bio lecture c9

Diarthrosis (synovial)

joint in which two bones are separated by a joint cavity, Most are freely mobile
Most structurally complex type of joint
Most likely to develop painful dysfunction

articular cartilage

layer of hyaline cartilage that covers the facing surfaces of two bones
Usually 2 or 3 mm thick

joint (articular) cavity

separates articular surfaces

synovial fluid

slippery lubricant in joint cavity
Rich in albumin and hyaluronic acid
Gives it a viscous, slippery texture like raw egg whites
Nourishes articular cartilage and removes waste
Makes movement of synovial joints almost friction free

joint (articular) capsule

connective tissue that encloses the cavity and retains the fluid
Outer fibrous capsule: continuous with periosteum of adjoining bones
Inner, cellular, synovial membrane: composed mainly of fibroblast-like cells that secrete synovial fluid and macrophages that remove debris from the joint cavity

shock absorber

function: In a few synovial joints, fibrocartilage grows inward from the joint capsule
Articular disc forms a pad between articulating bones that crosses the entire joint capsule

Bursa

fibrous sac filled with synovial fluid, located between muscles, where tendons pass over bone, or between bone and skin
Cushions muscles, helps tendons slide more easily over joints, modifies direction of tendon pull

tendon sheath

elongated cylindrical bursa wrapped around a tendon
In hand and foot

tendon

strip of collagenous tissue attaching muscle to bone

ligament

strip of collagenous tissue attaching one bone to another

warms

Exercise __________ synovial fluid

Becomes less viscous, more easily absorbed by cartilage

cushion, warm up period

Cartilage then swells and provides a more effective ________

_________ before vigorous exercise helps protect cartilage from undue wear and tear

more rapidly

Without exercise, cartilage deteriorates _______ from inadequate nutrition and waste removal

lever

any elongated, rigid object that rotates around a fixed point called a fulcrum, bones

rotation

occurs when an effort applied overcomes resistance (load) at some other point

Structure of the articular surfaces

Strength and tautness of ligaments and joint capsules

Action of the muscles and tendons

ROM determined by

1.__________

2.__________

3.___________

Elbow—olecranon of ulna fits into olecranon fossa of humerus

Stretching of ligaments increases range of motion

Double-jointed people have long or slack ligaments

Nervous system monitors joint position and muscle tone

Muscle tone—state of tension maintained in resting muscles

stationary axis

A moving bone has a relatively ____________ of rotation that passes through the bone in a direction perpendicular to the plane of movement

Multiaxial joint

3 planes of movement,

shoulder joint has ___three__ degrees of freedom or axes of rotation

Other joints are monoaxial or biaxial

1

how many degrees of freedom does the elbow have

ball and socket joint

Smooth, hemispherical head fits within cup-like socket
Only multiaxial joints in body
Examples: shoulder, hip
3 planes of movement=more unstable

Condylar (ellipsoid) joints

Oval convex surface of one bone fits into a complementary-shaped depression on the other
Biaxial joints—movement in two planes
Examples: radiocarpal joint, metacarpophalangeal joints

saddle joint

Both bones have an articular surface that is shaped like a saddle, one concave, the other convex
Biaxial joints
Examples: trapeziometacarpal (opposable thumb), sternoclavicular joint
more stable than ball and socket and condylar

plane (gliding) joint

Flat articular surfaces, bones slide over each other
Usually biaxial joints
Examples: between carpal bones of wrist; between tarsal bones of ankle; also between articular processes of vertebrae
occasionally monoaxial

hinge joint

One bone with convex surface fits into a concave depression of another bone

Monoaxial joints—move freely in one plane

Examples: elbow, knee, joints within fingers, toes

pivot joints

A bone spins on its longitudinal axis
Monoaxial joints
Examples: atlantoaxial joint (C1 and C2), radioulnar joint at the elbow

monoaxial

What kind of joint is the most stable?

zero position

the position of a joint when a person is in the standard anatomical position
Joint movements described as deviating from the zero position or returning to it
pair opposites together
palms anterior in anatomical pos

flexion

movement that decreases joint angle
Common in hinge joints

extension

movement that straightens a joint and returns a body part to the zero position

Hyperextension

extension of a joint beyond the zero position
Flexion and extension occur at nearly all diarthroses, hyperextension is limited to a few

abduction

movement of a body part in the frontal plane away from the midline of the body
Hyperabduction: raise arm over back or front of head

adduction

movement in the frontal plane back toward the midline
Hyperadduction: crossing fingers, crossing ankles

elevation

movement that raises a body part vertically in the frontal plane

depression

movement that lowers a body part in the same plane

protraction

the anterior movement of a body part in the transverse (horizontal) plane

retraction

posterior movement

roatation

movement in which a bone spins on its longitudinal axis
Rotation of trunk, thigh, head, or arm
Medial (internal) rotation turns the bone inward
Lateral (external) rotation turns the bone outward

pronation

forearm movement that turns palm to face either posteriorly or downward
Head of radius spins
Radius crosses stationary ulna like an X

supination

forearm movement that turns palm to face anteriorly or upward

Forearm supinated in anatomical position

Radius is ____paralell___ to the ulna

lateral flexion

tilting the head or trunk to the right or left at the midline

lateral excursion

right or left movement from the zero position of mandible

flexion, extension

______ vs. _____ of fingers —curling vs. straightening them

radial abduction

moving thumb away from index finger (90°)

medial excursion

movement back to the median, zero position

___side to side______ grinding during chewing

synovial fluid

_____________ less abundant and articular cartilage thinner or absent producing friction that causes pain

Osteoarthritis is common cause of physical disability