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345 Cards in this Set
- Front
- Back
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VC segments =
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7C, 12T, 5L, 5S, and 4 coccygeal
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what's the VC do?
(2) |
protects SC and SN's
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how many pairs of SN's are there?
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31
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***ventral root =
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motoer/efferent axons FROM spinal cord
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***dorsal root =
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sensory/afferent axons TO spinal cord
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SN =
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v. root + d. root
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SN then splits into
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ventral and dorsal rami
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which rami are bigger?
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the ventral
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**dorsal rami innervate:
(3) |
1. **intrinsic** back muscles
2. skin of back 3. facet joints of VC |
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what are the primary curves?
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Thoracic and Sacral
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primary curves are called such because:
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they're in the same direction as fetal curves
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which curves are secondary curves?
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Cervical and Lumbar
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secondary curves develop during:
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infancy
- first the cervical, then the lumbar |
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3 kinds of abnormal spinal curves:
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1. kyphosis
2. lordosis 3. scoliosis |
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kyphosis =
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accentuated **Thoracic** curve
- hunchback |
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what causes kyphosis?
(2) |
poor posture, osteoporosis
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lordosis =
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accentuated Lumbar curve
- "hollowback" |
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what causes lordosis?
(3) |
weight gain, pregnancy, weak *trunk* muscles
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scoliosis =
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lateral curvature and rotation of the spine
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what causes scoliosis?
(3) |
1. difference in leg length
2. unilateral weakness of intrinsic back muscles 3. malformation of vertebrae |
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2 kinds of joints in the VC:
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1. intervertebral discs
2. facet joints |
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IV discs are found between:
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vertebral **bodies**
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facet joints are found between:
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vertebral ***processes***
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IV Discs:
(2) |
1. cartilaginous - very strong
2. adhere tightly |
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IV Discs are made up of:
(2) |
1. annulus fibrosus
2. nucleus pulposus |
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annulus fibrosus:
(2) |
1. outer
2. fibrocartilage |
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nucleus pulposus:
(2) |
1. inner
2. is gelatinous mass - high water content |
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what is the most important role of the nucleus pulposus?
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**shock absorption**
|
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pressure during the day pushes H2O out of the nucleus pulposus;
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sleeping flat lets it get back in
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zygapophyseal joints =
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facet joints
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facet joints:
(3) |
1. plane joints
2. contain synovial fluid 3. can become arthritic => back pain |
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all joints can become:
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arthritic
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intervertebral foramina:
(2) |
1. lateral openings
2. SN's come out of them |
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**arthritic facet joints can lead to:
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narrowing of intervertebral foramina => impinging of spinal nerves
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***most VC movements (flexion, rotation, etc.) are possible b/c of:
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shape and orientation of facet joints
|
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Cervical facet joint orientation =
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horizontal inclined
=> movement through multiple axes |
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Thoracic facet joint orientation =
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frontal
=> rotation |
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Lumbar facet joint orientation =
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sagittal
=> flexion/extension |
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how many ligaments does the VC have?
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6
|
|
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Anterior Long, Lig:
(2) |
1. unites bodies of VC anteriorly
2. **prevents hyperextension** |
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Post. Long. Lig location =
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***inside*** the VC, running across the *back* of vertebral bodies
|
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supraspinous ligament:
(2) |
1. connects spinous processes from sacrum to C7
2. after that called liamentum nuchae |
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interspinous ligaments connect:
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**adjacent** spinous processes
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intertranverse ligaments connect:
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adjacent transverse processes
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**ligamentum flavum:**
(4) |
1. yellow
2. elastic 3. connects adjacent **lamina** 4. ***prevents hyperflexion*** |
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lamina are more
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posterior
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pedicles are more anterior, connect to
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vertebral bodies
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ligaments ~
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stability
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superficial muscles of the back:
(2) |
1. control upper limb
2. traps, lats, rhomboids, levator scapulae |
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latissimus dorsi Action =
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**being handcuffed**
- adduct, extend, and medially rotate the humerus |
|
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lats are innervated by:
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the **thoracodorsal nerve**
(ventral rami of C6 - C8) |
|
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Traps Action =
(3) |
elevate, medially rotate, and retract shoulders
|
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Traps are innervated by:
(2) |
1. CN 11 (spinal accessory nerve) for motor,
2. C3 and C4 for sensory |
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**thoracolumbar fascia**
(5) |
1. strong, thick aponeurosis
2. attaches to spinous and transverse processes 3. **multi-layered** - a, p, and middle 4. surrounds and supports intrinsic back muscles 5. attachment site of different muscles |
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"aponeurosis" =
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tendon
|
|
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Intermediate muscles of the back:
(4) |
1. serratus post. sup. and inf.
