MS - Anat & Phys (Bone)

Question 1

What are 3 locations of bone that undergo endochondral ossification?

Answer 1

Bones of axial and appendicular skeleton, and base of the skull

Question 2

Explain endochondral ossification.

Answer 2

Cartilaginous model of bone is first made by chrondrocytes. Osteoclasts and osteoblasts later replace with woven bone and then remodel to lamellar bone.

Question 3

In what 2 contexts does woven bone occur in adults?

Answer 3

In adults, woven bone occurs after fractures and in Paget disease

Question 4

What are 2 locations of bone that undergo membranous ossification?

Answer 4

Bones of calvarium and facial bones

Question 5

Explain membranous ossification.

Answer 5

Woven bone formed directly without cartilage. Later remodeled to lamellar bone.

Question 6

What is the function and mechanism of osteoblasts?

Answer 6

Build bone by secreting collagen and catalyzing mineralization; Think: “osteoBlasts Build Bone”

Question 7

From what cells do osteoblasts differentiate, and where?

Answer 7

Differentiate from mesenchymal stem cells in periosteum

Question 8

What is the significant histology/morphology, function, and mechanism of osteoclasts?

Answer 8

Multinucleated cells that dissolve bone by secreting acid and collagenases

Question 9

From what cells do osteoclasts differentiate?

Answer 9

Differentiate from monocytes/macrophages

Question 10

What effects does parathyroid hormone have on bone at low, intermittent versus chronic high levels?

Answer 10

AT LOW, INTERMITTENT LEVELS, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect). CHRONIC HIGH PTH LEVELS (primary hyperthyroidism) cause catabolic effects (osteitis fibrosa cystica)

Question 11

What condition can cause chronic high PTH levels? What condition can result from the effects of chronic high PTH levels?

Answer 11

CHRONIC HIGH PTH LEVELS (primary hyperthyroidism) cause catabolic effects (osteitis fibrosa cystica)

Question 12

What effects does estrogen have on bone?

Answer 12

Estrogen inhibits apoptosis in bone-forming osteoblast and induces apoptosis in bone-resorbing osteoclasts

Question 13

What are 2 causes of estrogen deficiency? What impact may estrogen deficiency have on bone?

Answer 13

Under estrogen deficiency (surgical or postmenopausal), excess remodeling cycles and bone resorption lead to osteoporosis