Overview of Blood and Blood Components
What is blood?
Blood is the life-maintaining fluid that circulates through the entire body.
What is the function of blood?
Blood carries the following to the body tissues:
Blood carries the following away from the body tissues:
What are the components of blood?
The components of human blood are:
Where are blood cells made?
Blood cells are made in the bone marrow. The bone marrow is the spongy material in
the center of the bones that makes all types of blood cells.
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 function
of cells. The production and development of new cells in the bone marrow is a process
Blood cells formed in the bone marrow start out as stem cells. A stem cell (or hematopoietic stem cell) is the first phase of all blood cells. As the stem cell
matures, several distinct cells evolve. These include red blood cells, white blood
cells, and platelets. Immature blood cells are also called blasts. Some blasts stay
in the marrow to mature. Others travel to other parts of the body to develop into
mature, functioning blood cells.
What are the functions of blood cells?
The main job 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 main job 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
White blood cells:
Help heal wounds not only by fighting infection but also by ingesting matter, such
as dead cells, tissue debris, and old red blood cells.
Protect you from foreign bodies that enter the bloodstream, such as allergens.
Are involved in the protection against mutated cells, such as cancer.
The main job 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.
What is a complete blood cell count (CBC)?
A CBC count is a measurement of size, number, and maturity of the different blood
cells in the blood sample. A CBC can be used to find problems 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 mean there is 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 production of blood cells. For instance, an increase in the
immature white blood cells in a CBC can be associated with leukemia. Blood diseases,
such as anemia and sickle cell disease, will cause an abnormally low hemoglobin.
Common blood tests
CBC, which includes:
White blood cell count (WBC)
Red blood cell count (RBC)
Hematocrit red blood cell volume (hct)
Hemoglobin (Hgb) concentration. Hemoglobin is the oxygen-carrying pigment in red blood
Differential blood count
To help diagnose anemia and other blood disorders and certain cancers of the blood;
to monitor blood loss and infection; or to monitor response to cancer therapy, such
as chemotherapy and radiation
To diagnose and monitor bleeding and clotting disorders
Prothrombin time (PT) and partial thromboplastin time (PTT)
To evaluate bleeding and clotting disorders and to monitor anticoagulation (anticlotting)
Your healthcare provider will explain the purpose and results of any blood tests with