Human Skin

Question 1

The skin is the largest organ in the human body. It is made up of three layers:

Answer 1

• the epidermis which is the outermost layer
• the dermis which is below the epidermis
• the subcutaneous layer which is the bottom layer made up mainly of fat cells.

Question 2

skins role/detects what

Answer 2

stimuli such as touch, protecting the body against infection by pathogens and excessive water loss, and regulating body temperature.

Question 3

epidermis

Answer 3

made up of three layers:
cornified layer
living layer
malpighian layer

Question 4

dermis

Answer 4

biggest layer, contains capillaries, sweat glands
connective
tissue

Question 5

hair papilla

Answer 5

actively
dividing cells, form the hair

Question 6

sebaceous gland –

Answer 6

secretes oil to keep
the skin and hair soft

Question 7

cornified layer

Answer 7

dead cells rich in keratin. Layer is waterproof

Question 8

living layer

Answer 8

composed of living cells

Question 9

malpighian layer

Answer 9

contains melanin, a brown pigment

actively dividing cells that form the other layers of the epidermis and

Question 10

why living organisms need to maintain a consatnt interal body temperature

Answer 10

for enzymes to function correctly

Question 11

heat is lost mainly by

Answer 11

Heat is lost from the body mainly by conduction,convection and radiation through the skin, and evaporation of water during breathing and sweating.

Question 12

Role of the hypothalamus

Answer 12

The human skin plays a major role in regulating the body temperature. The hypothalamus of the braindetects if the body temperature rises above 37 °C or drops below 37 °C. It sends messages alongnerves to the skin causing the responses summarised

Question 13

if the body temperature rises above 37 degrees

Answer 13

the metabolic rate decreases so that less heat is produced in the body.

Question 14

If the body temperature drops below 37 °C

Answer 14

the metabolic rate increases so that more heat is produced and shivering may occur in muscles to generate even more heat.

Question 15

The skin and protection

Answer 15

• The epidermis protects against the entry of pathogens.
• The epidermis, being waterproof, protects against water loss by evaporation from body fluids.
• The melanin in the epidermis protects against the sun’s harmful ultra-violet rays.
• The epidermis protects against harmful chemicals in the environment.
• The subcutaneous layer protects against heat loss in low environmental temperatures.
• The subcutaneous layer protects against damageby acting as‘padding’.

Question 16

Skin bleaching

Answer 16

Skin bleaching refers to the practice of using chemical substances tolighten skin tone or to provide aneven skin complexion by reducing the production of melanin in areas of abnormal pigmentation, e.g.in moles, birthmarks and other darker patches. The chemicals usually work by inhibiting the action ofan enzyme (tyrosinase) that is necessary for the formation of melanin.

Question 17

Skin bleaching effects

Answer 17

hydroquinone found in lotions
can cause cancer
irritate the skin,
cause skin sensitivity
blue-black skin discolouration.