Unit II: Skeletal System

Question 1

What are somites?

Answer 1

Segmented paraxial mesoderm

Question 2

What does sclerotome give rise to?

Answer 2

Vertebrae and ribs

Question 3

What does dermomyotome give rise to?

Answer 3

Muscle and skin

Question 4

Sclerotomes form a loosely woven embryonic CT called ___

Answer 4

Mesenchyme

Question 5

Mesenchyme is derived from ___

Answer 5

Neural crest cells

Question 6

Mesenchyme may differentiate into:

Answer 6

1. fibroblasts
2. chondroblasts
3. osteoblasts

Question 7

What is intramembranous ossification?

Answer 7

Bone develops from mesenchyme directly within membranous sheaths

Question 8

What is endochondral ossification?

Answer 8

Hyaline cartilage models-> then ossify

Question 9

What encloses the brain?

Answer 9

Neurocranium

Question 10

What forms the face?

Answer 10

Viscerocranium

Question 11

Mesenchyme that forms the skull is derived from ___

Answer 11

Neural crest cells

Question 12

Which cells are susceptible to teratogens as they migrate?

Answer 12

Neural crest cells

Question 13

What does membranous neurocranium form?

Answer 13

Skull vault

Question 14

What does cartilaginous neurocranium form?

Answer 14

Base of the skull

Question 15

Notes on the anterior fontanelle

Answer 15

1. largest
2. closes at 1.5 years
3. “soft spot”

Question 16

Notes on the posterior fontanelle

Answer 16

Closes at 3 months

Question 17

4 fontanelles

Answer 17

1. anterior
2. posterior
3. anterolateral
4. posterolateral

Question 18

What is craniosynostosis?

Answer 18

Prenatal fusion of sutures

Question 19

What is scaphocephaly?

Answer 19

1. premature fusion of sagittal suture
2. skull is long, narrow, wedge-shaped
3. 50% of cases

Question 20

What is brachycephaly?

Answer 20

1. premature fusion of coronal suture

2. high, tower-like skull

Question 21

What is trigonocephaly?

Answer 21

1. premature fusion of frontal suture

2. eyes are far apart

Question 22

What is acrania?

Answer 22

1. partial or complete absence of the neurocranium
2. associated with defects of vertebral column and brain
3. incompatible with life

Question 23

What is the viscerocranium formed from?

Answer 23

Neural crest cells

Question 24

Uppermost cells of the caudal part form the ___ of the intervertebral disc

Answer 24

Anulus fibrosus

Question 25

3 primary centers of ossification of vertebrae

Answer 25

1. centrum- body

2. neural arch- arches

Question 26

5 secondary centers of ossification of vertebrae

Answer 26

1. spinous process
2. TVP
3. anular epiphyses

Question 27

What is Klippel-Feil Syndrome?

Answer 27

1. short neck, fused vertebrae, etc

2. genetic mutation

Question 28

What is a hemivertebrae?

Answer 28

1. chondrification centers fail to appear

2. congenital scoliosis

Question 29

Which condition doesn’t have the characteristic of fused cervical vertebrae?

Answer 29

Hemivertebrae

Question 30

What are accessory ribs?

Answer 30

1. lumbar- most common, no symptoms

2. cervical- C7, neuromuscular symptoms

Question 31

What is pes excavatum?

Answer 31

1. concave depression at lower sternum
2. overgrowth of lower costal cartilages
3. more common in boys

Question 32

Which is the first bone to begin ossification?

Answer 32

Clavicle

Question 33

Which is the second bone to begin ossification?

Answer 33

Femur

Question 34

What is achondroplasia?

Answer 34

1. dwarfism
2. disturbance in endochondral ossification
3. autosomal dominant