1. Skeletal systempart 1: bone Honors Anatomy & Physiology

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. FUNCTIONS 5. BLOOD CELL PRODUCTION • red bone marrow produces RBCs, WBCs, & platelets 6. TRIGLYCERIDE STORAGE • yellow bone marrow stores triglycerides (chemical energy reserve)

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

7. 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

8. metaphysis

9. Articular cartilage

10. Structure of Long Bones 5. PERIOSTEUM • tough , dense, irregular CT surrounds bone wherever it is not covered by hyaline cartilage • helps in repair of fractures • Attachment pt for ligaments 6. MEDULLARY CAVITY • aka Marrow Cavity • space w/in diaphysis that contains yellow bone marrow in adults

11. periosteum

12. Medullary cavity

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

14. 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

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

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

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

18. 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

19. Osteoclasts

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

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

23. 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

24. Compact bone

25. 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

26. Spongy bone

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

28. Bone growth: longer

29. Bone growth: wider

30. 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

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

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

33. 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

35. 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

36. Types of Fractures of Bone

37. Types of Bone Fractures

38. Types of Bone Fractures

39. Types of Bone Fractures

40. Fracture Repair

41. 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)

42. 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)

44. 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