2.9 Anatomy Chapter 9

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2.9 Anatomy Chapter 9
2010-09-27 02:41:33
Joints Articulations Body Movements

Classification of Joints, Fibrous, Cartilaginous, Synovial; Types of Body Movements
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  1. Classification of Joints
    • Functional Classification: based on amount of movement
    • - synarthroses: immovable joints (largely restricted to axial skeleton)
    • - amphiarthroses: slightly movable joints (largely restricted to axial skeleton)
    • - diarthroses: freely movable joints (predominate in limbs)
    • Structural Classification: based on material that binds the bones together, presence/absence of a joint cavity
    • - fibrous, cartilaginous, or synovial joints
  2. Fibrous Joints
    • "seams"
    • Bones are tightly bound by minimal amount of fibrous tissue
    • - Occur only in bones of the skull; fibrous tissue is continuous with periosteum
    • - Edges of joining bones are wavy and interlocking
    • - Also allows growth for expansion of skull; ossifies during middle age

    Functionally classified as: synarthrosis
  3. Fibrous Joints
    • Bones are connected exclusively by ligaments
    • Amount of movement depends on length of connecting fibers
    • ex: short fibers in distal tibiofibular articulation - little to no movement allowed
    • - longer fibers in interosseous membrane between radius and ulna - allows large amounts of movement

    Functionally classified as: either synarthrosis or amphiarthrosis
  4. Fibrous Joints
    "peg-in-socket" joint

    Only example is the articulation of a tooth with its socket; connecting ligament is periodontal ligament

    Functionally classified as: synarthrosis
  5. Cartilaginous Joints
    A joint where hyaline cartilage unites the bones.

    ex: epiphyseal plates; joint between first rib's costal cartilage and the manubrium of the sternum

    Functionally classified as: synarthrosis
  6. Cartilaginous Joints
    A joint where fibrocartilage unites the bones. Functions to reduce tension and compression stresses.

    ex: intervertebral discs, pubic symphysis

    hyaline cartilage forms articular surfaces on bones

    Functionally classified as: amphiarthrosis
  7. Synovial Joints
    General Structure
    "Joint eggs"; the most movable joints of the body (all diarthrosis); mostly in limbs

    • 1. Articular Cartilage: the ends of opposing bones are covered by hyaline cartilage that helps absorb compressive forces
    • 2. Joint (synovial) Cavity: a space that holds a small amount of synovial fluid; unique to synovial joints
    • 3. Articular Capsule: the joint cavity is enclosed by a double-layered capsule. Outer layer is a fibrous capsule of dense irregular connective tissue that is continuous with the periosteum. Inner layer is synovial membrane composed of loose connective tissue. Functions to make synovial fluid
    • 4. Synovial Fluid: viscous liquid inside the joint cavity (resembles egg white); primarily a filtrate of blood from the synovial membrane. Also contains glycoproteins that make it a slippery lubricant. Also present within the articular cartilages.
    • 5. Reinforcing Ligaments: some synovial joints are reinforced by ligaments, mostly capsular (thickened parts of the capsule)
    • 6. Nerves and Vessels: richly supplied with sensory nerve fibers that innervate the articular capsule; detects pain and mostly monitors how much the capsule is being stretched. Rich blood supply that mostly supplies the synovial membrane where synovial fluid is produced.

    • *articulating discs/ meniscus occur when joining bones have different articulating shapes
    • - bursae: "purse" a flattened fibrous sac lined by a synovial membrane; occur where ligaments, muscles, tendons, or bones overlie each other and rub together
    • - tendon sheaths: essentially an elongated bursa that wraps around a tendon; occur only on tendons that are subject to friction, ex. those travelling through cavities/crowded canals
  8. Synovial Joints
    Movements Allowed
    • 1. Gliding: nearly flat surfaces of two bones slip across each other; as between carpals/tarsals/vertebrae
    • 2. Angular movements: increase or decrease the angle between two bones
    • - flexion: decreases the angle, bringing the bones closer together. ex. neck, trunk, fingers, forearn to arm
    • - extension: reverse of flexion; increases the angle between two bones
    • - hyperextension: bending a joint beyond its normal range of motion (head back, looking up)
    • - Abduction: "moving away"; movement of limb away from the body midline
    • - Adduction: "moving toward"; movement of limb toward the body midline; opposite of abduction
    • - Circumduction: "moving in a circle"; moving a limb/finger so that it describes a cone in space
    • 3. Rotation: the turning movement of a bone around the longitudinal axis; the only movement allowed btwn the first two vertebrae (atlas/axis), entire vertebral column also rotates, as well as hip/shoulder joints; classified as medial or lateral rotation in the limbs
    • 4. Special movements: do not fit in prior categories
    • - elevation/ depression: lifting superiorly or moving inferiorly, ex. during chewing, mandible is elevated/depressed
    • - protraction/ retraction: nonangular movements anteriorly or posteriorly; ex. mandible
    • - supination/ pronation: movements of the radius around the ulna; supination "palms up", pronation "palms down", radius and ulna form an "X"
    • - opposition: saddle joint between metacarpal 1 (of thumb) and carpals allows movement whereby thumb can touch the tips of other digits
    • - inversion/eversion: special movements of the foot. Inversion turns the sole medially, eversion, laterally.
    • - dorsiflexion/plantar flexion: up and down movements of the foot at the ankle. Lifting the foot so that toes point up is called dorsiflexion; depressing the foot or elevating the heel where toes point down is called plantar flexion.
  9. Synovial Joint
    Types of Synovial Joints
    • 1. Plane joint: flat surfaces, allows short gliding or translational movements; nonaxial movement
    • 2. Hinge joint: cylindrical end of one bone fits into trough-shaped end of another bone; angular movement allowed in just one plane; ex. elbow, ankle, fingers; uniaxial movement
    • 3. Pivot joint: rounded end of one bone fits into a ring that is formed by another bone plus an encircling ligament; allows rotational movement; ex. proximal radioulnar joint; uniaxial movement
    • 4. Condyloid joint: "knuckle-like"; egg-shaped end of one bone fits into oval concavity of another bone; allow flexion/extension and abduction/adduction movements; biaxial movement
    • 5. Saddle joint: each bone surface has both convex and concave areas, like a saddle; ex. first carpometacarpal joint in the ball of the thumb; same movements as condyloid; biaxial movement
    • 6. Ball-and-socket joint: spherical head of one bone fits into round socket in another; ex. hip and shoulder; multiaxial movement
  10. Disorders of Joints
    Joint Injuries
    Torn Cartilage: usually occurs when a meniscus is subjected to both high compression and shear stress; cartilage is avascular, so it doesn't heal; remove fragments and repair ligaments

    Sprains: ligaments reinforcing a joint are stretched or torn; common in lumbar back region, ankle, and knee; heal slowly due to poor vascularization.

    Dislocations: (luxation) when bones of a joint are forced out of alignment; accompanied by sprains, inflammation, pain, difficulty moving the joint
  11. Disorders of Joints
    Inflammatory and Degernerative Conditions
    • Arthritis: most widespread crippling disease in the US, affecting 1 in 7 Americans; accompanied by pain, stiffness, and swelling of the joints
    • - osteoarthritis: degenerative joint disease; "wear and tear"; articular cartilages soften, fray, crack, and erode.
    • - rheumatoid arthritis: a chronic inflammatory disorder; causes pain and swelling of joints, manifests osteoporosis, muscle weakness, and problems with heart and blood vessels; autoimmune disease
    • - gouty arthritis: gout; caused by accumulations of uric acid crystal precipitates