(a)+HDS+overview

(1) Describe the type of responses against pathogens carried out by each of the following levels of defense (a) First line of defense (b) Second line of defense (c) Third line of defense

** a) SKIN ** -micro-organisms can only penetrate the skin when it is broken

** b)WHITE BLOOD CELLS (Leucocytes) **

-when a pathogen does enter the body, you get an infection

->leucocytes are the body's defense in this case-> they produce antibodies -leucocytes are found in blood and body tissue i.e the lungs

-there are different types of leucocytes; i.e phagocytic

-> they eat any cell that is not recognized as the body's own

*red blood cells don’t have a nucleus, but white blood cells do!

** c)ANTIBODIES **

First, know the difference between antigen and antibody!!

Antigen: a molecule that an organism recognizes as foreign, causing an immune response.

i.e bacteria, viruses

Antibody (3rd defense line): produced by plasma cells in the immune system as a response to an antigen

-> the antibody neutralizes the antigen

**(a) Non-specific resistance**
 * (2) Distinguish between the following categories of resistance to pathogens **


 * Also known as innate resistance
 * Protection against a great range of pathogens.
 * Mechanisms include:
 * Species resistance
 * Some species are resistant to some pathogens that other species are not.


 * Mechanical barriers:
 * Skin
 * Mucus barriers
 * They prevent the entrance of some pathogens.


 * Chemical barriers:
 * Such as enzymes, salt, acid, etc.
 * Fever


 * Natural Killer Cells:
 * Special lymphocytes


 * Inflammation:
 * Inflammation is a tissue response to damage, injury, or infection.


 * Phagocytosis.
 * Definition: Phagocytosis is the process by which specialized cells engulf and ingest foreign particles in order to destroy them.

**(b) Specific resistance**


 * Also known as adaptive resistance or immunity.


 * Protection against particular disease-causing agents.


 * 1) Antigens
 * Definition: An antigen is a molecule that is recognized by the organism as foreign. It will cause an immune response.


 * 1) Lymphocytes
 * They originate in bone marrow
 * They are processed into T-cells
 * They are transported through the blood to lymphatic organs and here they act in immune responses against foreign antigens.
 * They produce antibodies


 * 1) T-cells
 * Help lymphocytes to produce antibodies

(3) Briefly define the following terms and give a short explanation of their role in internal defense

(b) __Resistance__ - the ability to keep pathogens out of the body
=== In the role of internal defense, when the pathogen enters the body, the body will create anti-bodies to the pathogen to kill the pathogens and makes the body resistant to that particular pathogen so it does not harm the body again. ===

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