2. also considered extrinsic 3. ~ respiration 4. very thin |
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what are the 3 layers of the Intrinsic Back Muscles?
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1. Superficial layer
2. Intermediate Intrinsic layer 3. Deep Intrinsic layer |
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****ALL intrinsic back muscles are innervated by:****
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dorsal rami
|
|
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superficial intrinsics:
(4) |
1. splenius capitis, cervicus
2. bandage the deeper muscles 3. A bilat. = extension of neck 4. A unilat. = ipsilateral rotation |
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Intermediate layer also called:
|
Erector Spinae
SLI |
|
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A of intermediate intrinsics =
(3) |
extension, controlled flexion, lateral flexion
**~ posture** |
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3 deep intrinsics =
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1. semispinalis
2. multifidus 3. rotatores |
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**ALL deep intrinsics course from:
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transverse processes TO spinous processes
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semispinales:
(2) |
1. span 4-6 segments
2. most superficial |
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multifidus:
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span 2-4 segments
|
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rotatores:
(2) |
1. span 1-2 segments
2. deepest of the deep layer |
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***deep intrinsics: A => ***
(3) |
1. posture
2. rotation 3. proprioception |
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rami have BOTH
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sensory and motor function
|
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embryologists start development at
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0 weeks
|
|
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3 basic stages of development:
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1. cleavage (1st week)
2. embryonic period (wks 2-8) 3. fetal period (wks 9-40) |
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the fetal period consists of FEW:
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major changes; it's mostly growth
|
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zona pellucida =
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membrane that contains the zygote and subsequent blastomeres
|
|
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when does the zona pellucida break down?
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when enough fluid comes into the blastocyst
|
|
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cleavage:
(3) |
1. from fertilization to implantation
2. zygote undergoes repeated divisions into smaller cells (blastomeres) 3. after 3 days, blastomeres form the morula (mulberry) |
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what major structure forms during cleavage?
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the blastocyst
- fluid-filled cavity |
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blastomeres segragate into:
(2) |
inner and outer populations,
ICM and trophoblasts |
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trophoblasts form the:
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chorion,
part of the placenta |
|
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ICM (inner cell mass) =>
(2) |
embryo and embryonic membranes
|
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Implantation takes:
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6 days
|
|
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implantation =
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ICM separates into 2 layers,
1. epiblast (inner) 2. hypoblast (outer), as trophoblast becomes part of uterine wall |
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|
during the 2nd week (embryonic period):
(3) |
1. fluid collects between epiblast and trophoblast cells
2. epiblast cells form amniotic cavity 3. hypoblast cells form the yolk sac |
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***bilaminar embryoblast*** =
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place where epiblast and hypoblast cells meet after having formed their respective cavities
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**formation of bilaminar embryoblast =
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end of implantation
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during the 3rd week, what major processes occur?
(3) |
1. gastrulation
2. notochord formation 3. induction of neuroectoderm |
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gastrulation =
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epiblast becoming ecto, meso, and endo,
as hypoblast is displaced |
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ecto+meso+endo =
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trilaminar embryoblast
|
|
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gastrulation occurs because:
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epiblast cells move toward primitive streak and node
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once epiblast cells pass through the streak and node, they migrate:
(2) |
caudally and laterally
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epiblast cells migrating caudally and laterally after passing the streak and node form:
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***the endoderm,***
which displaces the hypoblast |
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(cranial =
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toward future head)
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the mesoderm is formed when:
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epiblast cells fill in the space *above* the ectoderm
- remaining epiblast becomes ectoderm |
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**regression =
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node and streak moving caudally
- gastrulation proceeds stepwise, occurring cranially first, then in the middle, then caudally |
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gastrulation is complete at the end of
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the 3rd week
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caudal dysplasia =
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failure of gastrulation to complete
(mesoderm formation is interrupted) |
|
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most common form of caudal dysplasia =
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lower limb fusion
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most common cause of caudal dysplasia =
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gestational diabetes
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sacralcoccygeal teratoma =
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failure of gastrulation to stop.
