150 Ch6 Skeletal


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150 Ch6 Skeletal

  1. 1. Anatomy and Physiology, Seventh Edition Rod R. Seeley Idaho State University Trent D. Stephens Idaho State University Philip Tate Phoenix College Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Chapter 06 Lecture Outline *
  2. 2. Skeletal System Functions <ul><li>Support . Provides structural support for the entire body. A framework for attachment of soft tissues or organs. </li></ul><ul><li>Protection . Skull around brain and inner ear; ribs, sternum, vertebrae protect organs of thoracic cavity </li></ul><ul><li>Leverage . Act as levers for muscles that contract and produce movement by pulling on bones via tendons. </li></ul><ul><li>Storage . Acts as a reservoir for calcium and phosphorous. Fat stored in marrow cavities </li></ul><ul><li>Blood cell production (Hematopoiesis) . Bone marrow gives rise to blood cells and platelets </li></ul>
  3. 3. Bone Shapes <ul><li>Long bones </li></ul><ul><ul><li>Upper and lower limbs </li></ul></ul><ul><li>Short bones </li></ul><ul><ul><li>Carpals and tarsals </li></ul></ul><ul><li>Flat bones </li></ul><ul><ul><li>- Ribs, sternum, skull, scapulae </li></ul></ul><ul><li>Irregular bones </li></ul><ul><ul><li>Vertebrae, facial bones </li></ul></ul>
  4. 4. Long Bone Structure <ul><li>Diaphysis </li></ul><ul><ul><li>Tubular shaft that forms the axis </li></ul></ul><ul><ul><li>Composed of compact bone that surrounds the medullary cavity </li></ul></ul><ul><ul><li>Yellow marrow (fat) stored in medullary cavity. </li></ul></ul><ul><ul><li>Shaft covered with periosteum </li></ul></ul><ul><ul><li>Medullary cavity lined with endosteum </li></ul></ul><ul><li>Epiphysis </li></ul><ul><ul><li>Expanded end of the bone </li></ul></ul><ul><ul><li>Interior is cancellous bone (spongy bone) </li></ul></ul><ul><ul><li>Joint surface covered with articular (hyaline) cartilage </li></ul></ul><ul><ul><li>Epiphyseal line: separates diaphysis from epiphysis </li></ul></ul><ul><ul><ul><li>Composed of hyaline cartilage </li></ul></ul></ul><ul><ul><ul><li>Bone growth in lengths occurs here </li></ul></ul></ul>
  5. 5. Bone Membranes <ul><li>Periosteum – double-layered protective membrane </li></ul><ul><ul><li>Outer fibrous layer is dense regular connective tissue </li></ul></ul><ul><ul><li>Inner osteogenic (bone forming) layer is composed of osteoblasts and osteoclasts </li></ul></ul><ul><ul><li>Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina </li></ul></ul><ul><ul><li>Secured to underlying bone by Sharpey’s fibers </li></ul></ul><ul><li>Endosteum – delicate membrane covering internal surfaces of bone </li></ul>
  6. 6. Structure of Long Bone Figure 6.3
  7. 7. Structure of Short, Irregular, and Flat Bones <ul><li>Flat Bones </li></ul><ul><ul><li>No diaphysis or epiphysis </li></ul></ul><ul><ul><li>Sandwich of cancellous between compact bone </li></ul></ul><ul><ul><li>Periosteum covers outer surface while endosteum lines interior </li></ul></ul><ul><li>Some flat and irregular bones of skull have sinuses lined by mucous membranes (Frontal, Maxillary, Ethmoid, and Sphenoid bones) </li></ul>
  8. 8. Cells of Osseous Tissue (1) <ul><li>Osteogenic cells in endosteum, periosteum or central canals give rise to new osteoblasts </li></ul><ul><ul><li>arise from embryonic fibroblasts </li></ul></ul><ul><ul><li>multiply continuously </li></ul></ul><ul><li>Osteoblasts mineralize organic matter of matrix </li></ul><ul><ul><li>Synthesize and secrete collagen protein and other organic compounds of matrix </li></ul></ul><ul><ul><li>Produce new bone in a process known as osteogenesis </li></ul></ul><ul><li>Osteocytes are osteoblasts trapped in the matrix they formed </li></ul><ul><ul><li>cells in lacunae connected by gap junctions inside canaliculi </li></ul></ul>
