ANATOMY & PHYSIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site joint A joint, or articulation, is a place where two bones come together. All of the bones in the human skeleton, except for one (the hyoid bone in the neck), form a joint with another bone. In terms of the amount of movement they allow, there are three types of joints: Diarthroses – freely movable joints Amphiarthroses – slightly movable joints Synarthroses – immovable or fixed joints Diarthroses (synovial joints) A diarthrosis or synovial joint Types of synovial joint Credit: Lucile Packard Children's Hospital Most joints in the adult body are diarthroses, or freely movable joints. The singular form is diarthrosis. In this type of joint, the ends of the opposing bones are covered with hyaline cartilage, the articular cartilage, and they are separated by a space called the joint cavity. The components of the joints are enclosed in a dense fibrous joint capsule, also called an articular capsule. The outer layer of the capsule consists of the ligaments that hold the bones together. The inner layer is the synovial membrane that secretes synovial fluid into the joint cavity for lubrication. Because all of these joints have a synovial membrane, they are sometimes called synovial joints. Types of diathroses or synovial joints include: Ball and socket joints, like your hip and shoulder joints. These are the most mobile type of joint in the human body. They allow you to swing your arms and legs in many different directions. Ellipsoidal joints, such as the joint at the base of your index finger>. These allow bending and extending, rocking from side to side, but rotation is limited. Gliding joints. These occur between the surfaces of two flat bones that are held together by ligaments. Some of the bones in your wrists and ankles move by gliding against each other. Hinge joints, like in your knee and elbow. These enable movement similar to the opening and closing of a hinged door. Pivot joints. The pivot joint in your neck allows you to turn your head from side to side. Saddle joints. The only saddle joints in your body are in your thumbs. The bones in a saddle joint can rock back and forth and from side to side, but they have limited rotation. Synarthroses (fibrous joints) Synarthroses are immovable joints. The singular form is synarthrosis. In these joints, the bones come in very close contact and are separated only by a thin layer of fibrous connective tissue. The sutures in the skull are examples of immovable joints. Amphiarthroses (cartilaginous joints) Slightly movable joints are called amphiarthroses. The singular form is amphiarthrosis. In this type of joint, the bones are connected by hyaline cartilage or fibrocartilage. The ribs connected to the sternum by costal cartilages are slightly movable joints connected by hyaline cartilage. The symphysis pubis in the pelvis is a slightly movable joint in which there is a fibrocartilage pad between the two bones. The joints between the vertebrae and the intervertebral disks are also of this type. Related category    • ANATOMY AND PHYSIOLOGY Source: National Cancer Institute Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP