Wendy has taught high school Biology and has a master's degree in education.
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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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.
Functions of Plasma
As mentioned earlier, plasma is made mostly of water. This allows our blood to flow freely through our blood vessels, transporting a variety of substances throughout our entire body. We can think of plasma as the river upon which particles can travel and be delivered where needed. Red blood cells, white blood cells, and platelets are carried in the current of the plasma, transporting oxygen, providing an immune response, and delivering clotting agents when we have a cut.
But within the plasma itself, there are many dissolved substances which are crucial for maintaining the health of our bodies. Various proteins constitute about 7% of the solutes in plasma. These proteins are produced primarily by the liver, and include albumins, globulins, and fibrinogen. Albumins serve as transport proteins for fatty acids and hormones. Some globulins serve as antibodies, while others transport iron, lipids, and vitamins. Fibrinogen is a clotting agent, helping us to prevent excessive blood loss when we have a cut or scrape.
Plasma contains other substances that are transported for use by the body. Electrolytes, such as Na+, K+ and Ca+, are one example. These are important for the function of certain cells.
Nutrients from the food we eat are dissolved in plasma and are delivered to parts of our body by the bloodstream. These include amino acids and glucose. In addition, gases, enzymes, and hormones are moved through the body for use in our cells. Finally, waste products are transported through the blood to organs for later excretion.
Blood plasma is the watery, liquid component of blood. It suspends red blood cells, white blood cells, and platelets. Within plasma, there are many important dissolved substances, such as proteins, electrolytes, nutrients, gases, and waste products. Because of plasma, these particles can be transported throughout the body, keeping our bodies functioning properly and maintaining overall health.
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What Is Blood Plasma? - Function & Components
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