The perichondrium is a tough, fibrous membrane that covers most cartilage in the body, excluding articular cartilage (the cartilage at the ends of bones in joints). Think of it as a protective covering and a source of new cartilage cells.
Structure and Composition
The perichondrium is composed of two distinct layers:
- Outer Fibrous Layer: This layer is primarily made up of dense irregular connective tissue, containing fibroblasts (cells that produce collagen and other extracellular matrix components). It provides structural support and protection to the underlying cartilage.
- Inner Chondrogenic Layer: This layer contains chondroblasts, cells responsible for producing new cartilage matrix. This layer is crucial for the growth and repair of cartilage.
Several sources highlight the perichondrium's density, noting it's particularly dense in infants and children, playing a significant role in appositional growth (growth from the outside) of cartilage. [Source: ScienceDirect Topics]
Function
The perichondrium's main functions are:
- Protection: It acts as a protective barrier, shielding the cartilage from damage and infection.
- Nutrition: While cartilage is avascular (lacks blood vessels), the perichondrium's blood supply provides nutrients to the underlying cartilage.
- Growth and Repair: The chondrogenic layer's chondroblasts contribute to cartilage growth and, to a limited extent, its repair. This is particularly important during development. [Source: Osmosis, Wikipedia, ScienceDirect - article on contributions to long bone development]
Similarities to Periosteum
The perichondrium is often compared to the periosteum, the membrane covering bones. Both are dense connective tissue layers with roles in growth, protection, and nutrition of the underlying tissue. However, the perichondrium covers cartilage, while the periosteum covers bone. [Source: Cleveland Clinic]
Clinical Significance
Damage to the perichondrium, as seen in perichondritis (inflammation of the perichondrium), can impede cartilage repair and lead to complications. [Source: MedlinePlus] Research also uses the perichondrium in gene expression studies, comparing it to the periosteum to understand skeletal development. [Source: NCBI PMC - Identification of unique molecular subdomains].
