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248 Cards in this Set

  • Front
  • Back
Layers of epidermis from inside out
Stratum Basale
Stratum Spinosum
Stratum Granulosum
[Stratum lucidum]
Stratum Corneum
Stratum Basale characteristics
Single layer of basophilic cells
Rests on Basement membrane
Bound to BM by desmosomes
Contains stem cells
Has intense mitotic activity
responsible in part for renewal of epidermal cells (along with first part of spinosum)
Contain intermediate keratin filaments
Stratum spinosum characteristics
cubpodal or slightly flattened cells
central nucleus
has processes filled with keratin filament bundles
Cells bound together by filament filled cytoplasmic spines and desmosomes
Part of the spinosum is mitotic
Stratum granulosum charactersitics
3-5 layers of flattened polygonal cells
Cytoplasm has coarse basophilic granules (keratohyalin)
Has lamellar granules (seen in EM) that discharge lipid layers into granulosum
What is the basophilic granule content of stratum granulsom cells made of?
What are the 2 types of granules in stratum granulosum?
keratohyalin granules
lamellar granules
What do you call the keratin bundles visible in stratum spinosum cells?
Stratum lucidum characteristics
More apparent in thick skin
translucent, thin layer
extremely flattened eosinophilic cells
mainly dense packed keratin in matrix
Stratum corneum characteristics
15-20 layers of flattened nonnucleated keratinized cells
cytoplasm filled with keratin
What is the major cell type of the epidermis?
Where are melanocytes derived from?
Neural crest
Appearance of melanocytes in LM
clear/pale staining
small, dark nucleus
wedged in between basal layer keratinocytes
What to melanocytes do?
Inject keratinocytes with melanosomes
Appearance of langerhans cells
Apear as pale staining in suprabasal epidermal layers
Appearance of langerhans cells II
pale staining in suprabasal layers
by EM, heve indented nucleus and tennis racket structures in cytoplasm
what are birbek's granules?
tennis racket-like (as seen by EM) inclusions in cytoplasm of langerhans cells
What do langerhans cells do?
macrophages of the epidermis
associated with immune response/antigen presentation to T cells
stimulate keratinocytes to make an epidermal thymocyte-activating factor
What do merkel's cells look like?
Pale staining
located in basal layer
primarily in thick epidermis
have small dense granules in cytoplasm
frequently close to nerve endings
structure of the dermal-epidermal junction
1) basal cell PM
2) basal lamina
lamina lucida
lamina densa
3) underlying fibrous zone (with anchoring fibers, type III collagen, etc)
What do you call the projections of dermis that interdigitate with projections of the epidermis?
Dermap papillae
What is underneath the basal lamina underneath the epidermis?
lamina reticularis (net of reticular fibers)
Contents of dermis
Rich blood/lymph supply
some arteriovenous shunts for T reg
hair folicles
sweat and sebaceous glands
2 layers of dermis
papillary dermis (thin, loosely packed collagen/elastin fibers)

reticular dermis (coarse elastin fibers and thick collagen bundles)

[underneath this is hypodermis (subcutaneous layer))--usually just fat
Describe the vasculature of the skin
there is a vascular plexus on each side of the hypodermis
Another vascular plexus supplies capillaries in dermal papillae

Each papilla has one ascending arterial branch and one decending venous branch

These arteriovenous anastomoses in the papillae can shut off and shunt blood to underlying capillary beds

Sympathetic stimulation turns off the shunt, allowing blood to bypass the capillary beds, thus conserving heat.

This was all kind of unclear.
Where is hair follicle found?
deep in hypodermis
How is hair follicle formed?
invagination of epidermis
what is the pilosebaceous unit?
Hair follicle
attached smooth muscle
sebaceous gland
describe the structure of exposed hair
Similar to stratum corneum tissue:
anucleate cells filled with keratin filaments in a matrix
Describe hair differentiation
the growth of hair is discontinous.
Undergoes active growth period followed by decline and then inactivity
Fine structure of har follicle
Terminal dilation: hair bulb

dermal papilla: little thing that contains capillary network for follicle, at end of bulb

medulla: moderately keratinized
cortex: heavily keratinized
cuticle: farther toward periphery of the hair
Internal root sheath: surrounds hair, but dissapears above level of sebaceous glands
external root sheath: continuous with the epidermis
glassy membrane: separates follicye from the dermis; noncellular hyaline layer

arector pili muscles: connects glassy membrane to the dermis; smooth muscle
What is the malphigian layer?
Where all mitoses in the epidermis are confined to. Namely, the stratum basale and the first bit of the stratum spinosum.
Where are sebaceuos glands found?
embedded in the dermis over most of the body
structure and fxn of sebaceous glands:
several acini open into short duct
duct usually opens into upper portion of a hair follicle

Epithelium of acini dproliferate and differentiate, filling the acini with rounded cell with a lot of fat in cytoplasm

Nucleii shrink, cells fill with fat and burst

Product of this is sebum, which gradually moves to skin surface
what is a holocrine gland? Give an example.
Product of secretion is released with remnants of dead cells.

