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SECTION 6-1: Introduction to the skeletal system

SECTION 6-1: Introduction to the skeletal system . Skeletal system includes: Bones of the skeleton Cartilages, ligaments and other connective tissues that stabilize and connect Functions of skeletal system Support Storage of minerals and lipids Blood cell production Protection Leverage.

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SECTION 6-1: Introduction to the skeletal system

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  1. SECTION 6-1:Introduction to the skeletal system Skeletal system includes: • Bones of the skeleton • Cartilages, ligaments and other connective tissues that stabilize and connect Functions of skeletal system • Support • Storage of minerals and lipids • Blood cell production • Protection • Leverage

  2. SECTION 6-2:Classification of Bones • Long • Flat • Short • Irregular • Sesamoid • Sutural Bone shapes Bone Structure • Compact bone (dense) • Spongy bone (cancellous)

  3. Figure 6.1 Classification of Bones by Shape Figure 6.1

  4. A typical long bone includes • Diaphysis • Epiphyses • Metaphysis • Articular cartilage • Marrow cavity • Filled with red or yellow marrow • Articularcartlilage

  5. Figure 6.2 Bone Structure Figure 6.2

  6. SECTION 6-3: Bone Histology Osseous tissue • solid matrix- Crystals of hydroxyapatite Ca3(PO4)2+ Ca(OH)2 • Collagen- • Vascular-

  7. SECTION 6-3: Bone Histology 4. Wrapped a. Endosteum b. Periosteum i. fibrous layer ii. Cellular layer(osteogenic)- iii. Sharpey’s Fibers

  8. Cells in bone: • Osteocytes = mature bone cells -Maintain, repair bone 2. Osteoblasts= synthesize new matrix - become osteocyte 3. Osteoclasts=dissolve bone matrix -multicuncleated, differentiate from WBC 4.Osteoprogenitor =cells differentiate into osteoblasts, repair fractures

  9. Figure 6.3 The Histology of Compact Bone Figure 6.3a

  10. Figure 6.3 The Histology of Compact Bone Figure 6.3b, c

  11. Compact bone and spongy bone • Basic unit of compact bone is an osteon • Osteocytes arranged around a central canal • Perforating canals extend between adjacent osteons • Spongy bone contains trabeculae

  12. Figure 6.4 The Structure of Osseus Tissue Figure 6.4

  13. Figure 6.5 The Distribution of Forces on a Long Bone Bones and stress • Compact bone located where stresses are limited in direction • Spongy bone located where stresses are weaker or multi-directional Figure 6.5

  14. SECTION 6-4: Bone development and growth • Ossification = converting other tissue to bone 1. Intramembranous 2. Endochondral • Calcification = depositing calcium salts within tissues

  15. deposition of Ca++ salts w/in a tissue Calcification

  16. 1. Intramembraneous Ossification • Bones form w/in a thin CT membrane • Used to form flat bones (cranium, mandible, clavicle)

  17. forming bone: red cartilage: blue Intramembranous ossification • Begins with osteoblast differentiation • Dermal bones produced • Begins at ossification center

  18. Steps of Intramembraneous Ossification in cranium • Mesenchymal cells form a thin CT membrane covering brain • Some mesenchymal cells differentiate into osteoblasts in the center of each membrane.(Occurs 6 weeks after fertilization) • Osteoblasts secrete bone @ these locations(called primary centers of ossification) • Ossification spreads in all directions

  19. Steps of Intramembraneous Ossification in cranium • @ birth ossification is not complete, membrane remains as sutures and fontanels(soft spots) Fetal skulls at 13-34 weeks gestation; fontanels typically close at 6 months

  20. Fontanelles • indentations of fibrous membrane between bones of fetal skull • Intramembranous ossification is not complete until 20-22 months • anterior • posterior • sphenoid • mastoid

  21. Figure 6.7 Intramembranous Ossification Figure 6.7

  22. Endochondral ossification • Cartilage model gradually replaced by bone at metaphysis • Increasing bone length • Timing of epiphyseal closure differs • Appositional growth increases bone diameter

