Development of MSK

Question 1

What do cells derived from the primitive node create bilaterally along the neural tube?

Answer 1

Paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm

Question 2

What does the notochord form?

Answer 2

Nucleus pulposus

Question 3

What does the paraxial mesoderm form?

Answer 3

Head and somites

somites form: Sclerotome, myotome, dermatome, syndetome, endothelial cells

Question 4

What does the intermediate mesoderm form?

Answer 4

Kidney and gonads

Question 5

What does the lateral plate mesoderm form?

Answer 5

Splanchic (circulatory system), somatic (limb bones, body cavity, pelvis), extraembryonic

Question 6

At what stage in development does the paraxial mesoderm differentiate and form bilateral somite pairs?

Answer 6

At the end of the 3rd week

Question 7

In what sequential fashion to somites form?

Answer 7

Cranial to caudal

Question 8

By the end of the 5th week, how many somite pairs have formed?

Answer 8

42-44

Question 9

What do the somites create?

Answer 9

Sclerotome, myotome, dermatome

Question 10

Shortly after forming, each somite separates into subdivisions, what are those subdivisions?

Answer 10

Ventromedial, dorsal, intermediate

Question 11

What does the ventromedial subdivision of the somite create?

Answer 11

Sclerotome

Question 12

What does the dorsal subdivision of the somite create?

Answer 12

Dermamyotome – dermatome and myotome eventually

Question 13

What does the intermediate subdivision of the somite create?

Answer 13

Syndetome = tendons of the vertebral column

Question 14

The sclerotome will then further migrate and differentiate, what regions will it form?

Answer 14

Ventral, dorsal and lateral migrations

Question 15

Where does the ventral sclerotome go and what will it form?

Answer 15

To surround the notochord to form the vertebral bodies

Question 16

Where does the dorsal sclerotome go and what will it form?

Answer 16

To surround the neural tube to form the vertebral arch and spine

Question 17

Where does the lateral sclerotome go and what will it form?

Answer 17

Out laterally to form the transverse processes and ribs

Question 18

How does the neural tube and notochord become fully enclosed in sclerotome?

Answer 18

Because the somites are BILATERAL pairs

Question 19

Sclerotomes are then divided cranial and caudal subdivisions due to what?

Answer 19

Gene expression and cell density
Cranial = loosely packed cells
Caudal = densely packed cells

Question 20

What divides the cranial and caudal subdivisions of one sclerotome?

Answer 20

Intrasegmental boundary (von ebner’s fissure)

Question 21

What cells help to form the IV disc?

Answer 21

Caudal cells

Question 22

The remaining caudal cells then fuse with what?

Answer 22

Cranial cells adjacent to them to form the centrum

Question 23

The notochord expands to form the nucleus pulposus and the caudal cells that migrated there do what?

Answer 23

Surround the notochord to form the annulus fibrosis

Question 24

At what day in development do ribs begin to extend?

Answer 24

Day 35

Question 25

Paired sternal bars arise form what layer?

Answer 25

Somatic layer of the lateral plate mesoderm

Question 26

What gene codes for vertebral identity?

Answer 26

Hox

Question 27

If Hox10 is removed, what vertebrae will form?

Answer 27

Thoracic

Question 28

If Hox10 is added to another layer it is not commonly found, what vertebrae will form?

Answer 28

Lumbar

Question 29

Pectus excavatum

Answer 29

Depressed sternum

Question 30

Pectus carinatum

Answer 30

Anteriorly protruding sternum

“pigeon chest”

Question 31

Describe myogenesis

Answer 31

Mesenchymal cells become myoblasts
myoblasts fuse to form myotubes
Myofilaments form in cytoplasm of myotubes

Question 32

When is most skeletal muscle developed?

Answer 32

Before birth and by 1 year of age

Question 33

What does the myotome divide into?

Answer 33

Epimere and hypomere

Question 34

What will the epimere become?

Answer 34

Epaxial muscles of the neck and back

Question 35

What will the hypomere become?

Answer 35

Hypaxial muscles everywhere else

Question 36

What innervates epaxial muscles?

Answer 36

Dorsal rami

Question 37

What innervates hypaxial muscles?

Answer 37

Ventral rami

Question 38

What is poland syndrome?

Answer 38

Absence of pectoralis minor and partial loss of pectoralis major
Ipsilateral breast hypoplasia
More frequent in males

Question 39

What is prune belly syndrome?

Answer 39

Loss of abdominal musculature; fluid accumulates that distends the abdomen
Can also result in cryptorchidism - failure of 1 or both testes to descend

Question 40

What myotome division is responsible for poland syndrome and prune belly syndrome?

Answer 40

Hypomere