Definition of the Joint .
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| Synarthrosis: Fibrous joint |
[1]. Joint is a junction between two or more bones or cartilages.
[2]. It is a device to permit movements. However, immovable joints are primarily meant for growth and may permit moulding during childbirth.
[3]. There are more joints in a child than in an adult because as growth proceeds some of the bones fuse together, e.g. the ilium, ischium and pubis to form the pelvic bone; the two halves of the infant frontal bone, and of the infant mandible; the five sacral vertebrae and the four coccygeal vertebrae.
Classification of the Joint .
[A] Structural classification of Joint .
[B] Functional Classification of Joint .
[C] Regional Classification of Joint .
[D] Articular classification of Joint .
[A] Structural classification of Joint .
1. Fibrous joints
(a) Sutures .
(b) Syndesmosis .
(c) Gomphosis .
2. Cartilaginous joints .
(a) Primary cartilaginous joints or synchondrosis .
(b) Secondary cartilaginous joints or symphysis .
3. Synovial joints.
(a) Ball-and-socket or spheroidal joints .
(b) Sellar or saddle joints .
(c) Condylar or bicondylar joints .
(d) Ellipsoid joints .
(e) Hinge joints .
(f) Pivot or trochoid joints .
(g) Plane joints .
[B] Functional Classification of Joint .
1. Synarthrosis (immovable), Joint .
[1]. Synarthroses are fixed joints at which there is no movement.
[2]. The articular surfaces are joined by tough fibrous tissue.
[3]. Often the edges of the bones are dovetailed into one another as in the sutures of the skull . like – fibrous Joint .
2. Amphiarthrosis (slightly movable) joints .
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| Amphiarthrosis: Secondary cartilaginous joint |
[1]. Amphiarthroses are joints at which slight movement is possible.
[2]. A pad of cartilage lies between the bone surfaces, and there are fibrous ligaments to hold the bones and cartilage in place.
[3]. The cartilages of such joints also act as shock absorbers, e.g. the intervertebral discs
between the bodies of the vertebrae, where the cartilage is strengthened by extra collagen fibres . like – Cartilaginous Joint .
3. Diarthrosis (freely movable) joints .
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| Diarthrosis: Simple synovial joint |
[1]. Diarthroses or synovial joints are known as freely movable joints, though at some of them the movement is restricted by the shape of the articulating surfaces and by the ligaments which hold the bones together.
[2]. These ligaments are of elastic connective tissue. A synovial joint has a fluid-filled cavity between articular surfaces which are covered by articular cartilage.
[3]. The fluid, known as synovial fluid, produced by the synovial membrane which lines the cavity except for the actual articular surfaces and covers any ligaments or tendons which pass through the joint.
[4]. Synovial fluid acts as a lubricant . Like -Synovial Joint .
-: The movements possible at synovial joints :-
[1] Angular .
[1]. flexion : decreasing the angle between two bones .
[2]. extension : increasing the angle between two bones .
[3]. abduction : moving the part away from the mid-line .
[4]. adduction : bringing the part towards the mid-line .
[2] Rotatory .
[1]. Rotation : turning upon an axis .
[2]. circumduction: moving the extremity of the part round in a circle so that the whole part inscribes a cone .
[3] Gliding .
one part of the Joint slides on another .
[C] Regional Classification of Joint .
1. Skull type: immovable.
2. Vertebral type: slightly movable.
3. Limb type: freely movable.
[D] Articular classification of Joint .
1. Simple joint: When two bones articulate, e.g. interphalangeal joints .
2. Compound joint: More than two bones articulate within one capsule, e.g. elbow joint, wrist joint .
3. Complex joint: When joint cavity is divided by an intra-articular disc, e.g., temporomandibular joint and sternoclavicular joint. disc, e.g., temporomandibular joint and sternoclavicular joint.