Ex: sebaceous gland, which releases lipids, waxes, cholesterol, etc
Where does the sebaceous gland arise from?
from differentiating epithelium in proliferative area adjacent to basement membrane.
Are sebaceous glands innervated?
no, but it seems they are responsive to the sex hormones.
what are the 2 types of sweat glands?
General structure and location of sweat glands
Simple, coiled tubular glands

contain myoepithelial cells for discharging contents

Secretory portion is a convoluted tube in hypodermis

Conducting portion is a spiralling duct through dermis and epidermis
Details of merocrine/eccrine sweat glands
simplle, coiled tubular

secretory part embedded in dermis; surrounded by myoepithelial cells which contract to help discharge secretion

2 kinds of cells in secretory portion : dark and clear

Dark: pyramidal cells. Line most of the lumen. Have secretory granules in apical cytoplasm.

Clear: no secretory ranules. Basal plasmalemma has numerous invaginations.
Sweat contents
Water, NaCL, urea, ammonia, and uric acid
Apocrine sweat gland detainls
Present in axillary, areolar, and anal regions

Much larger in diameter (3-5 mm)

Embedded in dermis and hypodermis

Open into hair follicles

Produce viscous secretion that is initially odorless but may aquire odor due to bacterial decomposition.

Innervated by adrenergic nerve endings (eccrine get cholinergic fibers)
Meisnerrs Corpuscles details:
Small, encapsulated receptors sensitive to light touch

Found in papillary layer of dermis

Comprised of flattened, transversely arranged Schwann cell-type cells and helically arranged unmyelinated nerve fiber
Pacinian corpuscle details
Larger than Meisner's

Found in the dermis and hypodermis

concentric layers of flattened Schwann cells with collagen layers. Oniony.

Sensitive to pressure, course touch.
Thickness of the 2 skin layers:
Epidermis: 75-150 um (thin), 400-600 (thk)
Dermis: varies: up to 4 mm (on back)
vascularity of the 2 skin layers:
epidermis: none?
dermis: plexus between papillary and rticular layers, and between dermis and subcutaneous dissue.
Embyronic layer of origin of the 2 skin layers:
Epidermis: ectoderm
Dermis: paraxial mesoderm
Opaque, white posterior five sixthes of tehe external layer of the eye is the
What is the external layer of the eye?
Tunica fibrosa
What is the sclera made of?
Dense CT
What is the anterior one sixth of the tunica fibrosa?
What is the structure of the cornea?
5 layers:

Bowman's membrane
Descemet's membrane
What is the structure of the corneal epithelium?
5-6 layers of stratified squamous.

Mitotic figures in the basal part of the epithelium

One of the richest sensory nerve supplies of any eye tissue
What is the structure of bowmans' membrane?
Homogenous layer

Collagen fibers crossing ot random

No cells

contributes to stability of cornea
What is the structure of the stroma?
Many layers of paralell collagen bundles, crossing at apx. right angles

Between the layers, extensions of fibroblasts are flattened like butterfly wings

cells and fibers immersed in glycoprteins and chondroitin

Avascular, but may be some lymphoid cells
Descemet's membrane structure:
Thick homogenous structure

Fine collagenous filaments in 3d network
Corneal endothelium structure
simple squamous epithelium

Helps with ion transport ot keep the stroma relatively dehydrated
What is the limbus?
The corneoscleral junction.

Highly vascularized, compared to the avascular cornea

Contain's Schlemm's canal, which drains fluid from the anterior chamber to the venous system.
Name the 3 parts of the middle layer of the eye
Ciliary body
What is the choroid?
A highly vascularized coat

With loose CT high in fibrobalasts, macrophages, lymphocytes, collagen, elastic, melanocytes.

Has inner latyer called choriocapillary layer; separated from retina by Bruch's membrane (hyaline)
What is the choriocapillary layer?
Inner layer of the choroid that is richer in small vessels

Provides nutrients to retina
What is Bruch's membrane?
A thin hyaline membrane separating choriocapillary layer from the retina
What is the optic papilla?
Region where the optic nerve enters the eyeball
Structure of the ciliary body?
Anterior expansion of the choroid at the level of the lens

Continuous thickened ring lying in the inner surface of the anterior portion of the sclera

Forms a triangle in transverse section (facing vitreous body, sclera, and lens/posterior chamber)

Mainly loose CT surrounding ciliary muscle
Ciliary muscle structure
2 bundles of smooth muscle fibers
Insert on sclera anteriorly, different ciliary body regioons posteriorly.

