Blood Investigation

Look at these blood samples. The one on the left was just drawn and the one on the right has been sitting for a while.

What do you notice?

​These photos are of a museum exhibit. This person donated their body to science. Only the blood vessels were preserved.
What do you notice and wonder?

​Keep in mind these questions as you read:


What are all those PARTS of the mixture DOING for the body?

Why is blood so important that it goes EVERYWHERE?

QUESTIONS FOLLOW THE TEXT!

​It’s red and a little thicker than water. Blood is a fluid that has several vital functions for any animal whose body contains it. The heart pumps blood through blood vessels that are found all over the body. As blood travels through these vessels, it brings all the different parts of the body what they need, such as oxygen, water, and nutrients (food particles, vitamins, and electrolytes). Blood also helps the body to support and respond to illness and injury.

Blood is a mixture of blood cells, water, food particles, vitamins, and electrolytes (different types of salts a body needs). In humans, blood cells make up about 45 percent of the volume of blood. The other 55 percent is blood plasma. The blood plasma itself is a yellowish liquid that is about 92 percent water. About 7 percent of blood plasma is food particles. Vitamins and electrolytes make up the other 1 percent of blood plasma. One of the most important jobs of the blood plasma is to transport nutrients to various parts of the body. Blood plasma also carries waste products away from parts of the body.

When blood is drawn from a body, all its parts are mixed together. However, after it sits still for a while, the less dense blood plasma rises to the top and the denser blood cells settle toward the bottom.

There are three main components found in the denser part of the blood that each serve different functions: red blood cells, white blood cells, and platelets. Most of the blood cells are red blood cells. Red blood cells have a round, flat, flexible shape with a dent in the middle on each side. They carry oxygen from the lungs throughout the body, and they can bend to fit in the smallest blood vessels. The blood also contains white blood cells, which aid in responding to diseases and infections. White blood cells generally have a sphere-like shape and are often, but not always, larger than red blood cells. The stain used on most slide preparations of blood makes the insides of white blood cells appear dark purple.

​electron microscope image of a red blood cell, platelet and white blood cell

blood on a light microscope

Finally, the job of the platelets is to help the blood clot--to help it form a “plug” when a blood vessel has been broken open or injured. Platelets stretch out tentacle-like arms and stick together on and around a damaged area. This helps prevent the blood from leaking out. When blood forms a clot on the surface of wounded skin and dries out to cover and protect the wound, it’s called a scab.

By volume, red blood cells make up much more of the blood than white blood cells or platelets. Altogether, white blood cells and platelets make up only about 1 percent of the blood’s volume.

In the body, through the blood vessels, blood cells move around freely in the blood plasma. The food particles and other components of the plasma which are too small to see, even with a microscope, also move freely around the body through the blood vessels.

Sources:

●      American Society of Hematology (2020). Blood basics. Retrieved from https://www.hematology.org/education/patients/blood-basics

●      Hirsch, L.(2019, January). Blood (for teens)--Nemours KidsHealth. Retrieved from https://kidshealth.org/en/teens/blood.html

●      Dean, L. (2005). Blood and the cells it contains. In Blood Groups and Red Cell Antigens. Bethesda, MD: National Center for Biotechnology Information. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK2263/

●      American Red Cross. (2020). Blood components. Retrieved from https://www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-components.html

●      James, G. N. (2016). Platelets. Retrieved from https://www.ouhsc.edu/platelets/Platelets/platelets%20intro.html

●      American Red Cross. (2020). Blood components. Retrieved from https://www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-components.html

●      James, G. N. (2016). Platelets. Retrieved from https://www.ouhsc.edu/platelets/Platelets/platelets%20intro.html

Do all the parts look the same?

Can you see differences?

100 x

400 x

Watch a video to learn more about the parts of blood and the parts' functions.