Phagocytosis

Pedagogy
TO CHRIST BE THE GLORY

1. PHAGOCYTOSIS Dr AnuPriya J

2. Scheme Definition Phagocyte – cell types Steps of phagocytosis Summary

3. Phagocytosis Phagein = "to devour",  kytos = "cell“, osis = “process” (from Ancient Greek) Phagocytosis is the process of engulfment and destruction of solid particles such as bacteria, dead tissue and foreign particles by the cells.

4. Phagocytes The cells performing phagocytosis are called phagocytes . The cell types are N eutrophils M onocytes and M acrophages

5. Steps Margination Diapedesis Chemotaxis Opsonization → attachment stage Engulfment stage Secretion ( degranulation ) stage Degradation stage

6. Margination

7. Diapedesis

8. Chemotaxis

9. Chemotaxis Potent chemotactic substances or chemokines are Leukotriene B4 (LT-B4) C5a, C3a Cytokines

10. Opsonization refers to the process of coating of bacteria by the opsonins . The opsonin coated bacteria gets attached to the surface of phagocyte through the opsonin receptors. The principal opsonins are IgG opsonin and C3b opsonin . Opsonization → Attachment stage

11. Engulfment stage Pseudopodia

12. Engulfment stage Phagocyte Lysosome

13. Degranulation stage Release of lysosomal enzymes into the vesicles

14. D egradation stage Oxygen dependent bactericidal mechanism mediated by oxidizing agents . Oxygen independent bactericidal mechanism mediated by lysosomal enzymes .

15. SUMMARY Margination Diapedesis Chemotaxis Opsonization → attachment stage Engulfment stage Secretion ( degranulation ) stage Degradation stage

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17. Engulfment Formation of cytoplasmic pseudopods by the phagocytes around the bacteria. The bacteria is endocytosed and is contained in a vesicle thus forming a phagosome The phagosome fuses with nearby lysosome to form phagolysosome .