- multipotent nature of epiblast cells => hair, teeth, etc. in this resulting tumor |
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the notochord begins as:
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the **notochordal process**
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notochordal process = hollow tube that eventually extends from:
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oropharyngeal membrane to cloacal membrane
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both the oropharyngeal and cloacal membranes are fusions of
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ecto and endo
- no mesoderm |
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the hollow notochord process fuses with the _________, then unfuses as the rod-like __________
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endoderm;
notochord |
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notochord =
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central organizer
|
|
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the mesoderm is split into 4 parts:
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1. paraxial meso
2.lateral plate meso 3. intermediate meso 4. cardiogenic meso |
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neuralation induces the ectoderm to:
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become the neuroectoderm
(initially called the neural plate) |
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later, the neural plate =>
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neural tube => brain, SC
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as neural tube closes, a population of neural crest cells, escape; ==>
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become PNS
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4th week ~
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body folding
|
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A. lateral body folding =
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lateral edges brought together, toward midline
=> forms tube out of endoderm, in the center |
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B. Cranial body folding =
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structures that lie cranially to the neural plate fold ***ventrally***
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cranial folding =>
(2) |
1. formation of foregut
2. heart in right place (it was formerly most cranial) |
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caudal body folding is just like cranial; forms:
(2) |
hindgut, future anus
|
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consequences of body folding:
(4) |
1. foregut, midgut, and hindgut formed
2. vitrillene formed (=> bladder) 3. amnion now surrounds embryo 4. cranial, caudal, and lateral edges of embryoblast are now located ventrally |
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surface ecto becomes:
(4) |
epidermis, hair, nails, enamel
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neural crest =>
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lots of things
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paraxial meso => somites =>
(3) |
1. sclerotome (bone/cartilage)
2. myotome 3. dermatome |
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intermediate meso =>
(2) |
1. urinary system
2. gonads |
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lateral plate meso =>
(2) |
1. somatic layer => limb bones and sternum
2. splanchnic layer => gut (*except for lining*) |
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endoderm becomes:
|
the lining of the tube from pharynx to anus
|
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vertebral foramen =
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circle between body and arch
|
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all vertebral foramina together form the
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vertebral canal
|
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the vert. canal protects:
(2) |
1. SC
2. meninges |
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***at what level does the SC end?***
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~ T12- L2
called the Conus Medullaris (white on cadaver) |
|
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SC only occupies ____ of vertebral canal
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2/3rd's
(in an embryo, the SC occupies 100% - but bones outgrow cord) |
|
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***cauda equina =***
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collection of **lumbar and saccrococcygeal** nerve ROOTS
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the nerve roots that make the cauda equina are much longer because:
|
they have to reach their respective *IV foramina*
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where does the dural sac begin and end?
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begins at base of skull, ***ends at S2***
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what fiber extends out of the conus medullaris?
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**filum terminale**
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what does the filum terminale do?
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anchors the SC inferiorly
|
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the internal filum terminale runs from:
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from conus medullaris to end of dural sac (S2)
|
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the external filum terminale runs from:
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S2 to sacrum/coccyx
|
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what are the two enlargements of the spinal cord?
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Cervical and Lumbar
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why are the Cervical and Lumbar regions of the SC enlarged, respectively?
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Cervical due to innervation of the upper limbs, Lumbar due to innervation of the lower limbs
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whats the relationship b/w VC and SC levels?
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**they are different**
|
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SN C1 comes out _____ C1 vertebra
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above
|
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SN C8 comes out _____ C7 vertebra
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below
|
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Dura mater:
(3) |
1. outermost
2. forms dural sac 3. extends into dural sleeves |
|
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dural sleeves:
(2) |
1. **surrounds ventral and dorsal roots**
2. blends into the outer covering of the SN's |
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***recurrent meningeal nerves arise from SN's to convey:***
|
sensory info FROM dura TO
SC |
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Arachnoid:
(2) |
1. delicate
2. lines inside of dura *and dural sleeves* |
|
|
subarachnoid space:
(3) |
1. contains CSF
2. pushes arachnoid against dura 3. **continuous with the subarachnoid space of the brain** |
|
|
Pia mater:
(2) |
1. firmly *adheres* to surface of SC and overlying blood vessels
2. extends as denticulate ligaments |
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denticulate ligaments:
(3) |
1. extensions of pia
2. anchor the SC *laterally* 3. found b/w dorsal and ventral roots |
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epidural space =
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space b/w dura and VC bone
|
|
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***what important sturcture does the epidural space contain?***
|
the **internal (epidural) venous plexus**
|
|
|
the internal venous plexus drains blood from:
(2) |
1. veins on surface of SC
2. vertebral bodies, via the basivertebral vein |
|
|
***neither the internal venous plexus nor the basivertebral vein have:***
|
valves
|
|
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the internal venous plexus is continuous with veins of the:
(3) |
1. thoracic walls
2. pelvis 3. head |
|
|
neoplastic cells from certain organs can enter the venous plexus and cause:
(2) |
1. VC bone cancer
2. brain cancer |
|
|
which two kinds of blood vessels are necessary for adequate perfusion of the SC?
