Blood
is a type of fluid, which is present in human body that provides all
essential nutrients and oxygen to the cells of the body and transports
carbon dioxide and waste materials away from the cells. An
adult human being has approximately 5 liters of blood, which takes
up about 7% to 8% of the body weight. The blood is pumped by the heart
through arteries, capillaries, and veins to all parts of the body
providing nutrition and homeostasis to the body. The
cells, tissues, and all the organ systems get the nutrients from the
blood.
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The blood consists of blood cells and plasma. The plasma is a fluid part of the blood and it represents 55% of the blood. The cells of the blood remain suspended in the plasma fluid medium. The plasma contains plasma proteins, hormones, glucose, mineral ions, oxygen, and carbon dioxide. The blood cells contained in the blood are red blood cells (RBCs) or erythrocytes, white blood cells (WBCs) or leukocytes, and the platelets. The most numerous cells in the blood are the RBCs. The blood is red in color due to the presence of hemoglobin in the RBCs. Hemoglobin is a transporter of oxygen and therefore it has a role in exchange of gasses with the help of iron present in it. White blood cells are present in the blood that helps to fight against infections and parasites. The platelets are those cells, which help in formation of a clot when there is an injury or cut to the body. Blood cells are produced by the bone marrow. The process by which blood is produced by the body is called hematopoiesis.
The blood consists of blood cells and plasma. The plasma is a fluid part of the blood and it represents 55% of the blood. The cells of the blood remain suspended in the plasma fluid medium. The plasma contains plasma proteins, hormones, glucose, mineral ions, oxygen, and carbon dioxide. The blood cells contained in the blood are red blood cells (RBCs) or erythrocytes, white blood cells (WBCs) or leukocytes, and the platelets. The most numerous cells in the blood are the RBCs. The blood is red in color due to the presence of hemoglobin in the RBCs. Hemoglobin is a transporter of oxygen and therefore it has a role in exchange of gasses with the help of iron present in it. White blood cells are present in the blood that helps to fight against infections and parasites. The platelets are those cells, which help in formation of a clot when there is an injury or cut to the body. Blood cells are produced by the bone marrow. The process by which blood is produced by the body is called hematopoiesis.
Photo credit: beltina.org
Functions of Blood
1. Respiratory
Function: The hemoglobin in the RBCs takes oxygen from the lungs and as
it circulates throughout the body, discharges the oxygen to the cells
and tissues. The carbon dioxide that is formed in the body as a result
of the metabolism of food is transported back by the blood from the
cells and tissues to the lungs where it is discharged by the process of
diffusion of gasses. The hemoglobin present in the RBCs of blood help
the transportation of gases.
2.
Nutritional Function: Nutrient substances such as glucose, amino acids,
and fatty acids are transported from their storage sites to various
parts of the body, where it is needed. The nutritional substances
that are digested by the intestines and GI tracts are transported
through the blood to the liver for processing and then to various parts
of the body for the replacement of cells and tissues as well as for the
growth.
3.
Excretory Function: Substances such as urea and lactic acid that
accumulates in the tissues of muscles are transported by the blood to be
filtered out. The kidneys are the organs that filter these waste
products present in the blood. The waste materials that are formed as
a result of the metabolism of the cells are transported by the blood to
the kidneys where it is filtered to form urine.
4.
Coagulation Function: The blood has a clotting function when an injury
happens to the cells or tissues. It is a self repair mechanism to
prevent any further blood loss that may occur when there is bleeding
from an open wound. The clotting factors of the blood and platelets play
a role in the clot formation.
5.
Homeostatic Function: The various homeostatic functions of the body
include regulation of the temperature, pH, concentration of
vitamins, minerals, glucose, hormones, etc. The homeostatic functions
are carried out to maintain the levels of these substances within the
normal limits. The temperature of the body is kept constant around 37
+/- 4 degree centigrade. This allows the performance of all biological
activities and function of the hormones to be kept normal. The blood
transports the heat from areas of high metabolic activity to the outside
by sweating etc. As a result of metabolism, there is production and
accumulation of acids that tends to drift the pH to the lower side. The
pH of the blood is kept around 7.35 to 7.45, which is necessary for the
body to function
properly. The homeostatic mechanism that acts through the respiratory
and urinary system regulates the acid base balance and the pH is
maintained.
6. Defense Function: Blood has a defense function against bacteria, virus, pathogens, and other foreign bodies. The leukocytes or WBCs in the blood acts against these invading pathogenic organisms. The lymphocytes have an immune mechanism that provides immunity from further infection by the same pathogenic bacteria or viruses. The plasma has antibodies which acts against disease causing organisms.
6.
Transport Function: Blood transports various drugs, hormones,
glucose etc from where it is administered to the different parts of the
body for their action.
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