What Is Synovial Fluid? - Definition & Function

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  • 0:03 Synovial Fluid Explained
  • 1:11 Synovial Fluid Function
  • 2:22 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

Learn information about synovial fluid and how it functions within our bodies to aid in movement. You'll also learn about why synovial fluid is so important to us.

Synovial Fluid Explained

I want you to think for a minute about something that you have probably encountered at some point in your life. Have you ever noticed the hinges on a door in your house squeaking? Or maybe you've heard a rubbing noise as you are driving your car? When these things happened, you likely decided to look at the door hinge or the car engine and then quickly realized that the moving parts in the hinge or engine were dry and rubbing against each other every time the door opened or the engine was running. Then, you probably used some type of lubricant in order to moisten the door hinge or add engine oil in order to moisten the engine parts.

By doing this, you made the parts smooth and moist so they could glide past each other without rubbing together and making the squeaking noise. The other thing that happened when you did this is that you decreased the amount of damage that would occur to the door hinge or engine, which helps to make them lasts longer. This is what synovial fluid does for us.

Synovial fluid is the clear, pale yellow fluid that is contained in every joint in our bodies. It is derived from plasma, which is the protein-salt solution that makes up the liquid portion of our blood. Synovial fluid contains large amounts of hyaluronic acid, which helps to make the fluid more viscous, or thicker.

Synovial Fluid Function

The synovial fluid in our joints is there to allow the bones that make up the joint to be able to slide past each other without causing damage to the ends of the bones. There is a thin layer of cartilage, called the articular cartilage, that is there to protect the ends of the bones. The cartilage must be maintained in order for the bones to not fracture or crack every time we move.

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