|
1. longitudinal branches
2. feeder/helper branches |
|
|
longitudinal branches come off of:
|
vertebral arteries
|
|
|
***what are the 3 longitudinal arteries?***
|
1 anterior spinal artery,
2 posterior spinal arteries |
|
|
feeder/helper branches enter the vertebral canal via:
|
**IV foramina**
|
|
|
posterior intercostals => feeder/helper arteries =>
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radicular arteries
|
|
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***radicular arteries perfuse:
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***the dorsal and ventral roots***
|
|
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large feeder/helper branches are called:
|
segmental medullary arteries
|
|
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**relationship of segmental medullary arteries to anterior and posterior spinal arteries:
|
***segmental medullary arteries anastomose with and reinforce the longitudinal arteries***
|
|
|
what's the biggest segmental medullary artery?
|
the artery of Adamkiewicz
|
|
|
the artery of Adamkiewicz reinforces circulation to the
|
inferior 2/3rd's of the SC
|
|
|
lumbar spinal tap:
(3) |
1. obtains sample of CSF
2. ***L3-L5 is ideal - avoids SC*** 3. patients flex spine |
|
|
a lumbar spinal tap passes these layers to get to the CSF:
(5) |
1. supraspinous ligament
2. interspinous ligament 3. lig. flavum 4. dura 5. arachnoid |
|
|
Caudal Epidural Block:
(2) |
1. anesthesia is injected into the **epidural space**, via sacrum
2. *blocks lumbar and sacral nerves* from conveying pain/sensation |
|
|
the anterior and posterior longitudinal ligaments are closely associated with the
|
IV discs
|
|
|
anterior and posterior longitudinal ligaments **prevent**
|
herniated discs
|
|
|
herniated =
|
slipped
|
|
|
problem: post. long. lig. is weak: where?
|
***laterally***
|
|
|
lateral weakness of post. long. lig, =>
|
posterolateral herniation
|
|
|
posterior herniations are also
|
possible,
especially as the annulus weakens with age but posterolateral are more common |
|
|
herniations => compression of:
(3) |
1. SC
2. SN's 3. nerve roots of cauda equina |
|
|
95% of **Lumbar** herniated discs occur either at:
|
L4/L5 or L5/S1
- will affect the SN between them |
|
|
neural tube defects (NTD's) can be either
|
open or closed
|
|
|
open NTD =
|
skin is missing
|
|
|
MMC =
|
myelomeningocele = bones of VC aren't completely formed
|
|
|
folic acid helps prevent MMC;
|
a fluid-filled sac is common
|
|
|
placode =
|
abnormal, splayed neural tissue
|
|
|
associated abnormalities of MMC:
|
1. hydrocephalus
2. Chiari II/Hindbrian herniation |
|
|
hydrocephalus occurs because SC won't:
|
reabsorb CSF, so it stays in the brain
=> large ventricles |
|
|
solution to hydrocephalus =
|
shunt in head, valve
=> keeps fluid cycling, rather than collecting in the head |
|
|
chiari II / hindbrain herniation =
|
smaller posterior fossa forces parts of cerebellum and hindbrain through the foramen magnum
|
|
|
the LOWER the NTD, the higher
|
the rate of survival, quality of life
- less likely to need shunt |
|
|
bottom line for MMC:
|
can close, the wound, but
***significant morbidity, emotional stress, and cost*** |
|
|
treatment of MMC =
|
operate within 24 hours
- *cannot* restore neurological function |
|
|
prenatal repair =
|
intra-uterine MMC repair (IUMR)
|
|
|
IUMR =>
|
less shunts, higher survival
- but higher risk of being born premature - unclear long-term results |
|
|
characteristics of Cervical vertebrae:
(4) |
1. large, triangular foramen
2. small bodies 3. bifid spinous processes 4. only ones that have two extra holes - 2 transverse foramen for vertebral arteries |
|
|
characteristics of Thoracic vertebrae:
(5) |
1. circular vertebral foramen
2. heart-shaped body 3. 2 superior and 2 inferior costal facets on each body 4. transverse costal facets on transverse processes 5. long, slanted spinous processes |
|
|
exception to Thoracic bodies' costal facets:
(2) |
T11 and T12 have only ONE costal facet on each side,
and NO transverse costal facets |
|
|
characteristics of Lumbar vertebrae:
(4) |
1. triangular vertebral foramen
2. **massive** vertebral bodies 3. hatchet-shaped spinous processes 4. mammillary processes - small bony elevations on the superior articulating processes of lumbar vertebrae |
|
|
