Joints (235 #9) Flashcards
Joint Classification
structural classification of joints is based on two criteria:
1) the presence or absence of space between the articulating bones (synovial cavity)
2) the type of connective tissue that binds the bones together
FIBROUS
CARTILAGINOUS
SYNOVIAL
functional classification of joins relates to degree of movement:
SYNARTHROSIS (no movement)
AMPHIARTHROSIS (slightly movable)
DIARTHROSIS (freely movable)
Fibrous Joints
there is no synovial cavity, and the bones are held together by dense irregular connective tissue that is rich in collagen fibres. permit little or no movement:
1) suture
2) syndesmoses
3) interosseous membranes
Cartilaginous Joints
there is no synovial cavity and the bones are held together by hyaline or fibrocartilage, allows little or no movement:
1) synchondroses
2) symphases
Synovial Joints
the bones forming the joint have a synovial cavity and are united by the dense irregular tissue of an articular capsule and often by accessory ligaments. Allows considerable movement (diarthroses). The articulating surfaces are covered by articular cartilage (hyaline) which reduces friction and absorbs shock.
Suture
fibrous joint composed of a thin layer of dense irregular connextive tissue, occuring only between bones of skull. irregular interlocking edges add strength. In infants/children they are amphiarthroses, while in older adults, synarthroses. When they fuse into bone, they become SYNOSTOSIS (synarthroses). If a suture persists beyond age 6, it is called a frontal or metopic suture.
Syndesmoses
fibrous joint in which there is a greater distance between the articulating surfaces and more dense irregular connective tissue than in a suture - typically arranged as a ligament (bundle) which allows limited movement.
1) distal tibiofibular joint - Amphiarthrosis
2) gomphosis or dentoaveolar joint - cone shaped peg fits into a socket. Synarthrosis.
Interosseous Membrane
a fibrous joint with a substantial sheet of dense irregular connective tissue that binds neighbouring long bones (amphiarthrosis).
1) radius and ulna
2) tibia and fibula
Synchondroses
a cartilaginous joint in which the connecting material is hyaline cartilage.
e.g) epiphyseal (growth) plate - connects diaphysis and epiphyses of long bones
Immovable (synarthroses) - may also ossify and become synostosis.
e.g.) first rib and manubrium
Seen as dark areas between white-appearing bone tissue in an x-ray.
Symphyses
cartilaginous joint (amphiarthrosis) in which the ends of the articulating bones are covered in hyaline cartilage but a broad, flat disc of fibrocartilage connects the bones:
1) pubic symphysis
2) intevertebral joints
3) manubrium and body of sternum.
Articular (joint) Capsule
encloses the synovial cavity and unites the bones. Composed of:
1) outer fibrous membrane - dense irregular connective (mostly collagen) that attaches to the periosteum, literally a thickened continuation of periosteum. Allows considerable movement but great tensile strength prevents dislocation. LIGAMENTS - parallel bundles that are highly adapted for resisting strains.
2) an inner synovial membrane - areolar connective tissue with elastic fibres, sometimes includes accumulations of adipose tissue, called articular fat pads (like infrapatellar fat pad in knee).
Synovial Fluid
secreted by fibroblastlike cells in the synovial membrane, a clear or pale yellow viscous fluid. Hyaluronic acid and interstitial fluid filtered from blood plasma.
1) reducing friction by lubricating joint
2) absorbing shock
3) supplying oxygen and nutrients, removing wastes from chondrocytes in cartilage
4) contains phagocytes for removal of wear & tear-related debris
More viscous when cold, less when warmed up.
CRACKING JOINTS - suction from expansion of synovial cavity pulls CO2 and O2 into bubbles in fluid, then when volume decreases, gas is forced back into solution (popping sound)
accessory ligaments
1) extracapsular ligaments - outside the articular capsule, e.g. fibular and tibial collateral ligaments
2) intracapsular ligaments - within the capsule, but outside the synovial cavity by folds of synovial membrane (ACL, PCL of knee).
Articular Discs or Menisci
crescent-shaped pads of fibrocartilage lying between the articular surfaces of the bones and bind strongly to the fibrous capsule. Subdivide the synovial cavity into two spaces, allowing moved to occur in each space.
1) shock absorption
2) better fit between bony surfaces
3) adaptable surfaces for combined movements
4) weight dist over larger surface area
5) dist of synovial fluid across articular surfaces
Labrum
prominent in the ball & socket joints of shoulder and hip - fibrocartilaginous lip that extends from the edge of the joint socket to deepen it and increase the area of contact between socket & ball.
Strain
stretched or partially torn muscle or muscle and tendon - occurs when muscle contracts suddenly and powerfully
Sprain
forcible wrenching or twisting of a joint that stretches or tears it’s ligaments but does not dislocate the bones
Bursae
sac-like structures that are strategically situatied to alleviate friction insome joints, such as the shoulder and knee joints. Not part of synovial joints, but their walls consist of:
1) outer fibrous membrane of thin dense connective tissue
2) synovial membrane lining - filled with small amount of synovial-like fluid.
Tendon sheath
tubelike bursae that wrap around certain tendons that experience considerable friction as they pass through tunnels of connective tissue and bone.
1) inner visceral layer is attached to surface of tendon
2) outer parietal layer is attached to bone.
Between layers is small amount of synovial fluid. e.g. tendon of biceps brachii, wrist and ankle, fingers and toes. TENOSYNOVITIS
Movements - Gliding
movement of relatively flat bone surfaces back and forth and side to side over another; little change in angle between bones. e.g. Intercarpal and Intertarsal joints.
Movements - Angular
increase/decrease in angle between bones:
1) flexion - decrease in >, sagittal (flexion of thumb is across palm)
2) lateral flexion - movement of trunk in frontal plane
3) extension - increase in >, sagittal
4) hyperextension - extension past anatomical position
5) abduction - bone away from midline, frontal (spread fingers, toes)
6) adduction - bone towards midline, frontal (close fingers, toes) (thumb to palm in sagittal plane)
7) circumduction - flexion, abduction, extension, adduction and rotation in succession (distal end of body part moves in circle)
Movements - Rotation
movement of bone around longitudinal axis; in limbs may be medial (toward midline) or lateral (away from midline) e.g. shake ‘no’, turn trunk from side to side. If the ANTERIOR SURFACE of a bone of the limb is turned toward the midline, it is medial (internal) rotation, if it is turned away from the midline, it is lateral rotation. Hip is opposite to what you think!
Movements - Special
occur at specific joints:
1) elevation
2) depression
3) protraction
4) retraction
5) inversion
6) eversion
7) dorsiflexion
8) plantar flexion
9) supination
10) pronation
11) opposition
