All humans have blood, but what is blood? What is blood’s composition? What is blood’s purpose? How is blood produced? How does the blood circulatory system work? What are the types of blood? Do all animals have blood? Is blood always red? This report will tackle these questions and provide a scientific answer to each.
Blood is composed of two components: the plasma, and formed elements. The plasma, a clear extracellular fluid, is made up of a mixture of proteins, enzymes, nutrients, wastes, hormones and gases. Since the plasma is mostly water, it is created from the absorption of drinks by the intestines. These plasma proteins transport hormones throughout the body.
Formed elements are enclosed inside a plasma membrane and they can be further divided down to three categories: erythrocytes (red blood cells), leukocytes (white blood cells) and platelets. They are all produced in the bow marrow. Erythrocytes’ primary purpose is to deliver oxygen to the body tissues. These red blood cells are rich in hemoglobin; Hemoglobin is the cause for the red colour in our blood. Leukocytes are the cells that protect the body against infectious diseases. Lastly, platelets serve the role of stopping bleeding by interacting with clotting proteins. Together they also serve additional roles that are essential for our survival such as transporting essential nutrients to cells, carrying carbon dioxide back to the lungs to be exhaled, and regulating the body temperature and acidity levels.
The heart and blood vessels play an integral role in the blood circulatory system. Blood is carried away through the arteries from the heart and it is returned to the heart through veins. Blood types are categorized based on the presence and absence of antibodies. Antibodies is a type of protein that is produced by the immune system to help fight off antigens. The blood type plays a crucial role during blood donations and transfusions as antibodies will attack other blood cells with an unrecognizable antigen. There are four major blood groups, A, B, AB, and O, and each group can be RhD positive or negative. RhD refers to a form of antigen from red blood cells.
An interesting fact is that not all animals have blood. Many invertebrate animals such as jelly fish do not have blood as they are able to absorb nutrients and excrete waste directly. As mentioned previously, hemoglobin causes our blood to be red. In other animals, blood can come in a variety of colours. Earthworms and inspects have green blood, starfish has yellowish blood, and lobster has blue blood.