characteristics of Sacral vertebrae:
(5) |
1. apex articulates with coccyx
2. transverse ridges = fusion sites 3. sacral cornu = dorsal horns 4. **sacral hiatus is found at S5** (site of epidural blocks) 5. sacral foramina protect d. and v. roots |
|
|
both the superior and inferior articulating processes come off of the:
|
laminae
|
|
|
***the inferior processes are more _______ to the superior***
|
Medial
|
|
|
Scotty Dog =
|
one side of all the articulating processes
|
|
|
pars interarticularis =
|
neck of Dog
|
|
|
Scotty Dog parts:
pedicle = superior articulating process = transverse process = spinous process = inferior articulating process = |
eye;
ear; head; body; foremost leg |
|
|
***spondylolysis =
|
broken neck of Scotty Dog
|
|
|
***spondylolisthesis = ***
|
broken pars AND vertebra slipped forward
|
|
|
MRI: in the T1 version, water is
|
***dark***
|
|
|
what's the best kind of CT to view spinal fractures?
|
axial and reformatted
|
|
|
lumbar punctures should be made at the level of:
|
L3/L4
or L4/L5 |
|
|
when performing a spinal tap on *older* patients and those with *scoliosis*, make sure to use:
|
fluoroscopy
|
|
|
subscapular fossa ~
|
*anterior* of the scapula
|
|
|
serratus anterior lies beneath:
|
subscapularis
|
|
|
humerus:
(5) |
1. little contact with glenoid
2. greater tubercle is LATERAL 3. lesser tubercle is anterior 4. surgical neck is right below tubercles 5. deltoid tuberosity is lateral, mid-shaft |
|
|
***internal rotation of the humerus =
|
turning lesser tubercle IN
|
|
|
ABduction of humerus above the head ~ lateral rotation of:
|
**the inferior angle of the scapula**
|
|
|
as humerus ABd's, the scapula slides along the:
|
conceptual scapulothoracic joint
|
|
|
***also during ABd'n, the humerus rotates _____________, so that:
|
**externally;**
the greater tubercle avoids rubbing against the acromion process |
|
|
serratus anterior: Action =
(3) |
1. lateral rotation
2. protraction 3. holding scapula to thoracic wall |
|
|
serratus anterior helps you to:
|
raise your arm above your head
|
|
|
serratus anterior: N=
|
long thoracic nerve
|
|
|
***long thoracic nerve is exceptional because it's one of the few nerves that:
|
runs ON TOP OF its muscle
=> easily injured |
|
|
because the long thoracic nerve runs on top of serratus anterior, it's easily injured => =>
|
**winged scapula**
(because scapula no longer held to thoracic wall) |
|
|
winged scapula/ damage to serratus anterior =>
|
***unable to ABd arm above head***
|
|
|
winged scapula can also result from:
|
damage to trap or CN 11
|
|
|
3 layers of Posterior Shoulder Muscle:
|
1. Superficial
2. Deep Posterior 3. Scapulohumeral |
|
|
superficial posterior shoulder muscles:
(2) |
1. lats and traps
2. extrinsic |
|
|
deep posterior shoulder muscles:
(3) |
1. rhomboids, levator
2. extrinsic 3. N = dorsal scapular nerve |
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|
A of rhomboids =
(2) |
retract, rotate scapula
|
|
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A of levator scapula =
(2) |
elevate, rotate scapula
|
|
|
**both the rhomboids and levator do what to the scapula?**
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rotate it, tilting the glenoid fossa downward
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**what are the Scapulohumeral posterior shoulder muscles?**
(6) |
1. deltoid
2. T. Major 3. supraspinatus 4. infraspinatus 5. t. minor 6. subscapularis |
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|
deltoid: N =
|
Axillary
|
|
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deltoid: A =
|
**principal** ABductor of the arm
(though supraspinatus initiates first 15 degrees) |
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|
***fracture of surgical neck => damage to:
|
Axillary nerve => loss of deltoids => loss of most ABduction of arm,
+ **loss of sensation on lateral shoulder** |
|
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T. Major: Insertion =
|
medial lip of bicipital groove
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T. Major: N =
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*lower* subscapular nerve
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T. Major: A =
(2) |
adduction, medial rotation of arm
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|
|
what 4 muscles adduct and medially rotate the humerus?
