Musculoskeletal Embryology I

Question 1

Intraembryonic mesoderm lateral to the notochord and neural tube thickens to form two longitudinal columns of what?

Answer 1

paraxial mesoderm which is segemented into blocks caled somites

Question 2

Sclerotome

Answer 2

the ventromedial part that form the vertebrae and the ribs

Question 3

Dermomyotome

Answer 3

myotome region form myoblasts and dermatome region forms the dermis (fibroblasts)

Question 4

Mesodermal cels give rise to loosely organized embryonic connective tissue called what?

Answer 4

the mesenchyme

Question 5

Intramembranous bone formation

Answer 5

mesenchymal cells form membranous sheaths and the bone is formed by osteoblasts and osteoclasts

Question 6

Endochondral bone formation

Answer 6

the model of the bone is formed by chondrocytes and osteoblasts within the cartilage form bone

Question 7

Vertebrae develop by what formation?

Answer 7

endochondral bone

Question 8

How is the body of each vertebra formed?

Answer 8

resegmentation

Question 9

What does the centrum do?

Answer 9

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

Question 10

The notochord degenerates where the developing vertebral bodies are formed but persists between adjacent vertebral bodies to become what?

Answer 10

nucleus pulposus of intervertebral discs

Question 11

When do chondrification and ossification occur?

Answer 11

6 weeks and 8 weeks

Question 12

If migration and differentiation of sclerotomal cells around the neural tube fails on one side, what results? TEST QUESTION

Answer 12

failure of half of vertebra to form which produces scoliosis of vertebral column

Question 13

What does imperfect fusion of vertebral arches lead to?

Answer 13

spina bifida- this leaves the spinal cord, spinal nerves, and meninges vulnerable to injury

Question 14

What is spina bifida occulta?

Answer 14

the failure of formation of the vertebral arch in lumbar vertebrae although the spinal cord, spinal nerves, and meninges are normal (defect marked by a tuft of overlying hair)

Question 15

What is spina bifida cystica?

Answer 15

more severe, the neural tube fails to close, involve the protrusion of the spinal cord, the meninges, or both through the defects in vertebral arches (usually associated with significant neurological deficits)

Question 16

What are ribs derived from?

Answer 16

the mesenchymal costal processes of throacic vertebrae

Question 17

How does the sternum develop?

Answer 17

from mesenchymal condensations called sternal bars

Question 18

Epaxial divisions of the myotomes form the segmental muscles of what?

Answer 18

the main body axis, the extensor muscles of the neck and vertebral column (deep back muscles)

Question 19

Hypaxial divisions of cervical myotomes form what?

Answer 19

the scalene, prevertebral, geniohyoid, and infrahyoid muslces

Question 20

At limb forming levels, what invades the developing lumb buds and give rise to the limb musculature?

Answer 20

hypaxial myoblasts

Question 21

As the somites develop, each is associated with what?

Answer 21

a corresponding spinal nerve growing out from the neural tube

Question 22

Each spinal nerve with branch to what?

Answer 22

a dorsal ramus to innervate the skin and muscles of the back and a ventral ramus to innervate the skin and muscles of the anterolateral trunk as well as the limbs