BMSP 2135 Chapter 9
BMSP 2135 Chapter 9 2135 BMSP
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Date Created: 10/09/16
CHAPTER 9: Joints JOINTS (ARTICULATIONS) Articulation: any point where two bones meet, whether or not the bones are movable at that interface Arthrology: science of joint structure, function, and dysfunction Kinesiology: the study of musculoskeletal movement JOINTS AND THEIR CLASSIFICATION joint name: typically derived from the names of the bones involved ‾ atlantooccipital, glenohumeral & radioulnar joint joints classified according to the manner in which the adjacent bones are bound to each other, with differences in how freely the bones can move four major joint categories: ‾ bony joints ‾ fibrous joints ‾ cartilaginous joints ‾ synovial joints FIBROUS JOINTS (SYNARTHROSIS) fibrous joint, synarthrosis, or synarthrodial joint – a point at which adjacent bones are bound by collagen fibers that emerge from one bone, cross the space between them, and penetrate into the other three kinds of fibrous joints ‾ sutures ‾ gomphoses ‾ syndesmoses SUTURES sutures immovable or slightly movable fibrous joints that closely bind the bones of the skull to each other sutures can be classified as: ‾ serrate suture: interlocking wavy lines ‾ lap suture: overlapping beveled edges ‾ plane (butt) suture: straight, nonoverlapping edges TYPES OF SUTURES Serrate suture Lap suture Plane suture GOMPHOSES gomphosis attachment of a tooth to its socket held in place by fibrous periodontal ligament ◦ collagen fibers attach tooth to jawbone ◦ allows the tooth to move a little under the stress of chewing SYNDESMOSIS syndesmosis: a fibrous joint at which two bones are bound by longer collagenous fibers giving the bones more mobility interosseus membrane ‾ between radius and ulna is more moveable ‾ between tibia and fibula is less moveable FIBROUS JOINTS SYNARTHROSIS Sutures ‾ serrate, lap, plane Gomphosis ‾ tooth to socket Syndesmosis ‾ interosseous membrane CARTILAGINOUS JOINTS cartilaginous joint, amphiarthrosis or amphiarthrodial joint – two bones are linked by cartilage two types of cartilaginous joints ‾ synchondroses ‾ symphyses CARTILAGINOUS JOINT SYNCHONDROSIS synchrondrosis bones are bound by hyaline cartilage ◦ temporary joint in the epiphyseal plate in children ◦ first rib attachment to sternum other costal cartilages joined to sternum by synovial joints CARTILAGINOUS JOINT – SYMPHYSIS symphysis: two bones joined by fibrocartilage ‾ interpubic disc: between pubis bones to form the pubic symphysis ‾ intervertebral discs: between vertebral bodies only slight amount of movement between adjacent vertebrae collective effect of all 23 discs gives spine considerable flexibility CARTILAGINOUS JOINT AMPHIARTHROSIS Synchondrosis: Hyaline Cartilage ‾ epiphyseal plate ‾ first rib to sternum Symphysis: Fibrocartilage ‾ Pubic symphysis – interpubic disc ‾ Intervertebral joints – intervertebral discs BONY JOINT (SYNOSTOSIS) bony joint, or synostosis – an immovable joint formed when the gap between two bones ossify, and they become in effect, a single bone ‾ frontal bones in infants ‾ mandibular bones in infants ‾ cranial sutures in elderly ‾ attachment of first rib and sternum in elderly can occur in either fibrous or cartilaginous joints Use the meaning of the word roots to help remember the different classes of joints. Bony joint = synostosis (syn = together, osteon = bone) ‾ Immoveable Fibrous joints = synarthrosis (syn = together, arthrosis = joint) ‾ Slightly moveable Cartilaginous joint = amphiarthrosis (amphi = both, arthrosis = joint; a cartilaginous joint is slightly moveable – both a little moveable and a little not) ‾ A little more moveable Synovial joint = diarthrosis (di = two; arthrosis = joint) ‾ The most moveable Use the meaning of the word roots to help remember the different classes of joints. Bony joint Fibrous joints ‾ Suture (suture = join) ‾ Gomphosis (to bolt together) ‾ Syndesmosis (syn = together, desmo = bond) Cartilaginous joint ‾ Synchondrosis (syn = together, chondro = cartilage) ‾ Symphysis (sym = together, physis = grow) Synovial joint SYNOVIAL JOINT synovial joint, diarthrosis or diarthrodial joint – joint in which two bones are separated by a space called a joint cavity most are freely movable most structurally complex type of joint most familiar type of joint & most likely to develop painful dysfunction ‾ their mobility make them important to quality of life SYNOVIAL JOINT ANATOMY articular cartilage: layer of hyaline cartilage covering the articulating surfaces of bones ‾ usually 2 or 3 mm thick joint (articular) cavity: separates articular surfaces synovial fluid: slippery