Blood: Elements, Functions, and Diseases


Blood diseases are a large and heterogeneous class of diseases that are associated with various malfunctions in the work or structure of blood cells. Blood cells include erythrocytes, platelets, or leukocytes, and diseases include an excessive increase or decrease in their number and blood plasma problems (Haybara, et al., 2019). All blood diseases are extremely dangerous for the life and health of the patient. An untimely visit to a doctor can lead to the impossibility of a complete cure and even death. Blood plays a significant role in the body and has many different functions.

Blood Functions

Blood performs various functions in the body, including it, as a vehicle, maintaining the constancy of the internal environment of the body, and playing a significant role in protecting against foreign substances. Blood carries gases — oxygen and carbon dioxide, as well as nutrients to the liver and other organs after absorption in the intestine (Parati et al., 2020). Such transport ensures the supply of organs and metabolism in tissues, as well as the subsequent transfer of the final products of metabolism for their excretion from the body by the lungs, liver, and kidneys. The blood also carries out the transfer of hormones in the body.

Another function of blood is maintaining a water balance between the circulatory system, cells, and the extracellular environment. The acid-base balance in the blood is regulated by the lungs, liver, and kidneys (Haybara, et al., 2019). Maintaining body temperature also depends on blood-controlled heat transport. Also, blood protects the body from foreign molecules and cells penetrating it and has non-specific and specific defense mechanisms. The particular defense system includes cells of the immune system and antibodies. To prevent blood loss in case of damage to blood vessels in the blood, there is an effective coagulation system — physiological clotting. The dissolution of blood clots is also provided by blood.

Blood Cells

Blood as a tissue includes the shaped elements of blood and the intercellular substance – plasma. The ratio between plasma and shaped elements is a hematocrit number, that is, the hematocrit is relatively constant. In humans, plasma volume is 55-60%, and cells – are 40-45% of the total blood volume (De Larochellière et al., 2019). The hematocrit gives an idea of the total volume of red blood cells and characterizes the degree of hemoconcentration – hydremia, i.e., the water content in the blood.

The insoluble elements of blood are erythrocytes, leukocytes, and platelets. Erythrocytes are red blood cells, the most numerous blood cells. Formally, they are not cells since they lose many of the structures necessary for cells in the process of maturation. The red blood cells give the blood a red color due to the hemoglobin content. Red blood cells do not last forever, over time, they wear out and eventually die. However, the bone marrow is constantly producing new cells and maintaining the right level of red blood cells (Pretini et al., 2019). Various adverse circumstances can reduce or, conversely, increase their reproduction rate and affect their life expectancy – thus, the balance of blood composition is disturbed. An increase or decrease in red blood cells is associated with various pathological conditions.

The boundaries of the norm vary depending on gender, age, and other characteristics. Red blood cells can be elevated due to a variety of reasons, ranging from banal dehydration to chronic leukemia. The causes of increased red blood cell levels include a reduction in the volume of fluid in the body, oxygen deficiency, congenital heart disease, genetic causes, and the rare disease polycythemia (Pretini et al., 2019). Increased production of red blood cells threatens blood thickening, slowing blood flow, and related problems such as headache, dizziness, vision problems, and excessive blood clotting.

Reduced red blood cells are a relatively common pathology. A small number of red blood cells and hemoglobin is called anemia. If there are few red blood cells, there is less hemoglobin in the bloodstream, respectively, which carries oxygen. Thus, the body experiences oxygen starvation, and we feel weakness, drowsiness, loss of vitality, and dizziness (Parati et al., 2020). Against the background of anemia, hair falls out, and the skin becomes pale and dry. The reasons for the decrease in the number of red blood cells are an unbalanced diet with a deficiency of iron, vitamin B12, or folic acid, bone marrow damage, chronic inflammatory processes, bleeding in the digestive tract, and large-scale blood loss.

