The presentation is all about the etymology, definition and mechanism of phagocytosis also with a glimpse about phagocytic cells

2. Definition
❖ Phagocytosis forms the second line
of defence
❖ In Greek “phagein” means to eat
“cyte” means the cell and “osis”
means the process
❖ “Phagocytosis is a process of
ingestion and uptake of microbes
and other substances by a cell”
❖ It is used by Phagocytic cells of our
immune system to get rid of the
pathogens which have breached first
line of defence
Antimicrobial
substances
Phagocytosis
Natural killer
cells
Inflammation
and Fever
Second line of Denfence

3. Phagocytes
❖ The cells that perform phagocytosis are known as Phagocytes
❖ The main types of phagocytes of immune system are
1. Monocytes
2. Macrophages
3. Neutrophils
4. Dendritic cells
❖ Function of these phagocytes is to destroy the engulfed pathogens
❖ These phagocytes are equipped with certain intracellular
compartments such as lysosomes which contains microbicidal
substances (Lysozymes, Nucleases, Proteases, Lipases, H2O2 etc,.)
Dendritic cells : These are special group of
phagocytic cells, since besides performing the
processing of engulfed pathogen they well
present the same antigen (which is a part of
Adaptive immune system)

4. Mechanism of Phagocytosis

5. Steps
1. Recognition : Recognition of antigens will take place by Pathogen
Recognition Receptors (PRRs) present on the plasma membrane of
phagocytes which will recognize specific molecular patterns on the
invading microbes called Pathogen Associated Molecular Patterns
(PAMPs)
2. Ingestion : The phagocyte will extends its plasma membrane to
form finger like projections called pseudopodia around the
adhered pathogen
3. Formation of Phagosome : The membrane after surrounding the
pathogen will pinches off from its surface to form a sac known as
“phagosome” or “phagocytic vesicle” to internalize the pathogen

6. 4. Formation of phagolysozome : The phagocytic vesicle will now
fuse with one or more lysosomes present in the cytoplasm to form
larger structure called “Phagolysosome”
5. Digestion or Killing : The phogolysosome has lower pH (acidic
environment) and variety of microbicidal enzymes which will
contribute in the destruction of internalised microbe
6. Formation of residual bodies : Once the killing and digestion of the
engulfed microbial cell happens only indigestible materials remain
in sac and this sac containing indigestible materials is called
“Residual body”

7. 7. Elimination or Exocytosis : The formed residual body will move
towards the cell boundary and discharges its contents outside the
cell
That's all folks..
Thank you!!!