Deck · USMLE Step 1
Musculoskeletal, Skin & Connective Tissue
Bone and muscle biology, arthritis, bone disorders and tumors, collagen and connective-tissue disease, dermatology, and MSK/derm pharmacology.
130 cards · audited · SM-2 spaced repetition
Included with the full USMLE Step 1 program — 14 decks, 1,546 cards.
Sample cards
Which cell forms bone by secreting osteoid, and what is its embryologic origin?
The osteoblast forms bone by secreting osteoid (type I collagen + matrix), which it then mineralizes. Osteoblasts derive from mesenchymal stem cells.
What is the origin and function of the osteoclast?
The osteoclast is a large multinucleated cell from the monocyte/macrophage (hematopoietic) lineage that resorbs bone by secreting H+ and acid hydrolases, dissolving hydroxyapatite and collagen.
How does the RANK/RANKL/OPG system regulate osteoclast activity?
Osteoblasts express RANKL, which binds RANK on osteoclast precursors to stimulate their differentiation and activity. Osteoblasts also secrete osteoprotegerin (OPG), a decoy receptor that binds RANKL and inhibits osteoclastogenesis.
What is the difference between endochondral and intramembranous ossification?
Endochondral ossification replaces a cartilage model with bone (forms long bones and the axial skeleton). Intramembranous ossification forms bone directly from mesenchyme without a cartilage intermediate (forms flat bones of the skull, clavicle).
What is the primary mineral component of bone matrix?
Hydroxyapatite, a crystalline calcium phosphate [Ca10(PO4)6(OH)2], deposited on a scaffold of type I collagen.
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