22.14:
Structure and Function of Leukocytes
A healthy individual has about 4,500 to 11,000 leukocytes or white blood cells per microliter of blood, accounting for about 1% of blood volume.
Unlike erythrocytes, this group of cells lacks hemoglobin but is considered complete as they possess a nucleus and other cellular organelles.
Most leukocytes reside in the connective tissues, mainly in the lymphatic organs like the spleen and lymph nodes, with a small fraction in circulating blood.
As part of the immune system, leukocytes protect the body from threats like pathogens, toxins, and abnormal body cells.
In case of an infection or injury, the circulating leukocytes are activated, and their numbers double up in a few hours, a process called leukocytosis.
The damaged or infected tissues and circulating pathogens release chemical stimuli, attracting activated leukocytes in the blood.
Some leukocytes are capable of phagocytosis. These leukocytes can also adhere to and react with endothelial cells lining the blood vessel, squeezing out to enter the tissue.
As a result, they can clear the infected tissue cells and their debris along with circulating pathogens.
22.14:
Structure and Function of Leukocytes
An adult in good health typically has between 4,500 and 11,000 leukocytes, or white blood cells, per microliter of blood, which constitutes about 1% of the total blood volume. Unlike red blood cells, white blood cells contain a nucleus and other cellular organelles but do not have hemoglobin. Most white blood cells reside in connective tissues, particularly in lymphatic organs such as the lymph nodes, with only a small fraction present in circulating blood.
White blood cells protect the body from potential threats such as toxins, pathogens, and abnormal cells. When an infection or injury occurs, the circulating white blood cells become activated, and their numbers can increase rapidly within a few hours, a response known as leukocytosis. Chemical stimuli released by damaged or infected tissues and circulating pathogens attract these activated white blood cells to the site of infection or injury.
Some types of white blood cells are capable of phagocytosis. They can adhere to and interact with endothelial cells lining the blood vessels, squeezing through to enter the tissue. This capability allows them to clear infected tissue cells, debris, and circulating pathogens from the body.