Mammalian gas exchange and ventilation

Question 1

Why is it not possible to expel all air from the lungs?

Answer 1

• thorax cannot be completely flattened

- trachea/bronchi held open by cartilage

Question 2

Why are specialised exchange surfaces are needed by some organisms?

Answer 2

• they have a low SA:V so exchange surfaces increase that
• maximise efficiency of diffusion
• ensure the demand for oxygen and glucose is met

Question 3

What are the 4 features of efficient exchange surfaces?

Answer 3

• Increased surface area
• Thin layers
• Good blood supply
• Ventilation to maintain a diffusion gradient

Question 4

Why does an increased surface area make an exchange surface efficient?

Answer 4

Provides the area needed for exchange overcomes limitations of low SA:V ratio

Question 5

Why do thin layers make an exchange surface efficient?

Answer 5

the distances that substances have to diffuse across is short making it fast and efficient

Question 6

Why does a good supply make an exchange surface efficient?

Answer 6

the greater the difference in concentration the greater the rate of diffusion. A good supply means substances are constantly being delivered and removed, maintaining the steep concentration gradient

Question 7

Why does ventilation make an exchange surface efficient?

Answer 7

For gases ventilation helps to maintain concentration gradients

Question 8

How is the nasal cavity adapted for the gas exchange system?

Answer 8

• good blood supply warms air to body temperature
• cells secrete muscus to trap dust and bacteria to protect lung tissue
• moist surfaces reduce evaporation from the exchange surfaces which increase humidity

Question 9

How is the trachea adapted for the gas exchange system?

Answer 9

• supported by incomplete rings of strong, flexible cartilage to allow for movement and prevent the trachea from collapsing
• lined with ciliated epithelium and goblet cells

Question 10

What is the function of goblet cells?

Answer 10

Secrete mucus which traps dust and microogranisms

Question 11

What is the function of ciliated epithelial cells?

Answer 11

Cilia beat and move mucus away from the lungs, protecting them

Question 12

How are the bronchi adapted for the gas exchange system?

Answer 12

-supported by small rings of cartilage

Question 13

How are bronchioles adapted for the gas exchange system?

Answer 13

• contain no cartilage
• contain smooth muscle
• smooth muscle contracts when bronchioles constrict and relaxes when they dilate

Question 14

How are the alveoli adapted for the gas exchange system?

Answer 14

• very thin walls
• contain elastic fibres which allow alveoli to stretch as air is drawn n and when they return to size help squeeze air out
• good capillary blood supply
• coated in surfactant

Question 15

What is breathing?

Answer 15

The movement of air in and out of the lungs

Question 16

What is gas exchange?

Answer 16

the delivery of oxygen from the lungs to the bloodstream and the elimination of carbon dioxide from the blood stream

Question 17

Outline the steps in inspiration

Answer 17

• diaphragm flattens and contracts
• external intercostal muscles contract making the ribs move up and out
• this increases the volume of the thorax so reduces pressure
• pressure is more negative than the atmosphere air
• air is drawn into the lungs to equalise the pressures inside and outside the chest

Question 18

Outline the steps in normal expiration

Answer 18

• diaphragm relaxes and curves upwards
• external intercostal muscles relax so ribs move in
• decreases volume of the thorax
• pressure in the lungs is less negative than atmospheric air
• air moves out of the lungs until pressure inside and out is equal

Question 19

Outline the steps in forced expiration

Answer 19

• abdominal muscles contract, pushing diaphragm upward quickly making lung pressure less negative
• internal intercostal muscles contract pulling ribs down hard and fast

Question 20

What is inspiration?

Answer 20

the movement of air into the lungs

Question 21

What is expiration?

Answer 21

the movement of air out of the lungs

Question 22

Does inspiration require energy?

Answer 22

Yes

Question 23

Does expiration require energy?

Answer 23

No, it is a passive process

Question 24

What are the 3 ways lung capacity can be measured?

Answer 24

• peak flow metre
• vitalographs
• spirometer