What Is Blood Plasma? - Function & Components

Lesson Transcript
Instructor: Wendy McDougal

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

Making up more than half of the composition of blood, blood plasma is primarily made of water and plays an important role in transporting nutrients, electrolytes, and other substances. Learn more about the function and components of blood plasma. Updated: 08/25/2021

An Overview of Blood

Blood is a substance that elicits a wide variety of reactions from people. Some individuals study it, while others need only a glimpse of it to get weak in the knees. However, despite the various opinions on blood, one thing is clear: we would not exist without it.

Blood serves three main purposes in our bodies. First, it is a transport system. Blood delivers oxygen and nutrients, transports hormones and enzymes, and delivers waste products to be excreted. Second, blood helps regulate our pH, as well as our temperature. Finally, products in our blood protect us against disease and also provide clotting agents to stop bleeding.

So, we are all familiar with this somewhat thick, red liquid that courses through our body. But what, exactly, makes up this life-giving substance? In this lesson, we will look closely at the liquid component that makes up over half of our total volume of blood. This part of blood is known as blood plasma.

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  • 0:03 An Overview of Blood
  • 1:06 Components of Plasma
  • 2:15 Functions of Plasma
  • 3:47 Lesson Summary
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Components of Plasma

The components of blood can be put into essentially two categories. First, there are the solid particles. This category includes red blood cells, white blood cells, and platelets. The rest of the blood is composed of blood plasma, or simply plasma. It's a pale-yellowish, watery solution that suspends all of the other parts of the blood. It makes up about 55% of the total volume of our blood. Plasma itself is made up of 91.5% water. It acts as a solvent for important proteins, nutrients, electrolytes, gases, and other substances essential to life.

To get a better idea of the separate parts of blood, we can examine a diagram showing blood that has been spun in a centrifuge. A centrifuge is used by scientists to isolate the solids from liquids in a solution. This machine spins the solution very quickly, and because of centrifugal force, the heaviest particles sink to the bottom. In blood, the red blood cells are the heaviest and will separate to the bottom of the vial. Sitting on the top of this layer will be the white blood cells and platelets, also known as the 'buffy coat.' And remaining on the top is the watery plasma.

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