The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinters, distinguishing them from the organism's own healthy tissue.
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6. There are four main non-specific defense mechanisms:
• defense at body surfaces
• phagocytosis
• natural antimicrobial substances
• the inflammatory response.
Sebum and sweat secreted onto the skin surface contain antibacterial and antifungal
substances.
Hairs in the nose act as a coarse filter and the sweeping action of cilia in the respiratory
tract move mucus and inhaled foreign materials towards the throat.
Phagocytosis
Phagocytes trap particles either by engulfing them with their body mass or by
extending long pseudopodia towards them, which grasp them and reel them in
7. natural antimicrobial substances
Hydrochloric acid.
Lysozyme. present in granulocytes, tears,
Antibodies. These are present in nasal secretions and saliva
Saliva.
Interferons. -produced by T-lymphocytes and by cells that have been invaded by
viruses. They prevent viral replication within cells and the spread of
viruses to other cells.
The inflammatory response
The cardinal signs of inflammation are:
redness
heat
pain
swelling
loss of function
9. Increased blood flow
Following injury, both the arterioles supplying the damaged area and the local
capillaries dilate, increasing blood flow to the site.
12. T lymphocyte…
processed by the thymus gland,
T-lymphocyte has been programmed to recognize only one type of antigen,
T-lymphocytes provide cell-mediated immunity,
B-lymphocytes. These are processed in the bone marrow. Their role is in producing
antibodies (immunoglobulins), which are proteins designed to bind to and cause the
destruction of, an antigen. As with T lymphocytes, each B-lymphocyte targets one
specific antigen; the antibody released reacts with one type of antigen and no other. B-
lymphocytes provide antibody-mediated immunity