bone development

Question 1

roles that specific bone cells play in formation of bone tissue

Answer 1

osteogenic –> stem cells

osteoblasts –> forms new bone

osteocytes –> mature bone cell in bone matrix

osteoclasts –> bone breakdown

Question 2

intramembranous formation

Answer 2

occurs within membrane of mesenchymal connective tissue

steps
1. mesenchymal cells grouped into clusters around vessel and become osteoblasts to secrete osteoid
3. form ossification center
4. osteoid traps osteoblasts to become osteocytes
5. osteoid production and mineralization continue
6. trabecular matrix of immature spongy bone forms
7. external mesenchyme forms periosteum
8. compact bone develops from spongy bone
9. central spongy bone matures

Question 3

what bones are formed from endochondral bone formation

Answer 3

most bones

Question 4

what bones are formed from intramembranous formation

Answer 4

flat bones of skull, clavicle, and mandible

Question 5

endochondral bone formation

Answer 5

uses hyaline cartilage as template

steps
1. cartilage model from mesenchyme
2. mesenchymal cells differentiate into osteoblasts to secrete osteoid (bony collar)
3. chondrocytes hypertrophy to form 1st ossification center (cuts of circulation)
4. deterioration forms cavity
5. cartilage on ends grows
6. periosteal bud (nerves/marrow)
7. osteoblasts form spongy bone
8. osteoclasts break down spongy bone to open medullary cavity
9. secondary ossification after birth where spongy bone is retained

Question 6

osteoblasts in bone growth, repair, remodeling

Answer 6

responsible for building new bone (growth)

works with osteoclasts which remove old bone and form new (repair/remodeling)

Question 7

osteoclasts during bone growth, repair, remodeling

Answer 7

osteoclasts make space for growth, repair, and remodeling of bone by breaking it down

Question 8

interstitial vs appositional growth

Answer 8

longitudinal: growth in length from epiphyseal plate

appositional: growth in diameter in which osteoclasts absorb old bone in endosteal surface and osteoblasts produce new bone in periosteal surface

Question 9

process of longitudinal growth

Answer 9

reverse cartilage in epiphyseal end
1. cell proliferation = multiplication and organization of chondrocytes
2. cell hypertrophy = growth of chondrocytes
3. calcification = connects epiphyseal plate of diaphysis
4. bone deposition = dead chondrocytes are converted to longitudinal channels, osteoblasts form concentric lamellae
5. when growth plate closes = full ossification

Question 10

hormonal regulation of skeletal growth

Answer 10

growth hormone: stimulates elongation of bone/cartilage at epiphyseal plate

thyroid hormone: enhances growth hormone

sex hormone: stimulate osteoblasts (growth during puberty)

Question 11

role of parathyroid hormone

Answer 11

increased osteoclast activity, decreased urinary excretion, increased synthesis of calcitriol
–> raises calcium levels

Question 12

role of calcitriol hormone

Answer 12

increases intestinal absorption of calcium and phosphate, decreases urinary excretion of calcium and stimulates osteoclast activity
–> raises calcium levels

Question 13

role of calcitonin hormone

Answer 13

increases mineralization in the bones, decreases activity of osteoblasts, increases urinary excretion
–> lowers calcium levels

Question 14

bone repair and remodeling

Answer 14

occurs in response to exercise or injury (hormone = if and when; stress = where)

Question 15

steps in fracture repair

Answer 15

1. hematoma formation
2. soft callus formation between broken ends
3. hard callus conversion to become bony collar
4. remodeling where osteoclasts eats old bone cells and osteoblasts from new bone

Question 16

how does the skeletal system participate in homeostasis of plasma calcium levels

Answer 16

acts as reservoir of calcium:
when levels are high –> calcium is deposited in bones
when levels are low –> release of calcium into blood

Question 17

osteoporosis

Answer 17

bone resorption outpaces bone deposit (weak bone)

Question 18

osteomalacia

Answer 18

poor bone mineralization which results in weak and soft bones (calcium deficiency)

Question 19

pagets disease

Answer 19

haphazard bone deposit/resorption which leads to high proportion of spongy bone