Joints, MSK Histology & Embryology

Question 1

classify the following joints:
a. sutures of skull
b. intervertebral disk
c. elbow joint

Answer 1

a. sutures of skull = fibrous joint: limited/no movement

b. intervertebral disk = cartilaginous joint: some movement

c. elbow joint = synovial joint: moveable

Question 2

what type of cartilage contains Type I collagen?

Answer 2

fibrocartilage - type I collagen

hyaline and elastic cartilage have Type II collagen

Question 3

from what embryonic tissue (specifically) do the somites originate from?

Answer 3

paraxial mesoderm: bilateral columns alongside midline, differentiates into somites

somitic mesoderm cells differentiate into sclerotome, dermatome, or myotome

Question 4

into what 3 components do the somitic mesoderm cells (from paraxial mesoderm tissue) differentiate, and what do these become, respectively?

Answer 4

1. sclerotome: form cartilage and tendons/ligaments around the midline + axial skeleton (except sternum)
2. dermatome: form dermis of the back
3. myotome: form skeletal muscles of the body wall and migrate to form skeletal muscles of limbs

Question 5

into what 2 components does the lateral plate mesoderm divide?

Answer 5

1. parietal/somatic mesoderm: form connective tissue away from the midline (cartilage, tendons/ligaments, bones of appendicular skeleton + sternum, dermis of skin)
2. visceral/splanchnic mesoderm

Question 6

somitic vs somatic mesoderm

Answer 6

somitic mesoderm: derived from paraxial mesoderm, forms MSK tissues around midline (axial skeleton)

somatic mesoderm: derived from lateral plate mesoderm, forms MSK tissues of appendicular skeleton + sternum

[note that all skeletal muscle initially originates from somite myotome cells, but some of these migrate away from midline to the somatic mesoderm to become appendicular skeleton]

Question 7

from what embryonic tissue is the annulus fibrosis vs nucleus pulposus of the intervertebral disc derived?

Answer 7

sclerotome (paraxial mesoderm somitic cells) —> annulus fibrosis (outer)

notochord —> nucleus pulposus (inner)

Question 8

the sternum + appendicular skeleton (and connective tissues) are derived from _____ mesoderm, while the axial skeleton (and connective tissues) are derived from _____ mesoderm

Answer 8

the sternum + appendicular skeleton (and connective tissues) are derived from somatic mesoderm, while the axial skeleton (and connective tissues) are derived from somitic mesoderm

Question 9

skeletal muscle is derived from _____ mesoderm, which differentiates first into ______, then further into _____

Answer 9

paraxial mesoderm —> somites —> myotomes (containing myoblasts)

myoblasts either remain in somite region (primaxial skeletal muscles of the back) or migrate to somatic mesoderm (primaxial skeletal muscles)

Question 10

amelia vs meromelia vs adactylyl

Answer 10

amelia = complete lack of limb
meromelia = partial lack of limb
adactylyl = absence of digits

due to disruptions in proximal-distal development (from loss of FGF signaling)

Question 11

during which week of embryogenesis do the limbs rotate?

Answer 11

week 7 - this causes the dermatome pattern of innervation of the limbs to be twisted into a spiral (why dermatomes appear diagonal)

Question 12

in the spine, ____ contributes to anterior border of intervertebral foramen, while ______ contributes to posterior border of IV foramen

Answer 12

in the spine, IV disc contributes to anterior border of intervertebral foramen, while zygapophyseal joint contributes to posterior border of IV foramen

Question 13

which ligament contributes to posterior wall of vertebral canal?

Answer 13

ligamentum flavum