lubricant in joint cavity ‾ rich in albumin and hyaluronic acid ‾ gives it a viscous, slippery texture ‾ nourishes articular cartilage and removes waste ‾ reduces friction joint (articular) capsule – connective tissue that encloses the cavity ‾ outer fibrous capsule: continuous with periosteum of adjoining bones ‾ inner, cellular, synovial membrane : composed mainly of cells that secrete synovial fluid and macrophages that remove debris from the joint cavity in a few synovial joints, fibrocartilage grows inward from the joint capsule and forms articular discs or menisci ‾ articular disc a pad between articulating bones that crosses the entire joint capsule temporomandibular joint, distal radioulnar joint Menisci of the knee (singular = meniscus, plural = menisci) ‾ do not cross the entire joint capsule ‾ these cartilages absorb shock and pressure ‾ guide bones across each other, improve the fit between bones ‾ stabilize the joints, reducing the chance of dislocation Accessory structures associated with synovial joints ‾ tendons the most important structures in stabilizing a joint ‾ ligaments Accessory structures associated with synovial joints bursa: a fibrous sac filled with synovial fluid ‾ located between adjacent muscles or where tendon passes over bone or between bone and skin ‾ cushion muscles, helps tendons slide more easily over joints, modify direction of tendon pull ‾ Plural = bursae (BURsee) tendon sheaths: elongated cylindrical bursae wrapped around a tendon EXERCISE AND ARTICULAR CARTILAGE How does warming up before exercise benefit cartilage? exercise warms synovial fluid synovial fluid becomes less viscous as it warms and more easily absorbed by articular cartilage cartilage then swells and provides a more effective cushion against compression warmup period before vigorous exercise helps protect cartilage from undue wear and tear How does regular exercise benefit cartilage? repetitive compression of cartilage during exercise squeezes fluid and metabolic waste out of the cartilage when weight removed, cartilage absorbs synovial fluid like a sponge taking in oxygen and nutrients to the chondrocytes without exercise, cartilage deteriorates more rapidly from inadequate nutrition and waste removal ‾ Cartilage is avascular, and does not have a blood supply to provide nutrition and waste removal JOINTS AND LEVER SYSTEMS long bones act as levers to enhance the speed or power of limb movements lever – any elongated, rigid object that rotates around a fixed point called a fulcrum rotation occurs when an effort applied overcomes resistance (load) at some other point ‾ resistance arm and effort arm are described relative to fulcrum MECHANICAL ADVANTAGE advantage conferred by a lever: ‾ to exert more force against a resisting object than the force applied to the lever moving a heavy object with help of crowbar ‾ to move the resisting object farther or faster than the effort arm is moved movement of rowing a boat ‾ a single lever cannot confer both advantages as one increases, the other decreases mechanical advantage (MA) of a lever – the ratio of its output force to its input force mechanical advantage is calculated from the length of the effort arm divided by the length of the resistance arm MA > 1.0 – the lever produces more force, but less speed and distance, than the force exerted on it MA < 1.0 – the lever produces more speed or distance, but less force than the input ‾ contraction of the biceps brachii muscle puts more power into the lever than we get out of it, but the hand moves faster and farther (MA <1.0) RANGE OF MOTION range of motion (ROM) –the degrees through which a joint can move ‾ an aspect of joint performance ‾ physical assessment of a patient’s joint flexibility Range of motion determined by: ‾ structure of the articular surfaces elbow: olecranon of ulna fits into olecranon fossa of humerus ‾ strength and tautness of ligaments and joint capsules stretching of ligaments increases range of motion “doublejointed” people have long or slack ligaments ‾ action of the muscles and tendons nervous system monitors joint position and muscle tone muscle tone: state of tension maintained in resting muscles AXES OF ROTATION a moving bone has a relatively stationary axis of rotation that passes through the bone in a direction perpendicular to the plane of movement ‾ Note the blue bar in each picture, which represents the axis of rotation Monoaxial: has one degree of freedom or axis of rotation ‾ Example: interphalangeal joint (curl and uncurl your fingers) Biaxial: has two ‾ Example: metacarpophalangeal joint (spread out your fingers, move finger up and down to tap your desk) Multiaxial joint: