Cartilage is a specialized type of supporting connective tissue characterized by being avascular, firm, and elastic.
Here's a breakdown of its key characteristics:
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Avascular: Cartilage lacks its own blood supply. This means it relies on diffusion from surrounding tissues for nutrients and waste removal. This slow diffusion contributes to its slow healing rate.
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Firm: Cartilage is more rigid than other connective tissues like ligaments or tendons but less rigid than bone. This firmness provides support and shape to various structures in the body. This firmness is due to the extracellular matrix.
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Elastic: Cartilage possesses a degree of flexibility, allowing it to withstand some deformation without permanent damage. The elasticity is due to the presence of elastic fibers, especially in elastic cartilage.
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Composition:
- Cells: Cartilage contains specialized cells called chondrocytes and chondroblasts. Chondroblasts produce the extracellular matrix, and chondrocytes maintain it.
- Extracellular Matrix: The matrix is abundant and consists of:
- Collagen fibers: Provide tensile strength.
- Elastin fibers: Provide elasticity (primarily in elastic cartilage).
- Ground substance: A gel-like substance rich in glycosaminoglycans (GAGs) and proteoglycans, which attract water, contributing to cartilage's resilience and ability to withstand compression. Hyaluronic acid, chondroitin sulfate, and keratan sulfate are examples of GAGs found in cartilage.
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Appearance: Cartilage appears as a white or yellowish solid mass.
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Types of Cartilage: There are three main types of cartilage, each with slightly different characteristics:
- Hyaline Cartilage: The most common type, found in articular surfaces of bones, the nose, and trachea. Provides smooth surfaces for joint movement and support for respiratory structures.
- Elastic Cartilage: Contains many elastic fibers, making it highly flexible. Found in the ear and epiglottis.
- Fibrocartilage: Contains a large amount of collagen fibers, making it very strong and resistant to tension. Found in intervertebral discs and menisci of the knee.
In summary, cartilage is a vital connective tissue distinguished by its avascular nature, firmness, elasticity, and unique composition that enables it to provide support, flexibility, and shock absorption throughout the body.
