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Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
Skeletal System
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Skeletal System

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  • 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

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