  9. 9. Cells of Osseous Tissue (2) <ul><li>Osteoclasts develop in bone marrow by fusion of 3-50 stem cells </li></ul><ul><li>Remove and recycle bone matrix </li></ul><ul><ul><li>Secrete acid and proteolytic enzymes that dissolve matrix and release the stored minerals; called osteolysis </li></ul></ul><ul><li>Reside in pits that they ate into the bone </li></ul>
  10. 10. Matrix of Osseous Tissue <ul><li>Dry weight = 1/3 organic and 2/3 inorganic matter </li></ul><ul><li>Organic matter </li></ul><ul><ul><li>collagen, glycosaminoglycans, proteoglycans and glycoproteins </li></ul></ul><ul><ul><li>Gives bone is resilience, flexibility </li></ul></ul><ul><li>Inorganic matter </li></ul><ul><ul><li>85% hydroxyapatite (calcium phosphate) </li></ul></ul><ul><ul><li>10% calcium carbonate </li></ul></ul><ul><ul><li>Other minerals (fluoride, potassium, magnesium) </li></ul></ul><ul><ul><li>Gives bone its hardness </li></ul></ul><ul><li>Combination provides for strength and resilience </li></ul><ul><ul><li>minerals resist compression; collagen resists tension </li></ul></ul><ul><ul><li>bone adapts by varying proportions </li></ul></ul>
  11. 11. Bone Matrix <ul><li>If mineral removed, bone is too bendable </li></ul><ul><li>If collagen removed, bone is too brittle </li></ul>
  12. 12. Histology of Compact Bone <ul><li>Osteon = basic structural unit </li></ul><ul><ul><li>cylinders formed from layers ( lamellae ) of matrix around central canal (osteonic canal) </li></ul></ul><ul><ul><ul><li>collagen fibers alternate between right- and left-handed helices from lamella to lamella </li></ul></ul></ul><ul><ul><li>osteocytes connected to each other and their blood supply by tiny cell processes in canaliculi </li></ul></ul><ul><li>Perforating canals or Volkmann canals </li></ul><ul><ul><li>vascular canals perpendicularly joining central canals </li></ul></ul>
  13. 13. Microscopic Structure of Compact Bone Figure 6.6a, b
  14. 14. Structure of Cancellous (Spongy) Bone <ul><li>Spongelike appearance formed by plates of bone called trabeculae </li></ul><ul><ul><li>spaces filled with red bone marrow </li></ul></ul><ul><li>Trabeculae </li></ul><ul><ul><li>Oriented along stress lines </li></ul></ul><ul><ul><li>Have few osteons or central canals </li></ul></ul><ul><ul><li>No osteocyte is far from blood of bone marrow </li></ul></ul><ul><li>Provides strength with little weight </li></ul><ul><ul><li>Trabeculae develop along bone’s lines of stress </li></ul></ul>
  15. 15. Bone Development <ul><li>Osteogenesis and ossification </li></ul><ul><ul><li>The process of bone tissue formation, which leads to: </li></ul></ul><ul><ul><ul><li>Formation of the bony skeleton in embryos </li></ul></ul></ul><ul><ul><ul><li>Bone growth until early adulthood </li></ul></ul></ul><ul><ul><ul><li>Bone thickness, remodeling, and repair </li></ul></ul></ul><ul><li>Begins at week 8 of embryo development </li></ul><ul><li>Two major methods used: </li></ul><ul><ul><li>Intramembranous ossification </li></ul></ul><ul><ul><ul><li>Takes place in connective tissue membrane </li></ul></ul></ul><ul><ul><li>Endochondral ossification </li></ul></ul><ul><ul><ul><li>Takes place in cartilage </li></ul></ul></ul><ul><ul><li>Both methods of ossification </li></ul></ul><ul><ul><li>Produce woven bone that is then remodeled </li></ul></ul><ul><ul><li>After remodeling, formation cannot be distinguished as one or other </li></ul></ul>
