NUR 0012 Lecture 14 Anatomy and Physiology 1 Lecture: Jake DechantOutline of Last Lecture I. Bone continuedA. Long bone1. Compact/corticala. Osteonsb. Central canalc. Perforating/Volkman’s canald. Concentric lamellaee. Interstitial lamellaef. Circumferential lamellae2. Concellous/spongy3. Proximal epiphysis4. Diaphysis5. Distal epiphysis6. Epiphyseal line7. Periosteum8. Yellow bone marrow9. EndosteumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.B. Bone cells: osteocytes, osteoblasts, osteoclasts, osteogenic Outline of Current LectureI. Ch. 6 continuedA. Hydroxyapatite B. Intramembranous ossificationC. Endochondral ossificationD. Bone growthE. Bone remodeling and calcium homeostasisCurrent LectureI. Ch. 6 continuedA. Hydroxyapatite crystals: main inorganic component of bone matrix (35% organic, 65% inorganic)B. Intramembranous ossification: occurs mainly in flat bones of the skull and clavicle1. Ossification centers appear in fibrous connective tissue membranea. Selected centrally located mesenchymal cells cluster and differentiate intoosteoblasts, forming an ossification center2. Bone matrix (osteoid) secreted within fibrous membrane and calcifiesa. Osteoblasts begin to secrete osteoid3. Woven bone (very loosely organized spongy bone) and periosteum form4. Lamellar bone replaces woven bone, just deep to the periosteum, red marrow appearsC. Endochondral ossification: starts with a hyaline cartilage model1. Bone collar forms around hyaline cartilage model2. Cartilage in the center of diaphysis (primary ossification center location) calcifies and then develops cavities (cavitation), blood vessels can now easily invade shaf3. Periosteal bud invades internal cavities and spongy bone begins to form4. Diaphysis elongates and a medullary cavity forms as ossification continues. Secondary ossification centers appear in the epiphyses (secondary ossification center location) in preparation for stage 55. Epiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages (lef over from hyaline cartilage model)D. Bone can’t grow interstitially like cartilage or ligaments1. Bones increase thickness via appositional growth2. Zone of resting cartilage3. Proliferation zone: cartilage cells undergo mitosis4. Hypertrophic zone: older cartilage cells enlarge/grow 5. Calcification zone: matrix becomes calcified, cartilage cells die, matrix begins to deteriorate6. Ossification zone: calcified cartilage converted by osteocytes into new bone E. Bone remodeling is in equilibrium for most our lives1. Calcium homeostasis of blood: 9-11 mg/100 mL2. Falling blood Ca2+ levels: parathyroid glands release parathyroid hormone (PTH)3. Osteoclasts triggered to degrade bone matrix and release Ca2+ into blood bringing the level back up to normal 4. Problem: bones can get very weak/brittle5. Several hormones interact to help maintain calcium homeostasis in bodya. Calcitriol (Vitamin D): increases blood levels of Ca, aids in absorption of Ca in digestive tract, ensures Ca we take in as part of our diet gets absorbed1) From melanocytes when exposed to sunlightb. PTH: increases blood levels of Cac. Calcitonin: secreted by thyroid gland, decreases blood levels of Ca, has a weaker and weaker effect of depositing bone as you
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