Honors Anatomy & Physiology

 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

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

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

 Diaphysis: shaft or body; the long cylindrical portion of the bone 2. Epiphysis: distal & proximal ends of 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

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

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

 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

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

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

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

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

 Compact bone  few open spaces  outer bone layer of all bones  Spongy bone  inside bones

 strongest form of bone  beneath periosteum of all bone  functions:  protection & support  resists stresses produced by weight & movement

 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

 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

1. longer: epiphyseal plate 1. wider:  called appositional growth  periosteal osteoblasts on outer surface of bone  osteoclast remove compact bone inner border

 Most bones are formed b/4 birth but each one continually renews itself for rest of life  ~5% of bone being any given time  bone remodeling is the ongoing replacement of old bone tissue by new bone tissue 1. Bone Resorption 2. Bone Deposition

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

 addition minerals & collagen fibers to bone by osteoblasts

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

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

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

 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)

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