1. Skeletal System1 Honors Anatomy copy version

2. Bone • a combination of CT, epithelial & nervous tissues • 18% of weight of human body • Skeletal System includes bones & cartilage • Part 1: Bone • Part 2: Axial Skeleton • Part 3: Appendicular Skeleton • Part 4: Joints

3. FUNCTIONS • SUPPORT • skeleton serves as structural framework by supporting soft tissues & providing attachments for tendons of muscle 2. PROTECTION • Protects most important soft tissue organs from injury

4. FUNCTIONS 3. MOVEMENT • Skeletal muscles attach to bones, when the muscle contract the bones move 4. MINERAL HOMEOSTASIS • Bone stores calcium, phosphorus which both help make bone strong • If body needs these minerals bone releases them

5. Parts of a long bone • Diaphysis: shaft or body; the long cylindrical portion of the bone 2. Epiphysis: distal & proximal ends of bone

6. Parts of a long bone 3. Metaphysis: • region between diaphysis & epiphysis • in growing bone includes metaphyseal plate (hyaline cart. that allows bone to lengthen 4. Articular Cartilage: • layer of hyaline cartilage covering part of epiphysis where bone forms a joint with articulating bone

7. metaphysis

8. Structure of Long Bones 7. ENDOSTEUM • thin membrane that lines marrow cavity • contains 1 layer of bone-forming cells and CT

9. Histology of bone • bone consists of widely separated cells surrounded by large amts extracellular matrix • *bone is hard due to crystallized inorganic mineral salts • *bone is flexible due to collagen

10. Types of Bone Cells • OSTEOGENIC CELLS • Stem cells from mesenchyme (origin of all CT) • only bone cells to divide

11. Types of Bone Cells 2. OSTEOBLASTS • bone-building cells • synthesize & secrete collagen fibers • initiate calcification

12. Types of Bone Cells 3. OSTEOCYTES • mature bone cells • main cells in bone • maintain exchange of nutrients & wastes with blood

13. Types of Bone Cells 4. OSTEOCLASTS • huge cells that form by merging of many (50)monocytes • in endosteum • ruffled border faces bone surface: releases lysosomal enzymes & acids that digest underlying bone (bone resorption): part of normal maintenance, growth, development, & repair of bone

14. Types of bone (2) • Compact bone • few open spaces • outer bone layer of all bones • Spongy bone • inside bones

15. COMPACT BONE • strongest form of bone • beneath periosteum of all bone • functions: • protection & support • resists stresses produced by weight & movement

16. Parts of Compact Bone • OSTEON: • aka Haversian Systems • repeating units thru out compact bone • each one has central canal with concentrically arranged lamellae (rings), lacunae (filled with 1 osteocyte) • aligned in same direction along lines of stress • space between osteon filled with interstial lamellae

17. Compact bone

18. Spongy Bone • absence of osteons • made of lamellae arranged in irregular columns called trabeculae • makes up most of inside of short, flat, or irregular bones & epiphysis of long bones • lighter than compact bone • Function: • support & protect red bone marrow

19. Spongy bone

20. Bone growth • longer: • @ epiphyseal plate • wider: • called appositional growth • periostealosteoblasts on outer surface of bone • osteoclast remove compact bone inner border

21. Bone growth: longer

22. Bone growth: wider

23. Bone Remodeling • Most bones are formed b/4 birth but each one continually renews itself for rest of life • ~5% of bone being remodeled @ any given time • bone remodeling is the ongoing replacement of old bone tissue by new bone tissue • Bone Resorption • Bone Deposition

24. Bone Resorption • removal of minerals & collagen fibers from bone by osteoclasts • results in destruction of bone extracellular matrix

25. Bone Deposition • addition minerals & collagen fibers to bone by osteoblasts

26. Factors AffectingBone Growth & Remodeling • Minerals • Ca, P, F, Mg, Fe, Mn • Vitamins • C needed to make collagen fibers & for osteoblast osteocyte • E & B12 needed for protein synthesis • Hormones • IGF’s in childhood (insulin-like growth factors) • estrogens & androgens important in puberty

27. Fracture & Repair of Bone • Fracture: any break in a bone • Fractures named by: • severity • shape or position of fracture line • person who 1st described it

28. Fracture Repair

29. Calcium Homeostasis • Bone is body’s main reservoir for calcium (stores 99% of total body Ca) • Normal blood level Ca 9 -11 mg/100mL • Calcium important for: • Muscle contraction • Nerve impulses • Blood clotting • Many enzymes require Ca as cofactor)

30. Control of Calcium • 2 hormones control Ca in/out bone: • Calcitonin • Decreases blood Ca levels by putting more Ca into bone • Parathyroid Hormone (PTH) • Increases blood Ca levels by taking Ca out of bone (increasing osteoclastresorption)

32. Homeostatic Imbalances in Bone • Osteoporosis • condition of porous bones (resorption > deposition) • causes: deficient Ca in diet • USA: > 1 million fractures (hip, wrist, vertebrae) & afflicts 30 million Americans • decreased stature, hunched back, bone pain

33. Homeostatic Imbalances in Bone • Osteoporosis • condition of porous bones (resorption > deposition) • causes: deficient Ca in diet • USA: > 1 million fractures (hip, wrist, vertebrae) & afflicts 30 million Americans • decreased stature, hunched back, bone pain