Ventilation

Question 1

Define ventilation.

Answer 1

Air moved in and out of lungs as a result of pressure changes in thorax caused by breathing movements

Question 2

What is the diaphragm?

Answer 2

A broad, domed sheet of muscle, forming the floor of the thorax

Question 3

Where are the internal and external intercostal muscles?

Answer 3

Between ribs

Question 4

What is the thorax lined with?

Answer 4

Pleural membranes

Question 5

What do the pleural membranes surround?

Answer 5

Lungs

Question 6

What is the space between the pleural membranes called? What is its function?

Answer 6

Pleural cavity - filled with thin layer of lubricating fluid so membranes can easily slide over each other as you breathe

Question 7

Is inspiration an active or passive process?

Answer 7

Acive

Question 8

What are the 5 steps of inspiration?

Answer 8

1. Diaphragm contracts, flattening and lowering.
2. External intercostal muscles contract, moving ribs upwards and outwards.
3. Volume of thorax increases so pressure reduces.
4. Pressure in thorax now lower than atmospheric pressure, so air is drawn into lungs.
5. This equalises pressure inside and outside of thorax.

Question 9

Is expiration an active or passive process?

Answer 9

Passive

Question 10

What are the 5 steps of expiration?

Answer 10

1. Diaphragm relaxes so moves up into resting dome shape
2. External intercostal muscles relax, so ribs move down and inwards due to gravity
3. Elastic fibres in alveoli return to normal length
4. The volume of the thorax is decreased, so pressure inside thorax is now greater than atmospheric pressure
5. Air moves out of lungs until pressure inside and outside of thorax is equal

Question 11

What happens when you exhale forcibly?

Answer 11

1. Internal intercostal muscles contract, pulling ribs down fast and hard
2. Abdominal muscles contract, forcing diaphragm upwards to increase pressure in lungs rapidly