Joints: Meaning, Fibrous (or Immovable) Joints, Cartilaginous Joints, Synovial Joints, Ball-and-Socket Joints, Hinge Joints and Compound Joints
Meaning of Joint
A joint or place of articulation is the location where two or more skeleton bones are joined to one another.
When two or more bones in the body come into close contact with one another and are joined by ligaments or cartilage, the result is a joint or place of articulation.
Various Joint Types
The degree and kind of movement that joints permit can be used to categorize them.
Different types of joints can be identified:
1. Immovable (or fibrous) joints
A thin layer of strong connective tissue holds these joints firmly in place. The skull’s sutures and the teeth in their sockets are examples of bones that are immobile.
2. Cartilagenous Joints
The articular surfaces of the bones that make up cartilaginous joints are joined to one another by white fibrocartilaginous discs and ligaments, which restrict the range of motion.
The cartilage in the joint between the sacrum and the hip bone, the cartilage in the symphysis that connects the pubic bones at the front of the pelvic girdle, and the cartilaginous between the vertebrae are a few examples.
3. Synovial Joints
These joints can move freely. The majority of the body’s joints are synovial.
The main features of a synovial joint are as follows:
1. In the joint areas, articular cartilage, a layer of smooth hyaline cartilage, covers the ends of the bones. Fricton is decreased at the spot as a result.
2. A bag-like capsular ligament completely encloses the joint, keeping it together and aiding in the containment of synovial fluid.
3. A synovial membrane lines the capsular ligament. This membrane waterproofs the joint by acting as a seal and secreting synovial fluid into the synovial cavity.
4. The joint is lubricated by the synovial fluid. Strong, resilient ligaments composed of dense connective tissue hold the bones together in addition to the capsule.
5. During regular movement, these ligaments guard against dislocation. Adjacent bones have reciprocally formed articulating surfaces.
The following classes of synovial joints can be distinguished based on the kinds of movements they perform:
Ball-and-Socket Joints
These joints, like the hip and shoulder joints, are formed when the rounded head of one bone slides into the cup-shaped, hollow socket of another bone. All axes of movement are possible with these joints.
Hinge Joints
These joints are formed when the convex surface of one bone slides into the concave surface of another, allowing only one plane of motion. These joints include the elbow and knee joints, for example. The ligaments in hinge joints are primarily found at their sides.
Gliding Joints
This kind of joint enables flat surfaces to glide over one another, allowing for gliding motions between them. There is restricted mobility in certain areas, such as the joints connecting the tarsal bones, the carpal bones, and the articular processes (zygapophyses) of succeeding vertebrae.
Pivot Joints
These joints arise when: a bony ring revolves around the pivot (axis) of another bone, such as the atlas, which resembles a ring and revolves around the odontoid process of the axis to enable side-to-side head movement. When the palm is moved inwards or outwards, the end of one bone rotates around the axis of another bone, such as the end of the radius revolving around the ulna.
Compound Joints
These joints consist of many joints connecting various bones. A range of movements, including the movement of the head on the spinal column, are made possible by the various ways in which the bones articulate with one another.