Lecture One - Joints Flashcards
What are the two general types of joints?
Synovial joints - the skeletal elements are separated by a cavity.
Solid joints - there is no cavity and the components are held together by connective tissue.
Describe sinovial joints.
Synovial joints are connections between skeletal components where the elements involved are separated by a narrow articular carity.
A layer of cartilage (usually hyaline cartilage) covers the articulating surfaces of the skeletal elements.
As a result, when viewed in radiographs, the gap between bones in a joint seems very large, when in reality much of this gap is filled with cartilage.
There is a joint capsual consisting of an inner synovial membrane and an outer fibrous membrane. This encloses the articular cavity.
The synovial membrane is highly vascular and therefore lubricated the joint.
Closed sacs of synovial fluid called synovial bursae or tendon sheaths occur out side the joints. These intervene between structures such as tendons and bone, tendons and joints or skin and bone to reduce the amount of friction between the structures moving agains one another.
The fibrous membrane is made of dense connective tissue and sounds and stabilizes the joint. Part sof the fibrous membrane may thicken to form ligaments to futher stablize the joint.
Describe the common but not universal characteristics of synovial joints.
Articular discs - Usually composed of fibrocartilage. Absorb compression forces, adjust to changes in the contours of joint surfaces during movements and increase the range of movements that can occur at joints.
Fat pads - Usually occur between the synovial membrane and the capsule and move into and out of regions as joint ontours change during movement.
Describe synovial joints based on thier shape.
Plane (flat)
Hinge
Pivot
Bicondyla (two sets of contact points)
Condylar (ellipsoid)
Sadle
Ball and socket
Describe the plane joint.
Allow sliding or gliding movements when one bone moves acress the surcae of another.
E.g. Acromioclavicular joint.
Describe the hinge joint.
Allow movement around on axis that passes transversly through the joint, permit flaxion and extension.
E.g. Elbow.
Describe the pivot joint.
Allow movement around one axis that passes longitudinally along the shaft of the bone, permit roation.
E.g. Atlanto-axial joint.
Describe the bicondylar joint.
Allow movement around one axis with limited rotation around a second axis. Formed by two convex condyles that articulate with concave or flat surfaces (e.g. knee joint).
Describe the condylar joint (ellipsoid).
Allow movement around two axes that are at right angles to each other, permit flexion, extension, abduction, adduction and circumduction (limited).
E.g. Wrist joint.
Describe the saddle joint.
Allow movement around two axes that are at right angles to each other, the articular surfaces are saddle shaped, permit flexion, extension, abduction, adduction and circumduction.
E.g. carpometacarpal joint of the thumb.
Describe the ball and socket joint.
Allow movement around multiple axes, permit flexion, extension, abduction, adduction, circumduction and rotation.
E.g. the hip joint.
What are solid joints?
Connections between skeletal elements where the adjacent surfaces are linked together either by fibrous connective tissue or by cartilage, usually fibrous cartilage.
Movement in these joints are more restricted than synovial joints.
Fibrous joints and cartilaginous joints are both solid joints.
Describe the different types of fibrous joints.
Sutures occur only in the skull where adjacent bones are linked by a think layer of connective tissue termed a sutural ligament.
Gomphoses occur only between the teeth and adjacent bone. In these joints, short collagen tissue fibers in the periodontal ligament run between the root of the tooth and the bony socket.
Syndesmoses are joints in which two adjacent bones are linked by a ligament. E.g. the ligamentum flavum, which connects adjacent vertebral laminae and an interosseous membrane, which links, for example the radius and the ulna in the forearm.
Describe the different types of cartilaginous joints.
Synchondroses Occur where two ossification centers in a developing bone remain separated by a layer of cartilage. E.g. the growth plate that occurs between the head and shaft of developing long bones. These joints allow bone growth and eventually become completly ossified.
Symphses occur where two separate bones are interconnected by cartilage. Most of these types of joints occur in the midline and include the pubic symphysis between the two pelove bones, and intervertebral dics between adjacent vertebrae.