|
1. lats
2. T. major 3. subscapularis 4. Pec. Major |
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musculocutaneous cuff =
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tendons of SITS
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what does the musculocutaneous cuff do?
(2) |
stabilizes head of humerus,
protects glen-humeral joint |
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supraspinatus:
(3) |
1. A = first 15 deg. of ABd'n
2. I = sup. facet of greater tubercle 3. N = suprascapular nerve |
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infraspinatus:
(4) |
1. A = ***prime lateral rotator of scapula***
2. I = middle facet of greater tubercle 3. N= suprascapular nerve 4. bigger than supraspinatus |
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t. minor:
(3) |
A = *weak* lateral rotator of scapula
I = inferior facet of greater tubercle N = Axillary nerve |
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subscapularis:
(3) |
A = adduction, Medial rotation of arm
I = lesser tubercle N = upper AND lower subscapular nerves |
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***supraspinatus goes through ____________ to insert onto the greater tubercle***
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the tiny subacromion space
=> ***easily irritated/injured*** |
|
|
bursae =
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sacs of synovial fluid
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|
|
what does the subacromion bursa do?
|
allows supraspinatus to *glide* as it passes under acromion
- does the same for deltoids |
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bursitis =
|
inflammation of subacromial bursa
- needs PT, cortisone to treat |
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when does bursitis hurt most?
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as you rotate arm UP
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|
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acute tears of supraspinatus occur in:
|
violent sports
- need surgery to repair |
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gateways of shoulder allow:
|
neurovasculature to pass from anterior to posterior
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|
|
what runs over the suprascapular notch to create a foramen?
|
the superior transverse longitudinal ligament
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|
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what structure goes THROUGH the suprascapular notch?
|
the suprascapular nerve
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|
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what structure goes OVER the suprascapular notch?
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the suprascapular artery
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what nerve serves BOTH supra- and infraspinatus?
|
suprascapular nerve
|
|
|
the sup. transverse long. lig. can ossify; =>
|
impingement of suprascapular nerve => decreased ability to
ABduct arm the first 15 degrees AND rotate scapula laterally |
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what two major structures come out of the quadrangular space?
|
1. Axillary nerve
2. PHCA |
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dermatomes =
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areas of skin innervated by specific SC levels
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|
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dermatomes ~
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sensory information
so ~ dorsal **roots** |
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|
shingles is a result of which virus?
