Cartilage structure and growth

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Cartilage structure and growth


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Cartilage structure and growth

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Cartilage is a strong, flexible type of connective tissue that makes up part of your nose, your ear, and provides cushioning between your joints.

Its job is to support and connect various parts of your body, like the costal cartilage that connects your ribs to your sternum or breastbone.

Usually, there’s a layer of connective tissue that wraps around cartilage called the perichondrium.

The perichondrium has an outer layer that contains fibrous connective tissue and blood vessels, and it has an inner layer that contains chondroblasts.

Chondroblasts secrete the proteins that make up the extracellular matrix of the cartilage - which has a gel-like consistency.

Eventually, these chondroblasts get trapped inside the very matrix that they create, in small holes called lacunae. When that happens chondroblasts turn into chondrocytes.

Chondrocytes don’t make much extracellular matrix, instead they maintain and repair the extracellular matrix.

The extracellular matrix is composed of protein fibers like collagen which gives it strength and elastin which gives it flexibility.

And these protein fibers are embedded in a viscous gel, made of water and proteoglycan aggregates which are large molecules that look a bit like a centipede.

A long chain of hyaluronic acid molecules called a hyaluronan makes up the body of this proteoglycan aggregate, and hundreds of proteoglycans make up the legs.

These proteoglycan legs are basically proteins attached to long chains of sugars called glycosaminoglycan or GAGs.

Now, cartilage has two patterns of growth, appositional growth and interstitial growth.

Appositional growth occurs when chondroblasts secrete new matrix along existing surfaces and this causes the cartilage to expand and widen.


Cartilage is a type of connective tissue that is found in the body. It has a smooth, rubbery texture made of chondrocytes embedded in the extracellular matrix, all of which are enveloped by a connective tissue known as the perichondrium. Cartilage is found in different body parts, such as joints, the external ear, and the nose. It helps to support and protect the body's joints and assists with growth. Cartilage major function is to provide structural support to the parts where it's found. The cartilage grows in two major distinct patterns: Appositional and interstitial growth patterns. Appositional cartilage growth occurs when cartilage cells grow from the perichondrium. On the other hand, if the cartilage cells grow from the chondrocytes within the cartilage, it is called interstitial growth.


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  4. "Principles of Anatomy and Physiology" Wiley (2014)
  5. "Cartilage growth and remodeling: modulation of balance between proteoglycan and collagen network in vitro with β-aminopropionitrile" Osteoarthritis and Cartilage (2008)
  6. "Viscoelastic properties of human articular cartilage." Journal of Applied Physiology (1971)
  7. "The secreted glycoprotein lubricin protects cartilage surfaces and inhibits synovial cell overgrowth" J Clin Invest (2005)

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