The blood smear test evaluates the cells which are present in the blood. This includes three main components, namely red blood cells
, also known as RBCs, white blood cells, also known as WBCs, and platelets, also known as PLTs. The test helps in detecting a number of conditions and diseases, ranging from leukemia to infections and anemia. Blood cells are produced by and reach maturity in the bone marrow. They are released by the bone marrow into the bloodstream as needed after they mature. Red blood cells are also known as erythrocytes. Made in the bone marrow, they are released in the blood cell when they mature. The primary function of red blood cells is to carry oxygen
around the body. They contain a protein called hemoglobin
which enables them to do so. A red blood cell lasts up to 120 days. The bone marrow must consistently produce red blood cells in order to replace those which have aged or have degraded or lost through injury and bleeding. There are a variety of disorders that can cause a decline in the production of red blood cells and shorten their lifespan. In some cases, heavy bleeding may occur. Red blood cells have a uniform size and shape, but their appearance can be deformed by factors like deficiencies of vitamin B12, iron, and folate. White blood cells, on the other hand, are also known as leukocytes. These cells are present in the bloodstream, the tissues, and the lymphatic system. White blood cells constitute an essential part of the body’s immune system, which fights against foreign invaders to protect the body. White blood cells play a pivotal role in protection against infections, inflammations, and allergic reactions. There are five categories of white blood cells, each of which performs a different function. These include monocytes, eosinophils, neutrophils, lymphocytes, and basophils. White blood cells are present in the blood at a continuum in stable numbers. However, this number may change in response to what is going on in the internal environment of the body. When there is an infection in the body, the bone marrow may produce a more significant number of neutrophils to attack the bacterial infection. In the case of allergens, there may be a greater number of eosinophils present in the body. Diseases also alter the number of white blood cells present in the body; in leukemia, the uniformity of cells also changes, as white blood cells, which are abnormal, multiply rapidly. Platelets are also called thrombocytes. These are small cell fragments that circulate in the blood and are crucial for normal blood clotting. In the case of injury, platelets clump together at the site of the wound to form a temporary plug. They also release signals which prompt the clumping of additional cells at the site until the injury heals. Low platelets in the blood can increase the risk of bleeding and bruising.