On average, men have about 5.5 liters of blood in their bodies and women have about 4.5 liters, which is usually about 8% of the total body weight.
Blood is the most important fluid in the body.
Blood is the most important fluid in the body and is composed of two parts, the tissues and the plasma, which are collectively referred to clinically as “whole blood”. There are three types of cells in the blood, each with a specific function.
Red blood cells
Most of the cells in human blood are red blood cells, abbreviated as “RBCs”.
Red blood cells resemble the shape of a doughnut and contain a protein component called hemoglobin. It is hemoglobin that gives blood its red color and helps red blood cells carry oxygen from the body’s lungs to all parts of the body. Such cells also carry the carbon dioxide produced by metabolism back to the lungs, where it is exchanged for gas by respiration.
Red blood cells, similar to all other blood cells, are produced by bone marrow hematopoietic cells. They survive in the human circulation for about 110 to 120 days, after which they will gradually die.
White blood cells
These cells are an important part of the body’s defense system and are known by the acronym “WBC”. In a healthy body, white blood cell levels are nowhere near the order of magnitude of red blood cells. However, when a disease occurs, such as a viral or bacterial infection, the body produces a large number of white blood cells to fight off foreign pathogens.
There are several different types of white blood cells:
- Granulocytes: help suppress infection and promote healing. They destroy pathogens that enter the body and any other foreign substances that enter the body.
- Lymphocytes: There are 2 types – B cells and T cells. B cells make a special protein called an “antibody” to fight a specific virus or bacteria. T cells secrete and produce a variety of cytokines and help immune cells work together.
- Monocytes: attack and kill viruses and bacteria in the body.
Most white blood cells enter the circulation with a survival time of less than a day.
Platelets
Their role is to assist in blood clotting in wounds when the body is traumatized.
The platelets move to the rupture of a blood vessel and adhere to the lining of the broken vessel, then mobilize other related clotting factors in the blood to converge on the damaged vessel. The platelets and clotting factors form a small dam to prevent more blood from leaking.
Platelets can survive in the body’s circulation for about 9 days, after which they are removed by the spleen and then die off.
Plasma
Plasma
This is the fluid component of human blood, consisting mainly of water, fat, sugar, and protein.
Plasma makes up 60% of human blood, and its own color is pale yellow.
It delivers nutrients, proteins, and hormones throughout the body and carries away metabolic waste. The body’s cells dissolve various wastes into the plasma and remove them as the blood circulates.