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U2: Joints/Articulat
Question | Answer |
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Joints/articulations | a junction of two or more bones; hold bones of skeleton together, yet many allow for mobility of the skeleton. Functional and structural classifications. |
Functional classification | joint classification; based upon the amount of movement allowed at a joint. Ex. Freely moveable joints are diarthroses joints and are predominate in limbs. |
Structural classification | joint classification; two criteria-kind of connective tissue binding articulating bones together and presence or absence of a joint cavity between the articulation joints; 3 classes-fibrous, cartilaginous, synovial |
Fibrous joints | bones tightly joined by fibrous connective tissue; no joint cavity; immobile. Ex. Skull sutures. |
Cartilaginous joints | bones joined by cartilage, no joint activity, slightly moveable, ex. Intervertebral joints of spine, pubic symphasis (both connected with fibrocartilage. |
Synovial joints | bones are joined by a synovial membrane and fibrous capsule. Joint cavity is present; freely moveable joints; functionally are diathroses joints; ex. Shoulder, elbow, wrist, hip, knee, ankle |
Features of synovial joints | articular/joint capsule, fibrous capsule, synovial membrane, synovial fluid, articular cartilages, reinforcing ligaments, blood vessels, nerves |
Articular/joint capsule | two layered sleeve that encloses joint cavity; consists of fibrous capsule and synovial membrane. |
Fibrous capsule | outer layer of articular/joint capsule |
Synovial membrane | inner layer of articular/joint capsule; covers/lines all the internal joint surfaces except where articular cartilage occurs. |
Synovial fluid | slippery, lubricating fluid that’s secreted by the synovial membrane into the joint cavity. Also moves into and out of articular cartilages in asstn with pressure placed on joints during normal movement. Helps nourish articular cartilages |
Articular cartilage | layer of hyaline cartilage tissue covers articulating surfaces of bones in a synovial joint; reduces friction, shock absorption |
Reinforcing ligaments | ligaments that strengthen the fibrous capsule |
Nerves of synovial joints | fibers that innervate the articular capsule; detect pain and monitor how much the capsule is being stretched which tells nervous system posture and body movements. |
Bursae | in some synovial joints;flat, synovial fluid-filled sacs lined w/ synovial membrane; reduce friction b/t joint related structures that rub against one another during mvnt.In places where ligaments, tendons, muscles, bones, or skin rub together (knee) |
Menisci/articular discs | pads of fibrocartilage that improve the fit between bones in certain synovial joints (knee and temporomandibular joint); tearing of this in the knee is a “torn cartilage” injury |
Factors that influence stability of synovial joints | shapes of articular bone surfaces; ligaments, muscle tone |
Types of movement allowed at synovial joints | flexion, extension, hypertextension, abduction, adduction, rotation, pronation, supination, inversion, eversion, dosiflexion, plantar flexion, protraction, retraction, elevation, depression |
Flexion | decreases the angle beteween bones of a joint and brings them closer together, ex. Bending the forearm at the elbow or bending leg at the knee, tilting head toward chest, angular forward and upward movement of thigh or arm |
Extension | increases angle and distance between bones. Returns bones to anatomical position after being flexed; ex. Straightening forearm at the elbow, straightening leg at the knee from flexed positions |
Hyperextension | extension beyond the anatomical position, i.e. tilting the head so chin is pointing at sky. One cannot do this usually without injury at forearm at elbow or leg at the knee |
Abduction | movement of limb away from the midline of body |
Adduction | movement of limb toward midline of body. |
Rotation | sort of a semicircular movement of a bone; occurs at shoulder joint and hip joint; occurs at joint formed between dens/odontoid process of the axis and atlas |
Pronation | moving palm and forearm from an anterior or upward facing postitoin to a posterior or downward facing position. Occurs when radius rotates around the ulna crossing over ulna to form “x” position |
Supination | moving palm and forearm from a posterior or downward facing postitoin to an anterior or upward facing position; occurs when the radius rotates around the ulna to bring these bone into a parallel position relative to one another |
Inversion | turning the sole of the foot so it faces medially |
Eversion | turning sole of the foot so it faces laterally |
Dorsiflexion | movement at the ankle that moves the instep (top) of foot up and toward shin. |
Plantar flexion | movement at the ankle that moves the foot downward; occurs when you stand on your toes |
Protraction | non-angular movement in which a bone is moved straight forward. Ex. Drawing the shoulder (mainly scapula) directly forward. |
Retraction | non-angular movement in which bone is moved straight back. Ex. Squaring the shoulders |
Elevation | non-angular movement in which bone is moved straight up, ex. Shrugging the shoulders |
Depression | non-angular movement in which a bone is moved straight down; ex. Dropping the shoulders |
Types of synovial joints | classified by shapes of articulating surfaces; hinge, pivot, ball and socket |
Hinge joint | allows for flexion and extension; ex. Knee, elbow, joint between atlas and occipital condyles (atlanto-occipital joint) |
Pivot joint | allows for rotation; ex. Atlanto-axial joint, proximal radio-ulnar joint |
Ball and socket joint | allows for a wide variety of movements; ex. Shoulder and hip joints |
Temporomandibular joint (TMJ) | junction of-head/mandibular condyle of mandible & mandibular fossa of temporal bone. B/c of shallow mandibular fossa, most commonly dislocated joint in body; cause of painful disorder common in people; asstd w/ chewing muscles |
Wrist joint | mainly involves the articulation of radius with scaphoid and lunate bones which are 2 specific carpal bones. |
Shoulder joint | ball and socket type joint; consists of articulation of head of humerus with glenoid cavity/fossa of scapula. Loose fit of humerus head w/ shallow glenoid fossa/cavity makes it most freely moving body joint. Prone to dislocate. |
Rotator cuff | provides stability to shoulder joint; comprised of muscle and tendons. Encircles shoulder joint and includes supraspinatus, infraspinatus, subscapularis, and teres minor. Prone to strains & tears when arm is vigorously moved. Baseball pitcher injuries. |
Elbow joint | hinge joint; consists of fit of the trochlea of humerus into trochlear notch of ulna |
Hip joint | ball and socket joint formed by articulation of head of femur with the acetabulum of hip/coxal bone |
Knee joint | largest, most complex joint in body. Consists of wheel shaped condyles of femur with flat condyles of tibia. Articulation of patella w/ anterior, distal end of femur. Review ligaments of knee joint on pg. 10 and 11 of notes. |
Ankle joint | articulation of distal tibia and distal fibula w/ talus. |
Joint disorders | sprain, dislocation, torn cartilage injury of knee, bursitis, arthritis |
Sprain | stretched or torn ligament; partly torn will eventually repair themselves but heal slowly |
Dislocations | when bones of a joint are forced out of the normal alignment; one time of this injury will make joint susceptible to repeat injuries |
Torn cartilage injury of knee | involves tearing of meniscus in knee joint; menisci rarely repairs itself; usually torn pieces are surgically removed. |
Bursitis | inflammation of bursa; sometimes called “water on the knee” |
Arthritis | several different kinds, but all present with pain and stiffness of joints. |
Osteoarthritis | called “wear and tear” arthritis; involves degeneration of articular cartilage. Common and practically part of the aging process for humans. |
Rheumatoid arthritis | autoimmune disease; involves inflammation and degeneration of synovial membrane followed by formation and ossification of scar tissue in the joint which can fuse bone ends together and cause deformity. |