University:
MacEwan University
Course:
HLSC 120 | Human Anatomy
Academic year:

2023
Views:

162

Pages:

2
Author:

Arthur M.

A. Bone Remodeling •Remodeling: bone resorbed & deposited@endo/periosteum -Remodeling Units: collections of osteoblasts/osteoclasts 1) BONE DEPOSITION Oblasts secrete osteoia which is mineralized later Req diet rich in protein, vitamins, calcium, phosphorus, etc. • Alkaline Phosphatase: enzyme required for mineralzation of bone 2) BONE RESORPTION • Accomplisned by a clasta •O.clast secretion of -Lysosomal Enzymes: digest organic matrix. HCL (Hydrochloric acid) that dissolves calcium salts Le Dissolve matrix is transcytosed acr. osteoclast cell then secreted into blood •Importance of calcium -Necessary for transm. of nerve impulses, musc. contraction, blood clotting, secr. by glands & nerve cells, cell division Bc of imp. there is a hormonal mechanism that regulates calcium homeostasis 3) CONTROL OF BONE REMODELING •Two control loops: 1) Hormonai Mechanism: maintains Ca?" homeostasis in blood • Primarily controlled by parathyroid hormone (PTH) Falling blood Ca² levels Parathyroid gland release PTH ↓ PTH stims oclasts to degrade b. matrix, rel. Ca2+ ↓ Increased Blood Ca2+ levels •Controlled on lesser extent by calcitonin Rising blood Cast levels. Thyroid gland rel. calcitonin ↓ Oblasts deposit calcium salts. + Falling Blood Ca2+ levels 2) Mechanical & Gravitational forces act on skeleton affecting bone structure • Wolff's law bone grows or remodels in response to forces/demands placed on it •Supporting Wolff's Law: -Curved bones thickest where most likely to buckle -Long bones thickest midway along shaft -Trabeculae in spongy bones form along stress lines - Large bony projections where big muscles attach