GENERAL ARTHROSYNDESMOLOGY
Plenty of joints contribute in the human body (more than 230 synovial joint, about 1000 ligaments, synchondroses etc.).
Development of joints
The skeleton goes through three developmental stages: connective tissue, cartilaginous, and bony. Since the transition from one stage to another is also associated with change of the tissue located between the bones, the joint of bones also goes through three developmental phases as a result of which the following three types of synarthroses are distinguished: fibrous joints, cartilaginous joints, bony unions. Bones of the cranium with two developmental phases (no cartilaginous) are connected by fibrous and bony tissues.
Joints begin to develop during the sixth week, and by the end of the eighth week they resemble the adult joint. During the development of fibrous joints, the interzonal mesenchyme between the developing bones differentiates into dense fibrous tissue. During the development of cartilaginous joints, the interzonal mesenchyme between the bones differentiates into hyaline cartilage or fibrocartilage. During the development of syno-vial joints, the interzonal mesenchyme between the bones differentiates as follows. Peripherally it forms capsular and other ligaments. Centrally it disappears and the resulting space becomes the synovial cavity. Where it lines the fibrous capsule and articular surfaces it forms the synovial membrane. Probably as a result ofjoint movements, the mesenchymal cells subsequently disappear from
the surfaces of articular cartilages. Cartilage is surrounded by condensed mesenchyme which differentiates into a bilaminar perichondrium. Articular surfaces are spheroid or plane, articular cavity is large. Additional apparatus will form till the end of intra-uterine development.