The Skin

Question 1

What are the functions of the skin?

Answer 1

1. Sense organ
2. Protection
3. Homeostasis - temperature control

Question 2

How is the skin a sense organ?

Answer 2

The skin is a sense organ for the sense of touch. The dermis contains receptors for pressure, temperature change and pain.

Question 3

How does the skin protect the body?

Answer 3

1) The dead outer epidermis acts as a physical barrier and protects the body from damage. Also prevents the entry of pathogens.
2) The dermis protects the internal organs.
3) The sebum is a moisturiser produced by the sebaceous gland that prevents cracking of the skin barrier. Sebum also contains anti- microbial chemicals.
4) Symbiotic microbes like bacteria and yeast inhabit the skin. They compete against pathogens that are trying to enter the body through the skin.
5) Melanin protects the skin from UV radiation.

Question 3

What happens if conditions get too cold?

Answer 3

1. Vasoconstriction.
2. Piloerection.
3. Shivering.

Question 4

What is vasoconstriction?

Answer 4

The arterioles contract. This reduces blood flow to the surface capillaries, which reduces heat loss through the skin.

Question 5

What is piloerection?

Answer 5

The hairs on the skin stand up. This is caused by the contraction of the erector muscles and it results in goose bumps. A layer of insulating air is trapped by the erect hairs close to the skin, so that heat loss is reduced.

Question 6

What happens if conditions get too hot?

Answer 6

1. Sweating.
2. Vasodilation.
3. The hairs lie flat.

Question 7

Sweating

Answer 7

The sweat glands start to secrete water and its evaporation from the skin removes heat.

Question 8

Vasodilation

Answer 8

The arterioles dilate. This increases blood flow to the surface capillaries, which increases heat loss through the skin.

Question 9

The hairs lie flat?

Answer 9

This is caused by the erector muscles relaxing, so that less insulating air is trapped close to the skin and heat can be lost more easily.

Question 10

What is an endotherm?

Answer 10

An animal whose body temperature is independent of the environment temperature.

Question 11

What is an ectotherm?

Answer 11

An animal whose blood temperature varies with the environmental temperature.

Question 12

Examples of Endotherms

Answer 12

Birds, humans

Question 13

Examples of Ectotherms

Answer 13

Worms, insects, reptiles.