The average adult has about 5 liters (5-6 quarts) of blood, which is divided
into plasma and cells. Plasma, which accounts for about 3 liters, is the liquid
portion of blood. The cells, which account for about 2 liters, are referred
to as the formed elements or cellular component of blood.
Blood Cells
into plasma and cells. Plasma, which accounts for about 3 liters, is the liquid
portion of blood. The cells, which account for about 2 liters, are referred
to as the formed elements or cellular component of blood.
Blood Cells
Blood cells are classified as erythrocytes (red blood cells), leukocytes (white
blood cells), and thrombocytes, also called platelets. Each type of blood cell
has specific functions. A brief description of the cell, its functions, and
unique characteristics follows.
blood cells), and thrombocytes, also called platelets. Each type of blood cell
has specific functions. A brief description of the cell, its functions, and
unique characteristics follows.
Erythrocytes:
Erythrocytes are the most numerous cells, second in size, and
easily identified by their unique biconcave disk shape. Red blood cells are
formed in the red bone marrow, live about 120 days, and are removed from
the blood stream by phagocytes, cells that are able to engulf and digest cellular
debris. The spleen is the primary site of phagocytosis of aged red
blood cells. The liver and bone marrow also play a role in removing or recycling
red blood cells.
The main functions of erythrocytes are to carry oxygen to all parts of
the body and to bring carbon dioxide to the lungs. The hemoglobin in the
red blood cell is the carrier for oxygen and carbon dioxide . Therefore, in
order for oxygen and carbon dioxide to move throughout the body, an adequate
number of mature, functioning red blood cells must be available .
The red blood cells must also contain the appropriate amount of hemoglobin.
easily identified by their unique biconcave disk shape. Red blood cells are
formed in the red bone marrow, live about 120 days, and are removed from
the blood stream by phagocytes, cells that are able to engulf and digest cellular
debris. The spleen is the primary site of phagocytosis of aged red
blood cells. The liver and bone marrow also play a role in removing or recycling
red blood cells.
The main functions of erythrocytes are to carry oxygen to all parts of
the body and to bring carbon dioxide to the lungs. The hemoglobin in the
red blood cell is the carrier for oxygen and carbon dioxide . Therefore, in
order for oxygen and carbon dioxide to move throughout the body, an adequate
number of mature, functioning red blood cells must be available .
The red blood cells must also contain the appropriate amount of hemoglobin.
Leukocytes:
Leukocytes are the largest in size and represent the fewest number
of blood cells. There are two major types of leukocytes: granulocytes and
agranulocytes. Granulocytes, also called polymorphonuclear leukocytes
(PMNs), are the most numerous and have dark-staining granules in the cytoplasm.
These cells are further classified as neutrophils, eosinophils, and basophils.
Agranulocytes, also called mononuclear leukocytes, do not have
dark-staining granules in the cytoplasm. Agranulocytes are further classified
as lymphocytes or monocytes.
Leukocytes are chiefly responsible for fighting infection by identifying,
engulfing, and destroying foreign organisms . They are active in the immune
response by producing antibodies to foreign organisms. Additional infor
mation about the function of each type of leukocyte is discussed with the
blood cell tests related to the specific type of leukocyte.
of blood cells. There are two major types of leukocytes: granulocytes and
agranulocytes. Granulocytes, also called polymorphonuclear leukocytes
(PMNs), are the most numerous and have dark-staining granules in the cytoplasm.
These cells are further classified as neutrophils, eosinophils, and basophils.
Agranulocytes, also called mononuclear leukocytes, do not have
dark-staining granules in the cytoplasm. Agranulocytes are further classified
as lymphocytes or monocytes.
Leukocytes are chiefly responsible for fighting infection by identifying,
engulfing, and destroying foreign organisms . They are active in the immune
response by producing antibodies to foreign organisms. Additional infor
mation about the function of each type of leukocyte is discussed with the
blood cell tests related to the specific type of leukocyte.
Thrombocytes:
Thrombocytes, also called platelets, are essential for coagulation.
Without an adequate number of functioning platelets, an individual
would bleed to death.
Without an adequate number of functioning platelets, an individual
would bleed to death.
Plasma
Plasma, the fluid or liquid component of blood, is about 90% water. The
remaining constituents of plasma include a variety of substances either
dissolved or suspended in this watery medium: proteins; minerals such
as calcium, potassium, and sodium; glucose; lipids; cholesterol; and
waste products. Other components include antibodies, enzymes, and hormones.
The primary functions of plasma are to transport nutrients and other
necessary chemicals to all body cells and to bring waste products to the
body systems and organs that serve as waste disposal centers.
remaining constituents of plasma include a variety of substances either
dissolved or suspended in this watery medium: proteins; minerals such
as calcium, potassium, and sodium; glucose; lipids; cholesterol; and
waste products. Other components include antibodies, enzymes, and hormones.
The primary functions of plasma are to transport nutrients and other
necessary chemicals to all body cells and to bring waste products to the
body systems and organs that serve as waste disposal centers.
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