Blood: what it is, blood types and components

Human blood is a tissue composed of several cells, being fundamental for life. The circulation of blood through veins, arteries and capillaries happens due to the heartbeat and aims to transport oxygen, nutrients and hormones to all cells of the body.

The number of blood cells says a lot about the health of the body, with the values above or below the reference values indicating diseases, such as anemia, leukemia, inflammation or infections. The test performed to assess the amount of blood cells is the blood count, which does not need fasting to be performed, but it is indicated to avoid alcoholic beverages 48 hours before the test and to avoid physical activities 1 day before, as they may interfere with the results. See what the blood count is for and how to interpret it.

Blood functions

Blood is a fluid substance that has fundamental functions for the proper functioning of the organism, such as:

Transport oxygen, nutrients and hormones to cells; Defend the body against foreign substances and invading agents; Regulation of the body.

In addition, blood is responsible for removing substances produced in cellular activities from the tissue and which should not remain in the body, such as carbon dioxide and urea.

Blood types

Blood can be classified according to the presence or absence of antigens A and B on the surface of red blood cells. Thus, 4 blood types can be defined according to the ABO classification:

Type A blood, in which red blood cells have antigen A on their surface and produce anti-B antibodies; Type B blood, in which red blood cells have B antigen on their surface and produce anti-A antibodies; Type AB blood, in which red blood cells have both types of antigen on their surface; Type O blood, in which red blood cells do not have antigens, with production of anti-A and anti-B antigens.

Blood type is identified at birth through laboratory analysis. Find out all about your blood type.

Learn more about blood types and understand how donation works in the following video:

Blood components

Blood consists of a liquid part and a solid part. The liquid part is called plasma, 90% of which is only water and the rest is composed of proteins, enzymes and minerals.

The solid part is composed of figured elements, which are cells such as red blood cells, leukocytes and platelets and that play fundamental roles for the proper functioning of the organism.

1. Plasma

Plasma is the liquid part of the blood, being viscous in consistency and yellowish in color. Plasma is formed in the liver and the main proteins present are globulins, albumin and fibrinogen. Plasma has the function of transporting carbon dioxide, nutrients and toxins produced by cells, in addition to being responsible for transporting medicines throughout the body.

2. Red blood cells or erythrocytes

Red blood cells are the solid, red part of the blood that have the function of transporting oxygen throughout the body, since it has hemoglobin. Red blood cells are produced by the bone marrow, last for about 120 days and after that period are destroyed in the liver and spleen.

The amount of red blood cells in 1 cubic mm in men is about 5 million and in women it is about 4.5 million, when these values are below expectations, the person may have anemia. This count can be done through an exam called a complete blood count.

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3. Leukocytes or white blood cells

Leukocytes are responsible for the defense of the organism and are produced by bone marrow and lymph nodes. Leukocytes are composed of neutrophils, eosinophils, basophils, lymphocytes and monocytes.

Neutrophils: They are used to fight small inflammations and infections caused by bacteria or fungi. This indicates that if the blood test shows an increase in neutrophils, the person may have some inflammation caused by a bacterium or fungus. Neutrophils comprise bacteria and fungi, rendering these aggressive agents useless, but then die giving rise to pus. If this pus does not leave the body, it causes swelling and abscess formation. Eosinophils: They are used to fight parasitic infections and allergic reactions. Basophils: They serve to fight bacteria and allergic reactions, they lead to the release of histamine, which leads to vasodilation so that more defense cells can reach the region necessary for the elimination of the invading agent. Lymphocytes: They are more common in the lymphatic system but are also present in the blood and are of 2 types: B and T cells that serve for antibodies that fight viruses and cancer cells. Monocytes: They can leave the bloodstream and are specialized in phagocytosis, which consists in killing the invader and presenting a part of that invader to the T lymphocyte so that more defense cells are produced.

Understand more about what leukocytes are and what are the reference values.

4. Platelets or thrombocytes

Platelets are the cells responsible for stopping bleeding with the formation of blood clots. Each 1 cubic millimeter of blood should contain 150, 000 to 400, 000 platelets. When the person has fewer platelets than normal, there is difficulty in stopping bleeding, there may be bleeding that can lead to death, and when there are more platelets than normal there is a risk of thrombus formation that can move around, clogging some blood vessel that can cause infarction, stroke or pulmonary embolism. See what high and low platelets can mean.