Cartilaginous Joints

Cartilaginous joints are joints held together by cartilage and lack a synovial cavity. They are structurally categorized into two types:

1. Synchondrosis

• Definition: Joints held together by hyaline cartilage. The term 'synchondrosis' combines 'sin' meaning together, and 'chondrosis' referring to cartilage.
• Functionality: These joints are synarthrotic, meaning they allow no movement.
• Examples:
  • Epiphyseal Plates: Also known as growth plates, made of hyaline cartilage. These plates eventually close to become epiphyseal lines, resulting in two bones fused together, known as synostosis.
  • First Costal Cartilage: Located between the first rib and the sternum. This is the only pair of costal cartilage considered synchondrosis, restricting movement.

2. Symphyses

• Definition: Joints held together by fibrocartilage, which lacks a perichondrium, a dense irregular tissue promoting growth.
• Functionality: These joints are amphiarthrotic, allowing slight movement.
• Examples:
  • Intervertebral Discs: Found between vertebrae, composed of fibrocartilage. They provide slight movement and absorb shock, crucial for the spine.
  • Pubic Symphysis: Located between the pubic bones, allowing slight movement, particularly important during childbirth when relaxin hormone increases to aid in widening the pelvic brim.

Additional Insights

• Herniated Discs: Occur when the nucleus breaks through the annulus of intervertebral discs, often in the lumbar region, leading to pressure on spinal nerves causing pain or numbness.

Recap

• Synchondrosis: Composed of hyaline cartilage found in epiphyseal plates and the first costal cartilage; synarthrotic (immovable).
• Symphyses: Found in intervertebral discs and pubic symphysis; composed of fibrocartilage, amphiarthrotic (slightly movable).