  16. 16. Intramembranous Ossification <ul><li>Takes place in connective tissue membrane formed from embryonic mesenchyme </li></ul><ul><li>Forms many flat bones of the skull, part of mandible, diaphyses of clavicles </li></ul><ul><li>When remodeled, indistinguishable from endochondral bone. </li></ul>
  17. 17. Intramembranous Ossification <ul><li>Produces flat bones of skull and clavicle. </li></ul>
  18. 18. Endochondral Ossification <ul><li>Begins in the second month of development </li></ul><ul><li>Uses hyaline cartilage as model for bone construction </li></ul><ul><li>Bones of the base of the skull, part of the mandible, epiphyses of the clavicles, and most of remaining bones of skeletal system </li></ul>
  19. 19. Stages of Endochondral Ossification
  20. 20. Growth in Bone Length <ul><li>Appositional growth - growth in length </li></ul><ul><ul><li>Interstitial growth cannot occur because matrix is solid </li></ul></ul><ul><ul><li>Occurs on old bone and/or on cartilage surface </li></ul></ul><ul><li>Growth in length occurs at the epiphyseal plate </li></ul><ul><li>Involves the formation of new cartilage by </li></ul><ul><ul><li>Interstitial cartilage growth </li></ul></ul><ul><li>Closure of epiphyseal plate : epiphyseal plate is ossified becoming the epiphyseal line. Between 12 and 25 years of age </li></ul><ul><li>Articular cartilage: does not ossify, and persists through life </li></ul>
  21. 21. The Metaphysis <ul><li>Regions of the Epiphyseal Plate </li></ul><ul><ul><li>Zone of reserve cartilage = hyaline cartilage </li></ul></ul><ul><ul><li>Zone of proliferation </li></ul></ul><ul><ul><ul><li>chondrocytes multiply forming columns of flat lacunae </li></ul></ul></ul><ul><ul><li>Zone of hypertrophy = cell enlargement </li></ul></ul><ul><ul><li>Zone of calcification </li></ul></ul><ul><ul><ul><li>mineralization of matrix </li></ul></ul></ul><ul><ul><li>Zone of bone deposition </li></ul></ul><ul><ul><ul><li>chondrocytes die and columns fill with osteoblasts </li></ul></ul></ul><ul><ul><ul><li>osteons formed and spongy bone is created </li></ul></ul></ul>
  22. 22. Growth in Bone Length
  23. 23. Long Bone Growth and Remodeling Figure 6.10
  24. 24. Bone Growth and Remodeling <ul><li>Bones increase in length </li></ul><ul><ul><li>interstitial growth of epiphyseal plate </li></ul></ul><ul><ul><li>epiphyseal line is left behind when cartilage gone </li></ul></ul><ul><li>Bones increase in width = appositional growth </li></ul><ul><ul><li>osteoblasts lay down matrix in layers on outer surface and osteoclasts dissolve bone on inner surface </li></ul></ul><ul><li>Bones remodeled throughout life </li></ul><ul><ul><li>Wolff’s law of bone = architecture of bone determined by mechanical stresses </li></ul></ul><ul><ul><ul><li>action of osteoblasts and osteoclasts </li></ul></ul></ul><ul><ul><li>greater density and mass of bone in athletes or manual worker is an adaptation to stress </li></ul></ul>
  25. 25. Factors Affecting Bone Growth <ul><li>Size and shape of a bone determined genetically but can be modified and influenced by nutrition and hormones </li></ul><ul><li>Nutrition </li></ul><ul><ul><li>Lack of calcium, protein and other nutrients during growth and development can cause bones to be small </li></ul></ul><ul><ul><li>Vitamin D </li></ul></ul><ul><ul><ul><li>Necessary for absorption of calcium from intestines </li></ul></ul></ul><ul><ul><ul><li>Can be eaten or manufactured in the body </li></ul></ul></ul><ul><ul><ul><li>Rickets : lack of vitamin D during childhood </li></ul></ul></ul><ul><ul><ul><li>Osteomalacia : lack of vitamin D during adulthood leading to softening of bones; pain when wt. put on affected bone </li></ul></ul></ul><ul><ul><li>Vitamin C </li></ul></ul><ul><ul><ul><li>Necessary for collagen synthesis by osteoblasts </li></ul></ul></ul><ul><ul><ul><li>Scurvy: deficiency of vitamin C </li></ul></ul></ul><ul><ul><ul><li>Lack of vitamin C also causes wounds not to heal, teeth to fall out </li></ul></ul></ul>
