White Blood Cells (WBC's) or Leukocytes

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White Blood Cells (WBC's) or Leukocytes


Objectives 1.morphology 2.classifications 3.counts 4.leucopoiesis Life span 5.movements 4. functions


Morphology: spherical cell with a nucleus, white in color because it lacks Hb, in stained preparations WBC's attract stain. Classification of WBC's: 1. Granulocytes (polymorphonuclear leukocytes): cytoplasm contains granules. This type is the most numerous which is subdivided into: Neutrophils. B. Eosinophils. C.Basophiles. 2. Agranulocytes: have agranular cytoplasm and subdivided into: a.Lymphocytes. b. Monocytes.


1. WBC count in the blood Total WBC count: there are normally 4000-11000 WBC/c.mm of human blood in both male and female. Average value in normal is 7500 WBC/ c.mm b. Differential WBC's count which indicates the percentage (%) of each of five kinds of leukocytes in total WBC count: Neutrophils: 60-70% Eosinophils: 1- 4% Basophiles: 0.5-1% Monocytes: 2- 8% Lymphocytes: 20- 30%


2. Leukopoiesis: a. Myeloblasts: from which granulocytes (neutrophils,eosinophils and basophiles). b. Lymphoblasts: from which lymphocytes (T-lymphocyte and B-lymphocyte) are developed. c. Monoblasts: from which monocyte develop.


3. Most leukocytes are mobile, exhibiting ameboid movement. Leukocytes leave the circulation and enter tissue by diapedesis (a process in which they become thin and elongated and slip between or in some cases walls). can then be attracted to foreign materials or dead cells within the tissue by chemotaxis. 4. Life span of WBC's: a. granulocytes in circulation are few hours and in tissues is few days. b. agranulocytes in circulation about few hours and in tissues is few weeks, months or even years.


Functions of WBC”s Protect the body against invasion of extrinsic pathogens. b. Save the organism from overrun by abnormal cells.


Specific Functions of Different types of Leukocytes Neutrophils: 1. the neutrophils have been called the body’s first line of defense against bacterial infection. In patients with bacterial infection the neutrophil count is greatly increased (neutrophilia). Lack of neutrophils called neutropenia. 2. Release lysosomal enzymes that kill microorganisms. 3. phagorytize microorganism and die after that 4. cause tissue damage and inflammation.


Basophils: 1. Release chemicals such as histamine which promotes inflammation. 2. Release heparin which prevents clot formation. 3. in allergic reactions basophil count are elevated. Eosinophils release enzyme that inhibit inflammation caused by chemicals such as histamine. 2. Release enzymes that kill some parasite so in patients with parasitic infection eosinophil numbers greatly increased. Mast Cells: 1. are heavily granulated wandering cells located at points of entry of microorganism into the body such as skin, lungs, GIT and urogenital tract. 2. Contain histamine which promotes inflammation. 3. Contain heparin which prevent clot. 4. have antibody IgE on their cell membrane.


Monocytes: are the largest type of leukocytes. 1. Leave the circulation, enter tissues, enlarge and transformed into macrophages which are important in late stages of infection. 2 Produce chemicals such as prostaglandins, interferons and complement that are important in immune system response. 3. Macrophages are given specific names such as dust cells in lungs and kupffer cells in liver. Lymphocytes:. are the smallest leukocytes. 2. Types are: T-lymphocyte. 2. B-lymphocytes which differentiated into plasma cells that produce antibodies or immunoglobulins (Igs). These antibodies responsible for destroying foreign antigens. 3. Natural killer cells.


Leukopenia: WBC count lower than normal and can indicate destruction of red marrow by radiation, drugs, tumors or a deficiency of vitamin B12 or folate. Leukolytosis: is an abnormally high WBC count. Bacterial infection causes leukocytosis. Leukemia: a tumor of the red marrow. Leukemia is characterized by greatly increased numbers of abnormal WBC's in the circulating blood.

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Last Updated: 8th March 2018

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