has three ‾ Example: glenohumeral joint (shoulder) CLASSES OF SYNOVIAL JOINTS BallandSocket Joints ‾ smooth, hemispherical head fits within a cuplike socket multiaxial joints only two in humans shoulder joint head of humerus into glenoid cavity of scapula hip joint head of femur into acetabulum of hip bone Condyloid (ellipsoid) Joints ‾ oval convex surface on one bone fits into a complementary shaped depression on the other radiocarpal joint of the wrist metacarpophalangeal joints at the bases of the fingers ‾ biaxial joints – movement in two planes Saddle Joints ‾ Both bones have an articular surface that is shaped like a saddle, concave in one direction and convex in the other trapeziometacarpal joint at the base of the thumb sternoclavicular joint – clavicle articulates with sternum ‾ biaxial joint more movable than a condyloid or hinge joint forming the primate opposable thumb Plane (gliding) Joints ‾ flat articular surfaces in which bones slide over each other with relatively limited movement ‾ usually biaxial joint carpal bones of wrist tarsal bones of ankle articular processes of vertebrae ‾ although any one joint moves only slightly, the combined action of the many joints in wrist, ankle, and vertebral column allows for considerable movement Hinge Joints ‾ one bone with convex surface that fits into a concave depression on other bone (like a door swinging on its hinge) elbow joint ulna and humerus knee joint femur and tibia interphalangeal joints ‾ monaxial joint – move freely in one plane Pivot Joints ‾ one bone has a projection that is held in place by a ringlike ligament ‾ bone spins on its longitudinal axis atlantoaxial joint (dens of axis and atlas) transverse ligament proximal radioulnar joint allows the radius to rotate during pronation and supination anular ligament ‾ monaxial joint MOVEMENT OF SYNOVIAL JOINTS vocabulary of movements of synovial joints used in kinesiology, physical therapy, and other medical fields ‾ need to understand anatomical planes and directional terms zero position: the position of a joint when a person is in anatomical position ‾ joint movement are described as deviating from the zero position or returning to it FLEXION, EXTENSION AND HYPEREXTENSION flexion: movement that decreases the a joint angle extension: movement that straightens a joint and generally returns a body part to the zero position hyperextension: further extension beyond zero position flexion and extension occur at nearly all diarthroses, hyperextension is limited to a few joints ABDUCTION AND ADDUCTION abduction: movement of a body part in the frontal plane away from the midline of the body ‾ hyperabduction: raise arm over back or front of head adduction: movement in the frontal plane back toward the midline ‾ hyperadduction: crossing fingers, crossing ankles ELEVATION AND DEPRESSION elevation: a movement that raises a body part vertically in the frontal plane depression: lowers a body part in the same plane PROTRACTION AND RETRACTION protraction: the anterior movement of a body part in the transverse plane retraction: posterior movement CIRCUMDUCTION circumduction: one end of an appendage remains stationary while the other end makes a circular motion sequence of flexion, abduction, extension and adduction movements ‾ baseball player winding up for a pitch ROTATION rotation – movement in which a bone spins on its longitudinal axis ‾ rotation of trunk, thigh, head or arm medial (internal) rotation turns the bone inwards lateral (external) rotation turns the bone outwards SUPINATION AND PRONATION supination: forearm movement that turns the palm to face anteriorly or upward ‾ forearm supinated in anatomical position ‾ radius is parallel to the ulna pronation: forearm movement that turns the palm to face posteriorly or downward ‾ radius spins on the capitulum of the humerus ‾ radius crosses stationary ulna like an X MOVEMENTS OF THE TRUNK flexion, hyperextension, and lateral flexion of vertebral column SPECIAL MOVEMENTS OF MANDIBLE lateral excursion: right or left movement from the zero position medial excursion: movement back to the median, zero position ‾ sidetoside grinding during chewing protraction: retraction elevation: depression SPECIAL MOVEMENT OF HAND AND DIGITS radial flexion: tilts the hand toward the thumb ulnar flexion: tilts the hand toward the little finger flexion of fingers: curling them extension of fingers: straightening them abduction of the fingers: spread them apart adduction of the fingers: bring them together again flexion of thumb: tip of thumb directed toward palm extension of thumb: straightening the thumb opposition: move the thumb to touch the tips of any of the