The General Defence System(Complete)

Question 1

What is the general defence system?

Answer 1

it is non specific and acts as a barrier against all pathogens trying to enter the body.

Question 2

What are the components of the general defence system?

Answer 2

The skin.
Ciliated mucous membranes.
Beneficial bacteria.
Phagocytes.
Inflammation.
Defence Proteins.
Fever.

Question 3

What is the role of the skin in the general defence system?

Answer 3

It is the outer structural barrier.
The outer skin cells are constantly flaking away taking pathogens with them.
Sweat contains the enzyme lysozyme which causes lysis and dissolves the cell walls of many bacteria.
Sebaceous glands secrete sebum which is an oil that prevents cracking. Cracking allows pathogens to enter.
Sebum also has chemicals that harm or kill bacteria.
Blood clotting aims to prevent the entry of pathogens.

Question 4

What is the role of the ciliated mucous membranes in the general defence system?

Answer 4

These membranes line the respiratory, digestive and reproductive tract.
In the respiratory tract:
Mucous traps pathogens.
Thin fine hair called cilia create a current to move the mucous and its trapped matter to the pharynx where it it then swallowed.
HCL in the stomach is antibacterial and kills many germs like bacteria.

Question 5

What is the role of the beneficial bacteria in the general defence system?

Answer 5

Lactic acid is produced by bacteria in the vagina- the acid inhibits the growth of pathogens.

Question 6

What is the role of the phagocytes in the general defence system?

Answer 6

Role 1- Phagocytosis:
Infected cells secrete chemicals which attract white blood cells.
Phagocytes engulf bacteria as follows:
Pseudopods surround the pathogen forming an internal vacuole.
Enzymes are secreted into the internal vacuole digesting the pathogen.
The breakdown products are absorbed by the phagocyte.

Role 2:
Phagocytes secrete chemicals which stimulate the general defence system and cause fevers killing the pathogens as the high temperatures denature the enzymes.

Question 7

What is pus?

Answer 7

The combination of white blood cells and dead pathogens.

Question 8

What is the role of inflammation/ histamine in the general defence system?

Answer 8

Infected cells release histamine.
This causes the blood vessels to dilate and the capillaries to become more porous.
More white blood vessels can reach the infected area causing inflammation.
Symptoms- redness, heat, swelling.

Question 9

What is a fever and what is its role in the general defence system.

Answer 9

Fever- inflammation that covers the whole body.

The high temperatures inhibit the reproduction of pathogens.

Question 10

What is the role of the defence proteins in the general defence system?

Answer 10

Complement- a set of 20 defence proteins found in plasma which are activated by infection.
Role- to cause lysis in pathogens causing them to burst.

Interferon- specific defence proteins produced by body cells after infection.
Role- to inhibit viral replication and prevent the spread of viral diseases.
To increase the activity of killer T cells.