Bundle placement allows for one bundle to stretch choroid and other to relax lens tension when contracted
Function of ciliary body
Produces aqueous humor

Stromal portion helps to focus lins via suspensory ligaments of the lens
Epithelium of iris is continuous with...
epithelium that lines the iris.
Structure of iris
Extension of the chorioid that partially covers lens

Anterior surface is irregular, formed by layer of pigment cells and fibroblasts

Posterior surface is covered by 2 layers of epithelium that also cover ciliary body/process

Surface layer of this epithelium is heavily pigmented
Dilator pupillae muscle
Overlapping myofilaments in the other epithelial cells of the posterior surface of the iris
What can be found in the strom a oof the iris?
Sphincter pupillae muscle
Smooth muscle bundoles dispose din circles concentric with pupillary margin

Parasympatheic innervation

constricts pupillary opening
3 components of the lens
Lens capsule
Subcapsular epithelium
Lens fibers
Lens capsule structure
Thick, carb rich capsule
Thick Basement membrane

Mainly Collagen IV and glcoprotein outside of surfasce epithelial cells
Subcapsular epithelium structure
Single layerof cuboidal epithelial cells on the ANTERIOR suruface of the lens,

The cells interdigitate with the lens fibers

Proliferation/elongation of these cells at the lens equator causese formation of more lens/lens fibers
Lens fiber structure
Elongated, thin flat structures

Highly differentiated cells derived from subcapsular epithelium

Eventually lose nuclei and other organelles and become elongated and filled with <b>crystallins</b>
What is the zonule?
Radially oriented fibers that connect lens capsule and ciliary body

Sililar to elastic fibrils

When ciliary muscles contract, there is forward displacement of choroid and ciliary body, reieving tensoun on zonule and allowing lens to become thicker
Content of vitreous body
99% waer
hyaluronic acid molecules
few cells
2 portions of the retina:
Posterior portion (photosensitive)
anterior portion (not photosensitive, forms interior/psterior lining of ciliary body and iris)
Describe pigment epithelium of retina
columnar cells with a basal nucleus
Basal regions adhere firmly to Bruch's membrane

Lateral cell membranes have lots of zonulae occludens and adherens at their apexes; also gap junctions and desmosomes

Apices have microvillia as well as sheaths that envelpo tps of photoreceptors
Layers of the optical part of retina
Outer layer: rods and cones
intermediate layer: bipolar neurons
internal layer: ganglion cells
What is between layer of rods and cones and teh bipolar cells? What happens there?
External plexiform layer

Synapses between rods/cones and bipolar cels occur
Where is tehe internal plexiform layer and what happens there?
Synapses between bipolar and ganglion cells occur there

It is between the ganglioin cell layter and the layer of bipolar cells
What is the origin of the outer segments of rods and cones?
They are modified cilia
What is the external limitin membrane
A series of junctional complexes between the photoreceptors and glial cells of the retina (Muller cells)

Both rod and cone cells pass through this

Nuclei of cones are near the ELM, whereas nucleus of rods lie near center of inner segment
Rod cell details
Thin, elongated cells

2 portions:
1) external photosensitive rod shaped portion, made mainly of flattened intermembranous disks (not continuous with PM) that contain rhodopsin

Low light sensitive, color insensitive
Cone cell detains
Elongated neurons

Similar to rods (outer/inner segments, basal body w/cilium, lots of mitochondria and ribosomes)

contain one of three kinds of iodopsin (for 3 colors of light)
Bipolar cell layer
1) diffuse bipolar cells (synapse with >1 photoreceptors), and
2) monosynaptic bipolar cells
Horizontal cells
establish contact between photoreceptors
Amacrine cells
establish contact between ganglion cells
Muller cells
extensively ramified

Processes bind neural cells of retina and extend from internal to external limiting membranes (where they bind to photoreceptors)

Analogous to neuroglia
What type of collagen is found in vitreous body?
type 2
Do retinal pigment epithelial cells form jucntions when they interdigitate with outer segmennts of rods and cones?
What is the point of highest visual acuity? What does it contain?

