Specific and non specific defences

Question 1

What do the mucus and cilia do?

Answer 1

Mucus lines the nasal air passages and traps bacteria

Cilia in the upper part of the respiratory tract beat to move the mucus to the stomach

Question 2

Describe phagocytosis

Answer 2

1) Phagocytes detect microbes by chemotaxis and sticks the microbes to its surface.
2) The microbe is engulfed and a vacuole is formed.
3) A lysosome attaches to the vacuole and breaks down the pathogen.

Question 3

Describe the humoral response

Answer 3

B cells produce specific antibodies in response to a specific antigen, which divide by mitosis to form a population of identical plasma cells. These will produce the same antibody and secrete it into the blood plasma. The antibodies bind to the antigens, forming an antibody antigen complex, causing agglutination, which makes it easier for phagocytes to engulf them. Some B cells develop into memory cells which can divide and produce more antibodies if the pathogen is encountered in the future.

Question 4

Describe the cellular response

Answer 4

Complementary Th lymphocytes bind to foreign antigen on APC. Releases cytokines that stimulate clonal expansion of complementary Th cells that become memory cells/ trigger humoral response or activate Tc cells to kill cells

Question 5

Describe the role of APCs

Answer 5

The macrophage displays antigens on its surface which enhances recognition by Th cells.