24_Articulations.pptx

Articulations Chapter 8, Human Anatomy (LibreTexts) "bone x-ray result" is in the Public Domain, CC0 Classification of Joints • Joint (articulation) is any place where adjacent bones or bone and cartilage come together (articulate with each other) to form a connection. • Joints can be classified...

Articulations Chapter 8, Human Anatomy (LibreTexts) "bone x-ray result" is in the Public Domain, CC0 Classification of Joints • Joint (articulation) is any place where adjacent bones or bone and cartilage come together (articulate with each other) to form a connection. • Joints can be classified • Functionally – the degree of movement • Structurally – material that connects the bones Functional Classification of Joints • Determined by the amount of mobility found between the adjacent bones. Tradeoff between stability and mobility: the more mobile joints are very unstable, and viceversa. • Three functional classifications • Synarthrosis: immobile or nearly immobile joint. • Example: Sutures of skull • Amphiarthrosis: limited mobility • Example: Vertebrae • Diarthrosis: Freely mobile • Example: Shoulder or hip joint Structural Classification of Joints • Determined by the material that forms the joint: dense regular connective tissue, cartilage or fluid. • Fibrous Joint: adjacent bones are united by dense regular connective tissue. • Cartilaginous Joint: bones are joined by hyaline cartilage or fibrocartilage. • Synovial Joint: bones are not directly connected, but instead come into contact with each other within a joint cavity that is filled with a lubricating fluid. Fibrous Joints • Bones are directly connected to each other by dense regular connective tissue • Three types • Suture between bones of the skull. These are synarthrosis. • Syndesmosis or interosseous membranes between radius and ulna or tibia and fibula. These are amphiartrhosis. • Gomphosis between teeth and alveolar processes. These are synarthrosis. Fibrous Joints (Image) "Fibrous Joints" by OpenStax is licensed under CC BY 3.0 Cartilaginous Joints • Bones are united by cartilage: hyaline cartilage or fibrocartilage • Two types • Synchondrosis: united by hyaline cartilage. Example: costochondral joints (between ribs and costal cartilage) and 1st sternocostal joint (between sternum and 1st rib). These are synarthrosis. • Symphysis: united by fibrocartilage. Example: pubic symphysis and intervertebral joints. These are amphiarthrosis. Cartilaginous Joints (Image) "Cartiliginous Joints" by OpenStax is licensed under CC BY 3.0 Synovial Joints • All joints that are not fibrous or cartilaginous. They are all diarthrosis. • Structural Features • Articular capsule includes a fibrous layer to for connection and a synovial membrane that secretes synovial fluid into the joint cavity. Synovial fluid is important to lubricate the articulating surfaces, to remove waste and to act as a shock absorber. • Articular cartilage that covers the epiphysis of the two bones. • Ligaments around the articular capsule to keep bones in place. • Additional Structures • Blood vessels and nerves • Bursae: sacs outside synovial joints where ligaments, muscles, tendons or bones rub. • Fat pads: packing material for protection Synovial Joints (Image) "Synovial Joints" by OpenStax is licensed under CC BY 3.0 Ligaments, Bursae and Fat Pads (Image) "Bursa" by OpenStax is licensed under CC BY 3.0 Types of Synovial Joints • Synovial joints are subdivided based on the shapes of the articulating surfaces of the bones that form each joint • Six Types • • • • • • Pivot Hinge Condyloid Saddle Plane Ball-and-socket Types of Synovial Joints (Image) "Types of Synovial Joints" by OpenStax is licensed under CC BY 3.0 Naming Joints • Take less-mobile bone/marking and change ending to -o • Add more-mobile bone in adjective form • Example: Temporal bone + mandible = Temporomandibular joint • Example: Glenoid cavity +humerus= Glenohumeral joint • Example: Tibia + Femur = Tibiofemoral joint Glenohumeral (Shoulder) Joint • Very mobile but very unstable. Most of the joint’s strength is due to the rotator cuff muscles that surround the joint. • Coracoacromial ligament runs between the acromion and coracoid process of the scapula. It prevents superior displacement of the head of the humerus. • Acromioclavicular ligament runs between acromion of the scapula and the clavicle, keeping these bones in place. • Subacromial bursa is located deep to deltoid and acromion. It reduces friction beneath the deltoid. Glenohumeral (Shoulder) Joint (Image) "Shoulder Joint" by Whitney Menefee is licensed under CC BY 3.0 / A derivative from the original work Knee Joint • Largest diarthrosis: very strong but often injured • When flexed, capable of slight rotation and lateral gliding • 2 articulations • Tibiofemoral joint between condyles of femur and condyles of tibia • Patellofemoral joint between patella and patellar surface of femur • Articular capsule encloses the medial, lateral, and posterior regions of joint but not the anterior region. • Kept in place by pairs of ligaments. Knee Joint Ligaments • Lateral (fibular) collateral ligament (LCL) prevent lateral movement. • Medial (tibial) collateral ligament (MCL) prevent medial movement. • Anterior cruciate ligament (ACL) connects posterior femur to anterior tibia to prevent hyperextension of knee. • Posterior cruciate ligament (PCL) connects anterior femur to posterior tibia to prevents hyperflexion of knee and posterior displacement of tibia on femur. • Lateral meniscus and medial meniscus are pads of fibrocartilage on tibial condyles to cushion and stabilize the joint. • Unhappy triad injury from lateral blow to knee: ACL, MCL and medial meniscus are torn. • Patella is held in place by tendon from quadriceps muscles and the patellar ligament that attaches patella to the tibia. Knee Joint (Image) – Sagittal and Superior View "Knee Joint" by OpenStax is licensed under CC BY 3.0 Knee Joint (Image) – Anterior View "Knee Joint" by OpenStax is licensed under CC BY 3.0