//fpnotebook.com/
Bone Physiology
Aka: Bone Physiology, Osteoblast, Osteoclast, Cortical Bone, Trabecular Bone
- See Also
- Bone Densitometry
- Bone Turnover Biochemical Marker
- Osteoporosis
- Paget's Disease of Bone
- Bone Types
- Cortical Bone (80%)
- Outer supporting structure (Dense)
- Sites
- Radius
- Skull
- Long bones
- Peak density: age 30 to 40 years
- Trabecular Bone (20%)
- Inner supporting structure (Spongy)
- Sites
- Hip
- Spine
- Femur
- Physiology
- Microfractures occur via everyday wear and tear
- Healed by ongoing bone remodeling
- Bone Remodeling
- Bone remodeling occurs in 120 day cycles
- Resorption by Osteoclasts over first 20 days
- Bone formation by Osteoblasts over last 100 days
- Osteoblasts
- Fill in bony cavity with bone matrix
- Triggers for activity
- Parathyroid Hormone
- Thyroxine
- Growth factors
- Interleukins (1, 6, 11)
- Insulin-Like Growth Factors
- Transforming Growth factor-B
- Releases Cytokines to attract Osteoclasts
- Osteoclasts
- Release proteases
- Dissolves bone mineral matrix
- Dissolves collagen
- Clears away damaged bone
- Releases matrix-bound growth factors
- Chemoattractant for Osteoblasts
- Chemicals involved in bone formation
- Calcitonin
- Inhibits bone resorption
- Inhibits intestinal Calcium, Phosphorus absorption
- Inhibits renal Calcium excretion
- Inhibits calcitriol production in Kidney
- Calcitriol
- Increases intestinal Calcium absorption
- Increases intestinal Phosphorus absorption
- Increases intestinal Magnesium absorption
- Decreases Parathyroid Hormone secretion
- Parathyroid Hormone
- Mobilizes Calcium and Phosphorus from bone
- Increases Calcitriol
- References
- Rosen (1998) Postgrad Med 104(4):101-14 [PubMed]