Unit 3 KA5 - non specific defences

Question 1

what is a pathogen?

Answer 1

organism such as bacterium/virus that causes disease

Question 2

what is the immune system? name the two parts

Answer 2

the body uses this to defend itself against pathogens

• non-specific
• specific

Question 3

what is meant by immunity?

Answer 3

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

Question 4

what is a non-specific defense?

Answer 4

defense mechanisms that will prevent the entry of all pathogens/destroy any random pathogen that gains entry to the body

Question 5

name the types of non-specifc defense mechanisms?

Answer 5

physical and chemical defenses, inflammatory response, and phagocytes

Question 6

describe and give examples of physical and chemical defenses

Answer 6

• layers of closely packed epithelial cells on the surface of the skin offers physical protection against bacteria and viruses
• mucous membranes that line the body’s digestive and respiratory tract are composed of epithelial cells that form a protective physical barrier
• skin and mucous membranes also provide chemical defenses against potential pathogenic microorganisms
• secretions such as tears and saliva contain the enzyme lysozyme which digests the cells walls of bacteria and destroys them
• cells in mucous membranes secrete sticky mucus which traps microorganisms
• epithelial cells lining the trachea are ciliated and sweep the mucus and trapped microbes up and away from the lungs
• acids secreted by cells in the epithelial lining of the stomach destroys many of the microbes that have been swallowed

Question 7

describe the inflammatory response

Answer 7

it is a localised defense mechanism in response to physical injury

• after injury, mast cells are activated and release large quantities of histamine
• histamine causes blood vessels to vasodilate and capillaries to become more permeable
• the increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of injury

Question 8

what are mast cells?

Answer 8

present in connective tissue throughout the body

a type of white blood cells that contains histamine

Question 9

what are phagocytes?

Answer 9

non-speciifc white blood cells that recognise and destroy pathogens by phagocytosis
they release cytokines that attract more phagocytes to the site of infection

Question 10

what is phagocytosis?

Answer 10

the engulfing of all pathogens and their destruction by digestive enzymes contained in lysosomes

Question 11

what are cytokines?

Answer 11

protein molecules that also act as a signal to specific white blood cells causing them to accumulate at the site of infection