B6-068 Bone Development

Question 1

osteocytes maintain bone matrix/calcium homestasis via […] which regulates serum phosphate

Answer 1

FGF23

Question 2

what germ layer generates the axial skeleton?

Answer 2

paraxial mesoderm

Question 3

what germ layer forms the appendicular/limb skeleton?

Answer 3

parietal/somatic layer of the lateral plate mesoderm

Question 4

what germ layer forms the craniofacial bones?

Answer 4

neural crest cells

Question 5

mesenchyme differentiates directly into osteoblasts, which form bone

Answer 5

intramembranous ossification

Question 6

the flat bones of the skull are formed via

Answer 6

intramembranous ossification

frontal, parietal, and upper occipital

Question 7

what bones are formed via endochondral ossification?

Answer 7

lower occipital
long bones of limbs
vertebrae
ribs
sternum

Question 8

lengthens due to ossification that occurs at the growth plates

Answer 8

diaphysis

**contains primary ossification center

Question 9

the primary ossification center develops in the

Answer 9

diaphysis

Question 10

secondary ossification occurs at […]

Answer 10

two growth plates

Question 11

the two growth plates of secondary ossification are located where?

Answer 11

between epiphyses and metaphyses

Question 12

how does vascularization occur in endochondral ossification?

Answer 12

chondrocytes secrete MMPs to degrade ECM
blood vessels invade those new spaces and bring osteoprogenitors

Question 13

5 zones of the epiphyseal plate

Answer 13

reserve/resting zone
proliferation zone
hypertrophic cartilage zone
zone of calcification of cartilage
zone of ossification

Question 14

[what zone?]
chondrocytes anchor plate to osseous tissue of epiphysis

Answer 14

reserve/resting zone

Question 15

[what zone?]
chondrocytes proliferate

Answer 15

proliferation zone

Question 16

[what zone?]
chondrocytes increase in size; accumulate ALP

Answer 16

hypertrophic cartilage zone

Question 17

[what zone?]
cartilaginous matrix calcifies, chondrocytes secrete MMPs and apoptose

Answer 17

zone of calcification of cartilage

Question 18

[what zone?]
chondroclasts on diaphyseal side break down calcified cartilage and osteoblasts and replace with mineralized bone

Answer 18

zone of ossification

Question 19

most common form of skeletal dysplasia

Answer 19

achondroplasia

Question 20

achondroplasia is caused by a mutation in […] that affects ability of cartilage to form bone

Answer 20

FGF receptor 3

Question 21

affects endochondral ossification resulting in short limbs, large skull, small midface, and prominent forehead

Answer 21

achondroplasia

Question 22

90% of babies with disproportionate dwarfism have

Answer 22

achondroplasia

Question 23

inhibits the proliferation and hypertrophic differentiation of cartilage cells when activated

Answer 23

FGF receptor 3

Question 24

a defective FGFR3 gene leads to

Answer 24

constitutive activation of FGFR3

-inhibits chondrocyte proliferation in zone of proliferation
-inhibits chondrocyte differentiation and hypertrophy in zone of hypertrophy
-slows ossification in zone of ossification

Question 25

conditions of hyperpituitarism [2]

Answer 25

acromegaly gigantism

Question 26

caused by a severe maternal deficiency of vitamin D

Answer 26

congenital ricketts

Question 27

linked to defects in COL1A1 or COL1A2

Answer 27

osteogenesis imperfecta

Question 28

head bones that protect the brain and sensory organs

Answer 28

neurocranium

Question 29

head bones that form the face, palatal bones

Answer 29

viscerocranium

Question 30

the membranous part of the neural cranium forms the [3]

Answer 30

frontal parietal **upper** occipital

Question 31

narrow seams of connective tissues that temporarily separate flat bones of the skull

Answer 31

sutures

Question 32

wide sutures where >2 bones meet

Answer 32

fontanelle

Question 33

the sutures and fontanelles of the skull eventually close via [...]

Answer 33

intramembranous ossification

Question 34

prechordal chondrocranium is derived from

Answer 34

neural crest

Question 35

chordal chondrocranium is derived from

Answer 35

paraxial mesoderm

Question 36

the prechordal and chordal cartilages of the neurocranium eventually fuse via [...]

Answer 36

endochondral ossification

Question 37

the viscerocranium is formed via [....] ossification

Answer 37

intramembranous

Question 38

the viserocranium is derived from

Answer 38

neural crest

Question 39

[...] cells are vulnerable to ethanol, retinoic acid

Answer 39

neural crest

Question 40

prematures closure of sutures

Answer 40

craniosynostosis

Question 41

premature closure of the sagittal suture results in

Answer 41

long, narrow head prominent fontal and occipital regions

Question 42

unilateral premature closure of the coronal suture

Answer 42

plagiocephaly

Question 43

plagiocephaly results in

Answer 43

asymmetric flattening of the skull

Question 44

bilateral premature closure of the coronal suture

Answer 44

brachycephaly

Question 45

brachycephaly results in

Answer 45

tall skull with flat frontal and occipital regions skull shortening in ventral/dorsal axis **coronal fusion

Question 46

delayed closure of fontanelles

Answer 46

cleidocranial dysostosis

Question 47

due to defect in Runx2 gene

Answer 47

cleidocranial dysostosis

Question 48

enlargement of skull bones wide set eyes under-developed clavicles

Answer 48

cleidocranial dysostosis

Question 49

skull fails to expand brain fails to grow to normal size causing intellectual disabilities

Answer 49

microcephaly

Question 50

what happens after re-segmentation during vertebral column formation?

Answer 50

1. lower and upper halves of 2 successive sclerotomes form a vertebrae 2. myotomes bridge the discs 3. arteries pass over vertebral bodies 4. spinal nerves lies near IV discs and leave the vertebral column via bilateral foramina

Question 51

lateral curvature of spine

Answer 51

scoliosis

Question 52

small defects in vertebral arches but spinal cord is relatively intact skin covers defect

Answer 52

spina bifida occulta

Question 53

vertebral arches fail to form neural tube fails to close

Answer 53

spina bifida meningocele

Question 54

sternum depressed posteriorly

Answer 54

pectus excavatum

Question 55

anteriorly projecting sternum

Answer 55

pectus carinatum

Question 56

mesenchymal progenitors differentiate to form chondroblasts which then form chondrocytes that make a cartilage model for subsequent bone formation

Answer 56

endochondral ossification

Question 57

bulging frontal and occipital regions with long and narrow head

Answer 57

premature closure of sagittal suture

Question 58

flat frontal and occipital regions indicates premature closure of

Answer 58

coronal suture

Question 59

responsible for creating new bone from cartilage models that results in lengthening of diaphysis

Answer 59

epiphysis

Question 60

widened region of bone on both ends of long bones near the epiphysis

Answer 60

metaphysis

Question 61

mesenchymal cells differentiate directly into osteoblasts

Answer 61

intramembranous ossification

Question 62

during endochondral ossification, as the matrix calcifies the chondrocytes are cut off from nutrients and apoptose forming the

Answer 62

medullary cavity

Question 63

bones increase in diameter via

Answer 63

appositional growth

Question 64

appositional growth occurs beneath the

Answer 64

periosteum