Musculoskeletal Embryology I

Question 1

Intraembryonic mesoderm lateral to notochhord and neural tube thickens to form two longitudinal columns of ___ ____

Answer 1

paraxial mesoderm

Question 2

By the end of the third week, the paraxial mesoderm becomes segmented into blocks - the ____ (42-44 pairs)

Answer 2

somites

Question 3

Each somite differentiates into two parts. What is the ventromedial part that form the vertebrae and ribs called?

Answer 3

Sclerotome

Question 4

Each somite differentiates into two parts. What is the dorsolateral part called?

Answer 4

dermomyotome

Question 5

The myotome region of the dermomyotome forms ____

Answer 5

myoblasts

Question 6

The dermatome region of the dermomyotome forms the ____

Answer 6

dermis

Question 7

Mesodermal cells give rise to loosely organized embryonic connective tissue called the ___

Answer 7

mesenchyme

Question 8

in this process, mesenchymal cells from membranous sheaths, and the bone is formed by osteoblasts and osteoclasts within the membranous model

Answer 8

intramembranous bone formation

Question 9

in this process, the model of bone is formed by chondrocytes and osteoblasts within the cartilage form bone

Answer 9

endochondral bone formation

Question 10

Vertebrae develop by ___ bone formation

Answer 10

endochondral

Question 11

At week ___, the sclerotomes appear as paired condensations of mesenchymal cells, migrate around the notochord and neural tube to merge from the opposing somite

Answer 11

4

Question 12

The body of each vertebra is formed by ____. The densely packed caudal half of one sclerotome grows and fuses with the loosely arranged cephalic half of the next caudal sclerotome to form the mesenchymal ____, the primordium of vertebral body.

Answer 12

resegmentation; centrum

Question 13

The _____ surrounds the notochord and serves as bony floor for the spinal cord

Answer 13

centrum

Question 14

The dorsal mesenchymal cells that surround the neural tube form the ___ ___, which is the primordium of the vertebral arch

Answer 14

neural arch

Question 15

The notochord degenerates where the developing bodies are formed but persists between adjacent vertebral bodes to become the ___ ___ of intervertebral discs

Answer 15

nucleus pulposus

Question 16

This outer part of the intervertebral discs is formed by original sclerotomal cells that migrate into that site

Answer 16

annulus fibrosus

Question 17

At six weeks, ____ centers appear in each vertebra and ____ begins during the eight week

Answer 17

chondrificaiton; ossification

Question 18

In normal circumstances, the developing vertebral bodies are formed from migration sclerotomal cells around the neural tube and appearance of chondrification centers that soon unite. If this migration and differentiation fails on one side, results in the failure of half of vertebra to form. These vertebral defects produce ____ of the vertebral column

Answer 18

scoliosis

Question 19

some lateral mesenchymal condensations called ___ processes develop in association with vertebral arches of all the developing neck and trunk vertebrae

Answer 19

costal

Question 20

In cervical vertebrae, the costal and transverse process give rise to lateral and medial boundaries of ___ foramen.

Answer 20

transverse

Question 21

At birth, each vertebra consists of three bony parts connected by cartilage. The bony halves of the vertebral arches fuse during __ to ___ years of life.

Answer 21

3; 5

Question 22

Imperfect fusion of vertebral arches can lead to a condition called ___ __, which leaves the spinal cord, spinal nerves and meninges vulnerable to injury

Answer 22

spina bifida

Question 23

This type of spina bifida is the failure of formation of the vertebral arch in lumbar vertebrae, although the spinal cord, spinal nerves, and meninges are normal. The defect is often marked by a tuft of overlying hair.

Answer 23

spina bifida occulta

Question 24

This type of spina bifida is more severe. The neural tube fails to close, and involves the protrusion of the spinal cord, the meninges, or both through the defects in vertebral arches. These defects are usually associated with significant neurological deficits.

Answer 24

spina bifida cystica

Question 25

True or false? Ribs are cartilaginous during the embryonic period but begin to ossify during fetal development.

Answer 25

true

Question 26

The lower 5 ribs have no connection to the ___

Answer 26

sternum

Question 27

The sternum develops independenttly from mesenchymal condensations called ___ ___, that are located in the ventrolateral body wall

Answer 27

sternal bars

Question 28

Each myotome splits into two structures, the dorsal epimere and ventral hypomere, which forms ___ and ____ muscles respectively

Answer 28

epaxial; hypaxial

Question 29

_____ divisions of the myotomes form the segmental muscles of the main body axis, the extensor muscles of neck, and the vertebral column (deep back muscles)

Answer 29

epaxial

Question 30

What happens to the embryonic extensor muscles that are derived from sacral and coccygeal myotomes?

Answer 30

they degenerate note: their adult derivatives are the dorsal and sacrococcygeal ligaments

Question 31

____ divisions of cervical myotomes form the scalene, prevertebral geniohyoid, and infra hyoid muscles

Answer 31

hypaxial

Question 32

The ____ myotomes form the lateral and ventral flexor muscles of the vertebral column (rectus abdominus, external abdominal oblique, transverse abdominus)

Answer 32

throacic

Question 33

The intercostal muscles are derived from the ___ myotome

Answer 33

hypaxial

Question 34

At limb forming levels, the hypaxial ___ also invade the developing limb buds and give rise to limb musculature

Answer 34

myoblasts

Question 35

The ___ myotomes form the quadratus lumborum muscle

Answer 35

lumbar

Question 36

Dermatome will become the dermis of the ___ and ___

Answer 36

neck; trunk

Question 37

As the somites develop, each is associated with a corresponding ___ ___ growing out from the neural tube.

Answer 37

spinal nerve

Question 38

each circumferential band of skin on the trunk receives sensory innervation from a single pair of ___ ___ spinal nerves

Answer 38

segmentally related