Joints

definition : junction between two or more bones

Found all over the body except the hyoid which is just held by muscles

Function

Hold the skeleton together

Allows for bone growth

Allows for movement and flexibility

Classes of Joints

Functional/Movement

Tissue type

Immovable - synarthrosis (over time, the two bones may fuse) Example: suture of skull # #

Cartilaginous : connected by cartilage only

Synovial : joint cavity filled with synovial fluid (most common)

Fibrous - no joint cavity, connected by fibrous connective tissue

types:

synarthrosis

connective tissue: mainly collagen

syndesmosis

Slightly moveable - amphiarthrosis / symphysis Example: intervertebral discs # #

Freely mobile - diathrosis Example: hip bone #

suture : between bones of skull

gomphosis :: binds teeth to bony sockets in maxillae and mandible

synostosis: when 2 bones fuse and the boundary between them disappears

Primary: Synchondroses between two articulating bones

Secondary: Symphyses between two pubic bones

united by hyaline cartilage or fibrocartilage and has no joint cavity

primarily immovable

ossify with age

plate of hyaline cartilage

articular surface covered with hyaline disc plate

connected by fibrocartilage

fibrous capsule

filled with synovial fluid

enclosed with articulating ends of bone

types

possess a joint cavity

hinge

saddle

plane

pivot

condyloid

ball and socket

outer fibrous membrane with inner synovial membrane

secreted by synovial membrane and has a high concentration of proteoglycans

provides nutrients for the area.

divided into menisci / articular discs

flat articular surface

shock absorption

lubrication

allow for gliding movement and movement in different directions

intercarpal and intertarsal joints

pulled shaped articular surface

elbow and knee joint

flexion and extension

fit into one another; one rounded, one concave

proximal radioulnar joint and atlantoaxis joint

rotation around a central axis

rounded chondyle

knee joint

two directions

reciprocally saddle shaped, concavoconvex, modified condyloid joint

between trapezium and metacarpal bone of thumb, sternoclavicular joints

wide range

ball shaped bone head, cup shape bone cavity, modified condyloid joint

hip and shoulder joint

widest range of movement. Permits movements in all planes

Other parts of joint

bursae

ligaments

reinforce joint capsule. They also support and strengthen the joint

types

extrinsic ligaments: located on either side of joint capsule

intra / extracapsular ligament:

intrinsic / capsular ligaments: localised thickenings

small, fluid filled cavity (filled with synovial fluid)

formed where a tendon or ligament rub against other tissues

reduce friction, act as shock absorbers

Movement

Flexion

Ab / Ad duction

Extension / Hyperextension

Plantar flexion

Dorsiflexion

Rotation

Supination / Pronation

Circumduction

Elevation/ Depression

Protraction / Retraction

Inversion / Eversion

Ab: away from longitudinal axis of body in the frontal plane

Ad : moving back to anatomical position

moving arm in loop

with reference to anatomical position

inversion: twisting movement of foot inwards

eversion: opposite

flexion of heel and elevation of sole

extend ankle and elevate heel

Protraction: moving body part anteriorly in horizontal plane

Retraction: reverse movement

Depression: opening mouth

Pronation: turns wrist and hand from front to facing back

Supination: opposing movement

Elevation: shrug shoulders