Joints and Articulations
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Joints And Their Classification A joint, or articulation, is any point at which two bones meet, regardless of whether they are movable at that point The science of joint structure, function, and dysfunction is called arthrology The study of musculoskeletal movement is kinesiology Joints And Their Classification Kinesiology is a branch of biomechanics, which deals with a broad range of motions and mechanical processes in the body, including the physics of blood circulation, respiration, and hearing. About Joints Tendons Ligaments Both are dense regular connective tissue About Muscles (acting at a joint) Characterizing Joints What type of movement does the joint allow? No movement, limited movement, free movement What tissue joins the bones? Fibrous Joints Fibrous connective tissue (suture, ligament, tooth) Cartilaginous Joints Fibrocartilage (pubic symphysis) Hyaline cartilage (epiphyseal plate, costal cart) Synovial Synarthrotic immoveable, allows no movement Amphiarthrotic allows only limited movement Diarthrotic Types of tissue between bones Suture (dense CT between bony plates) Syndesmosis (ligament) Gomphosis (tooth socket) Symphysis (fibrocartilage) Synchondrosis (hyaline cartilage) Synovial (fluid filled joint) A fibrous joint is two bones joined by fibrous connective tissue. It is immovable so it is categorized as a synarthrotic joint. No joint cavity Fibrous Joints Sutures Syndesmoses Gomphoses Suture In sutures and gomphoses, the fibers are very short and allow for little or no movement Syndesmosis In syndesmoses, the fibers are longer and the attached bones are more movable: ligament attaches! Gomphosis A cartilaginous joint is two bones joined by cartilage. The cartilage is either fibrocartilage (a symphysis joint) or hyaline cartilage (a synchondrosis). Fibrocartilage joints (symphyses) are amphiarthrotic (slightly moveable). Hyaline cartilage joints (synchondroses) are synarthrotic (immovable). Examples are epiphyseal plates and costal cartilages Symphysis In a symphysis, two bones are joined by fibrocartilage (A symphysis is amphiarthrotic: slightly moveable) Synchondrosis A synchondrosis is a joint in which the bones are bound by hyaline cartilage (A synchondrosis is synarthrotic: not moveable) A synchondrosis is a synarthrosis The most familiar type of joint and the most common. It allows a wide range of motion so it is functionally classified as a diarthrotic joint (a diarthrosis) Examples include the elbow, knee, knuckles, the joints between the wrist and ankle bones Synovial joints are the most structurally complex type of joint, (having a joint cavity) and are the most likely to develop uncomfortable and crippling dysfunctions Synovial Joints Characteristics Enclosed chamber, flexible fibrous capsule A cavity filled with fluid, synovial fluid An inner membrane that produces lubricating fluid, synovial membrane Articular cartilages covering ends of bones Reinforcing ligaments to stabilize Innervated and vascular Synovial Joint Structure In synovial joints, the facing surfaces of the two bones are covered with articular cartilage, a layer of hyaline cartilage about 2 mm thick These surfaces are separated by a narrow space, the joint (articular) cavity, containing a slippery lubricant called synovial fluid. This fluid is rich in albumin and hyaluronic acid, which give it a viscous, slippery texture. It nourishes the articular cartilages, removes their wastes, and makes movements at synovial joints almost friction-free Synovial Joint Structure In several synovial joints, fibrocartilage grows inward from the joint capsule and forms a pad between the articulating bones When the pad crosses the entire joint capsule it is called an articular disc Capsule A connective tissue membrane (articular capsule) encloses the cavity and retains the fluid. It has an outer fibrous capsule, which acts like a sleeve; it is continuous with the periosteum of the adjoining bones, and an inner, cellular synovial membrane Bursae A bursa is a fibrous sac filled with synovial fluid, located between adjacent muscles or where a tendon passes over a bone. Bursae cushion muscles, help tendons slide more easily over the joints, and sometimes enhance the mechanical effect of a muscle by modifying the direction in which its tendon pulls. The knee joint has at least 13 bursae Synovial Joint Bursitis is inflammation of a bursa, usually due to overexertion of a joint. Tendinitis is a form of bursitis in which a tendon sheath is inflamed There are six types of synovial joints, characterized by the motion allowed by the shapes of the bones. Plane Hinge Pivot Condyloid Saddle Ball and socket Plane Joints The carpal and tarsal bones, between the articular processes of the vertebrae, and at the sternoclavicular joint Hinge Joints The elbow, knee, and IPJ = interphalangeal (finger and toe) joints Pivot Joints The atlantoaxial joint between the first two vertebrae and proximal radioulnar joint, where the annular ligament on the ulna encircles the head of the radius Condyloid Joints Metacarpal-phalangeal joints: these are biaxial condyloid joints Saddle Joints At the base of the thumb (between the trapezium and metacarpal I) and sternoclavicular joint between the clavicle and sternum. Saddle joints are biaxial joints; in primate anatomy, allows for the opposable thumb Ball and Socket Joints Shoulder and hip joints are ball and socket. This type of joint is multiaxial. Three Important Synovial Joints Knee Joint Hip Joint Shoulder Joint The Knee Joint Tibiofemoral joint and patellofemoral joint The largest and most complex diarthrosis of the body Hinge joint, but has movements of gliding, rolling and rotation 3 articulations: lateral and medial articulations of femur and