Blood Volume Calculator
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the circulatory system is also known as peripheral blood, and the blood cells it carries, peripheral blood cells.
Blood Cell Types
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals
not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek erythros for
"red" and kytos for "hollow vessel", with -cyte translated as "cell" in modern usage), are the most common
type of blood cell and the vertebrate's principal means of delivering oxygen (O2) to the body tissues—via
blood flow through the circulatory system. RBCs take up oxygen in the lungs, or in fish the gills, and
release it into tissues while squeezing through the body's capillaries.
Adult humans have roughly 20–30 trillion red blood cells at any given time, constituting approximately 70% of all cells by number. Women have about 4–5 million red blood cells per microliter (cubic millimeter) of blood and men about 5–6 million; people living at high altitudes with low oxygen tension will have more. Red blood cells are thus much more common than the other blood particles: there are about 4,000–11,000 white blood cells and about 150,000–400,000 platelets per microliter.
White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are
involved in protecting the body against both infectious disease and foreign invaders. All white blood cells
are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells.
Leukocytes are found throughout the body, including the blood and lymphatic system.
The normal white cell count is usually between 4 × 10^9/L and 1.1 × 10^10/L. In the US, this is usually expressed as 4,000 to 11,000 white blood cells per microliter of blood. White blood cells make up approximately 1% of the total blood volume in a healthy adult, making them substantially less numerous than the red blood cells at 40% to 45%. However, this 1% of the blood makes a large difference to health, because immunity depends on it.
Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood
whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by
clumping, thereby initiating a blood clot. Platelets have no cell nucleus; they are fragments of
cytoplasm that are derived from the megakaryocytes of the bone marrow or lung, which then enter the
The number of platelets varies across individuals. The normal physiologic range is 200,000 to 500,000 per microliter of blood. Since they contain receptors for thrombopoietin (the protein that facilitates the maturation of megakaryocytes and release of platelets), a higher number of platelets binds more of the protein. Consequently, there is stimulation for more production of thrombopoietin in the liver and kidneys. This is the basis for the production of more thrombopoietin and, as a result, more platelets in the bloodstream during the blood clotting process.