Chapter 10 Essay

Submitted By RichardG11
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Pages: 6

Chapter 10 Joints Arthrology is the science concerned with joints. Joints are classified according to their relative freedom of movement. A diarthrosis is freely movable. An amphiarthrosis is slightly movable. A synarthrosis is immovable. Joints are also classified according to how the adjacent bones are joined. In fibrous joints, collagen fibers cross the gap between two bone matrices and join them. In cartilaginous joints, the two bones are held together by cartilage. In synovial joints, the bones are separated by lubricating synovial fluid. At fibrous joints, fibers of collage join two bones. Sutures are limited to the skull. Serrate sutures form wavy lines. Lap (squamous) sutures occur where two bones have overlapping beveled edges. Plane (butt) sutures occur where two bones have straight, nonoverlapping edges. Where a tooth attaches into its bony socket is a gomphosis. The tooth is held in place by a fibrous periodontal membrane. Syndesmoses are the most movable of the fibrous joints and are joined by an interosseous ligament. Example: tibia and fibula connection at the ankle. In cartilaginous joints, the two bones are joined by cartilage. In a synchondrosis, the bones are joined by hyaline cartilage (such as the attachment of a rib to the sternum). In a symphysis, two bones are joined by a fibrocartilage pad, such as an intervertebral disc. Some fibrous and cartilaginous joints ossify with age. The gap between adjacent bones fills with osseous tissue until the bones become one. This type of joint is a synostosis. The bones of a synovial joint are separated by a joint cavity containing lubricating synovial fluid. The adjoining surfaces of bones are covered with hyaline cartilage, further reducing friction within the joint. A joint capsule encloses the cavity, and is made up of an outer fibrous capsule lined with synovial membrane. Certain joints contain a pad of fibrocartilage called a meniscus that absorbs shock and pressure. Synovial joints are reinforced on the outside by tendons and ligaments, and sometimes inside by ligaments. Fluid-filled bursae underlie certain muscles, helping tendons glide easily over joints. Ball-and-socket joints occur at the shoulder and hip and are highly movable, multiaxial joints. Examples include the shoulder and hip joints. Hinge joints are monaxial, like a door hinge. Examples include the knee, finger and toe joints. Condyloid (ellipsoid) joints exhibit an oval convex surface that fits into a similar depression on the next. The metacarpophalangeal joints are an example. The body's only saddle joint occurs at the base of the thumb. Each bone in the joint is concave in one direction and convex in the other. This joint is the hallmark of primate anatomy: the opposable thumb. In pivot joints, one bone has a knobby projection that fits into the ring-like ligament on the other, such as between the first two vertebrae. In gliding joints, articular surfaces are mostly flat, such as between the carpal or tarsal bones. Flexion is movement that decreases the angle of a joint. Extension straightens the joint. Hyperextension increases the angle beyond 180o. Abduction is movement of a body part away from the midsagittal line. Adduction is movement toward the midsagittal line. Elevation is movement that raises a bone vertically. Depression is the opposite of elevation. Protraction is movement of a bone anteriorly. Retraction is movement posteriorly. Lateral and medial excursion refer to the side-to-side movements associated with mastication. During circumduction, one end of an appendage remains stationary while the other end makes a circular motion. Rotation is a movement in which a bone turns on its longitudinal axis. Supination and pronation are limited to the forearm. Supination is rotating the arm so the palm is upward. Pronation is rotating the arm so the palm is downward. Opposition is movement of the thumb toward the fingers. Reposition is movement back to anatomical position. These…