Contains only cones
What forms the external limiting membrane?
Muller cells attaching to photoreceptor cells via zonula adherens
What forms the internal limiting membrane?
Bases of muller cells and their basal lamina
What is in the external plexiform layer?
synapses of bipolar neurons and photoreceprors

horizontal cells
What is in the inner nuclear layer?
cell bodies of bipolar neurons
Muller cells
horizontal cells
amacrine cells
what is in inner plexiform layer?
processes and synaptic regions of bipolar neurons, ganglion cells, and amacrine cells
what is in ganglion cell layer?
ganglia cells
unmyelinated axons
blood vessels
Signal transduction in the retina: overview
1) rhodopsin exposed to light
2) this causes the 11-cis-retinal in rhodopsin to convert to all-trans-retinal
3) this causes conformational change in rhodopsin
4) this causes rhodopsin to activate G protein TRANSDUCIN
5) Transducin activates a cGMP phosphodiesterase
6) cGMP levels in outer segment fall
7) cGMP-sensitive ca/na channels in PM now close
8) PM befcomes hyperpolarized
9) glutamate (a neurotransmitter) now no longer is released
10) Bipolar cells detect lack of gluatmate and send signal
11) this leads to stimultaion of ganglion cells, which transmit signal to optic nerve and then to the brain
This is a <b>test</b>
What is a cause of glaucoma
Blockage in the canal of Schlemm-->poor drainage of aqueous humor-->increase intraocular pressure-->pressure on optic nerve
describe macular degeneration
Age related loss of central vision

Can be due to increased vascularizatoin of retina, leading to blood leakage and scar formation
Describe retinitis pigmentosa
Inherited condition

Causess degeneration of rods, then cones

Initially causes night vision and tunnel vision (due to rod degeneration, which give low light vision and are acentrally concentrated)
What is presbyopia?
Age related decrease in the elasticity of the lens, resulting in difficulty focusigngg on close objects (acommodation)
What is astigmatism:
abnormal curvature of the cornea, leading to more than one focal point
Four principal layers of GI tract
components of GI mucosa
1) epithelial lining
2) lamina propria (loose CT+vessels+some smoothe muscle)
3) muscularis mucosae (usually inner circular layer and outer liongitudinal layer...separates mucosa from submucosa)
GI submucosa componenets
Dense CT with blood and lymph vessels

Submucosay (meissner's) nerve plexus
GI muscularis components
smooth muscle cells that are spirally oriented and divided into 2 sublayers according to the direction the muscle cells follow

Internal sublayer: generally circular
External sublayer: generally longitudinal

Myenteric (auerbach's) plexus lies between the two sublayers
GI seros structure
Thin layer of loose CT
Simple squamous covering epithelium
In the abdominal cavity, serosa is continous with the mesenteries that support the intestines, and with the peritoneum
Where in GI tract layers are lymphoid nodules abundant?
Lamina propra (in mucosa) and submucosal layer
What is most of the conducting portion of the respiratory systme lined with?
respiratory epithelium
Describe respiratory epitelium
Ciliated, pseuudostratified columnar epithelium

lots of goblet cells

Typically 5 cell types:
1) ciliated columnar
2) mucous goblet
3) brush cells (microvili)
4) basal (short) cells: do not extend to lumen. Likely regenerative stem cells.
5) small granule cells: like basal, but with granules
What are the thick short hairs that filter large particles from inspired air?
what covers the three conchae?
Bottom two: respiratory epithelium
Superior: a specialized OLFACTORY epithelium
What are swell bodies?
Large venous plexuses in the lamina propria of the conchae

Every 20-30 min, swell bodies on one side become engorged, distending conchal mucosa and decreasing air flow. Gives that side's epithelium a chance to recover from dessication.
Structure of the olfactory epithelium
Pseudostrativied columnar epithelium

3 types of cells:
1) supporting cells: broad apex, narrow base, micvilli in fluid
2) basal cells: fomr single layer at epithelial base
3) olfactory cells: bipolar neurons

In lamina propria: glands of Bowman that secretes fluid to flood olfactory cilia
What are vocal ligaments made of?
large bundles of parallel elastic fibers
Structure of trachea
Lined with respiratory muchosa

In lamina propria are 16-20 C shaped rings of hyaline cartilage, with opening posteriorly

Fibroelastic ligament + smooth muscle joins open ends of C
what is the pulmonary root?
structure at hilum where artieries enter and veins + lymphatics leave. Surrounded by dense CT.
How many times does each primary bronchus divide?
Histological differences between bronchi and trachea
bronchial cartilage: at first, cartilage rings completely encircle bronchus. Then they become more irregular. Eventually rings are replaced by isolated plates/islands of hyaline cartilage.

Bneath epithelium is a smooth muscle layers of crisscrossing bundles of spirally arrange SM. Becomes mor ebrominent near respiratory zone.
Changes in bronchiolar epithelium
Starts out as ciliated pseudostratified columnar

Becomes ciliated simple (and lower) columnar or even cuboidal epithelium
Histo differences between bronchi and bronchioles
Bronchioles (unlike bronchi) have no cartilage and no glands in mucosa. They have only scattered goblet cells, and only initially.

