Blood is a red, viscous and slightly salty liquid, denser than water, which flows from one cell to another through the circulatory system (through the arteries, capillaries and veins of the body). The amount of blood in the body is variable, although it is usually about 5 liters.
Blood has an average temperature close to 37 ºC, and is composed of some formed elements or blood cells, and a liquid part known as blood plasma. The latter is a yellowish liquid, its main component is water, and in a smaller quantity there are mineral salts, proteins, toxic and waste substances, carbohydrates, vitamins, hormones, and other substances.
Blood cells are of three types: red blood cells or erythrocytes (they carry oxygen to the cells), white blood cells or leukocytes (they defend the body against diseases), platelets or thrombocytes (they intervene in wound healing by containing hemoglobin). All cell lines that will give rise to blood cells originate in the bone marrow.
Human blood is not exactly the same and is differentiated by the presence or absence of some proteins. There are four main blood types: A, B, AB and O. Each blood type has a slightly different composition than the others.
The Rh factor refers to the presence of certain proteins in the blood. Rhesus blood groups are called positive or negative. Being Rh (+) means having the protein. When it is lacking, it is said to be Rh negative.
There is no doubt that the role played by blood in our body is very important since it has functions such as transporting oxygen from the lungs to each and every one of the body cells; absorb digested food in the intestine and carry it to all cells; transport hormones through the body; it has the property of coagulating outside the blood vessels, thus preventing an injured person from losing blood and dying; and defends us from infections in the body, thanks to white blood cells.
It should be noted that in the study of any disease it is almost essential to carry out a blood test, since many of the characteristics of the disorder can be reflected in it.
On the other hand, the term blood is also referred to the race, lineage, family or social condition to which a person belongs by birth. For example: Despite being Latina, I carry European blood on my mother's side.
