We explain what blood is, how it is composed and the blood groups that exist. We also explain what their characteristics and functions are.
What is Blood?
The blood is a type of connective tissue in the body of vertebrate animals that circulates through your arteries, veins and capillaries transporting the various nutrients produced by metabolism as well as oxygen, essential for cellular respiration.
It has a characteristic red color and is a more or less dense liquidwhich contains a vast and complex set of cells and vital substances in a constant cycle called the cardiovascular system or blood system.
The blood It is vital for the functioning of the body and it is estimated that a human body contains between 5 and 6 liters of blood, which represents 7% of its total weight.
It is possible to extract it from its natural channelsa practice that is used as a method of analyzing the functioning of the different hormonal and metabolic systems of the body. However, a very drastic reduction in its quantity, density or content can cause death or serious damage to different organs and tissues.
Etymology of the term Blood
The word blood It comes from the Latin Sanguis and there are various theories regarding its etymological origin. One of them, documented by Saint Isidore of Seville (560-636 AD), claims that the word originated from the adjective for “soft”, since that was the texture of the substance when the first autopsies in history began to be performed.
General characteristics of blood
Is about a red liquid (dark in color when it is venous blood and light in color when it is arterial blood) and non-Newtonian, that is, whose viscosity varies with the temperature and shear stress applied to it.
Is a mostly aqueous solution and colloidal matrix, whose pH range oscillates between (7.36 and 7.44) and its temperature is around 37 degrees, under ordinary health conditions.
Components of blood
The blood is Composed primarily of water (91%), proteins (8%) and some other materials dissolved in it. Its characteristic color is due to the presence of hemoglobin, a pigment that is abundant in the red blood cells (erythrocytes) that compose it.
It is also made up of another large set of cells such as white blood cells (leukocytes) or plateletsas well as proteins such as enzymes, hormones, nutrients and other vital substances, such as glucose. The blood also carries waste substances, which are then filtered and removed from the body.
Blood parts
Blood is composed of two distinct phases, known as blood parts, which are:
- Solid phase. These are the formed elements, that is, solid objects dissolved in the blood, such as cells and proteins.
- Liquid phase. Also known as serum component, it is primarily blood plasma, a yellowish substance that makes up 55% of blood and is slightly denser than water.
Blood groups
Not all blood is identical and traditionally There are four blood types whose determination is congenital, that is, it does not change throughout life nor is it optional.
Blood transfusion, for example, must be done according to the recipient’s blood type, otherwise his or her body will receive the different blood as if it were a foreign substance and will defend itself against it.
This is due to the presence of certain defensive proteins called antigens and antibodies, which are found in both red blood cells and plasma.
These groups are:
- Group A. It presents A antigens in erythrocytes and anti-B antibodies in plasma.
- B Group. It presents B antigens in erythrocytes and anti-A antibodies in plasma.
- Group AB. It presents both A and B antigens on red blood cells, but no antibodies in plasma. This blood group can receive both A and B type blood and is known as a “universal recipient.”
- Group O. He/she does not have antigens A or B in his/her erythrocytes, but he/she does have anti-A and anti-B antibodies in his/her plasma. He/she can therefore donate to any other blood group, but can only receive from his/her own. This is why he/she is known as a “universal donor”.
Generation of blood
The process of blood formation is called hematopoiesis and takes place in organs and tissues of the body specialized in this function, such as the bone marrow inside the bones, together with the liver, endocrine glands and kidneys, responsible for producing its cellular, enzymatic and aqueous components.
Red blood cells live about 120 days.after which they are filtered by the liver for their degeneration and iron recycling, as well as the expulsion of residual bilirubin when hemoglobin breaks down. They are immediately replaced by fresh blood cells that perpetuate the cycle.
Functions of blood
The functions of blood are diverse, namely:
- Its primary function is to serve as a transport mechanism throughout the body for both cells and defensive, nutritive or supporting substances such as oxygen and glucose, which are essential for obtaining energy.
- It is essential for the cardiovascular cycle that carries oxygenated blood from the lungs to the heart and the entire body, and then CO2-laden blood to the heart and from there to the lungs to be reoxygenated.
- It also keeps body temperature stable since in the presence of heat it is ventilated by widening the capillary vessels and exposing it to cooling by the skin, and in the presence of cold the vessels are compressed to attenuate this effect.
- It performs defensive functions, transporting leukocytes and platelets to injured regions, preventing the access of infections and quickly plugging damaged tissues.
Blood circulation
Blood circulation It’s what keeps the body going and the various living and nourished tissues. The blood route reaches even the most unknown regions of the body through a wide system of conduits: arteries (for oxygenated blood), veins (for deoxygenated blood) and smaller blood capillaries.
The engine of this cycle is the heartwhich continuously pumps and sucks blood in, keeping it in continuous flow from the organs and tissues to the respiratory system and back to the confines of the body.
Blood diseases
The blood can suffer from numerous diseases or ailments, grouped based on four principles of action on it:
- Diseases of hemostasis. Those that unbalance the content of the blood, either by overloading it with some element or substance that is benign in other conditions, or by depriving it of some indispensable component. For example, diabetes.
- Diseases of the erythrocyte system. They affect red blood cells, reducing their oxygen-carrying capacity or shortening their lifespan. For example, certain syndromes and congenital diseases of red blood cell malformation.
- Diseases of the leukocyte system. They affect the immune system (white blood cells). For example, HIV-AIDS.
- Malignant haemopathies. Types of cancer and lymphomas that deteriorate blood quality.
Blood in culture
The blood has occupied an important role in the imagination of the human being from an early age. It has been associated with life and therefore with a certain sacred character that gave it central roles in rites, sacrifices and mythical narratives.
In Greco-Roman antiquity It was considered one of the four humors that make up the human body (in Hippocrates’ theory of humors) together with yellow bile, black bile and phlegm and, therefore, determining the health and character of individuals.
Numerous mythological stories They give it healing or poisonous propertiesdepending on the creature from which it is extracted, the beings that survive by ingesting other people’s blood have always been considered cursed or evil beings, as is the case with vampirism.