Tiêu đề 5. CLASSIFICATION OF JOINTS, TYPES OF MOVEMENTS OF JOINTS AND DISORDERS OF JOINTS.pdf ✅

PHARMD GURU Page 1 DEFINITION: Joint is a junction between two or more bones or cartilages. It is a device to permit movements. However, immovable joints are primarily meant for growth, and may permit moulding during childbirth. 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 JOINTS: A. STRUCTURAL CLASSIFICATION: 1. Fibrous joints 1) Sutures 2) Syndesmosis 3) Gomphosis 2. Cartilaginous joints 1) Primary cartilaginous joints or synchondrosis 2) Secondary cartilaginous joints or symphysis 3. Synovial joints 1) Ball-and-socket or spheroidal joints 2) Sellar or saddle joints 3) Condylar or bicondylar joints 4) Ellipsoid joints 5) Hinge joints 6) Pivot or trochoid joints 7) Plane joints B. FUNCTIONAL CLASSIFICATION (ACCORDING TO THE DEGREE OF MOBILITY): 1. Synarthrosis (immovable), like fibrous joints (Fig.3.1). CLASSIFICATION OF JOINTS, TYPES OF MOVEMENTS OF JOINTS AND DISORDERS OF JOINTS
PHARMD GURU Page 2 2. Amphiarthrosis (slightly movable), like cartilaginous joints (Fig. 3.2). 3. Diarthrosis (freely movable), like synovial joints (Fig. 3.3). Synarthroses are fixed joints at which there is no movement. The articular surfaces are joined by tough fibrous tissue. Often the edges of the bones are dovetailed into one another as in the sutures of the skull. Amphiarthroses are joints at which slight movement is possible. A pad of cartilage lies between the bone surfaces, and there are fibrous ligaments to hold the bones and cartilage in place. 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. 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. These ligaments are of elastic connective tissue. A synovial joint has a fluid-filled cavity between articular surfaces which are covered by articular cartilage. 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. Synovial fluid acts as a lubricant. The form of the articulating surfaces controls the type of movement which takes place at any joint. The movements possible at synovial joints are: ANGULAR:  Flexion : decreasing the angle between two bones;  Extension : increasing the angle between two bones;  Abduction : moving the part away from the mid-line;  Adduction : bringing the part towards the mid-line. ROTARY:  Rotation : turning upon an axis;
PHARMD GURU Page 3  Circumduction : moving the extremity of the part round in a circle so that the whole part inscribes a cone. GLIDING: One part slides on another. C. REGIONAL CLASSIFICATION: 1. Skull type: immovable. 2. Vertebral type: slightly movable. 3. Limb type: freely movable. D. ACCORDING TO NUMBER OF ARTICULATING BONES: 1. Simple joint: When two bones articulate, e.g. interphalangeal joints (Fig. 3.3). 2. Compound joint: More than two bones articulate within one capsule, e.g. elbow joint, wrist joint (Fig. 3.4). 3. Complex joint: When joint cavity is divided by an intra-articular disc, e.g., temporomandibular joint (Fig. 3.5) and sternoclavicular joint. The structural classification is most commonly followed, and will be considered in detail in the following paragraphs. FIBROUS JOINTS: In fibrous joints the bones are joined by fibrous tissue. These joints are either immovable or permit a slight degree of movement. These can be grouped in the following three subtypes. 1. Sutures: These are peculiar to skull, and are immovable. According to the shape of bony margins, the sutures can be: 1) Plane, e.g. internasal suture 2) Serrate, e.g. interparietal suture 3) Squamous, e.g. temporo-parietal suture 4) Denticulate, e.g. lambdoid suture 5) Schindylesis type (Fig. 3.6), e.g. between rostrum of sphenoid and upper border of vomer. Neonatal skull reveals fontanelles which are temporary in nature. At six specific points on the sutures in new born skull are membrane filled gaps