PHAGOCYTOSIS AND ANTI CLOTTING
PHAGOCYTOSIS
(Neutrophil
response during inflammation)
Definition: The process of engulfing of macromolecules like bacteria, dead
cells & particulate matter by neutrophils, monocytes & tissue
macrophages is called phagocytosis.
Steps involved in the
process
Margination: Neutrophils slow down in
the circulation & get attached to the capillary wall. The
cell adhesion molecules adherin,
Integrin & selectin are involved.
Diapedesis: Neutrophils squeeze
through the pores in the capillary wall into the tissues.
Chemotaxis : Neutrophils are
attracted towards the site of damage ( infection & inflammation)
by the chemicals
released at the site of damage.
Engulfing :
Microbes are coated with
complement & antibodies (opsonization)
↓
Neutrophil membrane
invaginates enclosing the microbe
↓
Formation
of vacuole
↓
Vacuole
fusing with lysosome
↓
Lysosomes
release hydrolyzing enzymes & bactericidal agents like hydrogen peroxide,
mycloperoxidase etc
↓
Killing
& digestion of the microbe.
4. ANTICLOTTING
MECHANISMS (Factors
that prevent intravascular coagulation)
1. Physical
characteristics of the endothelium (e.g) Smoothness of vascular
endothelium Atherosclerotic (deposit of fat) plague in the vascular endothelium
gives a rough surface which activates platelets & initiate clotting.
2. High blood flow
rates:
Increased velocity of blood flow prevents clotting.
3.Presence of natural
anticoagulants:
Anticoagulants like heparin, anti thrombin III & α2macro
globulin are some of the natural anti coagulants present in the circulation and
prevent the intra vascular clotting .
4. Fibrinolytic
system:
When small clots are formed in the vessels they are immediately lysed by the system.
Tissue Plasminogen Activator
(tPA)
↓
Plasminogen → Plasmin (digests the fibrin into soluble
fragments dissolving the clot)
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