  23. Bone Growth 1. Appositional- increases diameter, while medullary cavity hollowed out -

  24. Figure 6.10 Appositional Bone Growth Figure 6.10b

  25. Bone Growth 2. Interstitial- occurs at epiphyseal plates a. Chondroblasts produce new cells that are pushed toward epiphysis b. At the diaphysis end of plate older cartilage is converted into bone http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/bone/bone_growth4.swf

  26. Figure 6.9 Bone Growth at an Epiphyseal Cartilage Figure 6.9

  27. SECTION 6-5: Dynamic Nature of Bone continually changing • Remodeling • Exercise • Hormone levels • Growth hormone and thyroxine increase bone mass • Calcitonin and PTH control blood calcium levels

  28. Figure 6.12 A Chemical Analysis of Bone Figure 6.12

  29. The skeleton is a calcium reserve • 99% body’s calcium in the skeleton • Calcium ion concentration maintained by bones GI tract and kidneys • Calcitonin and PTH regulate blood calcium levels • Calcitonin decreases blood calcium levels • PTH increases blood calcium levels

  30. Effects on bone growth • Growth hormone- produced by pituitary gland; targets growth plate activity a. Excess causes giagantism

  31. b. Low levels cause pituitary dwarfism • normally proportioned • treatment with growth hormone

  32. Effects on bone growth 2. Testosterone- produced by the testes and adrenal glands in males and by the adrenal glands in females -Responsible for the growth “spurt’ at puberty -Overproduction in males causes closure of the epiphyseal line (Caution for anabolic steroid users)

  33. Effects on bone growth • Estrogen- produced by the ovaries in females; -stimulates osteoblasts -promotes closing of the epiphyseal line -MENOPAUSE causes bone loss!!!

  34. SECTION 6-7: Aging and the Skeletal System Effects of aging include 1. Osteopenia (inadequate ossification) begins between ages 30 and 40, • osteoblast activity declines, while osteoclast activity remains level, • Women lose 8% of bone mass per decade, while men lost only 3% in the same time period 2. Osteoporosis

  35. Osteoporosis When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis • When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis.

  36. Figure 6.16 The Effects of Osteoporosis Figure 6.16

  37. Effects on bone growth 4. Parathyroid hormone- produced by the parathyroid glands in the neck -Stimulates the osteoclasts to Ca++ to be released from the bone to enter the blood -Ca++ necessary for muscles and nerves to function properly

  38. Figure 6.13 Factors that Alter the Concentration of Calcium Ions in Body Fluids Figure 6.13a

  39. Effects on bone growth 5. Calcitonin- produced by the thyroid gland - Inhibits osteoclasts so Ca++ remains in the bone , promotes ostepoblasts

  40. Figure 6.13 Factors that Alter the Concentration of Calcium Ions in Body Fluids Figure 6.13b

  41. Effects on bone growth 6. Vitamin D- some is produced in the skin ; Most is ingested in food -Necessary for the absorption of Ca++ from the intestine into the blood • -Osteomalacia (Rickets in children) • causing softened, weakened bones • Main symptom is pain when weight is put on the affected bone

  42. Bone Fractures (Breaks) Bone fractures are classified by: Simple(closed) vs. compound(open)

  43. Types of Bone Fractures • Linear • the fracture is parallel to the long axis of the bone • Transverse • the fracture is perpendicular to the long axis of the bone

  44. Types of Bone Fractures • Greenstick • incomplete fracture where one side of the bone breaks and the other side bends • common in children

  45. Types of Bone Fractures • Comminuted • bone fragments into three or more pieces • common in the elderly

  46. Types of Bone Fractures • Spiral • ragged break when bone is excessively twisted • common sports injury

  47. Types of Bone Fractures • Depressed • broken bone portion pressed inward • typical skull fracture

  48. Types of Bone Fractures • Compression • bone is crushed; common in porous bones

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