|
herpes zoster
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the herpes zoster virus lies dormant in the DRG; when activated, it
|
travels along nerve to the area of the skin that the nerve innervates
=> painful shingles rash appears in dermatome |
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C5 dermatome ~
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tip of shoulder
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C6 dermatome ~
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thumb
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C7 dermatome ~
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index finger
|
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C8 dermatome ~
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pinky
|
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T1 dermatome ~
|
Medial arm
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|
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2 types of ossifications in the embryo:
|
1. intramembranous
- rare: skull, sesanoid bones 2. endochondal |
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|
endochondal ossification =
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***cartilage template*** that's replaced by bone
- much more frequent |
|
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the skeleton develops from 3 sources:
|
1. paraxial meso
2. somatic layer of LPM 3. nerual crest |
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paraxial meso =>
(3) |
1. base of skull
2. vertebrae 3. ribs |
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somatic LPM =>
(2) |
1. sternum
2. limbs |
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neural crest =>
(2) |
1. facial bones
2. cranium |
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|
in 3rd week, cells of the paraxial meso go from __________ to epithelial (tight)
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mesenchyme (loose)
|
|
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epithelial paraxial meso forms:
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somites
|
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somites =
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paired segments
|
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3 kinds of somites:
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1. sclerotome
2. myotomes 3. dermotomes |
|
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sclerotomes divide into:
(2) |
cranial and caudal components
|
|
|
adjacent cranial and caudal components join to form new groups of cells;
=> each vertebrae has portions of |
4 different somites
(2 caudal, 2 cranial) |
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|
exception: _______ pairs of occipital somites form the base of the skull
|
*four*
|
|
|
gradient of retinoic acid (with more toward the cranial region) =>
|
level of expression of hox genes, which determines axial skeleton formation
|
|
|
****different structures induce the sclerotome cells to form:
|
different parts of the skeleton
|
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sclerotome cells near notochord become:
|
vertebral bodies
|
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sclerotome cells near neural tube become:
|
vertebral arches
|
|
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slerotome cells near lateral edges become:
|
ribs
|
|
|
vetebrae have ______ ossificaiton centers
|
three
|
|
|
ossification is complete at ~
|
20 years
|
|
|
hemivertebra =
|
vertebra not fully formed
|
|
|
causes of hemivertebra =
(2) |
1. failure of proper ossification
2. improper subdivision of somites/sclerotomes |
|
|
hemivertabra = one cause of:
|
scoliosis
|
|
|
notochord contributes to ______________, while sclerotomal cells that don't contribute to vertebral bodies => _______________
|
nucleus pulposus;
annulus |
|
|
somatic LPM =>
(2) |
1. sternum
2. limbs |
|
|
localized expression of hox gene =>
|
proliferation of LPM => limb buds
|
|
|
legs develop one day
|
BEHIND arms
|
|
|
limbs develop in a:
|
proximal-to-distal direction
|
|
|
****Apical Ectodermal Ridge**** =
|
ecto on distal end of limb buds that stimulates distal somatic LPM to grow
- runs along length of bud |
|
|
removing AER =>
|
less/no limb development
- removing earlier = less limb |
|
|
development of each region of the limb depends on:
|
variable hox expression
|
|
|
***Amelia =
|
congenital absence of limb,
resulting from failure of limb outgrowth |
|
|
***phocomelia =
|
limb lacks ***intermediate/middle***parts
|
|
|
phocomelia is a result of:
|
temporary failure of outgrowth
|
|
|
temporary failure of outgrowth can be caused by:
|
teratogens like thialidomide
|
|
|
pre-axial =
|
cranial
|
|
|
***Zone of Polarizing Activity forms on postaxial border and imparts
|
digit identity
|
|
|
errors in ZPA =>
(2) |
1. polydactyl
2. triphalangeal thumb |
|
|
cell death between digits is a result of:
|
AER regression
|
|
|
improper AER regression =>
(2) |
1. webbed hand
2. syndactyl (fused digits) |
|
|
resegmentation of sclerotomes =>
|
vertebrae laying between spinal nerves and mytomes
|
|
|
clavicle:
(3) |
1. allows scapula to glide along thoracic wall
2. articulates with manubrium 3. ***transmits shock from upper limb to axial skeleton*** |
|
|
what is the most fractured bone in the body?
|
the clavicle
|
|
|
aspects of clavicle fractures:
(3) |
1. patients have to hold/support their arm
2. shoulder on broken side will sag 3.**80% of fractures occur in the middle 1/3** |
|
|
sternoclavicular joint:
(4) |
1. saddle joint
2. ***ONLY true articulation b/w upper limb and axial skel.*** 3. extremely strong 4. rarely dislocates |
|
|
although the sternoclavicular joint is really strong, it still has:
|
60 degrees of motion
|
|
|
the sternoclavicular joint is reinforced by 4 ligaments:
|
1. anterior sternoclavicular ligament
(really strong) 2. posterior sternoclavicular ligament 3. interclavicular ligament 4. costoclavicular ligament |
|
|
the interclavicular clavicle connects:
|
both clavicles
|
|
|
the costoclavicular ligament anchors the clavicle to:
|
the 1st rib
|
|
|
the intrarticular disc of the sternoclavicular joint acts as
|
a shock absorber
~ IV discs |
|
|
acromioclavicular joint:
(3) |
1. plane joint
2. surrounded by loose fibrous capsule 3. commonly injured |
|
|
which 4 ligaments strengthen the acromioclavicular joint?