  26. 26. Factors Affecting Bone Growth, cont. <ul><li>Hormones </li></ul><ul><ul><li>Growth hormone from anterior pituitary. Stimulates interstitial cartilage growth and appositional bone growth </li></ul></ul><ul><ul><li>Thyroid hormone required for growth of all tissues </li></ul></ul><ul><ul><li>Sex hormones such as estrogen and testosterone </li></ul></ul><ul><ul><ul><li>Cause growth at puberty, but also cause closure of the epiphyseal plates and the cessation of growth </li></ul></ul></ul>
  27. 27. Dwarfism <ul><li>Achondroplastic </li></ul><ul><ul><li>long bones stop growing in childhood </li></ul></ul><ul><ul><ul><li>normal torso, short limbs </li></ul></ul></ul><ul><ul><li>spontaneous mutation during DNA replication </li></ul></ul><ul><ul><li>failure of cartilage growth </li></ul></ul><ul><li>Pituitary </li></ul><ul><ul><li>lack of growth hormone </li></ul></ul><ul><ul><li>normal proportions with short stature </li></ul></ul>
  28. 28. Calcium Homeostasis <ul><li>Bone is major storage site for calcium </li></ul><ul><li>The level of calcium in the blood depends upon movement of calcium into or out of bone. </li></ul><ul><ul><li>Calcium enters bone when osteoblasts create new bone; calcium leaves bone when osteoclasts break down bone </li></ul></ul><ul><ul><li>Two hormones control blood calcium levels- parathyroid hormone and calcitonin. </li></ul></ul>
  29. 29. Calcium Homeostasis
  30. 30. Osteoporosis 1 <ul><li>Bones lose mass and become brittle (loss of organic matrix and minerals) </li></ul><ul><ul><li>risk of fracture of hip, wrist and vertebral column </li></ul></ul><ul><ul><li>complications (pneumonia and blood clotting) </li></ul></ul><ul><li>Postmenopausal white women (> 50) at greatest risk </li></ul><ul><ul><li>by age 70, average loss is 30% of bone mass </li></ul></ul><ul><ul><li>black women rarely suffer symptoms </li></ul></ul><ul><li>Risk factors include </li></ul><ul><ul><li>Smoking - lowers blood estrogen levels </li></ul></ul><ul><ul><li>Body wt - thin, anorexic, heavy exercisers (runners, ballet dancers - less adipose available to make estrogen </li></ul></ul><ul><ul><li>Body build - short females have less total bone mass </li></ul></ul><ul><ul><li>Calcium deficiency </li></ul></ul><ul><ul><li>Vitamin D deficiency </li></ul></ul><ul><ul><li>Certain drugs - alcohol, cortisone, tetracycline promote bone loss </li></ul></ul><ul><ul><li>Family history </li></ul></ul><ul><ul><li>Females with eating disorders including junk food diets </li></ul></ul>
  31. 31. Osteoporosis 2 <ul><li>Estrogen maintains density in both sexes (inhibits resorption) </li></ul><ul><ul><li>testes and adrenals produce estrogen in men </li></ul></ul><ul><ul><li>rapid loss after menopause, if body fat too low or with disuse during immobilizaton </li></ul></ul><ul><li>Treatment </li></ul><ul><ul><li>ERT (estrogen replacement therapy) - slows bone resorption, but increases risk breast cancer, stroke and heart disease </li></ul></ul><ul><ul><li>PTH slows bone loss if given daily injection </li></ul></ul><ul><ul><ul><li>Forteo increases density by 10% in 1 year </li></ul></ul></ul><ul><ul><ul><li>may promote bone cancer </li></ul></ul></ul><ul><ul><li>best treatment is prevention -- exercise and calcium intake (1000 mg/day) between ages 25 and 40 </li></ul></ul>
