Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Musculoskeletal System
Skeleton
Joint Classification - Age-Related and Functional Changes in Bone Articulations

Joints (synovial joints) begin to form during the 6th to 11th weeks of embryonic development. During this period, the articular surfaces of the articulating bones, the joint cavity, and other joint structures begin to form. The embryonic Connective Tissue between the two developing bones loosens, eventually giving rise to the joint cavity.

Newborns already possess all the anatomical elements of a joint. However, the epiphyses of the articulating bones consist of Cartilage. Endochondral ossification of most epiphyses begins after birth (during the 1st to 2nd years of life) and continues until adolescence. Between the ages of 6 and 10, The Structure of the Joint Capsule becomes more complex, the number of villi and folds in the synovial membrane increases, and vascular networks and nerve endings develop within the synovial membrane. In children aged 3 to 8, the fibrous membrane of the joint capsule experiences an increase in the number of Collagen fibers, which significantly thicken to ensure its strength. The final formation of all joint structures is completed by the age of 13 to 16. Under normal physiological conditions, joints maintain a constant range of motion for a long time and are relatively resistant to Aging. Physical activity, exercise, and sports help preserve the shape and mobility of joints. However, prolonged and excessive (mechanical) stress, as well as aging, lead to Structural and functional alterations in the joints: the articular cartilage thins and deforms, its Shock-absorbing properties decline, the fibrous membrane of the joint capsule and ligaments undergo sclerosis, and bony projections known as osteophytes form along the margins of the articular surfaces. These anatomical changes result in functional impairments, manifesting as restricted mobility and a reduced range of motion.

Review and Self-Assessment Questions:

1. Provide a fundamental Classification of bone joints.

2. Name the types of continuous joints you know and describe the structure of each.

3. List the essential components of a joint.

4. Describe the Classification of Joints based on the number of articulating bones, the shape of the articular surfaces, and other characteristics.

5. Which Structural Features of joints determine their mobility, axes, and range of motion?

6. Describe the STRUCTURE OF THE joint capsule and explain its Functions.

7. What structural Features of the articular cartilage provide its shock-absorbing properties?

8. At what age is The formation of joints completed in humans?