tibia; intermediate articulation of patella and femur. Note: Fibula does not articulate with the femur, only with the tibia. Extracapsular ligaments Patellar ligament (patellar tendon) Passes from the apex and margins of the patella distally to the tibial tuberosity Medial collateral ligament Extends from the medial epicondyle of the femur to the medial condyle of the tibia At its midpoint, its fibers are attached to the medial meniscus, Lateral collateral ligament Extends inferiorly from lateral epicondyle of femur to lateral surface of the fibular head Two ligaments lie outside the joint capsule: tibial (medial) collateral ligament. fibular (lateral) collateral ligament The two collateral ligaments prevent the knee from rotating when the joint is extended. Cruciate ligaments There are two ligaments that lie inside the joint capsule. They are deep within the joint cavity, but they are not inside the fluid-filled synovial cavity. These ligaments cross each other in the form of an X: the anterior cruciate ligament (ACL) posterior cruciate ligament (PCL) Intracapsular ligaments Cruciate ligaments join proximal tibia with distal femur, crisscrossing in the articular capsule Anterior cruciate ligament (ACL) Weaker of the two cruciates Arises from anterior intercondylar area of tibia, attaches at the posteromedial side of the femoral lateral condyle. Slack when knee is flexed, taut when fully extended Prevents posterior displacement of femur and hyperextension of knee joint Posterior cruciate ligament (PCL) Arises from posterior intercondylar area of tibia, attaches to the anterolateral surface of the medial condyle of femur. Taut during flexion, prevents anterior displacement of femur on the tibia Is the main stabilizing factor when weight-bearing during flexed knee position (ie. Walking downhill.) Menisci Medial and Lateral Menisci Crescent (C-) shaped plates of fibrocartilage located over the medial and lateral tibial condyles Thicker laterally, thinner inside the joint capsule Act like shock absorbers Thicker laterally, taper to thin unattached edges at interior of the joint. In the knee, two fibrocartilages extend inward from the left and right but do not entirely cross the joint Each is called a meniscus Menisci absorb the shock of the body weight jostling up and down on the knee and prevent the femur from rocking from side to side on the tibia Anterior View of Flexed Knee When the knee is extended, the ACL is pulled tight and prevents hyperextension. The PCL prevents the femur from sliding off the front of the tibia and prevents the tibia from being displaced backward. The ACL and PCL are named according to whether they attach to the anterior or posterior side of the tibia, (not for their attachments to the femur.) Knee Joint Be able to label the drawing with the names of all of the structures of the knee joint, including the bones, ligaments, cartilage, membranes, capsule, menisci, etc. Know the movements allowed and the movements prevented by the anatomy of the knee. 10 pt Essay Question: Label this (1/2 point each) Essay Answer (a) Essay Answer (b) Lateral Collateral ligament Patellar ligament (patellar tendon) Medial Collateral ligament Lateral Collateral ligament Anterior Cruciate ligament Posterior Cruciate ligament Lateral Collateral ligament Medial Collateral ligament Posterior Cruciate ligament Lateral Collateral ligament Medial Collateral ligament Anterior Cruciate ligament Hip Joint Strong, stable ball and socket joint, most moveable of all joints Transverse acetabular ligament (which bridges the acetabular notch) holds head in beyond its equator. Hip Joint Ligaments Iliofemoral ligament Y shaped; Attaches to ant infer iliac spine and acetabular rim proximally and inferior intertrochanteric line distally Prevents hyperextension of the hip during standing Pubofemoral ligament Runs from the superior ramus of the pubis and passes laterally and to the intertrochanteric line (passing deep to the iliofemoral ligament.) Prevents overabduction of the hip joint Ischiofemoral ligament Runs from ischial part of acetabular rim, to the neck of femur (best seen from posterior view.) Prevents hyperextension of the hip by screwing the femoral head deeper into the acetabulum Ligament of the head of the femur (ligamentum teres) Weak, little importance in strengthening hip joint Runs from the transverse acetabular ligament and attaches to the pit (fovea capitis) of head. Hip Joint Posterior View of the Hip Joint Hip Ligaments Be able to label the drawing with the names of the ligaments that attach to the hip. 10 pt Essay Question: Label this Essay Answer: 1 pt each The Shoulder Joint Diarthrotic, ball and socket joint: Humeral head in glenoid cavity Shoulder Joint (Glenohumeral Joint) Ligaments: Glenohumeral ligaments : 3 fibrous bands From the anterior glenoid labrum to the anatomical neck of humerus Reinforce the anterior part of the articular capsule (and are inside the capsule, not visible from outside.) Coracohumeral ligament From base of coracoid process to anterior aspect of greater tubercle of humerus Transverse humeral ligament Runs from greater to lesser tubercle of humerus Creates a channel , bridging over the intertubercular groove Site for tendon of long head of biceps brachii Coracoacromial ligament From inferior aspect of acromion to coracoid process Forms a protective “arch” preventing superior displacement of the head Supraspinatus muscle passes under this arch. Shoulder Ligaments Shoulder:Glenohumeral Joint Shoulder Ligaments Be able to label the drawing with the names of the ligaments that attach the clavicle to the scapula and to the head of the humerus. 10 pt Essay Question: Label this Essay Answer: ½ pt each Ligaments of the Ankle Joint Ligaments of the Ankle Joint
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