3.1.1d Ventilation

Question 1

What is inhalation

Answer 1

breathing in

Question 2

What is exhalation

Answer 2

breathing out

Question 3

Describe the process of inhalation

Answer 3

1. As the diaphragm contracts, it flattens & moves down.
2. The external intercostal muscles contract which lifts the ribs upwards & outwards.
3. The resulting increase in the volume of the thorax causes a decrease in the air pressure & fresh air is drawn through the nasal passages, trachea, bronchi, and bronchioles into the lungs
4. This equalises the pressure inside & outside the chest

Question 4

Describe the process of exhalation

Answer 4

1. The diaphragm relaxes & moves upwards into its resting domed shape
2. The external intercostal muscles relax & the ribcage drops downwards & inwards under gravity
3. This results in a decrease in the volume of the thorax. As a result, the pressure inside the thorax is greater than the pressure of the atmospheric air
4. So air in the lungs is pushed out until the pressure inside & out is equal again

Question 5

What type of process is inspiration

Answer 5

An ACTIVE PROCESS - it requires energy

Question 6

What type of process is exhalation

Answer 6

A PASSIVE PROCESS - it doesnt require energy

However, expiration can also be forced (eg. blowing out candles). During forced exhalation, the internal intercostal muscles contract, to pull the ribcage down and in