The Skin(Complete)

Question 1

What are the two layers of the skin called?

Answer 1

The epidermis.

The dermis.

Question 2

Describe the structure and role of the Malpighian layer.

Answer 2

Cells are formed by mitosis.
They are hardened by waterproof protein keratin to replace dead cells in the outer cornified layer.
Cells produce the pigment melanin

Question 3

Where is the protein keratin found?

Answer 3

The skin.
The hair.
The nails.

Question 4

What is the role of melanin?

Answer 4

To protect against UV radiation.

Question 5

Where is melanin found?

Answer 5

In the iris of the eye.
In the skin.
In hair.

Question 6

What is melanoma?

Answer 6

When the cells that produce melanin become cancerous.

Question 7

Describe the granular layer.

Answer 7

Cells are larger and keratinized as they migrate to the outer cornified layer.

Question 8

Why are cells dead in the cornified layer?

Answer 8

As no blood supply and cells are coated with too much keratin.

Question 9

Describe the cornified layer.

Answer 9

The outer layer of the skin with dead cells which is constantly shedding- the epidermis is replaced every 30 days.

Question 10

What are the main roles of the outer cornified layer?

Answer 10

Cells have keratin with a natural waterproof layer which prevents natural moisture from leaving the skin keeping it hydrated.
It acts as a barrier against all pathogens and protects against pressure changes.

Question 11

Describe the structure of the dermis.

Answer 11

Consists of live connective tissue with elastic and collagen fibres.

Question 12

What is inside of the dermis?

Answer 12

Receptors, sweat glands, hair follicles, arterioles and sebaceous glands are all embedded into the dermis.

Question 13

What is the role of the receptors?

Answer 13

The touch and temperature receptors detect a stimulus and generate impulses as a result.

Question 14

What is the role of sweat glands?

Answer 14

Sweat glands produce the excretory fluid sweat which is carried to the surface of the skin by sweat ducts. Sweat is evaporated to cool down the body.
Has a big role in thermoregulation.

Question 15

What is the role of sebaceous glands?

Answer 15

Sebaceous glands are connected to the side of the hair follicle.
They secrete sebum which is an oil which creates a moisturising layer, preventing the skin from cracking.

Question 16

Where are hair follicles formed?

Answer 16

In the infoldings of the Malpighian layer.

Question 17

What is hair?

Answer 17

A solid cylinder made of dead cells and keratin.
The root of the hair is under the skin surface.
The shaft of the hair is above the skin surface.
Hair erector muscles control the movement of hair and therefore contract to allow hair to stand upright-thermoregulation.

Question 18

Where is adipose tissue located?

Answer 18

Under the dermis.

Question 19

How is adipose tissue formed?

Answer 19

Subcutaneous tissue and fat cells.

Question 20

What are the roles of adipose tissue?

Answer 20

To insulate the body.

To act as a food store.

Question 21

What are the main functions of the skin?

Answer 21

Formation of vitamin D in the presence of UV radiation.
Acts as a sense organ.
Insulates and acts as a food store by means of subcutaneous fat.
Protection.
Excretory role.
Thermoregulation.

Question 22

Describe the role of the skin in the formation of vitamin D.

Answer 22

The skin produces vitamin D which is essential for the absorption of calcium.
Lack of this vitamin would result in rickets causing the bones to become soft and legs would become bowed.

Question 23

Describe the role of the skin in acting as a sense organ

Answer 23

The skin contains receptors on its surface which detect stimuli such as heat, cold and touch and generate impulses as a result.

Question 24

Describe the role of the skin in insulating the body and acting as a food store.

Answer 24

Adipose tissue contains fat cells which insulate the body and act as a food store.

Question 25

Describe the role of the skin in protection.

Answer 25

The outer cornified layer acts as a barrier against all pathogens.
It is constantly flaking away taking pathogens with it.
Sebaceous glands secrete sebum which is an oil that coats the skin and hair and moisturises the skin preventing cracking and the entry of pathogens.
The skin excretes sweat which contains the enzyme lysozyme which causes lysis in pathogens.
Melanin in the skin protects from UV radiation.
The hair acts as a barrier against many insect pests.

Question 26

Describe the role of the skin in its excretory role.

Answer 26

Sweat is an excretory fluid produced by sweat glands and is taken to the surface of the skin by sweat ducts.
Sweat excretes water, salts, urea and lactic acid.

Question 27

What is the body’s response to a rise in temperature?

Answer 27

Increased sweating- sweat evaporates using heat from the body which lowers body temperature.
VAsodilation- the arterioles widen which increases blood flow to the skin’s surface which increases heat loss.
The hairs lay flat to not trap warm air.

Question 28

What is the body’s response to a loss in temperature?

Answer 28

Vasoconstriction- arterioles narrow to decrease blood flow towards the skin’s surface and reduce heat loss.
Piloerection- hairs stand upright to increase warm air trapped close to the skin’s surface.

Question 29

Describe briefly the hormonal and nervous responses that occur when the internal body temperature drops.

Answer 29

Nervous- Shivering generates heat as muscles contract

Hormonal- Excess levels of thyroxine increase aerobic respiration which releases heat.

Question 30

State two ways in which the body is insulated against the loss of heat.

Answer 30

Subcutaneous fat.

Hair.

Question 31

Suggest a biological reasoning for the following:

A person’s fingers may turn white when exposed to low temperatures for a period of time.

Answer 31

Arterioles constrict.

Lessens blood flow to the fingers to reduce heat loss.

Question 32

What is the importance of thermoregulation?

Answer 32

To maintain the body temperature of 37.8C.
To help maintain a high rate of metabolism.
Prevents enzyme denaturation.

Question 33

What is an endoderm?

Answer 33

Their body temperature is independent of the temperature of the environment.
Can vary their metabolic rates.

Question 34

Give 2 examples of endoderms.

Answer 34

Mammals.

Birds.

Question 35

What is an ectoderm?

Answer 35

Their body temperature varies with the temperature of the environment.
Cannot vary their metabolic rates.

Question 36

Give 2 examples of ectoderms.

Answer 36

Reptiles.

Amphibians.

Question 37

How do ectoderms rely on behaviour to regulate body temperature?

Answer 37

They lie broadside to the sun or source of heat or move to hot areas to raise their body temperature.
Move to cold areas to lower their body temperature.

Question 38

What is the source of heat that allows the body to maintain a constant internal temperature?

Answer 38

Respiration of glucose in muscle and liver cells.

Question 39

What is the skin?

Answer 39

A self-replacing, self-healing barrier to invading pathogens.
It is our organ of touch.