lesson 2

Question 1

distinguish between specific and non specific

Answer 1

our defense mechanisms are classed into two groups:

-nonspecific: these work against all pathogens and are considered our first line of defense

• specific: these are directed at a particular pathogen

Question 2

explain what external (first line of defenses) are

Answer 2

they are there to stop pathogens from entering.
they are all non specific

Question 3

list 5 external defenses

Answer 3

skin
hairs
cilia
acids
cerumen

Question 4

each of he external defense barriers can also be classified as either:

Answer 4

physical barrier- stop pathogen from entering the body by blocking or trapping them

chemical barrier: kill pathogens before they can enter the body

Question 5

explain how the skin prevents pathogens entering the body.

Answer 5

-is the main barrier preventing microorganisms from entering due to:

stratified epithelial structure: cells held tightly, covered with a layer of dead epithelium that is too dry for most bacteria to grow on and as these dead cells are continuously sloughed off from the skin, they can carry bacteria and other pathogens with them.

bacteria- non pathogenic bacteria occupy area on the skin, so that pathogens find it difficult to get on the skin surface.

sebum- an oily secretion by oil glands in the skin- prevents cracking so that remains as an intact barrier.

sweat- contains salts and fatty acids that prevent growth of many microorganisms, helps physically wash microbes away.

Question 6

explain how mucus membranes prevents pathogens from entering:

Answer 6

-membranes that line body cavities open to the exterior

-membranes secrete mucus, which traps microorganisms and inhibits their entry into the organs of the body.

-mucus often contains lysozyme- an enzyme that kills bacteria by destroying their cell walls and causing lysis.

-cilia, the beating of the cilia moves the mucus containing trapped particles and microorganisms up towards the throat where it can be coughed up or swallowed.

Question 7

explain how acids prevents pathogens from entering the body:

Answer 7

the vagina has acid secretions that reduce the growth of microorganism

the sweat in the skin is slightly acidic which also reduces growth of some microorganisms

Question 8

what is a protective reflex and give examples:

Answer 8

a reflex is an involuntary, automatic response to a stimulus

-sneezing
-coughing
-vomiting
-diarrhoea

Question 9

sneezing:

Answer 9

stimulus= irritation of walls of nasal cavity

forceful expulsion of air from the lungs carries mucus, foreign particles an irritating gases out through the nose and mouth

Question 10

coughing:

Answer 10

stimulus= irritation in the lower respiratory tract (bronchi and bronchioles)

similar to sneezing- air is forced from the lungs to try and remove the irritant

Question 11

vomiting:

Answer 11

stimulus can be psychological, excessive stretching of the stomach or bacterial toxins

it is not the stomach that contacts to expel the stomach contents, but rather the abdomen and diaphragm

Question 12

diarrhea:

Answer 12

stimulus= irritation of the small and large intestines by bcateria, viruses or protozoans

the irritation causes increased contractions of the muscles in the walls of the intestines so that to irritant is removed ASAP.