Notes Ch. 8C Joints of the Skeletal System Anatomy and Physiology
Examples of Synovial Joints The shoulder, elbow, hip, and knee are large, freely movable joints. They have similarities but also are very different to make each specific function possible.
Shoulder Joint The shoulder joint is a ball-and-socket joint. It is made of the rounded head of the humerus and the cavity of the scapula. There are muscles, ligaments, and tendons that hold the bones together. Ligaments that are included in the shoulder are: The coracohumeral ligament - it is made of connective tissue that connects the scapula and humerus. The glenohumeral ligaments -have 3 bands of thick fibers. They also help connect the scapula and humerus. The transverse humeral ligament is a sheet of connective tissue.
There are several bursae in the shoulder joint. The shoulder joint has a wide range of movement. The movements include flexion, extension, adduction, abduction, rotation, and circumduction.
Elbow Joint The elbow joint is very complex. It has a hinge joint between the trochlea of the humerus and the trochlear notch of the ulna. There is a plane joint between the capitulum of the humerus and a shallow depression on the head of the radius. A joint capsule encloses and holds together these 2 joints.
The ulnar collateral ligament is a band of thick connective tissue that holds the joint in place. The radial collateral ligament is a fibrous band that keeps the radial head in contact with the radial notch of the ulna. There is a synovial membrane that forms the inner lining of the elbow. There are also fatty pads between the membrane and the joint capsule. They help protect bony areas during movement.
The movement in the elbow between the humerus and ulna are hinge type movements - flexion and extension. The head of the radius is free to rotate, this allows pronation and supination of the forearm.
Hip Joint The hip joint is a ball-and-socket joint that is made of the head of the femur and the cup- shaped acetabulum of the hip bone. The major ligaments found in the hip joint are: The iliofemoral ligament that is a Y-shaped band of strong fibers. This is the strongest ligament of the body. The pubofemoral ligament The ischiofemoral ligament is made of strong fibers.
There is less movement than in the shoulder because the muscles in the hip joint hold it closer together. Movement in the hip joint include flexion, extension, adduction, abduction, rotation, and circumduction.
Knee Joint The knee joint is the largest and most complex synovial joint. It is made from the end of the femur and the tibia. It is a hinge joint but it does allow some rotation. The joint between the femur and the patella is a plane joint.
The ligaments of the knee are: Patellar ligament - continues from the large muscle group in the thigh. Oblique popliteal ligament connects part of the femur to the tibia. The arcuate popliteal ligament is Y-shaped fibers that extend from the femur to the tibia. The tibial collateral ligament connects the femur to the tibia. The fibular collateral ligament is a strong, round cord.
Cruciate ligaments are strong bands of fibrous tissue and help keep everything in place. The movement of the knee joint is flexion and extension. When the knee is flexed rotation is possible.
Life Span Changes Joint stiffness is an early sign of aging. Range of motion may diminish. Exercise can help reduce stiffness. Fibrous joint are the first to change - the fontanels of the skull close at 2, 3, 12, and 18 to 24 months of age. Fibrous joints strengthen over a lifetime. Overtime the ligaments between vertebral discs will lessen in flexibility.