Approximate number of red blood cells (RBCs) in a single microliter of blood in women is:

Red blood cells (RBCs), also known as erythrocytes, are specialized cells in the blood responsible for carrying oxygen from the lungs to tissues and organs, and transporting carbon dioxide back to the lungs for exhalation. These cells contain hemoglobin, a protein that binds oxygen efficiently and is critical for maintaining proper cellular function.

In healthy adult women, the normal range of RBCs is approximately 4.0 to 5.2 million per microliter of blood. This count can vary slightly due to factors such as age, altitude, nutrition, and general health. RBCs are produced in the bone marrow through erythropoiesis, a process regulated by the hormone erythropoietin, which is secreted by the kidneys in response to oxygen levels in the blood.

RBCs have a distinctive biconcave shape, which increases their surface area for gas exchange and allows them to pass smoothly through the smallest blood vessels called capillaries. Each RBC has a lifespan of around 120 days, after which aged cells are removed by the spleen and liver, and replaced with new ones.

Maintaining a normal RBC count is crucial for proper oxygen delivery, energy production, and overall metabolic balance. Counts below this range may lead to anemia, causing fatigue, weakness, and reduced organ function. Conversely, abnormally high counts, or polycythemia, can increase blood viscosity and put additional strain on the heart and circulatory system.

Understanding the normal RBC range for women, 4.0 to 5.2 million per microliter, is fundamental in biology, especially in hematology and human physiology. It provides insight into how the body transports oxygen, maintains homeostasis, and supports life.