Gas exchange

Question 1

What is tidal volume?

Answer 1

The volume inhaled in resting conditions

Question 2

What is maximum pulmonary ventilation?

Answer 2

The total volume of air moved through the lungs in a given time

Question 3

What is vital capacity?

Answer 3

The largest amount of air that can be moved in and out within one breath.

Question 4

What is the order of airways in mammal lungs (largest to smallest)?

Answer 4

Trachea
Bronchi
Bronchioles
Alveoli

Question 5

What are the steps of passive ventilation?

Answer 5

Inhalation
• Diaphragm contracts
• Intercostal muscles contract
• Chest expands
• This increases the volume of the thorax and so pressure decreases below atmospheric pressure.
• Due to this change in pressure, air is sucked into the lungs until the pressure is regulated.
Exhalation
• Diaphragm relaxes
• Intercostal muscles relax
• Therefore, the chest returns to normal size
• The thorax volume decreases, increasing pressure to above active pressure.
• Air is pushed out of the lungs into the surroundings, returning the pressure to normal.

Question 6

How is forced ventilation different to passive ventilation?

Answer 6

Forced
Inhalation
• As well as the intercostal muscles and the diaphragm moving, the accessory muscles in the neck may also move to elevate the sternum and the first 2 ribs.
• This, along with maximum contraction means that the pressure decreases much more and so much more air flows in.

Exhalation
• The abdominal muscles contract and force the diaphragm upward.
• Contraction of the internal intercostal muscles actively pulls the ribs downwards.
• Therefore, a much higher pressure is created due to the smaller lung volume.

Question 7

Describe the alveoli

Answer 7

Small air sacs lined with collagen and elastic fibres
Provide a large, thin gas exchange surface
Wet surface increases diffusion rate
Water contains surfactant to stop walls from sticking together

Question 8

Why are squamous epithelia good exchange surfaces?

Answer 8

They are only one cell thick and have a large surface area

Question 9

How do goblet cells and cilia cells work together?

Answer 9

Goblet cells produce mucous in the trachea and bronchi which trap dirt and pathogens, whilst cilia move the mucous up to the oesophagus to be swallowed.

Question 10

What are the main parts of insect gas exchange systems?

Answer 10

Spiracle - Small pores forming the entrance to the tracheae. Can be closed.
Tracheae - Main tubes
Tracheoles - Small tube that connect to muscles. The ends are filled with water.

Question 11

How is insect ventilation performed?

Answer 11

The movement of the thorax and the abdomen

Question 12

How do insects conserve water?

Answer 12

With a thick, waterproof waxy cuticle over their exoskeleton.

Question 13

What do insects have instead of blood?

Answer 13

Haemolymph

Question 14

What do plants have for diffusion?

Answer 14

Root hair cells that have a large surface area and thin diffusion distance to increase the rate of diffusion of ions and water into the plant.

Question 15

How do fish gills work in terms as flow?

Answer 15

They have a counter-current flow system. This means that blood and water flow in opposite directions over the lamellae

Question 16

How do fish ventilate?

Answer 16

The buccal (mouth) cavity is increased to draw water in and the operculum (gill flaps) ensure water flows continuously over the gills to maintain the concentration gradient. 
High-oxygenated water meets high-oxygenated blood at the front of the filament, and low oxygenated water meets deoxygenated blood towards the back of the filament. This maintains the concentration gradient along the length of the lamellae. This is called counter-current exchange.