JOINTS.docx

6 Pages
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Department
Cellular, Anatomical and Physiological Sciences
Course Code
CAPS 391
Professor
Bruce Matheson

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Description
JOINTS Classified as synovial, fibrous, cartiladgenous according to major CT types binding bones together and whether a fluid filled joint capsule is present. Classified based on degree of motion: nonvovable, slightly movable, freely movable FIBROUS JOINTS 2 bones united by fibrous CT, no joint cavity, little/no movement Sutures > seems between bones of skull, some immovable in older adults, opposing bones have interlocking processes (interdigitate). Very stable, tissue between bones is dense regular collagenous CT, periosteum on inner/outer surfaces of adjacent bones continues over the joint. Periosteum + dense fibrous CT = sutural ligament Fontanel > soft spot, makes skull flexible in new born, allows for growth of head after birth, membranous area in sutures Sutures become ossified. Synotosis > 2 bones grow together across a joint to form a single bone. SYNDESMOSES Fibrous joint, bones are farther apart than suture joined by ligaments, flexible (some movement can occur). Ex. Radioulnar syndesmoses (binds radius and ulna). GOMPHOSES Joints consisting of pegs that fit into sockets, held in place by bundles of regular collagenous CT. Ex. Joints between teeth and sockets of the mandible and maxillae (CT bundles here are called periodontal ligaments). Allow give to teeth during mastication. CARTILADGENOUS JOINTS Unite 2 bones by hyaline catiladge or fibrocartiladge. SYNCHONDROSES 2 bones joined by hyaline cartiladge, little or no movement (epiphyseal plates of growing bones). Temporary, with bone replacing them to form synostoses. Some persist through life (sternocostal synchondrosis between first rib and sternum by 1 costal cartiladge. All costal cartiladge starts as synchondroses, movement occurs between them and sternum, all but the first develop synovial joints). SYMPHYSES Fibrocartiladge uniting 2 bones (Ex. Junction between manubrium, body of sternum, symphysis pubis, intervertebral disks), some are slightly moveable because fibrocartiladge is slightly flexible. SYNOVIAL JOINTS Contain synovial fluid allowing movement between articulating bones. Joints that unite bones of appendicular skeleton (greater mobility). Articular surface of bones covered with thin hyaline cartiladge (articular cartiladge), for smooth surface where bones meet. Some have articular disk (flat pad of fibrocartiladge) between articular cartiladge of bones. Circumference of disk attaches to a fibrous capsule (Joints w/ articular disks: temporomandibular, sternoclavicular, acromioclavicular joints). Meniscus > fibrocartiladge pad in joints like the knee and wrist. Like an articular disk, with hole in center, circumference is attached to a fibrous joint capsule. Articular surfaces of bones that meet at a synovial joint are enclosed within a synovial joint cavity, surrounded by a joint capsule. Holds bones together, allowing movement. Joint capsule has 2 layers > outer fibrous capsule (dense irregular CT, continuos with fibrous layer of the periosteum that covers bones united at the joint. Portions of this capsule may thicken, collagen fibers may become regularly arranged to form ligaments. Ligaments/tendons may be present outside fibrous capsule, strengthening/stabilizing joint while limiting movement) and inner synovial membrane (lines joint cavity, except over articular cartiladge/disks. Thin, delicate, modified CT cells mixed with part of fibrous capsule OR separated by layer of aereolar/adipose tissue. Produces synovial fluid, lubricating film that covers surface of a joint.) Synovial fluid > serum (blood fluid) filtrate and secretions from synovial cells. (polysaccharides, proteins, fats, cells. (hyaluronic acid provides slippery quality of lubrication). Bursa > extended synovial membrane as a pocket or sac in a distance away from rest of joint cavity (in shoulder and knee). Contains synovial fluid/cushion between structures that would otherwise rub together (tendons on bones). Some bursa (subcutaneous olecranon bursa) provide a cushion between skin and underlying body prominences where friction could be damaging. Some bursa extend along tendons forming tendon sheaths. Bursitis > inflammation of bursa, causes pain around joint and restricts movement. At peripheral margin of articular cartiladge, bvs form vascular circle that supplies cartiladge with nourishment, NO bvs penetrate the cartiladge or enter joint cavity. Other nourishment comes from underlying spongy bone and synovial fluid. Sensory nerves enter fibrous capsule/synovial membrane somewhat. Supply the brain with info about pain in the joint, furnish constant info about joint’s position/degree of movement. Nerves don’t enter cartiladge or joint cavity. TYPES OF SYNOVIAL JOINTS Classified according to shape of adjoining articular surfaces. 6 types: Plane Hinge Pivot Ball-and-socket Ellipsoid Movements are uniaxial (around one axis), biaxial ( 2 axes at right angles to eachother), multiaxial (several axes) Plane joint >2 flat bone surfaces about = size that can move in a gliding motion. Uniaxial, some rotation is possible but limited by ligaments/adjacent bone. Ex. Articular processes between vertebrae. Saddle joint > 2 saddle shaped articulating surfaces at right angles to eachother so complementary surfaces articulate. Biaxial. Ex. Carpometacarpal joint of thumb. Hinge joint > uniaxial where convex cylinder in one bone is applied to a corresponding concavity in the other bone. Ex. Elbow and knee Pivot > uniaxial, restricts movement to rotation around single axis. Has cylindrical bony process that rotates within a ring of part bone and part ligament. Ex. Articulation between head of radius and proximal end of the ulna. Ball-and-socket > has a ball at the end of one bone and socket in an adjacent bone where the ba
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