(b)+HDS+details

(4) Describe the functional role of the following defense mechanisms
(4) Describe the functional role of the following defense mechanisms (a) Skin (including sweat and sebum products): The best way to prevent disease is to prevent it from entering. When unbroken, it is almost impossible to penetrate the skin. The top layer of the skin is densely packed and dry, making it inhospitable for many bacteria. As sweat is secreted from the sweat glands, a hyperosmotic environment is created, which because of the high salt concentration dehydrates the bacteria. Sebaceous glands produce sebum (an oily secretion) which is secreted into the follicle, spearing over skin and hair. This makes skin and hair waterproof.

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

//Sometimes pathogens still manage to enter the body, which is called infection (invasion of pathogens does not always lead to disease). That is why we have white blood cells or leucocytes. These will surround any pathogenic cell that is not recognized by the body and ‘eat’ it. This is called phagocytosis. //  (c) Mucus secreting and ciliated membranes:

Any cavities that are not covered by skin and open to the environment have to protect themselves via other means. One of these means is by secreting mucus. This mucus is sticky and traps pathogens and bacteria. Cilia are little hairs that help more the mucus from the lungs to the throat so that we can swallow it.

(d) Defence secretions: tears, urine, saliva, gastric juice:

Tears:Contains the enzyme lysozyme, which breaks down wall of bacteria.

Urine: Acidic and therefore bacteria don’t live in the urinary trackt.

Saliva: Contains the enzyme lysozyme, which breaks down wall of bacteria.

<span style="color: #4f81bd; font-family: "Arial","sans-serif"; font-size: 13.33px;">Gastric juice: High pH = unfavorable for pathogens to live in.

<span style="color: #4f81bd; font-family: "Arial","sans-serif"; font-size: 13.33px;">These secretions also contain the enzyme lysozyme, which breaks down the wall of the bacteria.

(e) Antibody production

Antibodies (immunglobuli) is a soluble protein that is produced by the plasma cell. Antibodies recognize antigens and neutralize them. <span style="color: #000000; font-family: "Arial","sans-serif"; font-size: 13.33px;">(f) Fever and work faster to kill the pathogens. <span style="color: #4f81bd; font-family: "Arial","sans-serif"; font-size: 13.33px;">When the body is invaded by a pathogen macrophagers, fighting the pathogen, secret chemicals called pyrogens. These chemicals order the hypothalamus to raise the temperature of the body. The body therefore works harder to meet this increased temperature. The higher temperature can kill many bacteria as they cannot live under this rise in temperature and also, seeing that the body works faster more bacteria are killed. (g) Cell-mediated immunity

An immune response that does not involve antibodies. "Cellular immunity protects the body by: Source: []
 * 1) activating antigen-specific cytotoxic T-lymphocytes that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
 * 2) activating macrophages and natural killer cells, enabling them to destroy pathogens; and
 * 3) stimulating cells to secrete a variety of cytokines that influence the function of other cells involved in adaptive immune responses and innate immune responses."

(h) The inflammatory response

When a tissue is infected, the damaged cells produce a chemical called histamine. Histamine causes the damaged area to swell, get hot and become red (as the blood capillaries dialite and become more porous). This causes white blood cells to come to the dagamed tissue and fight the infection.