ch 6.txt

  1. FXNS of bone and skeletal system
    • 1 - support
    • 2 - protection
    • 3 - mineral homeostasis
    • 4 - blood cell production
    • 5 - assistance in movement
    • 6 - TRIglyceride Storage
  2. role and facts of mineral homeostasis
    • bone tissue acts as a reservoir of critical minerals
    • - 99% of body's CALCIUM is stored here
    • - PHOSPHORUS stored here
  3. most abundant mineral salt in bone tissue
    calcium phosphate
  4. extracellular matrix components
    • 25% H20
    • 25% collagen fibers
    • 50% crystallized MINERAL salts
  5. periosteum
    surrounds external bone surface
  6. endosteum
    surrounds interior lining of bone surface facing the medullary cavity
  7. medullary cavity
    marrow cavity - cylindrical space within the diaphysis - contains yellow bone marrow
  8. diaphysis
    bone's shaft or body
  9. epiphysis
    proximal or distal ends of bone
  10. types of cells present in bone tissue
    • Osteogenic Cells: undergo cell division, resulting cells develop into osteoblasts
    • Osteoblasts: bone building cells, synthesize extracellular matrix of bone tissue
    • Osteocytes: mature bone cells that exchange NUTRIENTS and WASTES with the blood
    • Osteoclasts: release enzymes that digest mineral components of bone matrix - RESORPTION
  11. Osteons or Haversion Systems
    arrangements of components of compact bone
  12. central canals
    run longitudinally through bones
  13. concentric LAMELLAE
    rings around central canals
    • small spaces between Lamellae
    • contain OSTEOCYTES
  15. CanaliCULI
    filled with extracellular fluid, radiate in all directions from the LACUNAE
  16. perforating canals
    run perpendicular to central canals
  17. Spongy bone
    LACKS osteons - lamellae are arranged around thin columns called TRABECULAE
  18. Trabeculae location
    They are oriented around lines of STRESS
  19. Blood and nerve supply
    • Periosteum is rich in sensory nerves sensitive to TEARING or TENSION
    • Endosteum very vascularized
    • process of bone formation, four types of occurances
    • 1 - formation of bone in an embryo
    • 2 - growth of bones until adulthood
    • 3 - remodeling of bone
    • 4 - repair of FRACTURES
  21. Formation of bone in an EMBRYO
    • Follows one of 2 pathways,
    • Intramembranous ossification: Flat bones of the skull and mandible are formed this way. Soft spots help fetus skull pass thru birth canallater become ossified
    • Endochondral ossification: replacement of CARTILAGE by bone, most bones of the body are formed in this way, ie long bones
  22. Endochondral ossification process
    • bone forms within the hyaline cartilage
    • 1 - hyaline cartilage develops
    • 2 - know primary ossification center (in diaphysis)
    • 3 - secondary ossification center (in epiphysis)
    • 4 - articular cartilage forms around edges of bone
  23. Bone Growth in Length
    • involves 2 events
    • 1. growth of cartilage on Epiphyseal plate
    • 2. replacement of cartilage by bone tissue in epiphyseal plate
    • - osteoclasts dissolve calcified cartilage and osteoblasts lay down the bone matrix
    • - below epiphyseal plate is ossified bone, above is the cartilage prior to replacement by bone
  24. epiphyseal line
    when in adulthood bone replaces the cartilage of the epiphyseal line, leaving a bony structure, called the epiphyseal plate
  25. REmodeling of bone
    • bone forms before birth and continually RENEWS itself
    • ongoing replacement of old bone tissue by new bone tissue
    • old bone is continuously destroyed and new bone is formed in its place throughout someone's life
  26. Osteoporosis and Osteomalacia
    • in osteoporosis, there is a loss of calcium which weakens the bones
    • in osteomalacia, bone becomes to flexible (also in rickets)
  27. Minerals in bone
    • mostly calcium and phosphorus
    • small amounts of Magnesium (Mg), Fluoride (Fl) and Manganese
  28. Vitamins that are helpful for bone growth
    • Vit A: stimulates osteoBLAST activity
    • Vit C: needed for COLLAGEN synthesis
    • Vit D: increasing absorption of Calcium from foods in GI tract into the blood
    • Vit K and B12: helpful for synthesis of bone proteins
  29. Hormones affecting bone growth
    • IGFs (growth factors): produced by liver stimulate osteoblasts, promote cell division at epiphyseal plate and enhance protein synthesis
    • Thyroid hormones: stimulate Osteoblasts
    • Insulin: increases synthesis of bone proteins
    • Estrogen & Testosterone: cause a SHUT down of growth at epiphyseal plate
  30. Calcitonin and PTH role in bone formation/resorption
    • calcitonin is secreted by Thyroid gland. It works to decrease Ca in the blood by INHIBITING osteoclast activity. It also promotes bone Formation
    • Parathyroid Hormone (PTH) works to INCREASE blood Ca by breaking down bone (osteoCLAST activity). PTH also acts on kidneys to decrease loss of Ca in urine
  31. hypocalcemia
    this is when there are LOW Ca levels in the blood…so to help this condition, Parathyroid hormone works to help INCREASE blood CA levels
  32. Open (Compound) Fracture
    • broken end of bone comes out through skin
    • Muscle loss occurs
  33. Closed (Simple) Fracture
    Does not break thru skin
  34. Comminuted Fracture
    bone splintered, crushed or broken into pieces
  35. Greenstick fracture
    partial fracture with one side of bone broken and other side BENDS
  36. Impacted Fracture
    One end of the fractured bone is forcefully driven into another
  37. Steps to repair a bone fracture
    • 1. Formation of a Fracture HEMATOMA: blood leaks from torn ends of blood vessels, a clotted mass of blood forms around site of fracture
    • 2. FibroCARTILAGINOUS Callus formation: fibroblasts invade fracture site and produce collagen fibers…bridging the broken ends of bone
    • 3. BONY Callus formation: osteoblasts begin to produce SPONGY bone
    • 4. Bone Remodeling: Compact bone replaces Spongy Bone
  38. What cells need Ca to function properly
    Nerve and Muscle cells
  39. Bone Strength when under STRESS
    Bone tissue becomes stronger through Mineral salts deposition and production of collagen fibers by osteoblasts
  40. Aging and Bone Tissue
    • As you get older and level of sex hormones diminishes, there is a DECREASE in bone mass.
    • Bone resorption by Osteoclasts outpaces bone deposition by osteoblasts
    • Loss of bone mass in old age has a larger affect in FEMALES than males.
  41. 2 Effects of Aging on Bone Tissue
    • 1. Loss of Bone Mass: results from loss of Ca from bone matrix (a symptom in osteoporosis)
    • 2. Brittleness: results from a decreased rate of Protein Synthesis. Collagen fibers give bone its tensile strength so when this is lost, the bones become BRITTLE and susceptible to fracture.
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ch 6.txt