JOINTS

Honors Anatomy & PhysiologyChapter 8

JOINTS

aka Articulations

2 Functions:1. Hold Bones Together2. Allows otherwise rigid

skeleton to have some flexibility

Classification of Joints

Functionally

Named according to how much movement allowed @ joint

Structurally Named

according to presence of fibrous tissue, cartilage, or a joint cavity separate the articulated bones

Functional Joints Synarthrosis

Immovable jointsSkull bones

AmphiarthrosisSlightly movable joints

Symphysis pubis Diarthrosis

Freely movable jointsBall & Socket or Hinge Joints

Structural Joints1. Fibrous Joints

Bones united by fibrous tissue Joint connecting distal tibia &

fibula

2. Cartilaginous Joints Bone ends connected by cartilage Pubic symphysis

3. Synovial Joints Articulating ends of bone

separated by joint cavity

4 Features of Synovial Joints1. Articular Cartilage

Hyaline cartilage covers ends of bones

2. Fibrous Articular Capsule Joint surfaces enclosed by capsule of

fibrous CT Capsule lined by synovial membrane

3. Joint Cavity Contains synovial fluid

4. Reinforcing Ligaments Reinforce fibrous articular capsule

General Structure of a Synovial Joint Articular Cartilage Joint Cavity Articular Capsule Synovial Fluid Reinforcing Ligaments Nerves & Blood Vessels Some also have: menisci, bursae,

tendon sheaths outside the joint proper

Factors Influencing Stability of Synovial Joints Joints must be stabilized to avoid

dislocation Stability of a joint depends on 3

factors:1. Articular surfaces: overall minor role2. Ligaments: prevent excessive or

undesirable motion at the joint3. Muscle tone: muscle tendons that

cross the joint most stabilizing factor

Types of Synovial Joints1. PLANE JOINT

Articular surfaces flat Allow gliding movement (w/out

rotation) Example: intercarpal joints of

wrist & ankle

Types of Synovial Joints2. HINGE JOINT cylindrical end of bone fits

into trough-shaped surface of another bone

Angular movement allowed in 1 plane

Examples: elbow, knee, interphalangeal joints

Types of Synovial Joints3. PIVOT JOINT Rounded end of 1 bone fits into

sleeve or ring of another bone allows 1 bone to rotate along

its long axis Example: joint between atlas &

dens of axis

Types of Synovial Joints4.CONDYLOID JOINT “knuckle-like” Egg-shaped end of 1 bone fits into

oval concavity in another bone Allows for moving bone to travel

side-to-side & back-and-forth but cannot rotate along its long axis

Example: metacarpophalangeal joint

4. CONDYLOID JOINT

Types of Synovial Joints5. SADDLE JOINTS Each articular surface has

convex & concave areas Same movements as condyloid

joints Example: twiddling your

thumbs

Types of Synovial Joints6. BALL & SOCKET JOINTS Spherical head of 1 bone fits

into a round socket formed by 1 or more bones

Allows movement is 3 dimensions(most freely moving of synovial joints)

Types of Movements @

Synovial Joints 1. Gliding relatively flat surfaces move back-

and-forth & side-to-side

Types of Movements @

Synovial Joints 2. flexion/extension/ hyperextension: opposite movements

flexion: decrease in angle between articulating bones

extension: increase in angle between articulating bones

hyperextension: continuation of extension beyond the anatomical position

Types of Movements @

Synovial Joints 3. abduction/adduction/

circumductionabduction: movement of bone away

from midlineadduction: movement of bone toward

midlinecircumduction: movement of distal

end of a body part in a circle

Types of Movements @

Synovial Joints 4. elevation/depression: elevation: upward movement of

part of body (closing mouth, shrugging shoulders)

depression: downward movement of part of body (opening mouth, returning elevated shrugged shoulders to anatomical position)

Types of Movements @

Synovial Joints 5. protraction/retraction protraction: movement of part of

body anteriorly in transverse plane retraction: returning a protracted

part of body to anatomical position

Types of Movements @

Synovial Joints 6. inversion/ eversion inversion: movement of soles

medially @ intertarsal joints (soles face each other)

eversion: movement of soles laterally @ intertarsal joints

Types of Movements @

Synovial Joints 7. dorsiflexion/ plantar flexion dorsiflexion: bending foot @ ankle

in direction of dorsum (superior surface)

plantar flexion: bending foot @ ankle in direction of plantar surface

Types of Movements @

Synovial Joints 8. supination/pronation supination: movement of forearm

in which palm is turned anteriorly pronation: movement of forearm in

which distal end of radius crosses over distal end ulna & palm is turned posteriorly

Types of Movements @

Synovial Joints 9. opposition movement of thumb in which

thumb moves across palm to touch tips of the fingers on same hand

Ball - & - Socket Joint ball-like surface of one bone fits

into a cuplike depression of another bone

permits movement around 3 axis + all directions in betweenflexionextensionabductionadductioncircumductionrotation

SPRAINS Ligaments or tendons

reinforcing a joint are damaged by excessive stretching or tearing

Both have poor blood supply so heal slowly

ARTHRITIS

“inflammation of a joint” General term for >100 different

diseases Most wide-spread, disabling

disease in USA Onset: same symptoms: joint

stiffness & swelling Synovial membrane inflammed

thickens less synovial fluid increased friction

Rheumatoid Arthritis

Autoimmune disorder Adult onset or Juvenile onset Women 3x more often than

men Any synovial joint could be

affected, often symmetrical involvement

disfiguring

Rheumatoid Arthritis

Osteoarthritis

Most common form of arthritis Chronic degenerative

condition: “wear-and-tear” Affects articular cartilage

(eventually breaks down) increased friction bone spurs develop restricts movement

Osteoarthritis

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