The blood tissue is called the blood that circulates through the vessels of vertebrates. It has a deep red color as a result of the existence of a pigment contained in erythrocytes or red blood cells. Blood is a connective tissue made up of red blood cells, white blood cells, platelets, and the so-called blood plasma; in this sense, a solid phase and a liquid phase are normally distinguished. The main function of blood or blood tissue is to achieve a distribution of oxygen, nutrients, etc., thus achieving an integration of the whole organism. In ancient times, blood was called circulatory humor based on a theory that accounted for four types of humors or substances.
The circulatory system is responsible for the circulation of blood tissue throughout the body. The organ that drives circulatory activity is the heart, which pumps blood through veins, arteries, and capillaries.
Red blood cells make up ninety-six percent of the semisolid part of the blood. Per microliter or cubic millimeter a woman has an average of four million eight hundred thousand of these, while a man owns approximately five million four hundred thousand. In mammals they lack a nucleus and organelles, having a cytoplasm entirely made up of hemoglobin, a protein that is responsible for transporting oxygen. Red blood cells are disc-shaped with a slight depression in the middle.
As for the white blood cells, they are part of the so-called immune system, using the blood as a means of access to the different corners of the body. These are responsible for the destruction of elements capable of generating infections and already infected cells; for this purpose secrete so-called antibodies. The normal thing is to have between four thousand five hundred and eleven thousand five hundred white blood cells per cubic millimeter, depending on the different circumstances.
Platelets, on the other hand, are cell fragments without a nucleus that serve to close the lesions that can affect the blood vessels through the coagulation process. Its production is made in the bone marrow; they are counted between one hundred and fifty thousand and four hundred and fifty thousand per cubic millimeter. They are the smallest cells in the blood.
Finally, blood plasma is the liquid where red blood cells, white blood cells, and platelets are immersed. It has a salty taste and a yellowish color. In addition to transporting cells, it carries nutrients and waste from cells. Besides water, it contains different proteins and inorganic substances. The components of plasma are formed in different parts of the body, such as the liver, intestine, and endocrine glands.
