Overview of Blood and Blood Components

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:

  • Nourishment

  • Electrolytes

  • Hormones

  • Vitamins

  • Antibodies

  • Heat

  • Oxygen

  • Immune cells (cells that fight infection)

Blood carries the following away from the body tissues:

  • Waste matter

  • Carbon dioxide

What are the
components of blood?

The
components of human blood are:

  • Plasma. The liquid component of the blood in which the following blood
    cells are suspended:

    • Red blood cells (erythrocytes). These carry oxygen
      from the lungs to the rest of the body

    • White blood cells (leukocytes). These help fight
      infections and aid in the immune process. Types of white blood cells
      include:

      • Lymphocytes

      • Monocytes

      • Eosinophils

      • Basophils

      • Neutrophils

    • Platelets (thrombocytes). These help in blood
      clotting.

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
called hematopoiesis.

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 following:

  • Neutrophils

  • Eosinophils

  • Lymphocytes

  • Monocytes

  • Basophils 

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 blood stream, 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

Test

Uses

CBC, which includes:

  • White blood cell count (WBC)

  • Red blood cell count (RBC)

  • Platelet count

  • Hematocrit red blood cell volume
    (Hct)

  • Hemoglobin (Hgb) concentration.
    The oxygen-carrying pigment in red blood cells

  • Differential blood count

To aid in diagnosing 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.

Platelet count

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) therapies.

Your
 healthcare provider will explain the purpose and results of any blood tests with
you.