Weeks 9-10 Handout Answers

Weeks 9-10 Handout Answers - Weeks 9-10 Handout TA: Manely...

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Weeks 9-10 Handout TA: Manely Leilah Yafeh 1. Name the two main layers of bone. Why are they significant? Compact bone: increased strength Trabecular: Increased elasticity 2. Name the three main types of cells found in bone. What are their functions? How do they exert their functions? Osteoblasts: Osteoblasts are mononucleated bone forming cells that contribute to linear growth and bone density maintenance in the adult. They produce enzymes and osteoid, a mixture of collagen and proteins that bind to calcium phosphate precipitate and form hydroxyapatite. Osteoblasts are also responsible for osteoclast activation and differentiation. Osteocytes are mature osteoblasts. When osteoblasts age and have laid down osteoid and are completely surrounded by bone matrix, they undergo biochemical and morphological changes and are transformed into osteocytes, which have long finger-like projections that they use to communicate with surrounding osteocytes and osteoblasts. Specifically, osteocytes are important for sensing and relaying mechanosensory input and may play an integral role in weight training induced bone hypertrophy. Osteoclasts are responsible for bone resorption and regulating bone growth and density. They are large, mobile, multinucleated cells that are derived from a monocyte stem cell lineage. Osteocytes retain the lysososmal characteristic of the monocyte precursor in that they form resorption pits, a type of external lysosome. Osteoclasts attach to the bone matrix via integrins and pump out protons via H+/K+ ATPases and they also exocytose proteases. Together, the acidic environment coupled with the proteases dissolve the bone matrix producing free Ca+2, inorganic phosphate, and water. Osteoclasts make cavities in the bone and the osteoblasts fill them in. As we age, starting at age 30, the OB:OC activity rate decreases and bone density falls. 3.
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Weeks 9-10 Handout Answers - Weeks 9-10 Handout TA: Manely...

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