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Skeletal system. 206 bones. General overview. Skeleton-Greek for dried up body Divided into 2 divisions Axial skeleton Forms the longitudinal axis of the body ~80 bones Skull Bones associated with skull Vertebral column Throacic cage Appendicular skeleton

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general overview
General overview
  • Skeleton-Greek for dried up body
  • Divided into 2 divisions
    • Axial skeleton
      • Forms the longitudinal axis of the body
        • ~80 bones
          • Skull
          • Bones associated with skull
          • Vertebral column
          • Throacic cage
    • Appendicular skeleton
      • Bones of the limbs and girdles
        • 126 bones
general overview cont
General overview cont.
  • Hardest material in the body
    • From calcium salts deposited in the matrix
  • Relatively lightweight
  • Remarkable ability to resist tension and other forces acting on it
    • Organic parts, especially the collagen fibers give flexibility
bone functions
Bone functions
  • Support

-structural support for the whole body framework for attachment of soft tissues and organs, gives shape to head, face, thorax, and limbs

  • Protection

-protect soft body organs

  • Movement

-acts as levers

Movements range from motion of fingertip to changing position of the whole body

  • Storage

-fat is stored in internal cavities(yellow marrow in adults)

-the bone itself stores inorganic salts mostly in the form of calcium and phosphorus

  • Hematopoiesis

-blood cell formation

Occurs in red marrow

Produces red blood cells, white blood cells, and platelets

skull, ribs, sternum, clavicles, vertebrae, and pelvis

  • 2 types of bone tissue
    • compact- dense, smooth, homogenous
    • Spongy- numerous branching bony plates and lots of open spaces
bone shapes
Bone shapes
  • Long bones- long and slender
    • All bones of limbs except wrist and ankles
  • Flat bones- have thin, roughly parallel surfaces provide protection for underlying soft tissues and extensive surface area for attachment of skeletal muscles
    • Roof of skull, sternum, ribs, and scapula
  • Sutural bones(Womian bones)
    • Small, flat, irregularly shaped bones between flat bones of the skull
      • Individual variations of number, shape, and location
bone shapes cont
Bone shapes cont.
  • Irregular bones- complex shapes with short, flat, notched, or rigid surfaces
    • Spinal vertebrae and bones of the pelvis
    • Several skull bones
  • Short bones- small, cube shaped
    • Mostly spongy bone
    • Carpal and tarsal
  • Sesmoid bones-small and flat
    • Develop inside tendon
    • Located near joints
      • patella
bone structure
bone structure
  • Diaphysis- tubular shaft
    • Most of bone’s length
    • Compact bone
    • Covered with periosteum
  • Marrow cavity/medullar cavity
    • Central space that stores marrow
    • Usually yellow marrow in adults
  • Epiphysis- expanded area at each end
    • Spongy bone
    • Covered with articular cartilage
  • Epiphyseal line- remnant of epiphyseal plate
    • Causes length growth of long bone
microscopic anatomy of compact bone
Microscopic anatomy of compact bone

Osteocytes- mature bone cells

Found in lacunae

Lacunae are within concentric circles called lamellae and Haversian canals

Haversian canals

run lengthwise

carry blood and nerves throughout the bone

Osteon- central canal and matrix

Canaliculi- radiate outward and connect all bone cells to nutrients

well nourished

heal quickly

Volkmann’s canal- communication pathway between exterior and interior of the bone

run into compact bone at right angles to the shaft

bone formation growth and remodeling
Bone formation, growth and remodeling
  • Skeleton formed from cartilage and bone
  • In embryos skeleton primarily hyaline cartilage
  • In young child hyaline cartilage has been replaced with bone
  • Cartilage remains only in isolated areas such as the bridge of the nose, parts of the ribs, and the joints
ossification bone formation
Ossificationbone formation
  • Hyaline cartilage model covered with bone matrixby bone forming cells  osteoblast
  • Then cartilage model is digested away opening up a medullary cavity within the newly formed bone
    • Begins in center of diaphysis
    • Primary ossification center
      • Bone tissue develops from here toward the ends of the cartilaginous structure
ossification cont
Ossification cont.
  • By birth most of the cartilage has been converted to bone except the articular cartilage and the epiphyseal plate
  • Articular cartilage- covers bone ends and persist for life
  • Epiphyseal plate- provide for longintudinal growth
secondary ossification
Secondary ossification
  • Epiphysis remains cartilage to grow
  • Secondary ossification appears in epiphysis and spongy bone forms in all directions
  • Bones must also widen while lengthening
  • Osteoblast add bone tissue to face of diaphysis
  • Osteoclast break down bone from the inside to form the medullary cavity
  • Appositional growth- process by which bone increases in diameter
    • Growth controlled by hormones
    • Once the ossification centers meet lengthening is no longer possible in that end of the bone
      • Ends during adolescence
      • Epiphyseal disk where ossification centers meet
bone remodeling
Bone remodeling
  • Continually remodeled based on two factors
    • Calcium levels in the blood
    • The pull of gravity and muscles on the skeleton
blood calcium levels
Blood calcium levels
  • When blood levels drop:
    • Parathyroid glands release parathyroid hormone
    • Activates osteoclast that break down the bone matrix and release calcium
  • When blood levels rise:
    • Calcium is deposited in the bone as hard calcium salts
bone remodeling1
Bone remodeling
  • Essential for bones to retain normal proportions and strength during long bone growth as body increases in size and weight
  • Bones are thicker and form large projections to increase their strength in areas with bulky muscles
  • Osteoblasts become trapped in bone matrix and become osteocytes
bone remodeling summary
Bone remodeling summary
  • PTH determines when bone is broken down in response to calcium
  • The stresses of muscle pull and gravity acting on skeleton determine where bone matrix is broken down or formed so that the skeleton can remain strong and vital as possible
bone fractures
Bone fractures
  • Treated by reduction– the realignment of the broken bone ends
    • Closed reduction– the bone ends are coaxed back into their normal positions by the physician’s hands
    • Open reduction– surgery is performed and the bone ends are secured together with pins or wires. It is then immobilized by a cast or traction to allow the healing process
    • The healing time for a simple fracture is 6 to 8 weeks, but can be much longer for larger bones and the elderly
repair of factures
Repair of factures
  • hematoma is formed
    • Blood vessels are ruptured and form blood filled swelling
    • Bone cells deprived of nutrition die
  • The break is splinted by a fibrocartilage callus
    • Growth of new capillaries and disposal of dead tissue by phagocytes
    • Connective tissue form a mass of repair tissue called fibrocartilage callus that acts as a splint for the broken bone
  • The bony callus is formed

