3.2 Gas Exchange

Question 1

How does an insect prevent water loss

Answer 1

Exoskeleton made of chitin and a waxy substance
Small SA: V
spiracles close via muscular valves
Hairs surrounding spiracles trap moist air

Question 2

Why are spiracles required?

Answer 2

Gases cannot diffuse through exoskeleton so spiracles are needed for gas exchange

Question 3

What happens if an insect undergoes high activity

What happens if lactic acid builds up?

Answer 3

The tracheal system is actively ventilated by pumping movements of the abdomen - compression of the abdomen and squeeze air into tracheal tubes

Water potential decreases, water in tracheoles diffuses via osmosis into surrounding cells to increase amount of air entering tracheoles

Question 4

Describe water flow in fish

(2 steps)

😮😐😮😐

Answer 4

1. The mouth opens, the operculum shits, the floor of the mouth lowers
   High volume, low pressure in mouth(opposite in operculum) - water enters
2. The mouth closed, the operculum opens, the floor of the mouth raises
   High volume, low pressure in operculum (opp in mouth) - water push over gills

Question 5

Describe gash exchange in fish

3. Why does water move in a counter current mechanism?

Answer 5

1. Water enters mouth and passes over gills
2. Water contains oxygen which diffuses into gill filaments into the blood. There are many gill filaments which contain lamellae to increase surface area and are 1 cell thick to reduce diffusion pathway
3. Water moves in a counter current mechanism to maintain a concentration and diffusion gradient of oxygen uptake into the lamellae across its whole length

Question 6

Describe the trachea

Answer 6

A flexible airway that is supported by rings of cartilage.
The Tracheal walls are made of muscle, lined with epithelium and goblet cells
Goblet cells produce mucus which are moved by the cilia

Question 7

Describe the bronchi

Answer 7

Two divisions of the trachea, each leading to one lung

They produce mucus and contain cilia to trap and remove dirt

Question 8

Describe the bronchioles

Answer 8

Series of branches bronchi. Walls are made of muscle lined with epithelial cells

Question 9

Describe the alveoli

Answer 9

Minute sacs lined with epithelium. They contain collagen and elastic which allows them to stretch when filled with air

Question 10

Describe inspiration

Answer 10

External intercostal muscles contract
Causing ribcage to expand up and out
Diaphragm contracts and moves down
Thoracic volume increases
Pressure in lungs decreases 
Air flows into lungs due to pressure gradient

Question 11

Describe expiration

Answer 11

Internal intercostal muscles contract
Causing ribcage to move inwards and down
Diaphragm relaxes and moves up
Thoracic volume decreases, pressure in lungs decreases
Air flows out of lungs due to pressure gradient

Question 12

What occurs during forced (heavy) breathing?

Answer 12

The abdominal muscles also contract to increase the force of expiration

Question 13

Define tidal volume

Answer 13

Volume of air breathed in or out per breath

Question 14

Define inspiratory/ expiratory reserve volume

Answer 14

Maximal amount of air forcibly inspired/ expired in additions to tidal volume

Question 15

Define vital capacity

Answer 15

Maximal amount of air exhaled after a maximal inspiration

Question 16

Define residual volume

Answer 16

Volume of air remaining in the lungs after a maximal expiration

Question 17

Define total lung capacity

Answer 17

Residual volume + vital capacity

Question 18

Minute ventilation

Answer 18

Tidal volume X breathing rate

Volume of air breathed in or out per minute

Question 19

What are the adaptations of the alveoli

Answer 19

Highly folded - increase SA
Contains a single layer of epithelium - short diffusion pathway
Contains phagocyte cells - kill bacteria trapped by mucus
Alveoli cells contain water which are diffused into alveoli as they contain soapy surfactant to reduce surface tension and stop the alveoli collapsing