Red blood cells (RBCs)
Red blood cells (RBCs), also known as erythrocytes, are a vital component of blood, responsible for transporting oxygen from the lungs to the body's tissues and returning carbon dioxide from the tissues back to the lungs for exhalation. Comprising about 40 to 45 percent of blood volume, RBCs contain hemoglobin, a protein that binds oxygen and gives blood its characteristic red color. The production of RBCs occurs in the bone marrow through a process called hematopoiesis, regulated by the hormone erythropoietin, and each RBC has a lifespan of approximately 120 days.
Various blood disorders can impact RBC production and function, most notably different forms of anemia, which can arise from nutritional deficiencies, genetics, or other medical conditions. Common types of anemia include iron-deficiency anemia, pernicious anemia, aplastic anemia, and sickle cell disease, each with distinct causes and symptoms. Symptoms of anemia may include fatigue, pale skin, and shortness of breath. While some anemias can be treated with supplements or transfusions, sickle cell disease is a genetic condition that typically requires ongoing management rather than a cure. Understanding the role and health of RBCs is crucial for overall wellbeing, as they are essential for delivering oxygen necessary for cellular energy production.
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Red blood cells (RBCs)
Red blood cells (RBCs) are one of the four main components of blood, along with white blood cells (WBCs), platelets, and plasma. RBCs are also called erythrocytes. They are responsible for carrying oxygen from the lungs to cells in the body's tissues and organs and for transporting carbon dioxide back to the lungs for expulsion from the body. Blood disorders can affect the production and function of RBCs. Among these disorders are various types of anemia, which may result from disease, genetics, or malnutrition.
Background
Blood is the red fluid that circulates throughout body. The heart pumps blood through a system of blood vessels composed of arteries, veins, and capillaries. Blood carries nutrients and oxygen to and waste products from cells in the body's tissues and organs. Arteries generally carry oxygen-rich blood, while veins generally carry oxygen-poor blood. Capillaries, the smallest of the body's blood vessels, are sites where cells exchange waste products for nutrients and oxygen.
Blood has four main components: plasma, RBCs, WBCs, and platelets. Plasma is the liquid component of blood in which RBCs, WBCs, and platelets are suspended. It accounts for more than 50 percent of blood volume. Plasma is a combination of water, sugars, proteins, fats, and salts. Plasma is responsible for transporting blood cells and platelets throughout the body. It also carries nutrients, hormones, and other materials that the body needs to function.
RBCs, or erythrocytes, account for between 40 and 45 percent of blood volume. RBCs contain hemoglobin, a protein that helps carry oxygen to cells and transport carbon dioxide away from cells. The hemoglobin found in RBCs is responsible for blood's red color.
WBCs, or leukocytes, are not as abundant as RBCs. The ratio of WBCs to RBCs in the blood is about 1 to 650. WBCs make up about 1 percent of total blood volume. These blood cells are responsible for fighting infections in the body. Five types of WBCs exist: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
Platelets, or thrombocytes, are less numerous than RBCs but more numerous than WBCs. The ratio of platelets to RBCs in the blood is about 1 to 20. Platelets are pieces of cells that assist with blood clotting. Platelets collect at a wound site, adhering to the wall of a blood vessel to form a clot and prevent bleeding. The clot acts like a natural bandage and serves as the foundation upon which new tissue can grow as a wound heals.
Overview
The body produces RBCs in bone marrow, a spongy material inside the body's bones, through a continuous process called hematopoiesis. A hormone called erythropoietin, which originates in the kidneys, controls the production of RBCs. It takes about two days for an RBC to form, but the body produces about two million RBCs per second. A normal RBC lasts in the body for about 120 days. Certain vitamins and minerals—including iron, copper, folic acid, and vitamins A, B6, B9, and B12—are necessary for the proper formation of RBCs. An inadequate amount of any of these nutrients can cause a hemoglobin deficiency or reduce RBC counts.
Normal RBCs are shaped somewhat like donuts without a hole in the middle—round, with thicker edges and thinner middles. They are flexible enough to change shape as they pass through the various blood vessels in the body. RBCs contain hemoglobin, an iron-rich protein. As blood moves through the lungs, hemoglobin acts like a magnet for oxygen molecules. The blood carries these oxygen-rich RBCs throughout the body. The RBCs deliver oxygen to cells in the body's tissues and organs. Cells depend on oxygen to carry out the processes that produce the energy the body needs to survive. As a result of these processes, cells produce carbon dioxide as waste. After delivering oxygen to cells, RBCs pick up the carbon dioxide and carry it back to the lungs, which expel it from the body through exhalation.
Genes, sickness, and malnutrition can cause several blood disorders that affect RBC production and hemoglobin levels. Anemia is the general name for a condition in which the body has too few RBCs or too little hemoglobin. One of the most common forms is iron-deficiency anemia, which may result from a lack of iron in the diet or blood loss (e.g., through ulcers, menstruation, etc.). The body needs iron to make RBCs, and if it does not get enough, it may produce smaller RBCs with less hemoglobin. Symptoms of anemia include fatigue, irregular heartbeat, pale skin, and shortness of breath. Many people with anemia often feel cold. Other forms of anemia include the following:
- Pernicious anemia. This form results from a vitamin B12 deficiency.
- Aplastic anemia. This form is often a side effect of medication, chemotherapy, pregnancy, or conditions such as hepatitis or HIV.
- Hemolytic anemia. This form results from an autoimmune response in which the body destroys RBCs faster than normal.
- Megaloblastic anemia. This form results when the bone marrow produces unusually large RBCs that cannot carry enough oxygen.
- Normocytic anemia. This form results when the bone marrow produces normal RBCs but does not produce an adequate supply to meet the body's needs.
Sickle cell disease, or sickle cell anemia, is a genetic disorder that causes malformed RBCs. People with sickle cell disease have RBCs shaped like sickles, or crescents. Sickle-shaped RBCs are stiffer and stickier than normal RBCs and cannot change shape as easily. Consequently, they tend to become lodged in blood vessels and hinder blood flow. These blockages can cause both chronic pain and short bursts of intense pain and may cause infections or harm tissues and organs. Sickle-shaped cells are more prone to rupturing and have a life span of just ten to twenty days. Because of this, people with sickle cell disease often have an inadequate supply of RBCs.
Some forms of anemia may be treated with oral supplements (such as iron pills or vitamins), blood transfusions, or hormone injections that promote production of RBCs. Sickle cell disease is considered a lifelong illness. Although a procedure called hematopoietic stem cell transplantation (HSCT) can cure it, most people opt for treatments designed to manage the disease and reduce its symptoms.
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