Musculoskeletal Embryology

Question 1

Paraxial mesoderm formation

Answer 1

2 longitudinal columns formed from the intraembryonic mesoderm

Question 2

Somites

Answer 2

segmented blocked formed from the paraxial mesoderm

Question 3

Sclerotome

Answer 3

Ventromedial portion of somites thats forms the vertebrae and ribs

Question 4

Dermatome

Answer 4

Dermis

Question 5

Myotome

Answer 5

myoblasts (primordial cells)

Question 6

Mesenchyme

Answer 6

embryonic connective tissue

Question 7

Intramembranous bone formation

Answer 7

Mesenchyme forms a membranous sheath; osteoblasts/clasts form bone

Question 8

Endochonral bone formation

Answer 8

Chondrocytes form bone; osteoblasts form bone while in cartilage

Question 9

Vertebrae formation (general process)

Answer 9

Sclerotomes form scaffold around notochord/neural tube, chondrification, then ossification

Question 10

Resegmentation

Answer 10

Dense caudal and loose cephalic halves of the sclerotome vertebral scaffolding fuse

Question 11

What is the early structure of the vertebral arch?

Answer 11

Neural arch

Question 12

What part of the intermediate disk does the notochord become?

Answer 12

Nucleus pulposus

Question 13

What embryonic structure forms the annulus fibrosis?

Answer 13

Sclerotomes

Question 14

What week does chondrification take place?

Answer 14

Week 6

Question 15

What week does ossification take place?

Answer 15

Week 8

Question 16

What two structures do myotomes split into?

Answer 16

Dorsal epimere and ventral hypomere

Question 17

Dorsal epimere

Answer 17

Muscles of the main body axis, neck extensor muscles, vertebral/deep back muscles

Question 18

Ventral hypomere

Answer 18

Cervical/ thoracic/ intercostal/ sacrococcygeal/lumbar myotomes, limb musculature

Question 19

What do superficial dermomyotomes develop into?

Answer 19

Dermis of the neck and trunk

Question 20

Hemivertebra

Answer 20

Only half of the vertebrae form resulting in scoliosis

Question 21

Spina bifida

Answer 21

Imperfect fusion of the vertebral arches

Question 22

Spina bifida occult

Answer 22

Lumbar arch is not fully formed, tuff of overlaying hair is a typical finding

Question 23

Spina bifida cystic

Answer 23

Neural tube fails to close, resulting in cord and/ or meninges protruding