Terminal bronchiolar epithelium also have CLARA CELLS, which have no cilia and have secretory granules in apex.

Bronchioles also have neuroepithelial bodies (80-100 cells with sec granules that receive cholinergic nerve endings)
Gross organization of ovary
1) simple squamous/cuboidal epithelium (GERMINAL EPITHELIUM)
2) tunica albuginea
3) cortical region (where follicles are)
4) medullary region (rich vascular bed)
Oocyte development
1) primordial germ cells migrate to gonads
2) divide -->oogonia (600K)
3) oogonia enter prophase of M1
Oogenesis 2
1) primordial germ cell migrate to gonad primordia
2) divide --> oogonia
3) enter prophase of M1 --> primary oocytes
4) --> become surrounded by follicular cells
5) many primary oocytes lost thru atresia
ovarian follicle structure
Oocyte surrounded by one or more layers of follicular cells (granulosa cells)

Oocytre has large nucleus and nucleolus

Basal lamina underlieds follicular ecslls and marks boundary between follicle and stroma
Describe the epithelium of the Trachea
pseudostratified ciliated columnar

contains goblet cells
What is Kategener's syndrome
Chronic respiratory infections due to immotile cilia in tracheal epithelium
What do ligaments in the trachea do?
prevent overdistention of the trachea
Describe the general histology of the brochi
similar to trachea (cartilage, glands, goblet cells, pseudostratified ciliated epi)

But more smooth muscle (spiral bundles)

Cartilage rings gradually replaced by irregular cartilage plates
What are bronchioles
Intralobular airways with diameters of 5 mm or less
Structure of bronchioles
1) no cartilage, No glands in mucosa
2) scattered goblets initially
3) ciliated pseudostratified columnar at first
4) becomes ciliates simple columnar or cuboidal
5) terminal bronhcioles have Clara cells
6) have specialized neuroepithelial bodies
What are Clara cells
In epithelium of terminal bronchioles

Devoid of cilia
Sec granules in apex
Secrete proteins to protect the bronchiolar lining gainst oxidative pollutants and inflammation
What are neuoepithelial bodies?
Specialized regions in bronchioles

80-100 cells
contain sec granules
Receive cholinergic nerve endings
function poorly understood; probably has to do with gas composition chemoreceptors
Bronchiolar lamina propria
Composed mainly of smooth muscle and elastic fibers.

Under control of vagus and the SNS
Effects of neural stimulation of bronchiolar SM
1) Vagal: decreases diameter
2) SNS: increases diameter
What is a respiratory bronchiole
Terminal bronchiole divides into 2 or more respiratory bnronchioles

Serves as regions of tranision between conducting and respiratory portions of the respiratory system
Structure of respiratory bronchioles
1) mucosa just like terminal bronchioles, except there are interruptions of walls with saclike alveoli
2) ciliated cuboidal epithelial cells and Clara cells
3) EXCEPT at rim of alvolar openings where it becomes coninuous with the Type I alveolar cells
4) cilia absent in more distal bronchioles
5) smooth muscle and elastic CT beneath epithelium
Alveolar ducts
1) when respiratory bronchiole wall becomes entirely openings to alveoli
2) lined with extremely attenuated squamous alveolar cells
3) network of smooth muscle surrounds rim of the alveolus
4) open into ATRIA that communicate with the alvveolar sacs.
1) saclike evaginations of rep broncioles, alveolar ducts, and alveolar sacs
2) small pockets open on one side
3) separated by interalveolar septa
Structure of interalvolar septum
1) 2 thin squamous epithelial layers
2) layer of capillaries, elastic/reticular fibers, and CT matrix in between (this is the INTERSTITIUM--where the richest cap bed in the body is found)
Name the 3 components of the blood air barrier
1) surface lining and cytoplasmof alveolar cells
2) fused basal laminae of teh closely apposed alveolar and endothelial cells
3) cytoplasm of endothelial cells
What does carbonic anhydrase do?
Liberates CO2 from H2CO3 that is in the RBC
(enzyme is in the RBC)
Describe capillary endothelial cells
Vey thin
Look like type I alveolars
CONTINUOUS endothelium
Type I alveolar cells
"Squamous alveolar cells"

97% of the surface
Very thin
Numerous pinocytotic vescicles that help with turnover of surfactant
Joined by desmosomes and occluding junctions to keep fluid out of airspace
Type II alveolar cells
1) interspersed among type 1's
2) occluding and desmosome junctions with type 1s
3) ROUNDED cells
4) grops of 2 or 3 along alvolar surface at junctions between type I cells
5) some stem cell function
6) contain lamellar bodies
What is the characteristic histology of type 2 cells?
Vescicular or foamy cytoplasm
What causes the foamy vescicular cytoplasm of type 2 cells?
Lamellar bodies

