Joints YEAR 1 PDF

JOINTS  JOINTS Meeting, joining, union or connection between different parts of skeleton either bones or cartilage. TYPES OF JOINTS: A. FIBROUS JOINTS: B. CARTILAGINOUS JOINTS: I. Primary Cartilaginous Joints. (Synchondroses) II. Secondary Cartilaginous Joints (Symphyses) C. SYNOVIAL...

JOINTS  JOINTS Meeting, joining, union or connection between different parts of skeleton either bones or cartilage. TYPES OF JOINTS: A. FIBROUS JOINTS: B. CARTILAGINOUS JOINTS: I. Primary Cartilaginous Joints. (Synchondroses) II. Secondary Cartilaginous Joints (Symphyses) C. SYNOVIAL JOINTS  JOINTS Meeting, joining, union or connection between different parts of skeleton either bones or cartilage. TYPES OF JOINTS: A. FIBROUS JOINTS: - 2 bones are connected together by fibrous tissue. -Tissue is mainly inelastic white fibers stretching between 2 bony ends and tightly connects them together. -No movement could be done ….fixed joints -The least common among all types of joints -Examples: 1. Sutures of the skull (coronal, sagittal,.) 2. Gomphosis (dentoalveolar syndesmosis); between root of teeth and their sockets in gums. 3. Inferior tibio-fibular joint (Syndesmosis) B. CARTILAGINOUS JOINTS: - 2 bones are connected by hyaline cartilage (1ry) or fibro-cartilage (2ry) that extends between bony ends. -Little or limited movement due to presence of a cartilaginous media. -More common than fibrous joints. I. Primary Cartilaginous Joints (Synchondroses): Hyaline cartilage is ossified later in life (transformed into bone at old age) No movement -Examples: 1. Epiphyseal plate of long bones; between epiphysis and metaphysis). 2. Spheno-occipital (basi-spheoid) joint; between basilar part of occipital bone and body of sphenoid, at base of the skull, ossified at about 23years. 3. Between costal cartilage of first rib with manubrium sterni. II. Secondary Cartilaginous Joints (Symphyses): -Nature of articulation preserved all over the life. -Examples:- 1. Intervertebral discs 2. Symphysis pubis 3. Manubrio-sternal joint C. SYNOVIAL JOINTS: -The most common type of joints in the body and the most movable one. Structure of the synovial joint: 1. Bony articular ends: 2 or more bony ends, usually large in size 2. Articular cartilage: A thin smooth layer of hyaline cartilage covers the opposed articular surfaces of the bony ends. Gives a smooth surface for the surface of articulation. Gives a sort of flexibility between the articulating bones, so it facilitates the movements’ in-between. 3. Fibrous capsule: Extends and connects opposed bony ends sharing in the articulation together. May be thickened to form ligaments. May be weakened by presence of openings in some sites. Sometimes, there are intra-capsular ligaments inside joint cavity. 4. Synovial membrane: A very thin highly vascular membrane Covers all intracapsular structures of the joint except articular surfaces. Lines inner surface of the fibrous capsule. Contains the synovial cells which secrete synovial fluid inside joint cavity. 5. Synovial fluid: Acts as a lubricant to prevent friction between the opposed bones. Facilitates movements in-between articulating bones Plays an important role in nourishment of articular cartilage. Subsidiary structures inside synovial joint: Articular disc of fibro-cartilage (temporomandibular, sterno-clavicular, acromio- clavicular, inferior radioulnar joints) Intra-capsular ligaments as cruciate ligaments of knee joint Menisci of cartilage that are present in knee joint Tendons of some muscles as long head of biceps brachii Pads of fat inside the joint cavity Blood supply: Articular twigs that come from the surrounding vessels. They pierce the fibrous capsule to reach the joint. Nerve Supply of Joints: Capsule and ligaments receive an abundant sensory nerve supply. A sensory nerve supplying a joint also supplies the muscles moving the joint and the skin overlying the insertions of these muscles, Hilton's law. STABILITY OF JOINTS: Depends on three main factors: shape, size, and arrangement of articular surfaces; ligaments; and tone of muscles around the joint. 1. Articular Surfaces: - Ball-and-socket arrangement of hip joint and arrangement of ankle joint are good examples of how bone shape plays an important role in joint stability. - However, shape of the bones contributes little or nothing to stability include acromioclavicular joint, calcaneocuboid joint and knee joint. 2. Ligaments: - Fibrous ligaments prevent excessive movement in a joint , but if the stress is continued for a long period, then fibrous ligaments stretch; ligaments of the joints between the bones forming arches of the feet will not by themselves support weight of body. - Should tone of muscles that normally support the arches become impaired by fatigue, then the ligaments will stretch and the arches will collapse, producing flat feet. - Elastic ligaments, return to their original length after stretching. Elastic ligaments of the auditory ossicles play an active part in supporting the joints and assisting in the return of the bones to their original position after movement. 3. Muscle Tone: - In most joints, muscle tone is major factor controlling stability. - Muscle tone of short muscles around the shoulder joint keeps hemispherical head of humerus in shallow glenoid cavity of the scapula; without action of these muscles, very little force would be required to dislocate this joint. - Knee joint is very unstable without tonic activity of quadriceps femoris muscle. - Joints between the small bones forming arches of feet are largely supported by tone of muscles of the leg, whose tendons are inserted into bones of feet CLASSIFICATION OF SYNOVIAL JOINTS: A. ACCORDING TO AXIS OF MOVEMENTS: Uni-axial joints: Move around single axis, either transverse or longitudinal; elbow, ankle joints. The movements occur at these joints are; flexion and extension. Bi-axial joins: Move around two axes; wrist and metacarpo- phalangeal joints. Movements occur are flexion & extension and adduction & abduction. Poly-axial joints: Move in three axes; shoulder and hip joints. Movements at these joints are flexion and extension & adduction and abduction & medial and lateral rotations. B. ACCORDING TO SHAPE OF ARTICULATING SURFACES: BALL AND SOCKET TYPE: Poly-axial; shoulder and hip joints HINGE TYPE: Uni-axial; elbow, ankle, inter-phalangeal joints. SADDLE-SHAPED TYPE: Bi-axial; the opposing surfaces are reciprocally concavo-convex, e.g. carpo-metacarpal joint of thumb (1stcarpo-metacarpal joint). GLIDING (PLANE) TYPE: Has two smooth opposing surfaces, e.g. inter- carpal, inter-tarsal and costo-vertebral joints. PIVOT TYPE: Uni-axial; where a pivot turns around a longitudinal axis, e.g. superior radio-ulnar and atlanto-axial joints CONDYLOID TYPE: Bi-axial, where two convex condyles articulate with two concave condyles, e.g. knee joint (modified hinge type). ELLIPSOID TYPE: Bi-axial, where one convex surface articulates with an elliptical concave surface, e.g. wrist joint.