Primary Defenses Against Disease.

Question 1

What is inflammation?

Answer 1

Swelling and redness of tissue caused by infection.

Question 2

What is the mucous membrane?

Answer 2

Specialised epithelial tissue that is covered by mucus.

Question 3

Define primary defences.

Answer 3

Those that prevent pathogens entering the body.

Question 4

What is the main primary defence?

Answer 4

The skin

Question 5

What are the cells called in the outer layer of the skin (epidermis)?

Answer 5

Keratinocytes.

Question 6

Describe keratinisation.

Answer 6

Keratinocytes are produced by mitosis at the base of the epidermis. Then they migrate out to the surface of the skin. As they migrate, they dry out and the cytoplasm is replaced by the protein keratin.

Question 7

How long does keratinisation take?

Answer 7

30 days.

Question 8

Clotting factors are released from platelets when a clot needs to be formed. What do the clotting factors cause?

Answer 8

An enzyme cascade.

Question 9

What does clotting involve?

Answer 9

Calcium ions and at least 12 clotting factors.

Question 10

Once the clot has formed it makes a scab. What is the importance of a scab?

Answer 10

A scab shrinks over time and bring the two side of the cut together. A scab is a kind of temporary seal for the body.

Question 11

How does the skin repair itself?

Answer 11

Fibrous collagen deposited under scab.

Stem cells in epidermis divide by mitosis, new skin cells.

Question 12

How is the new skin supplied with nutrients?

Answer 12

New blood vessels are formed to supply oxygen and nutrient to the new tissues.

Question 13

Why is mucus used by the airways?

Answer 13

They are thinner there to facilitate diffusion and are therefore less well protected from pathogens.

Question 14

How are the airways protected?

Answer 14

By the mucus membrane.

Question 15

What are mucus secreting cells called?

Answer 15

Goblet cells.

Question 16

How do the airways use mucus to combat pathogens?

Answer 16

The mucus traps the pathogens. The ciliated epithelium waft the layer of mucus in a coordinated fashion to the back of the throat where it is then either swallowed or coughed up by the animal.

Question 17

Where else are mucous membranes found?

Answer 17

Gut, genital areas, anus, ears and nose.

Question 18

What is the point of coughing or sneezing?

Answer 18

Coughing causes a sudden expulsion of air and with it the microorganisms which are irritating the body.

Question 19

Specialised cells called mast cells are triggered by infection. What is the substance called that these cells release?

Answer 19

Histamine

Question 20

What does histamine do?

Answer 20

Causes vasodilation and makes the capillary walls more permeable to white blood cells and some proteins.
Blood plasma and phagocytic white blood cells leave the blood and enter the tissue fluid.

Question 21

Why is it good that swelling occurs at the site of infection?

Answer 21

Swelling means that there is an increase in tissue fluid due to an influx in blood plasma and phagocytic WBC. The tissue fluid is then drained into the lymphatic system, where it can trigger an immune response, eventually killing the pathogen.

Question 22

Give three examples of other primary responses.

Answer 22

The eyes are protected by antibodies and enzymes in the tear fluid.
Ear canal is lined with wax, which traps pathogens.
Female reproductive system is protected by a mucus plug in the cervix and by maintain relatively acidic conditions in the vagina.