3.5 non-specific body defences

Question 1

Define the term ‘pathogen’.

Answer 1

A pathogen is any organism that can cause disease e.g. viruses, bacteria, fungi etc.

Question 2

State what is meant by ‘non-specific’ defence mechanisms.

Answer 2

Non-specific defence mechanisms do not target specific pathogens. They are defences that are designed to prevent any pathogens entering the body.

Question 3

Identify the main physical non-specific defence mechanisms.

Answer 3

The main physical defence barriers in the body are formed by epithelial cells. Epithelial cells are closely-packed together forming cohesive sheets that form an impenetrable barrier. They are found within the external skin and make up the inner linings of the digestive and respiratory systems.

Question 4

chemical non-specific defence mechanisms.

Answer 4

The body also produces chemical secretions to act against invading pathogens as part of the non-specific body defences.

Question 5

examples of the main chemical non-specific defence mechanisms. (stomach acid)

Answer 5

Stomach Acid – this is a secretion of hydrochloric acid which is strong enough to kill pathogens consumed in food/water or trapped in the respiratory mucus and then swallowed.

Question 6

Describe the non-specific inflammatory response.

Answer 6

Inflammation (swelling) is a non-specific defence response. The inflammatory response is triggered by the release of histamine by mast cells. Histamine causes local vasodilation and increased capillary permeability. This results in an increased blood flow which leads to an accumulation of phagocytes and blood clotting elements at the site of infection.

Question 7

Describe the role of phagocytes in non-specific defence.

Answer 7

Phagocytes are white blood cells involved in the non-specific defence response. These cells recognise pathogens and destroy them in a process called phagocytosis. During phagocytosis, the phagocytes engulf the pathogens and then destroy them using digestive enzymes released from structures called lysosomes.

Question 8

Cytokines

Answer 8

Phagocytes also release cytokines. Cytokines are protein molecules that act as a signal to attract more phagocytes, causing them to accumulate at the site of infection making the defence response more effective.

Question 9

examples of the main chemical non-specific defence mechanisms. (Tears and saliva)

Answer 9

Tears and saliva– secreted by the tear ducts and salivary glands, contain the digestive enzyme lysozyme which breaks down bacterial cell walls.

Question 10

examples of the main chemical non-specific defence mechanisms. (mucus)

Answer 10

Mucus – a sticky liquid that lines the inner surfaces of the respiratory and digestive systems to trap particles and pathogens.