the skeletal system n.
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  2. Vocabulary 5A appositional growth lacunae articular cartilage ossification canaliculi osteoblasts comminuted fracture osteoclasts compact bone osteocytes compound fracture osteon (Haversian system) compression fracture periosteum diaphysis rickets epiphyseal plate sesamoid bones epiphyses Sharpey's fibers greenstick fracture simple fracture hematopoiesis spongy bone (24)

  3. Bones (overview) A. skeleton subdivisions 1. axial skeleton – bones that form longitudinal axis of body 2. appendicular skeleton – bones of limbs and girdles B. bone functions 1. support a. forms internal framework b. supports and anchors all soft organs 2. protection protect soft body organs 3. movement attachment for skeletal muscles via tendons

  4. 4. storage a. stores fat in internal cavities b. storehouse for minerals (> imp. is Ca & P) 5. blood cell formation a. also called hematopoiesis b. occurs in marrow cavities of certain bones c. red marrow  blood cells

  5. C. bone classification 1. 2 basic types of bone (osseous) tissue: a. compact bone – dense, looks smooth and homogeneous b. spongy bone – composed of small needle-like pieces of bone & open space 2. classified according to shape: a. long bones 1. longer than they are wide 2. have a shaft w/ heads @ both ends 3. bones of limbs (except wrist & ankle)

  6. b. short bones 1. usu. cube-shaped & spongy bone 2. bones of wrist & ankle 3. sesamoid bones – *special type of short bone *form w/i tendons (patella) c. flat bones 1. thin, flattened, usu. curved 2. layer of spongy bone b/t 2 layers of compact bone 3. most bones of skull d. irregular bones 1. vertebrae (make up spinal col.) 2. hip bones (coxal)

  7. D. Long bone structure 1. gross anatomy a. diaphysis *shaft *makes up most of bone’s length *composed of compact bone b. periosteum *protective membrane-covering of diaphysis c. Sharpey’s fibers *also called perforating fibers *c.t. fibers that secure periosteum to bone

  8. d. epiphyses *ends of long bones *area of spongy bone enclosed in thin layer of compact bone e. articular cartilage *covers external surface of epiphyses *glassy hyaline cartilage *provides a smooth, slippery surface to reduce friction @ joints f. epiphyseal plate *flat plate of hyaline cartilage *seen in young, growing bone *causes lengthwise growth of a long bone

  9. g. medullary cavity *also called the yellow marrow cav. *cavity of the shaft *adultsstorage area for adipose tissue *infantscontains red marrow & forms blood cells (adults: red marrow is found only in spongy bone cavities of flat bones & epiphyses)

  10. 2. microscopic anatomy a. osteocytes *mature bone cells b. lacunae *tiny cavities w/i matrix *contain osteocytes c. lamella *concentric circles in wh/ lacunae are arranged d. Haversian canals *central canals around wh/ the lamella form NOTE: see page 92 for micrograph of the structure of bone

  11. e. osteon *also called Haversian system *each complex consisting of a central canal + matrix rings *canals run lengthwise carrying blood vessels & nerves to all areas of bone f. canaliculi *transportation system *connect bone cells to nutrient supply *radiate o/w from the central canals to all lacunae *reason bone cells are well nourished

  12. 3. bone markings (pg.134) a. fossa *shallow, basinlike depression in a bone *may serve as an articular surface b. fissure *narrow, slit-like opening c. foramen *round/oval opening through a bone *for blood vessels &/ nerves

  13. E. Bone formation, growth, remodeling 1. formation & growth a. ossification *process of bone formation *2 phases -osteoblasts (bone forming cells) cover hyaline cartilage -hyaline cartilage is digested away forming medullary cavity b. appositional growth *increase in diameter of bone c. osteoclasts *bone-destroying cells

  14. 2. bone remodeling a. nec. for bones to retain normal prop. & strength as body increases in size & strength b. PTH (parathyroid hormone) *determines when bone is to be broken down/formed *stresses (muscle pull, gravity) determine where bone matrix is to be broken down/formed c. allows skeleton to remain as strong & vital as possible during growth, injury, etc.

  15. F. Problems 1. Rickets a. childhood disease in wh/bones fail to calcify b. bones soften  bowing of legs c. usu. due to lack of Ca or lack of Vit. D wh/ is needed to absorb Ca into bloodstream

  16. 2. Fractures (bone breaks) a.simple (closed) *bone breaks cleanly *does NOT penetrate the skin b. compound (open) *bone ends penetrate through the skin Compound fracture Simple fracture

  17. c. comminuted fracture *bone breaks i/t many fragments *common in elderly (bones are more brittle) d. compression fracture *bone is crushed *common in porous bones e. greenstick *incomplete break *common in children (flexible bones) comminuted compression Greenstick ----------

  18. 3. fracture repair (pg. 138) 4 mj. Events: a.hematoma forms blood-filled swelling b. break is splintered by a fibrocartilage callus c. bony callus is formed fibrocartilage is gradually replaced by spongy bone d. bone remodeling occurs