Fibrous Joints

The neighbouring bones of a fibrous joint are directly attached to each other by fibrous connective tissue, and so there is no joint space between them. The space between the bones might be small or large. Fibrous joints are classified into three categories. A suture is a small fibrous junction located between the majority of the skull’s bones. The bones are more widely separated at a syndesmosis joint, but they are kept together by a small band of fibrous connective tissue called a ligament or a large sheet of connective tissue called an interosseous membrane.

What actually is a joint?

A joint is an area in the body where two or more bones come together to allow movement. A joint is essentially a junction that is required for the body’s flexible mobility. Joints are further categorised into three types: cartilaginous joints, fibrous joints, and synovial joints. The following are the many types of joints in our bodies:

• Immovable: These joints are fastened to one another and cannot be moved. It does not permit any movement. As an example, consider the skull’s suture junction.
• Slightly Movable: These joints enable just specific types of movement or very little movement. This is sometimes referred to as amphiarthrosis. Intervertebral discs in the spine and the pubic symphysis in the hip and lower half of the human body are examples of such movement.
• Freely Movable: These joints allow for complete movement or the greatest degree of movement in the body. It is referred to as diarthrosis joints. Any elbow, wrist, shoulder, or knee joint is an example of such a joint.

What are Fibrous Joints?

A fibrous joint is one that has thick or fibrous connective tissue connecting the two articulating bones.

Fibrous joints do not enable movement; hence, they are classified as immovable joints, fixed joints, or synarthrosis.

These joints are connected by thick connective tissue made up of main collagen fibres and lack a joint cavity.

They protect vital organs, provide strength to the body, and keep our physical structure stable.

Types of Fibrous Joints

Fibrous joints are classified into three types:

1. Suture: A thin layer of thick fibrous tissue and interlocking bone projections hold bones together. The connecting fibres that keep bones together are quite short. Crannial sutures are a kind of joint found solely in the skull.

The bones are widely spaced in the foetal skull, and the edges of neighbouring bones are generally smooth. A fibrous membrane connects the bones, resulting in a “soft spot” or fontanel. This design allows the infant skull’s bones to slightly overlap during delivery and also allows for development after birth. Bone is deposited towards the perimeter of the cranial bones as the diameter of the skull expands, eventually filling in the voids.

During adulthood, the fibrous tissue ossifies and the skull bones merge to form a single unit that protects the brain effectively.

2. Syndesmosis

A syndesmosis (“banded together”) is a form of fibrous joint in which two parallel bones are joined by fibrous connective tissue. The space between the bones might be tiny, with ligaments connecting the bones, or it can be vast, with a broad sheet of connective tissue termed an interosseous membrane filling it in.

An interosseous membrane connects the broad space between the shaft parts of the radius and ulna bones in the forearm.

Similarly, an interosseous membrane connects the shafts of the tibia and fibula in the leg. Furthermore, the articulating surfaces of the bones at the distal tibiofibular joint lack cartilage, and the tiny space between the bones is supported by fibrous connective tissue and ligaments on both the anterior and posterior portions of the joint. The tibiofibular syndesmosis is formed by the interosseous membrane and these ligaments working together.

3. Gomphosis

A gomphosis is a specialised fibrous joint that secures the root of a tooth into its bony socket within the skull’s maxillary bone (upper jaw) or mandible bone (lower jaw). A peg-and-socket joint is another name for a gomphosis. There are several small bands of thick connective tissue termed periodontal ligaments that run between the bony walls of the socket and the root of the tooth. Because a gomphosis is immobile, this form of joint is functionally characterised as a synarthrosis.

Conclusion

The neighbouring bones of a fibrous joint are directly attached to each other by fibrous connective tissue, and so there is no joint space between them. A suture is a small fibrous junction located between the majority of the skull’s bones. The bones are more widely separated at a syndesmosis joint, but they are kept together by a small band of fibrous connective tissue called a ligament or a large sheet of connective tissue called an interosseous membrane. A joint is an area in the body where two or more bones come together to allow movement.