> Immunity and immune system:
1.] Immunity means having resistance towards a disease causing organism of
harmful substance that tries to enter the living organism.
2.] Factors on which immunity depends:
> host resistance
> Virulence of organism
3.] Resistance can be of different types:
4.] There are other classes of immunity also such as herd immunity:
>The three walls of immunity:
>Innate immunity:
>ANATOMIC BARRIERS
 Image of cilia from lungs under electron microscope:
 Physiological barrier:
These kind of barrier refers to the physical conditions of the body which
includes:
1.] Temperature
2.] PH
3.] Oxygen tension: the activity of the molecules of oxygen dissolved in the
plasma.
4.] Soluble factors: lysozyme, interferon and complements.
Note: low oxygen level can supress immune response and can
affect the important function of immune cells.
 Phagocytic barrier:
Pinocytosis:
Note: Specific defense mechanism is the ability of the body to develop immunity
against specific pathogens, toxins or foreign things.
Nonspecific defense system with which you were born. It protects you against
all antigens.
 Inflammatory response:
Inflammation is an important defense mechanism of host to prevent infection.
It is induced in response to tissue damage caused by microorganism, toxins or
by mechanical means.
 Electron micrograph image showing migration of
neutrophils during acute inflammation:
Leukocytes assume marginal positions in the blood vessels. They intermittently
stick to the walls of the venules and roll along them until they become firmly
attached to the vessel wall (adhesion). At this point, they begin to move out of
the vessel.