The Excretory System

Question 1

Ectotherms

Answer 1

Gain or lose heat from or to their external environment

Fish, snakes, lizards

Question 2

Endotherms

Answer 2

Generate their own heat from metabolic reactions

Metabolism is independent of the external environment

Mammals

Question 3

Name the skin layers

Answer 3

Outer epidermis and inner dermis and adipose tissue

Question 4

Layers of epidermis are called

Answer 4

Cornified, granular and Malpighian layers

Question 5

Cornified layer consists of ___ skin cells

Answer 5

Dead

Question 6

Skin cells contain the protein

Answer 6

Keratin which makes hardened, tough and waterproof

Question 7

Malpighian layer contain ____ cells

Answer 7

Living cells

Actively dividing by mitosis to produce new epidermal cells

Question 8

Cells in the malpighian layer produce the pigment

Answer 8

Melanin which is a brown or black pigment that gives the skin, nails, hair its colour

Question 9

The Dermis is a layer which is found below the epidermis. It consists of:

Answer 9

Live connective tissue which contain elastic and collagen fibres to give skin its elasticity

It also contains
Blood vessels
Various receptors
Hair follicles 
Sweat glands

Question 10

Role of adipose tissue

Answer 10

Insulate the body and act as food storage

Question 11

6 functions of skin

Answer 11

Formation of vitamin D in UV light
Energy store 
Sense organ
Immunity
Excretory role
Temperature regulation

Question 12

Formation of Vit D in the presence of UV light. What is vit D needed for? What is a lack in vit D result in?

Answer 12

Essential for the absorption of calcium and phosphorous from the small intestine
Lack = rickets - bones become soft and this results in bowed legs

Question 13

Skin as an energy store. What is the tissue called below the dermis? What does it store?

Answer 13

Adipose tissue, stores energy as fat

Question 14

Skin as a sense organ, what does the skin contain

Answer 14

Numerous receptors which detect stimuli such as touch, pressure, cold and warmth

Question 15

Skin - immunity - general defence system role

Answer 15

Skin acts as a physical barrier to prevent pathogens and many toxins entering
Shedding of the cornified layer helps remove pathogens
Oily sebum is antibacterial and moisturises and waterproofs the skin, preventing cracking of the skin and pathogens entering
Sweat - lysozyme causes lysis of pathogen cells

Question 16

Skin - excretory role - what is excreted through the skin?

Answer 16

Sweat - secreted by the sweat glands, through the sweat duct on to the skin epidermis

Sweat helps to excrete excess water, salts and urea.

Question 17

Temp regulation by the skin. Core body temp is __ degrees

Answer 17

37 degrees - maintains high metabolism and prevents enzyme denaturisation.

Question 18

3 body responses to a rise in body temperature

Answer 18

1) increased sweating - evaporation of sweat removing heat so body cools down

2) arterioles dilate (vasodilation)
Increased blood flow to the blood capillaries in the dermis layer cause heat to radiate away from skin surface

3) hair lies flatter- layer of trapped air is thinner, giving less heat insulation so heat is lost quickly

Question 19

4 responses to a drop in body temp

Answer 19

1) arterioles constrict - vasoconstriction
Keeps in body heat as the flow of warm blood close to skin surface is reduced

2) hairs stand erect - traps a layer of warm air, heat insulation
3) shivering ( involuntary skeletal muscle activity) increases heat production
4) increased thyroxine levels speed up metabolic rate, generating heat.

Question 20

Definition of excretion

Answer 20

The elimination of metabolic waste from the body : CO2, water, urea, salts

Question 21

Homeostasis

Answer 21

The ability of an organism to maintain a constant internal environment