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Skeletal System Presentation Transcript

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