  32. 32. Spinal Osteoporosis
  33. 33. Other Pathologies of Bone <ul><li>Osteomyelitis - all infectious diseases of bone </li></ul><ul><ul><li>Organisms spread via the blood from wounds, boils, TB </li></ul></ul><ul><ul><li>Pott’s disease = tuberculosis of the spine (Hunchback) </li></ul></ul><ul><li>Osteosarcoma - malignant tumors of bone </li></ul><ul><ul><li>Capable of metastasizing to other tissues/organs </li></ul></ul><ul><li>Paget’s disease </li></ul><ul><ul><li>Characterized by excessive bone formation and breakdown </li></ul></ul><ul><ul><li>In males more than females </li></ul></ul><ul><ul><li>In skull (hat size changes), pelvis, extremities </li></ul></ul><ul><li>Myeloma - cancer of bone marrow </li></ul><ul><li>Osteogenesis imperfecta </li></ul><ul><ul><li>Familial in nature </li></ul></ul><ul><ul><li>Very fragile bones; may break while turning in bed </li></ul></ul><ul><ul><li>Due to an inborn error of metabolism - aminoaciduria </li></ul></ul>
  34. 34. Bone Fractures <ul><li>Open (compound)- bone break with open wound. Bone may be sticking out of wound. </li></ul><ul><li>Closed (simple)- Skin not perforated. </li></ul><ul><li>Incomplete- doesn’t extend across the bone. Complete- does </li></ul><ul><li>Greenstick: incomplete fracture that occurs on the convex side of the curve of a bone </li></ul><ul><li>Hairline: incomplete where two sections of bone do not separate. Common in skull fractures </li></ul><ul><li>Comminuted fractures: complete with break into more than two pieces </li></ul>
  35. 35. Bone Repair <ul><li>Hematoma formation . Localized mass of blood released from blood vessels but confined within an organ or space. Clot formation. </li></ul><ul><li>Callus formation . Callus : mass of tissue that forms at a fracture site and connects the broken ends of the bone. </li></ul><ul><ul><li>Internal - blood vessels grow into clot in hematoma. </li></ul></ul><ul><ul><ul><li>Macrophages clean up debris, osteoclasts break down dead tissue, fibroblasts produce collagen and granulation tissue. </li></ul></ul></ul><ul><ul><ul><li>Chondroblasts from osteochondral progenitor cells of periosteum and endosteum produce cartilage within the collagen. </li></ul></ul></ul><ul><ul><ul><li>Osteoblasts invade. New bone is formed. </li></ul></ul></ul><ul><ul><li>External - collar around opposing ends. Periosteal osteochondral progenitor cells  osteoblasts and chondroblasts. Bone/cartilage collar stabilizes two pieces. </li></ul></ul>
  36. 36. Bone Repair, cont. <ul><li>Callus ossification . Callus replaced by woven, cancellous bone </li></ul><ul><li>4. Bone remodeling . Replacement of cancellous bone and damaged material by compact bone. Sculpting of site by osteoclasts </li></ul>
  37. 37. Effects of Aging on Skeletal System <ul><li>Bone matrix decreases. More brittle due to lack of collagen; but also less hydroxyapetite. </li></ul><ul><li>Bone mass decreases. </li></ul><ul><ul><li>Highest around 30. </li></ul></ul><ul><ul><li>Men denser due to testosterone and greater weight. </li></ul></ul><ul><ul><li>African Americans and Hispanics have higher bone masses than Caucasians and Asians. </li></ul></ul><ul><ul><li>Rate of bone loss increases 10 fold after menopause. </li></ul></ul><ul><ul><li>Cancellous bone lost first, then compact. </li></ul></ul><ul><li>Increased bone fractures </li></ul><ul><li>Bone loss causes deformity, loss of height, pain, stiffness </li></ul><ul><ul><li>Stooped posture </li></ul></ul><ul><ul><li>Loss of teeth </li></ul></ul>