Facts About Blood
What is blood?
Blood is the life-maintaining fluid that circulates through the body's:
- heart
- arteries
- veins
- capillaries
What is the function of blood?
Blood carries to the body the following:
- nourishment
- electrolytes
- hormones
- vitamins
- antibodies
- heat
- oxygen
Blood carries away from the body the following:
- waste matter
- carbon dioxide
What are the components of blood?
Human blood consists of about 22 percent solids and 78 percent water.
The components of human blood include:
- plasma, in which the blood cells are suspended, includes the following:
- red blood cells (erythrocytes) - carry oxygen from the lungs to
the rest of the body.
- white blood cells (leukocytes) - help fight infections and aid
in the immune process. Types of white blood cells include the following:
- lymphocytes
- monocytes
- eosinophils
- basophils
- neutrophils (granulocytes)
- platelets (thrombocytes) - help to control bleeding.
- fat globules
- chemical substances, including the following:
- carbohydrates
- proteins
- hormones
- gases, including the following:
- oxygen
- carbon dioxide
- nitrogen
Where are blood cells made?
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.
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 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.
What are the functions of blood cells?
The primary function of red blood cells, or erythrocytes, is to carry oxygen
and carbon dioxide. 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:
- neutrophils
- eosinophils
- lymphocytes
- monocytes
- granulocytes
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.
- are our protection from foreign bodies that enter the blood stream,
such as allergens.
- are involved in the protection against mutated cells, such as cancer.
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.
What is a complete blood cell count (CBC)?
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.
Common hematology tests:
Some common hematology tests include the following:
| Test |
Uses |
Complete blood count (CBC), which includes:
- white blood cell count (WBC)
- red blood cell count (RBC)
- hematocrit red blood cell volume (HCT)
- hemoglobin concentration (HB) - the oxygen-carrying pigment
in red blood cells.
|
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
therapy, 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 physician 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 diseases
that can occur, including bleeding disorders, anemias, and blood cancers
known as leukemias.
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