1. Osteoblast and osteoclasts gradually replace the fibrocartilage with spongy bone

  • Bone remodeling occurs

1. Over the next weeks to months the bony callus is remodeled in response to mechanical stresses so that it forms a strong permanent patch at the fracture site

fetal skull
Fetal skull
  • ¼ as long as total body
  • Thin and somewhat flexible and less easily fractured than adult bones
  • Skeleton still unfinished especially in skull
  • Fontanels (“soft-spots”)- fibrous membranes connecting cranial bones
    • 2 frontanels
      • Anterior- larger and diamond shaped
      • Posterior – smaller triangular shaped
  • Allow fetal skull to be compressed slightly during birth
  • Allow brain to grow during later pregnancy and early infancy
  • Gradually converted to bone
    • Usually by age 2
vertebral column
Vertebral column
  • Axial support
  • Extends from skull to pelvis
  • 26 irregular bones
  • Surrounds and protects spinal cord
  • Before birth spine consist of 33 separate vertebrae
  • Single vertebrae are separated by invertebral discs(fibrocartilage) that cushion and absorb shock while allowing flexibility
    • In young people high water content and are spongy and compressible
    • Water amount decreases with age
  • Discs and S-shaped structure of vertebral column work together to prevent shock to the head and make trunk flexible
spinal curvatures
Spinal curvatures
  • Primary curvature
    • Present when born
    • Thoracic and sacral
  • Secondary curvature
    • Develop later
      • Cervical – when baby begins raising head
      • Lumbar- when baby begins to walk
female vs male pelvis
Female vs. male pelvis
  • Female inlet is larger and more circular
  • Female pelvis as a whole is shallower, and the bones are lighter and thinner
  • The female ilia flare more laterally
  • The female sacrum is shorter and less curved
  • The female ischial spines are shorter and farther apart; thus the outlet is larger
  • The female pubic arch is more rounded because the angle of the pubic arch is greater
  • Functional junctions
  • Vary in structure and function
  • Classified according to degree of movement that they make possible
    • Immovable, slightly immovable, freely movable
  • Grouped by type of tissue
    • Fibrous, cartilaginous, or synovial
  • Lie between bones that closely contact one another
  • Thin layer of dense connective tissue joins the bones at joints
  • No appreciable movement takes place at these joints
    • Ex. Sutures between flat bones in skull
    • Distal ends of fibula have limited movement
cartilaginous joints
Cartilaginous joints
  • Allow limited movement
  • Disk of fibrocartilage or hyaline cartilage connect bones
    • Ex. Joints of this type separate the vertebrae of the vertebral column
    • symphysis pubis and the first rib with the sternum
synovial joints
Synovial joints
  • Most joints of the skeletal system
  • Allow free movement
  • Articular ends of bones covered with hyaline and capsule of dense connective tissue holds them together
    • Composed of outer layer of ligaments and inner lining that is synovial membrane
      • Allows lubrication
  • May also have bursae which aid in movement of tendons
    • Bursae– fluid filled sacs
types of synovial joints
Types of synovial joints
  • Ball and socket joint
    • Consist of ball-shaped head that articulates with cup-shaped cavity of another bone
    • Allows a wider range of motion
      • Allows movement in all planes as well as rotational movement around a central axis
      • Ex. Shoulders and hipd
  • Condyloid joint
    • Oval shaped condyle fits into an elliptical plane of another bone
    • Permits a variety of movements in different planes but does not allow for rotational movement
    • Between metacarpals and phalanges
  • Gliding joint
    • Nearly flat or slightly curved
    • Sliding and twisting movements
    • Ex. Most within the wrist and ankle
types of synovial joints1
Types of synovial joints
  • Hinge joint
    • The convex surface of one bone fits into the concave surface of another bone
    • Resembles the joint of a door-permits movement in only one plane
    • Ex. Elbow and phalanges
  • Saddle joint
    • Between bones whose articulating surface have both concave and convex regions
    • The surface of one bone fits the complimentary surface of the other bone
    • Variety of movements
    • Joint between the carpal and metacarpal of the thumb
  • Pivot joint
    • The cylindrical surface of one bone rotates within a ring formed of bone and ligament
    • Limited to rotation around a central axis
    • Joint between proximal ends of the radius and ulna