Red blood cells
- They are biconcave in shape,with a diameter of about 8µm and a thickness of about 2µm.
- The total average volume is about 83µm.
- Concentration of RBC is higher in males than in females.
- It depends on age,sex and altitude.
- RBC value in male is 5.2+/-0.3 million/m3.
- Female RBC value is about 4.7 +/-0.3 million/m3.
Function of Red Blood Cells
- It contains hemoglobin which carries oxygen from the lungs to the tissue
- Contain carbonic anhydrase enzyme which catalyzes the reaction between water and carbon dioxide
- Hemoglobin in the Red Blood Cells acts as excellent acid/base buffer and it contributes to about 70% of the buffering power in the blood by transporting carbon dioxide from tissue to the lungs
If the amount of circulating Hemoglobin decreases below the normal range for an individual,this result to a state of anemia which will be discussed later.
White Blood Cells
White blood cells are also known as Leukocytes.They are divided into two major groups Granulocytes and agranulocytes which depends on the content of their cytoplasms.
They are white blood cells with granules in their cytoplasm and comprises of Neutrophils,eosinophils and Basophil
They do not contain granules in their cytoplasm and are made up of Monocytes,small and large lymphocytes.
White blood cells count in a normal adult is 4000 – 11000/mm³ of blood.When the value is below 4000 cells/mm³ ,the individual is said to suffer from Leukopenia.If the value is above 11000 cells/mm³ of blood,the person is suffering from Leukocytosis
Granulocytes are divided into three types depending on the ability of the granules to take up certain stain
- Eosinophils granules are stained to acidic red such as eosin
- Basophils granules are stained in blue dyes such as Methylene blue and haematoxylin
- Neutrophils are neutral in appearance and the granules are only faintly stained by both dyes
The life span of granulocytes is about 12 hours.The nucleus is divided into lobes or segments,giving them a name polymorphonuclear leukocytes or polymorphs.Deficiency of circulating granulocytes in blood is term Granulocytopenia
- The size is about 10 -45µm in diameter.They have fine granules that are pink in color
- The nucleus is divided into 2-5 lobes or more
Neutropenia is decrease number of circulating neutrophils while Neutrophilia is the increase in neutrophils.Africans have lower values of neutrophils due to chronic infections than caucasians
Functions of Neutrophils
- It has a Phagocytic action (Involved in bacteria infections)
- The number of neutrophils increases during allergic reactions
- Granules contain profibrinolysin which may be released at the site of fibrin deposition to dissolve the clot
- The size is about 10-12µm.
- The granules are larger and red or orange in color.
- The nucleus is usually bilobed.The granules are closely packed
Functions of Eosinophil
- The level of eosinophils is reduced by hormones from the adrenal cortex and by secretion of adrenocorticotropic hormones
- The granules contain digestive enzymes and the cells die when the enzyme are used up
- The pus of abscesses contain large number of dead neutrophils as well as bacteria and necrotic tissues
- Involved in parasitic infection
- Thy have a diameter of about 8-10µm.
- They have few but large granules
- The nucleus is usually bilobed or kidney shaped and the granules frequently obscure the nucleus
Function of Basophil
Their granules contain histamine and heparin which is an anticoagulant
Basophil is involved in allergic reactions
They lack granules in their cytoplasm as seen under the light microscope and their nuclei are seen as single lobes and are referred to as mononuclear leukocytes.
There are two types of Agranulocytes which are Lymphocytes and Monocytes
Lymphocytes are divided into two according to their size which are Large and small Lymphocytes.
Small Lymphocytes are about 7-10µm in diameter.They have no granules and the nucleus is round and is stain deep purple and occupies most of the cell leaving very small cytoplasm
Large Lymphocytes have ad diameter of about 12-15µm and have no granules.The nucleus is pale and have more plentiful cytoplasm than the small lymphocytes.
Lymphocytes also give rise to plasma cells.The plasma cells are derived from beta lymphocytes plasma cells produces antibody that fight infection.
Lymphocyte stay a few hours in the blood vessels and find themselves in the lymph nodes where they survive for more many days where some of them stay for about 100 days
- They have no granules in their cytoplasm and are about 16-22µm.
- The nucleus is horse-shoe or kidney shaped
- They live for a few hours in blood and wander into the tissues.When they increase in size,they are called Macrophages,because they are highly phagocytic.
- They constitute the first stage of defense whenever there is an infection In tissues,they can survive for many days with some of them staying up one year.
Properties of White Blood Cells
- White Blood cells squeeze through pores even though the pores are of smaller diameter than the white blood cell.This is called Diapedesis
- They enter tissues or tissues space by amoeboid motion at the rate of 40µm per minute
- The presence of chemical substances in the tissue causes white blood cell to move towards or away from them (Chemotaxis)
- They have phagocytic actions that is the ability to engulf any foreign organism dead or alive
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