Contain concentric/parallel lamellae limited by a unit membrane

Contain: pospholipids, GAGs, proteins

Give rise to: pulmonary surfactant, that lowers alveolar surface tension
Describe the surfactant layer contents and function
Contents: aqueous proteinaceous hypophase covered with a monomolecular PL film

Fxn: reduces surface tension, meining less inspiratory force needed to inflate the alveoli, keeps alveoli from collapsing on expiration

Constantly being recycled via pinocytic activity

Also removed via ciliary activity: passing up thru the airways, combining with bronchial mucus to form bronchoalveolar fluid
What are dust cells
Lung macrophages

Where : in interor of interalvolar septom and surface of alveolus

Function: dust is pinocytosed into interstitium, phages scavenge outer surface of epitelium within the surfactant layer, eventually coughed up and swallowed
What are alveolar pores?
Pores in the interalveolar septom that connect alvoli, equalizing pressure in the alveoli and promoting collateral circulation, if necessary
Describe pulmonary blood flow
1) pulmonary arteries come in along with branches of the bronchial tree.
2) from cab bed in interalveolar septua
3) venules originate from this bed, but are a little removed from the airways
4) they enter the interLOBULAR septa until they leave the lobule
5) then they follow the tree back toward teh hilum.

1) folow the bronchial tree up to respiratory bronchilole level
2) then they anastomose with small branches of PULMONARY ARTERY
Lymphatic flow in lung
1) Follow the bronchi and pulmonary vessels
2) also found in interlobular septum with veins
3) drain into hilar lymph nodes
4) NOT FOUND in termianl portions of bronchial tree (beyond alveolar ducts)

Vessels in the visceral pleura. Also drain toward hulum
What is the pleura
Serous membrane covering the lung

2 layers:
Parietal and visceral; continuous tat hilum

Mesothelial cells resting on a fine CT layer.
What does gas have to cross from airway to blood?
1) surfactant layer
2) alveolar cell PM/cytoplasm
3) fused BM with endothelial cell
4) cap endothelial cell
5) lumen of Cap
What distinguishes trachea and bronchus
Short answer: the organization of cartilage and SM

Bronchial cartilage: more irregular in shape. At first, it forms rings that can encircle lumen (compared to C-shaped rings). Gradually, rings are replaced with isolated plates

SM: Bronchus has crisscrossing bundles of SM in spirals, becming more prominent distally
What lines the oral cavity
Stratified squamous epithelium (may be keratinized, may not be)
What covers the soft palate, llips, cheeks, and floor of mouth?
Nonkeratinized squamous epithelium
General structure of digestive mucosa
1) epithelial lining
2) loose CT lamina propria
3) Muscularis mucosa--a SM layer (inner circular, outer longitudinal)
General structure of GI tract, inside out
1) mucosa
2) submucosa
3) Muscularis externa
4) Serosa
5) adventitia (upper and lower ends)
Where are esophageal glands located?
submucosal layer
What kind of glands are in the lamina propria of the region near the stomach? What do they do?
esophageal cardiac glands

Secrete mucus
Describe muscularity of esophagus
Distal: only smooth muscle
Mid: mixture of striated and smooth
Proximal: only striated
What enzyme promotes the initial digestion of proteins?
4 regions of the stomach
structure of stomach mucosa
1) surface epithelium
2) epithelial invaginations forming gastric pits
3) Branched, tubular glands empty into gastric pits
4) lamina propria=loose CT + SM and lymphoid cells
5) muscularis mucosae eparates mucosa and submucosa
what epithelium covers surface and lining of gastic pits? (What does it do?)
simple columnar (secrete alkaline mucus that protects stomach from acid)
Describe cardia mucosa
Contains simple or branched tubular cardiac glands. Terminatl portions are frequently coiled with large lumens.

A few parietal cells that make HCl
Stem cells: info
1) Where: in neck region of glands
2) Shape: low columnar with oval nuclei

3) high mitotic rate
4) differentiate into pit and surface mucous cells, mucous neck cells, aparietal, chief, and enteroendocrine cells.
Mucous neck cells
1) Found in clusters or singleets between parietal cells in neck region
2) secrete mucous that is different from epithelial mucous cells
3)irregular shape
4) secretory granules near the apical surface
Parietal cells
AKA oxyntic cells

1) mainly in upper half of gastric glands
2) scarce at base
3) rounded or pyramidal
4) inensely eosinophiilic
5) EM features: many mitos, intracellular canaliculus
6) Secretes HCl
What do parietal cells secrete
Why do parietal cells have so many mitochondria?
To pump out KCL, to pump in H+
Name a mechanism that stimulates parietal cell secretion
1) cholinergic nerves/sympathetic
2) histamine and gastrin
Chief cell facts
1) predominate in lower region of tubulalr glands
2) Basophilic (due to lots of RER)
3) pepsinogen granules
What is pepsinogen?
IOnactive form of pepsin that is secreted by chief cells.

