What Is Collagen? - Definition, Types and Diseases

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  • 0:30 Definition of Collagen
  • 1:47 Collagen in Connective Tissue
  • 3:20 Types of Collagen
  • 4:02 Skin Damage, Aging & Collagen
  • 5:03 Collagen-Related Diseases
  • 5:53 Lesson Summary
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Lesson Transcript
Instructor: Wendy McDougal

Wendy has taught high school Biology and has a master's degree in education.

Collagen is the most abundant protein in the body. It helps connective tissue to be strong and provides cushioning for various parts of the body. Learn more about this important protein and quiz yourself at the end.

Skin Texture Differences

Have you ever squeezed a baby's cheek? You press into the soft, firm skin and it feels like a cushion under your fingers. Now imagine doing the same to the cheek of an 80-year-old woman. The skin hangs more loosely, and that layer of cushion seems to be all but missing. What accounts for this difference? The answer lies within a protein called collagen. In this lesson, we will examine this important protein and learn more about its function within our body.

Definition of Collagen

You may be somewhat familiar with collagen if you buy skin care products or watch commercials for anti-aging creams. But the importance of collagen goes well beyond trying to look younger. Collagen is a type of protein fiber found abundantly throughout our body. It provides strength and cushioning to many different areas of the body, including the skin. More specifically, collagen is found in our various types of connective tissues such as cartilage, tendons, bones, and ligaments.

If we could look closely at a collagen fiber, we'd see that its structure is similar to that of a rope. Each individual fiber of collagen is made up of many small fibers, called macrofibrils, all bound together. And all of the macrofibrils are themselves made up of even tinier fibers called microfibrils. This structure accounts for the strong nature of collagen. Like a rope, collagen has great tensile strength and can be pulled without breaking.

While collagen is a strong fiber, it's also very flexible. This allows certain parts of our body to move and change without damage. For example, pinch the skin on your arm and move it around. It's flexible, allowing for plenty of movement. When you let go, it goes right back to its normal state. This is due in part to the collagen found within the deeper layers of our skin.

Collagen in Connective Tissue

Collagen is found within the many types of connective tissue. Connective tissue is made up of a material called a matrix, with cells embedded within. The matrix can be a variety of substances, including fluid or a gel-like material. Collagen fibers are also included within that matrix. Visually, let's imagine that the matrix is a gelatin mold, and the cells are blueberries suspended within. Now add coconut to represent the collagen fibers. If you try to pull the gelatin apart, the coconut will tend to hold it together. The same goes for the collagen within the connective tissues.

Sometimes collagen bundles are arranged in a very regular pattern. This is the case within a tendon. Feel the back of your ankle just above your heel, and you'll find your Achilles tendon. The strength of tendons comes from the regular parallel arrangement of collagen fiber bundles. Think of a single rubber band representing one collagen bundle. If you pull on it, it'll stretch fairly easily. Now imagine pulling on a hundred parallel rubber bands at the same time. This is much harder to stretch! Collagen bundles give tendons this tough but stretchy property.

In other types of connective tissue, collagen may be arranged in a more irregular manner. In our skin, there are collagen fibers, but they're not arranged in the same way as in tendons. You can feel the difference by touching your Achilles tendon and then pulling at your arm skin. Skin is softer and much looser. Although collagen is present in both, the structure is quite different.

Types of Collagen

There are many different types of collagen found throughout the body. Some of the most common are Type I and Type II.

Type I collagen is the most abundant and is found in scar tissue, skin, tendons, artery walls, and bones. It is a very strong type of collagen, with good tensile strength.

Type II collagen is found in hyaline cartilage like nose, ears, trachea, larynx, and smaller respiratory tubes, which is the most abundant type of cartilage in the body.

Type III collagen is found in blood vessels.

Many of the other types of collagen are found linked within Type I and Type II collagen, and some are found within other very specialized areas of the body.

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