Blood is the life-maintaining fluid that circulates through the body's:
Blood carries the following to the body tissues:
Blood carries the following away from the body tissues:
The components of human blood include:
Blood cells are made in the bone marrow. The bone marrow is the soft, spongy material in the center of the bones that produces about 95 percent of the body's blood cells. Most of the adult body's bone marrow is in the pelvic bones, breast bone, and the bones of the spine.
There are other organs and systems in our bodies that help regulate blood cells. The lymph nodes, spleen, and liver help regulate the production, destruction, and differentiation (developing a specific function) of cells. The production and development of new cells is a process called hematopoiesis.
Blood cells formed in the bone marrow start out as a stem cell. A stem cell (or hematopoietic stem cell) is the initial phase of all blood cells. As the stem cell matures, several distinct cells evolve, such as the red blood cells, white blood cells, and platelets. Immature blood cells are also called blasts. Some blasts stay in the marrow to mature and others travel to other parts of the body to develop into mature, functioning blood cells.
The primary function of red blood cells, or erythrocytes, is to carry oxygen from the lungs to the body tissues, and carbon dioxide as a waste product away from the tissues and back to the lungs. Hemoglobin (Hgb) is an important protein in the red blood cells that carries oxygen from the lungs to all parts of our body.
The primary function of white blood cells, or leukocytes, is to fight infection. There are several types of white blood cells and each has its own role in fighting bacterial, viral, fungal, and parasitic infections. Types of white blood cells that are most important for helping protect the body from infection and foreign cells include the following:
White blood cells:
The primary function of platelets, or thrombocytes, is blood clotting. Platelets are much smaller in size than the other blood cells. They group together to form clumps, or a plug, in the hole of a vessel to stop bleeding.
A complete blood cell count is a measurement of size, number, and maturity of the different blood cells in a specific volume of blood. A complete blood cell count can be used to determine many abnormalities with either the production or destruction of blood cells. Variations from the normal number, size, or maturity of the blood cells can be used to indicate an infection or disease process. Often with an infection, the number of white blood cells will be elevated. Many forms of cancer can affect the bone marrow production of blood cells. An increase in the immature white blood cells in a complete blood cell count can be associated with leukemia. Anemia and sickle cell disease will have abnormally low hemoglobin.
Some common hematology tests include the following:
|Complete blood count (CBC), which includes:
||To aid in diagnosing anemia and other blood disorders and certain cancers of the blood; to monitor blood loss and infection; to monitor a patient's response to cancer treatment, such as chemotherapy and radiation.|
|Platelet count||To diagnose and/or monitor bleeding and clotting disorders.|
|Prothrombin time (PT)||To evaluate bleeding and clotting disorders and to monitor anticoagulation (anti-clotting) therapies.|
Your health care provider will explain the purpose and results of any blood tests with you.
Because of the intricate complexities involved in the production of blood, and the function of blood to support the entire body, there are many blood diseases that can occur, including bleeding disorders, anemias, and blood cancers known as leukemias.
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Online Resources of Hematology & Blood Disorders