SYNOVIAL JOINTSCatubay, Jaymee C.Catubay, John Michael R.

Synovial Joints The bones forming the joint have synovial cavity and are united by the dense irregular connective tissue of an articular capsule, and often by accessory ligaments.

STRUCTURE OF SYNOVIAL JOINTS synovial ( joint) cavity - space between the articulating bones

Synovial (joint) cavity allows a joint to be freely movable (diarthroses) articular cartilage - layer of hyaline cartilage- covers the articulating surface of the bones with a smooth, slippery surface but does not bind them together- reduces friction between bones in the joint during movement- helps to absorb shock

Articular Capsule Sleevelike, surrounds a synovial joint, encloses the synovial cavity, and unites the articulating bones two layers: fibrous membrane (outer ) synovial membrane (inner ) fibrous membrane - dense irregular connective tissue that attaches to the periosteum of the articulating bones. - thickened continuation of the periosteum between the bones flexibility - permits considerable movement at a joint great tensile strength - helps prevent the bones from dislocating

Fibrous membrane fibers are arranged as parallel bundles of dense regular connective tissue that are highly adapted for resisting strains Ligaments - principal mechanical factors that hold bones close together in a synovial joint.

Synovial membrane areolar connective tissue with elastic fibers articular fat pads - accumulations of adipose tissueSynovial Fluid a viscous, clear or pale yellow fluid named for its similarity in appearance and consistency to uncooked egg white hyaluronic acid secreted by fibroblast-like cells in the synovial membrane and intersttial fluid filtered from blood plasma forms a thin film over the surfaces within the articular capsule reducing friction by lubricating the joint absorbing shocks supplying oxygen and nutrients to and removing carbon dioxide and metabolic wastes from the chondrocytes within articular cartilage Phagocytic cells that remove microbes and the debris that results from normal wear and tear in the joint.Accessory Ligaments Extracapsular ligaments - lie outside the articular capsule Intracapsular ligaments - within the articular capsule but are excluded from the synovial cavity by folds of the synovial membrane. knee, pads of fibrocartilage lie between the articular surfaces of the bones and are attached to the fibrous capsule. subdivide the synovial cavity into two spaces, allowing separate movements to occur in each space allow two bones of different shapes to fit together more tightly help to maintain the stability of the joint and direct the flow of synovial fluid to the areas of greatest friction.Nerve and Blood Supply Contain many nerve endings that are distributed to the articular capsule and associated ligaments Some convey information about pain from the joint to the spinal cord and brain for processing Other respond to the degree of movement and stretch at a joint The spinal cord and brain - sending impulses through different nerves to the muscles to adjust body movements. avascular, arteries in the vicinity send out numerous branches that penetrate the ligaments and articular capsule to deliver oxygen and nutrients Veins remove carbon dioxide and wastes from the joints arterial branches from several different arteries typically merge around a joint before penetrating the articular capsule chondrocytes - receive oxygen and nutrients from synovial fluid derived from blood joint tissues are supplied directly by capillaries

Bursae and Tendon Sheaths Bursae - Saclike structures, alleviate friction in some joints (shoulder and knee joints) not strictly part of synovial joints, but they do resemble joint capsules because their walls consist of connective tissue lined by a synovial membrane filled with a small amount of fluid that is similar to synovial fluid located between the skin and bones, tendons and bones, muscles and bones, or ligaments and bones fluid-filled bursal sacs cushion the movement of these body parts against one anotherTendon (synovial) sheaths tubelike bursae that wrap around certain tendons that experience considerable friction reduce friction at joints occurs where tendons pass through synovial cavities, such as the tendon of the biceps brachii muscle at the shoulder joint

Wrist and ankle, where many tendons come together in a confined space in the fingers and toes, where there is a great deal of movement

TYPES OF MOVEMENTS AT SYNOVIAL JOINTSGliding flat bone surfaces move back-and-forth and from side-to-side with respect to one another

no significant alteration of the angle between the bones limited in range due to the structure of the articular capsule and associated ligaments and bones intercarpal and intertarsal joints

Angular Movements increase or a decrease in the angle between articulating bones flexion, extension, lateral flexion, hyperextension, abduction, adduction, and circumduction Flexion (- to bend) there is a decrease in the angle between articulating bones Extension (- to stretch out) there is an increase in the angle between articulating bones

lateral flexion - occurs along the frontal plane and involves the intervertebral joints

hyperextension ( beyond or excessive) ,continuation of extension beyond the anatomical position

Abduction (ab- away; -duct to lead) is the movement of a bone away from the midline adduction ( ad- toward) is the movement of a bone toward the midline along the frontal plane

Circumduction (circ- circle) is movement of the distal end of a body part in a circle

not an isolated movement by itself but rather a continuous sequence of flexion, abduction, extension, and adduction does not occur along a separate axis or plane of movement (rota- revolve), a bone revolves around its own longitudinal axis

Special movements occur only at certain joints elevation, depression, protraction, retraction, inversion, eversion, dorsiflexion, plantar flexion, supination, pronation, and opposition Elevation ( to lift up) is an upward movement of a part of the body

Depression (to press down) is a downward movement of a part of the body

Protraction ( to draw forth) is a movement of a part of the body anteriorly in the transverse plane

Retraction (to draw back) is a movement of a protracted part of the body back to the anatomical position

Inversion (to turn inward) is movement of the sole medially at the intertarsal joints (between the tarsals)

Eversion (to turn outward) is a movement of the sole laterally at the intertarsal joints

Dorsiflexion - bending of the foot at the ankle or talocrural joint (between the tibia, fibula, and talus) in the direction of the dorsum (superior surface) Plantar flexion involves bending of the foot at the ankle joint in the direction of the plantar or inferior surface

Supination - movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly Pronation - movement of the forearm at the proximal and distal radioulnar joints in which the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly

Opposition - movement of the thumb at the carpometacarpal joint (between the trapezium and metacarpal of the thumb) in which the thumb moves across the palm to touch the tips of the fingers on the same hand

TYPES OF SYNOVIAL JOINTS planar joint - are flat or slightly curved primarily permit back-and-forth and side-to-side movements between the flat surfaces of bones Biaxial (many)

hinge joint - the convex surface of one bone fits into the concave surface of another bone produce an angular, opening-and-closing motion like that of a hinged door monaxial (uniaxial) permit only flexion and extension

pivot joint - the rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament monaxial

condyloid joint (condyl- knuckle) or ellipsoidal joint, the convex oval-shaped projection of one bone fits into the oval-shaped depression of another bone Biaxial (flexionextension and abductionadduction)

saddle joint - the articular surface of one bone is saddle shaped, and the articular surface of the other bone fits into the saddle as a sitting rider would sit modified condyloid joint in which the movement is somewhat freer triaxial, (flexionextension, abductionadduction, and rotation) ball-and-socket joint - consists of the ball-like surface of one bone fitting into a cuplike depression of another bone triaxial, (flexionextension, abductionadduction, and rotation)

Factors affecting contact and range of motion at synovial joints Structure or shape of the articulating bones Strength and tension (tautness) of the joint ligaments Arrangement and tension of the muscles Contact of soft parts Hormones Disuse

Reference Principles of Anatomy and Physiology 12th edition-Tortora pg 265-229