(b)+HDS+details

(4) Describe the functional role of the following defense mechanisms

(a) Skin (including sweat and sebum products):

The unbroken skin is a layer between the outside environment and the body, and is almost impossible for any microbe to penetrate the skin. This is a diagram of the main structure of human skin: The sweat on the skin flushes out pathogens.

(b) Phagocytosis by white blood cells (phagocytic leucocytes)://Draw a diagram & include the word phagocytosis.//

This role of defense is geared towards pathogens that manage to get inside the body. White blood cells/ leucocytes, which are found in the blood and tissues (lungs) kill pathogens by "eating the cell" through phagocytosis. The cell engulfs the pathogen, and then it destroys it.

(c) Mucus secreting and ciliated membranes:

These membranes allow for the elimination of harmful products from the body (such as dust and smoke). Mucous is secreted from the goblet cells in several areas of the body (such as in the intestinal tract). Production of mucous is triggered by the presence of irritants on the membrane, such as the lumen of the intestinal tract. After mucous is secreted, it travels across the membranes and picks up harmful irritants, and then mucous is removed form the body along with the irritants.

The cilia are small hair-like structures on the membranes that aid in guiding the mucous along the membranes (to sweep mucous and irritants out of the windpipe, for example) (d) Defence secretions: tears, urine, saliva, gastric juice:

Tears, urine and saliva:

They help to flush microbes off the surfaces of the body and out of the body. Tears and saliva also contain the enzyme lysozyme which can break open bacterial walls.

Gastric juice:

Destroys most bacteria and bacterial toxins.

(e) Antibody production: Antibodies are proteins produced by the immune system as a response to the presence of a pathogen (a molecule that is recognized by the organism as foreign). The increased antibody production when antigen are present means they can fight the foreign contaminants faster.

(f) Fever: One of the body's defense mechanisms for destroying viruses and bacteria; it's as a response to infection and injury. As the body temperature increases (which creates a fever) it enhances the body's defense against pathogens. It accelerates the replicating of white blood cells (leukocytes). <[]> <[]>

(g) Cell-mediated immunity: A response to antigen where T cells (lymphocytes) bind to the surface of other cells that display the antigen and trigger a response. The response may involve: <[]>
 * other lymphocytes and
 * any of the other leukocytes

(h) The inflammatory response: a series of local cellular and vascular responses triggered when the body is injured, or invaded by antigen - it occurs in order to protect the body. The reaction of pain results from swollen tissue putting pressure on nerve endings, which serves to alert the body that it has been injured. The inflammatory response also prevents the spread of microorganisms or antigen to other area, to dispose of any cellular debris, and to begin the healing process. <[]>