Plasma: the Liquid Portion
What is blood? Miriam-Webster defines blood as “the fluid that circulates in the heart, arteries, capillaries, and veins of a vertebrate animal carrying nourishment and oxygen to and bringing away waste products from all parts of the body.” Blood is a pretty special substance- it helps move molecules from one place in the body to another, so they can perform specific functions. It also helps move waste products to specific organs, so we can get rid of them.
Our blood has two major parts: blood cells and plasma. The blood cells make up around 45% of the total blood volume, and there are three main types. The plasma portion makes up about 55% of the total blood volume. This article is going to focus on the plasma portion of blood. If you’re interested in the cellular portion, please check out the article “RBCs, WBCs, and Platelets: Oh My!”
When you get a cut, you don’t see plasma- you see the red color from our red blood cells (RBCs). The cells and plasma are mixed together in our bodies; to separate them we spin tubes down in a centrifuge. Once spun down, we can see that the plasma separates to the top portion of the tube, and the cells end up in the bottom portion of the tube. This separation happens due to the density of the two components. Density is the mass of something; so based on how the tubes look we can see that plasma has a smaller density (mass) than the cells, so it goes to the top of the spun-down tubes. Just because it has a smaller mass doesn’t mean it’s not as important a component as the cells. Plasma has many parts within it, and they are all incredibly important in helping our body function well.
Plasma is considered the liquid portion of blood. It helps move cells throughout the body, as well as nutrients and waste. But what is plasma made out of? Mostly- it’s water. Plasma is about 92% water! So make sure to stay hydrated! The other 8% of plasma is made up of different proteins, minerals, vitamins, and hormones.
The main job of plasma is to move our blood cells throughout the body, so they can bring oxygen to all our other cells. Plasma also transports nutrients, waste products, proteins, hormones, and a whole bunch of other things all over the body. Plasma is mainly a transport system for all the important compounds within our blood, but transportation isn’t plasma’s only function. Plasma is important in maintaining blood volume and pressure. Blood pressure is defined as “ force of your blood pushing against the walls of your arteries (medlineplus.gov).” Plasma helps keep this force in a normal range, so our heart doesn’t over-exert itself trying to pump blood throughout the body.
Another important function of plasma is providing our body with clotting factors. In the previous article “RBCs, WBCs, and Platelets: Oh My!” we talked about platelets. Their job is to stop cuts from bleeding by forming a platelet plug and plugging up the cut. Platelets aren’t the only thing that helps our body stop a cut, though. There are important substances called clotting factors that help blood clot and stop bleeding. These substances are proteins found in your plasma, and they all play a role in helping your body clot and stop a cut from bleeding too much. Without these critical clotting factors, a serious cut could become life-threatening very quickly. Thankfully, there are a lot of these proteins floating around, ready to help stop a cut whenever necessary!
Plasma is an incredibly important part of our blood, just like our cells are. These two components work together seamlessly to make sure our blood can transport oxygen, nutrients, and other components to all parts of the body. Our blood is a valuable substance, one that keeps our bodies running as efficiently as they can.
References
Definition of blood: https://www.merriam-webster.com/dictionary/blood
Top photo credit: https://images.app.goo.gl/XtghsqasjGneAbtF7
Centrifuged tube photo: Wikipedia contributors. (2019, March 28). Blood fractionation. Wikipedia. https://en.wikipedia.org/wiki/Blood_fractionation
Plasma information- components, functions: https://www.redcrossblood.org/donate-blood/dlp/plasma-information.html
Plasma info: https://www.hematology.org/education/patients/blood-basics?
BP definition: https://medlineplus.gov/highbloodpressure.html