What is the composition of blood and its function ?

Blood is necessary for life. The body’s cells receive essential substances like oxygen and nutrients from the blood, which moves through the body. Additionally, it removes metabolic waste products from those very same cells. It cannot be substituted for It cannot be manufactured or made. Patients who require a blood transfusion can only obtain blood from generous blood donors. Approximately 8% of an adult’s weight is made up of blood. The composition of blood includes erythrocytes, leucocytes, thrombocytes (platelets), and plasma. About 45% of people have full blood with all the blood cells present (hematocrit). The remaining material is liquid plasma (e.g., water, plasma proteins, electrolytes, etc.).

composition of blood

Composition of blood

The main composition of blood is:

  • Plasma
  • Red blood cells (RBC)
  • White blood cells (WBC)
  • Platelets

RBC composition in blood

Red Blood Cells composition of blood
  • About 40% of the blood composition is made up of RBC, also known as erythrocytes.
  • Hemoglobin, a protein that gives blood its red color and enables it to transport oxygen from the lungs to all body tissues, is found in RBC.
  • Carbon dioxide is a waste product because oxygen is used by cells to produce the energy the body needs.
  • Carbon dioxide is carried by RBC from the tissues back to the lungs.
  • Anemia occurs when the number of RBC is too low; as a result, less oxygen is carried by the blood, leading to fatigue and weakness.
  • Blood can become too thick when the number of RBC is too high (erythrocytosis, like polycythemia vera), which can make it easier for blood to clot and raise the risk of heart attacks and strokes.

WBC composition of blood

White Blood Cells

The second main composition of the blood is white blood cells (leukocytes). A nucleus distinguishes leucocytes from mature erythrocytes. Leucocytes of various types can be found in the blood:

  • Neutrophil granulocytes (banded and segmented)
  • Eosinophil granulocytes
  • Basophilic granulocytes
  • Lymphocytes
  • Monocytes
  • Neutrophils kill and ingest bacteria, fungi, and foreign matter to protect the body from infections.
  • Lymphocytes cells (B lymphocytes), which develop into cells that produce antibodies cells (T lymphocytes) and natural killer cells, which both aid in the prevention of viral infections and are able to identify and eradicate some types of cancer.
  • Monocytes assist in the defense against numerous infectious agents and consume damaged or dead cells.
  • Eosinophils play a role in allergic responses, destroy cancer cells, and kill parasites.
  • Basophils are involved in allergic responses

While some WBCs move easily through the bloodstream, others stick to the walls of blood vessels. Some even break through the walls of blood vessels to enter other tissues. WBC release substances that attract additional WBC when they reach the site of an infection or other problem. The WBC are like an army that moves around the body but is always ready to come together to fight an invading organism.

This is done by WBC by engulfing and digesting organisms and by producing antibodies that attach to organisms to make their destruction easier.
Infections are more likely to occur when the number of WBC is too low (leukopenia). Leukocytosis, a condition in which the number of WBC is higher than normal, may not directly result in symptoms. However, the high number of cells may be a sign of an underlying condition. such as an infection, an inflammatory process, or leukemia.

Platelets composition of blood

  • The blood’s liquid composition, plasma, is where platelets, white blood cells, and red blood cells are suspended.
  • It is mostly water with proteins and dissolved salts (electrolytes) and makes up more than half of the blood’s volume. Albumin is the most abundant protein in plasma. Albumin binds to and transports substances like hormones and certain drugs, preventing fluid from entering tissues from blood vessels.
  • Antibodies (immunoglobulins), which actively protect the body from viruses, bacteria, fungi, and cancer cells, and clotting factors, which control bleeding, are two other proteins found in plasma.
  • Plasma serves other purposes. It serves as a reservoir that can either absorb excess water from tissues or replenish water that is lacking.
  • Plasma water is the first source of liquid when tissues in the body require more. By filling and continuously passing through blood vessels, plasma also helps maintain blood pressure and circulation throughout the body by preventing the collapse and clogging of blood vessels.
  • By transporting heat generated in core body tissues through regions that lose heat more quickly, like the arms, legs, and head, plasma circulation also regulates body temperature.

Function of blood

Messenger and waste removal

In the human body, blood is the most important medium for transport. It moves gases like oxygen, carbon dioxide, and nitrogen, among others,as well as the products of cell metabolism and nutrients (metabolism). As a result, the function of the blood is to guarantee the exchange of substances. It transports end products (such as carbon dioxide, urea, uric acid, creatinine, and others) in exchange for the blood’s gases and nutrients that it supplies to the tissues. to the organs that remove waste (kidney, liver, and lungs). In addition, it carries hormones—chemical messengers—to their intended organs.

Acid-Base Balance

Alveolar diffusion, or the diffusion of gases between alveoli and blood in the lung, controls acid-base homeostasis in the blood. As a result of the concentration gradient, oxygen diffuses from the alveoli into the blood. Hemoglobin, a protein that carries oxygen, absorbs it (hem = iron-containing, globin = protein). Conversely, carbon dioxide diffuses from the blood into the alveoli, where it is breathed out, due to its higher blood concentration.

Oxygen supply and carbon dioxide removal

The oxygen is carried by the blood from the alveoli to the body’s farthest cells. Plasma has a higher gas pressure than cells, which causes it to diffuse into the tissues.

Because of the higher gas pressure in the tissue, carbon dioxide diffuses from the cells into the blood. Carbonic acid (CO2 + H2O H2CO3), which dissociates into a hydrogen ion (H+) and bicarbonate (HCO3-), is formed here through a chemical reaction. As a result, carbonic acid (or rather hydrogen ion and bicarbonate) is transported as the metabolic end product, carbon dioxide. The aforementioned chemical reaction is reversed in the lung, and carbon dioxide is exhaled.
In conclusion, the gas exchange in the blood regulates acid-base homeostasis. Homeostasis, for example, is maintained by the blood by maintaining a balance between the water in the blood’s capillaries and the space inside and outside cells. Additionally, it keeps the body temperature constant.

What are the normal ranges for a complete blood composition?

Hemoglobin normal range:

  • Male (ages 15+): 13.0 – 17.0 g/dL
  • Female (ages 15+): 11.5 – 15.5 g/dL

Hematocrit normal range:

  • Male: 40 – 55%
  • Female: 36 – 48%

Platelet Count normal range:

  • Adult: 150,000 – 400,000/mL

White blood cell (WBC) normal range:

  • Adult: 5,000-10,000/mL

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