Joints

Joints - connections in the skeleton between any of its rigid component parts - bones or cartilage

1. Fibrous - a joint united by fibrous connective tissue

· sutures - bones of the skull; allows little or no movement

§ serrate - interlocking edges

§ squamous - overlapping edges

§ synostosis = complete fusion of the bones across suture lines

· syndesmoses - apposed bones joined together by abundant fibrous tissue

§ inferior tibiofibular joint

§ tympanostapedial joint of middle ear

§ interosseous membrane

1. radioulnar

2. tibiofibular (middle)

· gomphoses - between teeth and bony sockets

2. Cartilaginous - bones with intervening cartilage connecting them, either hyaline or fibrous cartilage

· 1° cartilaginous (synchnondrses)

§ epiphyseal plate in growing bones

§ cartilaginous union between the sternum and the first rib

§ synostosis = the conversion of a cartilaginous joint to bone

· 2° cartilaginous (symphyses) - skeletal elements' surfaces are covered by hyaline cartilage and joined by fibrous cartilage

§ intervertebral discs

§ pubic symphysis

3. Synovial - the most common type of joint, it has four characteristics:

§ a joint cavity

§ joint surfaces lined with articular cartilage

§ joint cavity lined by synovial membrane

§ joint space is covered by an articular capsule

· plane (gliding or sliding) - capable of movement in any direction, but generally within a single plane (uniaxial); joint surfaces are almost flat

1. articular joints of the vertebrae

2. carpal, tarsal, carpometacarpal (except 1st), tarsometatarsal joints

3. acromioclavicular joint

· hinge - permit movement in only one plane (two directions), flexion and extension

1. elbow (humeroulnar) joint

2. interphalangeal joints

· condyloid - similar to hinge joints, but ellipsoidal shaped joint surfaces permit more movement, generally in two planes, at right angles to each other (biaxial)

1. knee joint

2. wrist (radiocarpal) joint

3. metacarpophalangeal joints

· pivot - permit movement in only one direction, but around a longitudinal axis related to the bone

1. radioulnar joint

2. atlantoaxial joint

· saddle - articular surfaces are concavoconvex in shape and movements are in two planes (biaxial)

1. first carpometacarpal joint (of the thumb)

2. sternoclavicular joint

· ball and socket - one bone has a rounded convex head and the other has a concave socket; it permits movement in any direction; the freest of the synovial joints

1. hip

2. shoulder

· Structures associated with synovial joints

1. Ligaments - Bands or sheets of fibrous connective tissue connecting two structures, generally bones.

· intrinsic - intra-articular; within a joint cavity

· capsular - thickenings of the joint capsule

· extrinsic - extracapsular; connective tissue bands outside the joint capsule to provide joint stability

2. Joint cartilages - additions to synovial joints

· a] articular discs - fibrous cartilage pads which subdivide a joint cavity; they provide added cushion to the joint action

· b] meniscus and labrum - rims of fibro-(us)cartilage, for molding or increasing the size of the joint surface

· Cartilage - Specialized rigid connective tissue. In the skeleton cartilage serves as:

1. Growth plate for bones, especially the long bones

2. A bridge between adjacent bones

Category: Anatomy Notes