Pepsin is a highly active proteolytic enzyme
Where are enteroendocrinne cells foound?
near bases of gastric glands.
Compare cardiac glands ad pyloric glands
Pylori glands have longer pits and shorter coild secretory portions

Both secrete mucus and lysozme
What are G cells
Intercalated among mucous cells of pyloric glands.

Relese gastrin, whcih stimulates secretion of acid by parietal cells; has trophic effect on gastic mucosa.

Releas Inhibited by somoatostatin (Releasaed by G cells)
Stomach muscluaris
Smooth muscle fibers oriented in 3 directions:

External: longitudinal
Middle: circular
Internal:P oblique
What are the permanent folds in the lining of the small intestine?
Plicae circulares
In what segment are the plicae circulares most developed?
What are intestinal glands?
AKA "crypts"

1) Location: between intestinal vili
2) simple tubular glands
3) epithelium is continuous with epithelium of villi
4) contain: stem ccells, absorptive cells, goblet cells, paneth's cells, and enteroendcrine cells
What are absorptive cells (intestine)
1) tall columnar with nucleus in basal half
2) striated bruch border at apex, made of dense microvillus
3) FXN: absorb nutrient molecules, secrete peptidases and dissacharideases
What are intestinal goblet cells?
1) Where: interspersed between absorptive cells
2) less abundant in duodenum; increase toward ileum
3) Produce ACID GLYCOPRITEINS that help form mucus
What are Paneth's cells?
1) found in basal portion of intestinal glands
2) eosinophilic secretory granules in apical portions
3) granules contain lysozyme (antibacterial)
What are M cells?
1) Micrfold cells.
2) Specialized epithelial cells overlying lymphoid follicles of peyer's patches
3) numerous basal membrane invaginations that form pits containing lymphocytes and macrophaes
4) work to endocytose antigen and transport them to underlying phages and lymph cells
5) discontinuous basal lamina
What is the diffuse neuroendocrine system?
Widely distributed cells

Release secretory granules by exocytosis

May be "open type" or "closed type" depending on if they secrete into the lumen
Describe the small intestine lamina propria
1) loose CT with blood and lymph vessels, nerves, SM cells
2) penetrates core of intestinal villi
What are Brunner's glands
Duodenal glands

Alkaline ucous secreters
where are brunner's glands located?
submucosa of initial portion of duodenum
Structure of brunner's glands?

Ramified, coiled, tubular glands that OPEN into intestinal glands
What are lacteals?
Capillaries thar are the beginning of lymph vessels

Found in the middle of villi

Larger than blood cappilaries

Absorb lipids
What forms the innerevation of the intestines?
Intrinsic component
Extrinsic component
What makes up the intrinsic componenet of intestinal innervation?
Myenteric plexis (auerbach's), betwen the outer longitudinal and inner circular layers of the muscularis

Submocosal plexus in the submucosa
What makes up the extrinsic innervation?
Parasympatetic cholinergic nerve fibers that stumulate the activity of the intestinal smooth muscel

Sympathetic nerve fibers that depress intestinal smooth muscle activity
Gross structural differences in large intestine
1) mucosal membrane has no folds (except in distal portion)
2) no vili are present
Describe intestinal glands in the large intestine
1) long2) characterized by a great abundance of goblet cells and absorptive cells
2) small number of enteroendocrine cells
Characterize the lympoid tissue in large intestine
It is rich--a lot of GALT
Describe the muscularis in the large intestine
Two layers: inner circular, and outer longitudinal. The outer layer is in arrangged in 3 thick bands called teniae coli.
Differences between appendix and large intestine
1) fewer and shorter intestinal glands
2) no teniae coli
What do absorptive cells absorb?
How do goblet cell granules stain?
PAS positive
Basophilic (if preserved)
What do goblet cells secrete?
Acid proteoglycans