fingers reposition: return the thumb to the zero position SPECIAL MOVEMENT OF THE FOOT dorsiflexion: elevation of the toes as you do while swinging the foot forward to take a step (heel strike) plantar flexion: extension of the foot so that the toes point downward as in standing on tiptoe (toeoff) inversion: the soles are turned medially eversion: the soles are turned laterally supination of foot: complex combination of plantar flexion, inversion, and adduction pronation of foot: complex combination of dorsiflexion, eversion, and abduction TEMPOROMANDIBULAR JOINT temporomandibular (jaw) joint (TMJ) – articulation of the condyle of the mandible with the mandibular fossa of the temporal bone ‾ combines elements of condylar, hinge, and plane joints ‾ synovial cavity of the TMJ is divided into superior and inferior chambers by an articular disc ‾ two ligaments support joint ‾ deep yawn or strenuous depression can dislocate the TMJ condyles pop out of fossa and slip forward relocated by pressing down on molar teeth while pushing the jaw backward THE SHOULDER JOINT glenohumeral or humeroscapular joint – the head of the humerus articulates with the glenoid cavity of the scapula ‾ the most freely movable joint in the body ‾ shallow glenoid cavity and loose joint capsule sacrifice joint stability for freedom of movement ‾ glenoid labrum – fibrocartilage ring that deepens glenoid cavity shoulder supported by biceps brachii tendon anteriorly and also the rotator cuff tendons ‾ supraspinatus, infraspinatus, teres minor and subscapularis ‾ tendons fuse to joint capsule and strengthen it SHOULDER DISLOCATION very painful and sometimes cause permanent damage downward displacement of the humerus is the most common shoulder dislocation ‾ rotator cuff protects the joint in all directions but inferiorly ‾ joint protected from above by coracoid process, acromion, and clavicle dislocations most often occur when the arm is abducted and then receives a blow from above children especially prone to dislocation THE COXAL (HIP) JOINT coxal (hip) joint – the head of femur inserts into the acetabulum of the hip bone bears much more weight, have deeper sockets, more stable than shoulder ‾ dislocations rare: congenital dislocations in infants occur acetabular labrum – horseshoeshaped ring of fibrocartilage that deepens socket fovea capitis – pit on the head of femur ‾ ligament attaches to the acetabulum ‾ contains artery that supplies blood to the head of the femur THE KNEE JOINT tibiofemoral (knee) joint – largest and most complex diarthrosis of the body primarily a hinge joint ‾ capable of slight rotation and lateral gliding when knee flexed ‾ patellofemoral joint – gliding joint joint cavity contains two Cshaped cartilages ‾ lateral meniscus and medial meniscus ‾ joined by transverse ligament absorbs shock on the knee prevents femur from rocking sidetoside on the tibia medial and lateral meniscus absorb shock and shape joint two ligaments deep within joint capsule that cross each other to form an X ‾ synovial membrane folds around them, so they are excluded from the fluid filled synovial cavity ‾ anterior cruciate ligament (ACL) prevents hyperextension of knee when ACL is pulled tight one of the most common sites of knee injury posterior cruciate ligament (PCL) ‾ prevents femur from sliding off tibia ‾ prevents the tibia from being displaced backward knee joint has at least 13 bursae KNEE INJURIES highly vulnerable to rotational and horizontal stress most common injuries are to the meniscus and anterior cruciate ligament (ACL) heal slowly due to scanty blood flow arthroscopy – procedure in which the interior of the joint is viewed with a pencilthin arthroscope inserted through a small incision ‾ less tissue damage than conventional surgery ‾ recovery more quickly ‾ arthroscopic ACL repair – about nine months for healing to be complete ARTHRITIS arthritis a broad term for pain and inflammation of a joint most common crippling disease in the US rheumatologists – physicians who treat arthritis and other joint disorders osteoarthritis (OA) – most common form of arthritis ‾ ‘wearandtear arthritis’ ‾ results from years of joint wear ‾ articular cartilage softens and degenerates ‾ bone spurs develop on exposed bone tissue causing pain rheumatoid arthritis (RA) autoimmune attack against the joint tissues ‾ misguided antibodies attack synovial membrane, enzymes in synovial fluid degrade the articular cartilage, joint begins to ossify ‾ remissions occur, steroids and aspirin control inflammation arthroplasty the replacement of diseased joint with artificial device called prosthesis
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