Guided Notes on Joints and Skeletal Development

1. Joints, also called articulations, have two functions 1. Joints, also called articulations, have two functions. They are: to hold the bones together securely, and to give the skeleton mobility.

2. Joints are classified either functionally or structurally 2. Joints are classified either functionally or structurally. The functional classification focuses on the amount of movement allowed by the joint. Structurally, there are fibrous, cartilaginous, or synovial joints based on whether fibrous tissue, cartilage, or a joint cavity separates the bones.

The Different Types of Joints Joint Type Classification Example Description Syn-arthoses Functional Sutures of the cranium Immovable joints Amphi-arthroses Sternumn to ribs Slightly movable joints diarthroses Append-icular skeleton Freely movable joints fibrous structural Bones united by fibrous tissue

The Different Types of Joints Joint Type Classification Example Description Cartilag-inous Structural Inter-vertebral joints Bone ends connected by cartilage Synovial Elbow joint Bones separated by a cavity containing synovial fluid

All synovial joints have four distinguishing features. They are: Articular cartilage Fibrous articular capsule Joint cavity Reinforcing ligaments

5. Bursae and tendon sheaths are often found closely associated with joints. They reduce friction between adjacent structures during joint activity. Bursae are flattened fibrous sacs containing a thin film of synovial fluid.

6. The shapes of articulating bone surfaces determine what movements are allowed at a joint. Based on these shapes, synovial joints fall into 6 major categories.

Synovial Joints Plane Joint Hinge Joint Pivot Joint Name Description of Shape Movement Allowed Non-, Uni-, Bi-, or Multi-axial Examples Plane Joint Articular surfaces are flat Short slipping or gliding movements Non-axial No rotation Intercarpal joints Hinge Joint Cylindrical end of one bone (trough shaped) Angular movement in one plane Uni-axial elbow Pivot Joint Round end of 1 bone; sleeve of other bone Rotation around long axis Radio-ulnar joint Atlas/axis

Synovial Joints Condyloid Joint Saddle Joint Ball-and-Socket Joint Name Description of Shape Movement Allowed Non-, Uni-, Bi-, or Multi-axial Examples Condyloid Joint Egg-shaped surface fits into oval cavity Side-to-side or Back-and-forth Bi-axial Metacarpo-phalangeal joint Saddle Joint Each articular surface shaped like a saddle Thumb/carpals Ball-and-Socket Joint Spherical head/round socket Movement in all directions Multi-axial Shoulder or hip

7. In a sprain, the ligaments or tendons reinforcing a joint are damaged by excessive stretching, or they are torn away from the bone. Sprains heal slowly because they have a poor blood supply.

8. The term arthritis describes over 100 different inflammatory or degenerative diseases that damage the joints. Acute forms of arthritis result from bacterial invasion. The synovial membrane thickens, which leads to increased friction and pain.

9. Osteoarthritis, which is the most common form or arthritis, is a chronic degenerative condition that typically affects the aged. OA typically affects the articular cartilages. Over the years, there is a breakdown of the cartilage, and the exposed bone thickens. Bone spurs grow around the margins of the eroded cartilage. The joints most commonly affected are: the fingers, cervical and lumbar vertebrae, the knees, and the hips.

10. Rheumatoid arthritis usually occurs between the ages of 40 and 50 10. Rheumatoid arthritis usually occurs between the ages of 40 and 50. It affects 3 times as many women as men. RA is an autoimmune disease, which is a disorder in which the body’s immune system destroys its own tissues.

11. Gouty arthritis, or gout, is a disease in which uric acid accumulates in the blood and is deposited as needle-shaped crystals in the soft tissues of joints. Gout often occurs in a single joint, such as the great toe.

12. Most cases of abnormal spinal curvatures, such as scoliosis and lordosis, are congenital, but some can result from injuries. Abnormal curvatures are treated by surgery, braces, or casts.

13. Bones have to be physically stressed in order to remain healthy 13. Bones have to be physically stressed in order to remain healthy. When we remain active and muscles and gravity pull on the skeleton, the bones respond by becoming stronger.

14. Osteoporosis is a bone-thinning disease that afflicts half of women over age 65. It makes the bones so fragile that even a hug or sneeze can cause bones to fracture. The bones of the spine and neck of the femur are the most susceptible to osteoporosis. Collapse of the vertebrae often results in a hunched-over posture called a dowager’s hump.

15. Estrogen deficiency that occurs after a woman goes through menopause is strongly implicated as a cause of osteoporosis.