(form mucus)
What all does paneth cell secrete?
acid hydrolase
What does enteroendcrine EC cell do? Where is it?
1) secrete serotonin and motilin peptide
2) effects sm contraction and peristalsis
3) Where: stomach and intestines
What is enteroendocrine G cell? What does it do?
1) secrete gastrin polypeptides
2) this stimulates acid secretion by parietal cells and pepsinogen secretion by chief cells
3) where: pyloric stomach and duodenum
What do S ee cells do? where?
1) secretes secretin polypeptide
2) this effects bicarbonate secretion from bile ducts and pancreatic ducts
3) in the intestine
What do I ee cells do? where?
1) secretes cholecystokinin
2) effects pancreas zymogen secretion and gall bladder contractoin
3) in small intestine
Mucous cells of salivary glands
Usualyly cuboidal to columnar

Most often organized as tubules
Submandibular gland organization:
Mucous cells form tubules, but their ends are capped by serous cells (the serous deilunes)
What are the serous demilunes?
Serous cells that cap a mucous cell tube in the submandibular glands
What are intercalated ducts?
What secretory endpieces empty into.

Lined by cuboidal epithelial cells

Join to form striated ducts
What are striated ducts?
What intercalated ducts empty into.

Striated due ti infloldings of basal plasma membrane with numerous elongated mitos aligned paralel to it.
Where do striated ducts drain?
Into ducts in septa separating lobules, where they become interlobular/exretory ducts
Parotid gland structure
1) branched acinar gland
2) exclusively serouc cells with granules (no mucous cells)
3) secretions acount for hydrolysis of most carbs
Submandibular gland structure
1) branched tubuloacinar
2) secretory portion has mucus and serous cells
3) Mainly serous (basophilic cytoplasm)
4) serous cells secrete lysozyme (antbacterial)
Sublingual gland structure
1) branched tubuloacinar gland
2) serous and mucous, but mostly mucous, unlike submandubular
Pancreas, generally
Mixed exocrine/endocrine gland

Produces digestive enzymes and hormones
Exocrine portion of pancreas: structure
Compound acinar gland, similar to the parotid.

Releases enzymes
Distinguishhing the parotid from the exocrine portion of the pancreas:
Pancreas: no striated ducts. Has "centroacinar cells"

Parotid: no islets of langerhands
What are centroacinar cells?
INtercalated duct cell that sticks into the acinar lumen. Found only in pancreatic acini.
What all does the exocrine pancrease secrete?
phospholipase A
What are the main secretory products fo the exocrine pancreas/
Digestive enzymes
Where does pancreatic bicarbonate come from?
Ductule cells
What is the main function of the liver?
It is the organ where nutrients absorbed in the digestive tract ar processed and stored for use by other parts of the body.

IOW, the interface between the digestive system and the blood
Where does liver get its blood?
75% portal vein
25% hepatic artery
What is a liver lobule?
Formed of a polyganal mass of tissue .7 x .2 mm.

no defined separation between them.

Portal spaces at the corter (3-6 per lobule)
Portal spaces
Regions demarcating liver lobules

Contani bile ducts, lymphatics, nerves, BV
More structure of liver lobule
1) hepatocytes radially dispossed, arranged like bricks
2) cellular plates form a spongelike structure
3) structure between plates = liver sinusoids, which contain capillaries
What separates hepatocyte plates from sinusoid endothelium?
SPace of Disse
Structure of liver sinusoids
Irregularly dilated vesels--all fenestrated endothelial cells.
What else do sinusoids contain besides blood and endothelium?
Kupffer cells: macrophages
Outline facts on kupffer cells
monocyte derive phagocyte

peroxidase positve
What cells are found in the space of Disse?
Ito's cells (Stellate, fat-storing cells)

Store fat,

have vitamin A rich lipid inclusions

Desmin positive
Blood flow thru liver lobule
Branch of portal vein sends branches radially toward center of lobule as sinusoids.

Sinusoids converge cetreally on central vein.

Vein takes all the sinuosoid blood and empties into the sublobar vein, which empties into hepatic vein.

Arterial blood flows also radially toward center of lobule.
What are canals of hering?
What the bile canaliculi empty into at the periphery of the liver lobule
What does the liver synthesize?
plasma proteins
What endocrine functions does liver mediate?
glucose release and uptak
hormone metabolism
How many mitos do hepatocytes have?
2000. Up to 25% by volume.
Where is ilrubin formed?
In the mononuclear phagocyte system (including kupffer cells).

It is transported to the haptocytes, where it is conjugated in their SER to glucuonic acid.

Conjugated bilirubin then excreted in bile.
Where does gluconeogenesis occur?
What is hepatic, cystic, and common bile duct lined with?
Simple columnar epithelium
Describe epithelium of gall bladder
simple columnar (like duct)
no goblet cells
Intercellular spaces at or near base of cells
What is the capsule of Glisson?
Thin connective tissue capsule surrounding liver
What is the functional unit of the kidney?