of the body, while the parasympathetic only innervate the viscera. In systems that they both innervate, they work together rather than compete. Parasympathetic neurons usually only synapse with one or two postsynaptic neurons, while sympathetic neurons synapse with many, amplifying their action.
Visceral afferents carry either ____ or ____ sensation.
Pain, reflex
Where are nerve cell bodies of sensory neurons?
Dorsal root ganglia of spinal nerves or in sensory ganglia of cranial nerves
How do pain sensory neurons travel?
With sympathetics. They pass through the sympathetic ganglia but do not synapse with them. Both sensory and sympathetics that go to the same organ generally are associated with the same spinal cord level.
What kinds of afferent nerve fibers travel with the vagus nerve?
Visceral sensory afferent fibers from the thoracic and abdominal organs. (Info about reflexes and sensations like hunger and nausea) Cell bodies for these sensory neurons are in the sensory ganglia of the vagus.
Where is the thoracic duct located?
It originates in the upper abdomen at the cisterna chyli and receives all lymph from below the diaphragm. It enters the diaphragm along the aorta, originally on the right side of the vertebral column then shifts to the left side of the vertebral column in the upper thorax. It exits the thorax and passes behind the left subclavian artery and ends by joining the jugular and left subclavian veins.
What is chylothorax?
Accumulation of lymph in the pleura cavity after performation of the thoracic duct.
How does the azygos system work? Where is it located?
The azygos system is a set of veins that flank the vertebral column. The right azygos is the major vein. It connects the inferior and superior venae cavae and receives blood from the abdominal and thoracic walls through the posterior intercostal veins.
The hemiazygos (lower) and accesory hemiazygos (upper) veins are on the left side of the vertebral column. They have connections to the azygos vein that run along the vertebral column (most posterior).
The azygos system provides collateral circulation for venous drainage.