Think of blood production like a family tree. At the top of the tree are the blood stem cells or hematopoietic stem cells , which are the youngest most immature blood-forming cells. They can make copies of themselves. They also make new cells that are closer to being blood cells, called progenitor cells.
There are two types of progenitor cells that split the family tree: lymphoid cells and myeloid cells. These cells then develop into various types of blood cells:.
Myeloid stem cells develop into red cells and some white cells neutrophils, eosinophils, basophils and monocytes and platelets.
Immature myeloid stem cells are called myeloblasts or just blast cells. Lymphoid stem cells develop into T-cells and B-cells. Immature lymphoid stem cells are called lymphoblasts or just blast cells. Two types of white blood cells, T and B cells lymphocytes Lymphocytes One of the body's lines of defense immune system involves white blood cells leukocytes that travel through the bloodstream and into tissues, searching for and attacking microorganisms and See also Overview of Blood Overview of Blood Blood is a complex mixture of Plasma the liquid component Red blood cells the oxygen-carrying component White blood cells the cells that defend against infection Platelets particles that Within the bone marrow, all blood cells originate from a single type of unspecialized cell called a stem cell.
When a stem cell divides, it first becomes an immature red blood cell, white blood cell, or platelet-producing cell. The immature cell then divides, matures further, and ultimately becomes a mature red blood cell, white blood cell, or platelet. The rate of blood cell production is controlled by the body's needs.
Normal blood cells last for a limited time ranging from a few hours to a few days for white blood cells, to about 10 days for platelets, to about days for red blood cells and must be replaced constantly.
Certain conditions may trigger additional production of blood cells. When the oxygen content of body tissues is low or the number of red blood cells decreases, the kidneys produce and release erythropoietin , a hormone that stimulates the bone marrow to produce more red blood cells.
The bone marrow produces and releases more white blood cells in response to infections. It produces and releases more platelets in response to bleeding. Aging has some effect on bone marrow and blood cells, resulting in less cell-producing marrow.
Red blood cells are formed in the red bone marrow of bones. Stem cells in the red bone marrow are called hemocytoblasts.
They give rise to all of the formed elements in blood. If a stem cell commits to becoming a cell called a proerythroblast, it will develop into a new red blood cell. The formation of a red blood cell takes about 2 days. The body makes about two million red blood cells every second!
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