1. PART 1: BONES

2. made up of CT, epithelial tissue, & nerve tissue 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. 1. 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. 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. 5. BLOOD CELL PRODUCTION red bone marrow produces RBCs, WBCs, & platelets 6. TRIGLYCERIDE STORAGE yellow bone marrow stores triglycerides (chemical energy reserve)

6. 1. DIAPHYSIS: bone’s shaft or body: the long cylindrical, main portion of the bone 2. EPIPHYSIS: distal & proximal ends of the bone

7. 3. METAPHYSIS: Region in mature bone where diaphysis meets epiphysis in growing bone include metaphyseal plate (hyaline cartilage that allows bone to grow in length) 4. ARTICULAR CARTILAGE hyaline cartilage covering part of epiphysis involved in joint reduces friction & absorbs shock @ freely movable joints

9. 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. 7. ENDOSTEUM thin membrane that lines marrow cavity contains 1 layer of bone-forming cells and CT

12. bones are hard due to calcification: calcium carbonate & other minerals (Mg, F, K, S) form crystals around collagen fibers bone hardness depends on crystallized inorganic mineral salts bone flexibility depends on collagen fibers

13. 1. OSTEOGENIC CELLS stem cells from mesenchyme (origin of all CT) only bone cells to divide

14. 2. OSTEOBLASTS bone-building cells synthesize & secrete collagen fibers initiate calcification

15. 3. OSTEOCYTES mature bone cells main cells in bone maintain exchange of nutrients & wastes with blood

16. 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

18. has few spaces strongest form of bone beneath periosteum of all bone provides protection & support and resists stresses produced by weight & movement

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

22. absence of osteons made of lamellae arranged in irregular columns called trabeculae appears spongy but hard 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

24. 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 1. Bone Resorption 2. Bone Deposition

25. removal of minerals & collagen fibers from bone by osteoclasts results in destruction of bone extracellular matrix

26. addition of minerals & collagen fibers to bone by osteoblasts

27. 1. Minerals Ca, P, F, Mg, Fe, Mn 2. Vitamins C needed to make collagen fibers & for differentiation osteoblast  osteocyte E & B 12 needed for protein synthesis 3. Hormones IGF’s in childhood (insulin-like growth factors) estrogens & androgens important in puberty

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

34. 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)

35. 2 hormones control Ca in/out bone: 1. Calcitonin decreases blood Ca levels by putting more Ca into bone 2. Parathyroid Hormone (PTH) increases blood Ca levels by taking Ca out of bone (increasing osteoclast resorption)

37. 1. 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