Guided Notes on Joints and Skeletal Development

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. 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

Functional Sternumn to ribs

Slightly movable joints

diarthroses Functional Append-icular skeleton

Freely movable joints

fibrous structural Sutures of the cranium

Bones united by fibrous tissue

The Different Types of JointsJoint Type Classification Example Descriptio

n

Cartilag-inous

Structural Inter-vertebral joints

Bone ends connected by cartilage

Synovial Structural Elbow joint

Bones separated by a cavity containing synovial fluid

4. All synovial joints have four distinguishing features. They are:

a. Articular cartilageb. Fibrous articular capsulec. Joint cavityd. 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 JointsName Description

of ShapeMovement Allowed

Non-, Uni-, Bi-, or Multi-axial

Examples

Plane Joint

Articular surfaces are flat

Short slipping or gliding movements

Non-axialNo 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

Uni-axial Radio-ulnar jointAtlas/axis

Synovial JointsName Description

of ShapeMovement Allowed

Non-, Uni-, Bi-, or Multi-axial

Examples

Condyloid Joint

Egg-shaped surface fits into oval cavity

Side-to-side orBack-and-forth

Bi-axial Metacarpo-phalangeal joint

Saddle Joint

Each articular surface shaped like a saddle

Side-to-side orBack-and-forth

Bi-axial 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. 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. 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.