Leukocytes are an essential element of blood and the basis of the body’s immunity. Their main task is to protect the body from viruses, bacteria, and fungi attacking it. Although leukocytes are determined mainly in the blood, they are produced by a particular organ – the bone marrow (De Larochellière et al., 2019). Accordingly, they are formed in response to any tissue damage. There are five mature cell groups: basophils, eosinophils, neutrophils, monocytes, and lymphocytes (Das et al., 2022). Together they control the occurrence of allergic reactions, suppress allergens, regulate blood clotting, and neutralize toxins and poisons. In addition, they destroy foreign substances that have entered the body, purify the blood from dead leukocytes and produce interferon.

Elevated leukocytes in the blood – leukocytosis occurs due to pathological processes. When the aggressors invade the body, it releases many white cells into the blood to fight the threat. A condition characterized by a reduced level of white cells in the blood is called leukopenia (Kohn, 2019). Quite often, it is temporary, but if the indicator is consistently low, this may indicate serious pathologies. To restore the average value of leukocytes, it is necessary to detect the primary cause of pathology.

Platelets are shaped elements of the blood that help form clots and stop bleeding. They are produced in the bone marrow-the soft, porous core of most of your large bones. When a blood vessel is damaged, platelets accumulate directly at the site of injury and, together with clotting substances in the plasma, form a blood clot – a blood clot that stops bleeding. Platelet dysfunction is a condition in which platelets do not work correctly, resulting in bruising and bleeding.

Blood plasma is an aqueous solution of electrolytes, nutrients, metabolites, proteins, vitamins, trace elements, and signaling substances. With plasma, nutrients are delivered to the body’s cells, and from the cells, decay products are removed (Sloop et al., 2020). Plasma consists mainly of water, proteins, and clotting substances. Thanks to clotting substances, plasma, together with platelets, performs an essential function – it promotes the healing of damaged blood vessels and stops bleeding. By purification, concentration, and isolation of plasma components, more than 20 different effective drugs can be obtained (Kohn, 2019). They treat many diseases — such as immune deficiency, neurological, infectious, autoimmune diseases, heart failure, asthma, multiple abortions, bleeding, and hemophilia.

Blood Diseases, Diagnostics, Prevention

Many blood diseases occur depending on the damage to platelets, erythrocytes, leukocytes, and plasma. Anemia is a pathological condition characterized by a low level of erythrocytes and hemoglobin in the blood, which worsens the transfer of oxygen to the tissues and causes hypoxia (Sloop et al., 2020). There are several types of anemia: iron deficiency, folate deficiency, hemolytic, B-12-deficient, and posthemorrhagic. Leukocytosis is an excessively high content of leukocytes in the blood (Carmona et al., 2019). There is a physiological and pathological increase in the number of white blood cells. Thalassemia is the accelerated death of red blood cells associated with a failure to synthesize hemoglobin. Thrombocytopenia is a group of diseases in which there is a decrease in the number of platelets due to increased destruction or consumption and insufficient education. A thrombocytosis is an excessive number of platelets in the blood. To establish the diagnosis, various blood tests for diseases are carried out: a general blood test, a myelogram, an immunohematology analysis, the formation of the group, and the Rh factor.

Prevention of blood diseases includes maintaining a healthy lifestyle, a balanced diet, and taking essential vitamins. In addition, timely treatment of infectious diseases and parasitic diseases is necessary. To prevent the occurrence of complex blood diseases and possible complications, it is important not to self-medicate (Carmona et al., 2019). If alarming symptoms appear, it is essential to seek medical help. Regular blood donation for analysis will also help prevent the appearance of many diseases.


In conclusion, blood is a medium that transports various substances in the human body. Blood performs several functions that are necessary for the normal functioning of the entire human body. Blood unites the work of many physiological systems of the body and provides its homeostatic potential and the ability to withstand extreme influences thanks on perfect mechanisms of regulation of physiological functions. The central units of blood composition are erythrocytes, lymphocytes, and platelets. It is imperative to monitor the blood condition, as there are many blood diseases. Prevention is an integral part of the normal functioning of the blood.


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