|
1. AC lig.
2. coracoacromial lig. 3. and 4. coracoclavicular ligaments |
|
|
coracoclavicular ligaments are a PAIR of ligaments that unite the coracoid process and clavicle; both are:
|
**extrinsic**
- not part of the joint |
|
|
the AC ligament runs:
|
OVER the top of the AC joint
|
|
|
AC injuries: 1st degree =
|
stretch/minor tear of AC ligaments
|
|
|
AC injuries: 2nd degree =
|
*rupture* of AC ligament,
with rupture of AC joint |
|
|
AC injuries: 3rd degree =
|
*complete* tear of both AC ligament and **coracoclavicular ligaments**
|
|
|
3rd degree AC injury is also called a:
|
shoulder separation
- clavicle sticks up like a piano key |
|
|
Pec. Major:
(4) |
1. O = clavicle and sternum (2 heads)
2. I = lateral lip of bicipital groove 3. A = *powerful* adductor, medial rotator of arm 4. N = M and L pectoral nerves |
|
|
clavipectoral fascia connects:
|
clavicle to the floor of the axilla
- surrounds pec. minor and subclavius |
|
|
pec minor:
(3) |
1. I = coracoid process
2. A = pulls scapula against thoracic wall - small resp. function 3. A = Medial pectoral nerve |
|
|
***pec minor forms a bridge over:***
(3) |
1. axillary artery
2. axillary vein 3. brachial plexus |
|
|
subscapular artery is the largest
|
branch of the axilary
=> thoracodorsal artery, circumflex scapular artery |
|
|
AHCA and larger PHCA supply:
|
humerus and surrounding muscles
|
|
|
***many of the branches off the axillary artery anastamose around the scapula and surr. muscles; if thrombosis (blockage) of axillary artery occurs, these anastamoses will allow
|
blood to continue down the arm
|
|
|
***what forms the "roots" of the brachial plexus?***
|
***ventral RAMI***
- which means sensory information is retrograding along the plexus |
|
|
***the "roots" of the brachial plexus emerge between:***
|
the anterior and middle scalenes
|
|
|
**cords are named based on their position to:**
|
the axillary *artery*
|
|
|
the intercostobrachial nerve:
(2) |
1. a cutaneous branch of T2
2. sensory of *medial* arm |
|
|
***the intercostalbrachial nerve is the ONLY nerve of the upper limb that:***
|
DOESN'T originate from the brachial plexus
|
|
|
Musculocutaneous nerve ~
|
flexors of arm
|
|
|
Median nerve ~
(2) |
1. forearm flexors
2. some intrinsic hand muscles |
|
|
Ulnar nerve ~
(2) |
1. most intrinsic hand muscles
2. 1. 5 of the forearm flexors |
|
|
Radial nerve ~
|
ALL arm AND forearm extensors
|
|
|
the brachial plexus is surrounded by:
|
the axillary sheath
|
|
|
the clavicle is the most fractured bone of both adults and
|
of babies during delivery
|
|
|
somitic epithelium => myogenic progenitor cells =>
|
myoblasts (migrating)
=> myotube => myofiber (multinucleated) |
|
|
as sclerotome cells differentiate, remaining dermamyotome cells shed:
|
myogenic progenitor cells
=> that form myotomes |
|
|
Myotome cells form 2 populations:
|
1. epimere (dorsal)
2. hypomere (ventro-lateral) |
|
|
epimere cells become:
|
intrinsic back muscles
|
|
|
hypomere cells become:
|
body wall AND limb muscles
|
|
|
the dorsal rami track with
|
epimere cells as they migrate
|
|
|
ventral rami track with
|
hypomere cells as they migrate
|
|
|
myotomes that enter limb buds dorsally become:
(2) |
1. extensors
2. ABductors |
|
|
myotomes that enter limb buds ventrally become:
(2) |
1. flexors
2. adductors |
|
|
limb rotation: the upper limb buds rotate:
|
45 degrees clockwise
- so that dorsal part faces the posterior |
|
|
limb rotation: lower limbs rotate:
|
almost 180 degrees counter-clockwise
- that's why dermatome skin areas of the legs are weird |
|
|
***where does most SM come from?***
|
splanchnic LPM
- surrounds internal organs |
|
|
rest of SM comes from:
(2) |
1. somatic LPM
~ SM of blood vessels 2. neural crest ~ SM of eye |
|
|
***cardiogenic meso is oftentimes considered:***
|
splanchnic LPM
|
