Non-Specific Body Defences

Question 1

Pathogen

Answer 1

An organism that causes disease

Question 2

Immune System

Answer 2

The body system that defends against pathogens, toxins and cancer cells

Question 3

Immunity

Answer 3

The ability of the body to resist infection by a pathogen or destroy the organism if it succeeds in invading and infecting the body

Question 4

Physical Barrier e.g Skin

Answer 4

The surface of skin is composed of layers of closely packed epithelial cells which form a physical barrier again pathogens

Question 5

Physical Barrier e.g Inner Lining

Answer 5

Closely-packed epithelial cells are found in the skin and the inner linings of the digestive system and respiratory system

Question 6

Chemical Secreations Against Pathogens

Answer 6

Sweat glands and sebaceous glands in the skin keep the skin at a pH that is too low for most microbes to surive.
Tears and saliva contain the enzyme lysozyme which digests the cell walls of bacteria and destroys them
Mucous membranes secrete sticky mucus which traps microbes
Epithelial lining of the stomach secretes acid which destroys microbes

Question 7

Inflammatory Response

Answer 7

When the body suffers a physical injury such as a cut and/or invasion by microbes, it responds by a localized defense mechanism called an inflammatory response at the affected site

Question 8

Inflammatory Response Step 1

Answer 8

After injury, mast cells are activated and release large qualities of histamine resulting in blood vessels in the injured area undergoing vasodilation and capillaries becoming more permeable

Question 9

Inflammatory Response Step 2

Answer 9

The increased blood flow and permeability of capillary walls bring about the following beneficial effects-
-An accumulation of phagocytes to the damaged tissue as they are attracted by cytokines
-Rapid delivery of blood-clotting chemicals to the injured area

Question 10

Phagocytes

Answer 10

White blood cell that carry out a non-specific immune response and destroy them by phagocytosis

Question 11

Phagocytosis Step 1

Answer 11

Phagocytes detects surface antigen molecules present on a pathogen, and move towards it

Question 12

Phagocytosis Step 2

Answer 12

Phagocytes engulf the invader by enfolding of the cell membrane to create a vacuole

Question 13

Phagocytosis Step 3

Answer 13

Lysosomes present in the phagocyte’s cytoplasm fuse with the vacuole and release enzymes to digest the invading pathogen

Question 14

Phagocytosis Step 4

Answer 14

The breakdown products are absorbed by the phagocyte

Question 15

Phagocytosis Step 5

Answer 15

Once the invader is digested the phagocytes release cytokines which attract more phagocytes to the infected area to continue the battle against pathogens

Question 16

Phagocytosis Step 6

Answer 16

Dead bacteria and phagocytes accumulate at the infected site as pus

Question 17

Phagocytosis Step 7

Answer 17

After contact with a pathogen, phagocytes release cytokines which circulate in the bloodstream and stimulate the specfic immune response by activating lymphocytes

Question 18

Cytokines

Answer 18

Protein molecules that act as a signal to other white blood cells causing them to gather at the site of infection