Bone Tissue - PowerPoint PPT Presentation

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Bone Tissue

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  1. Bone Tissue • A. Physiology: functions of bone • B. Anatomy: structure of bone • C. Histology of bone • D. Bone homeostasis 1. Remodeling 2. Bone's role in calcium homeostasis

  2. Physiology: Functions of Bone • 1. support • 2. protection • 3. movement • 4. mineral homeostasis • 5. blood cell production (hematopoiesis) • 6. energy storage

  3. Shapes of Bones • 1. long • 2. short • 3. flat • 4. irregular

  4. Types of Bone • 1. compact (dense) • 2. spongy (cancellous)

  5. Long Bone Anatomy • 1. diaphysis • 2. epiphysis • 3. metaphysis • 4. epiphyseal plate (Read bone dvp. pg. 220-227) • 5. articular cartilage • 6. articular surfaces • 7. periosteum a. fibrous b. osteogenic • 8. medullary cavity • 9. endosteum

  6. Bone Cell Types • 1. osteoprogenitor cells • 2. osteoblasts -- (osteogenesis) • 3. osteocytes– (strain sensors) • 4. osteoclasts -- (bone resorption/osteolysis)

  7. Bone Matrix • 1. ground substance (25%) • 2. collagen (25%) • 3. mineral salts (50%) -- tricalcium phosphate (hydroxyapatite) -- ossification

  8. Bone Histology • 1. Haversian system • (osteon) • 2. Haversian canal • 3. lacuna • 4. lamella • 5. canaliculus

  9. Bone and Calcium Homeostasis • 1. remodeling • 2. serves to: • a. resist mechanical stress • b. remove worn bone • c. store calcium (1) parathyroid hormone and vitamin D (2) calcitonin

  10. Less kidney reabsorption (more calcium excretion) (osteogenesis) > 10.5 mg/dL (osteolysis) (Intestinal absorption too) < 9.5mg/dL

  11. CALCITONIN and BLOOD CALCIUM REGULATION negative feedback CONTROLLED CONDITION Normocalcemia (blood calcium = 9.5-10.5mg%) A stress or stimulus causes an increase in blood calcium RETURN TO HOMEOSTASIS Increased bone formation results in increased calcium deposition in bone – Return to normocalcemia RECEPTOR Parafollicular cells of thyroid gland recognize hypercalcemia (blood calcium >10.5 mg% EFFECTORS Reduced osteoclast activity Increased osteoblast activity CONTROL CENTER Parafollicular cells secrete calcitonin

  12. PTH and BLOOD CALCIUM REGULATION negative feedback CONTROLLED CONDITION Normocalcemia (blood calcium = 9.5-10.5mg%) A stress or stimulus causes a decrease in blood calcium RETURN TO HOMEOSTASIS Increased bone breakdown results in increased calcium release to blood – Return to normocalcemia RECEPTOR EFFECTORS Chief cells of parathythyroid glands recognize hypocalcemia (blood calcium <9.5 mg% Increased osteoclast activity Decreased osteoblast activity Increased urine phosphate output Decreased urine calcium output CONTROL CENTER Chief cells secrete PTH end

  13. Bone Growth, Stress and Osteoporosis