Mechanism Of Breathing

Question 1

What is the process ventilation?

Answer 1

Maintaining diffusion of gases across the alveolar epithelium by constantly moving air in and out of the lungs.

Question 2

What happens when the air pressure of the atmosphere is greater than in the lungs?

Answer 2

Air is forced into the lungs during inspiration (inhalation)

Question 3

What happens when the air pressure of the atmosphere is lower than in the lungs?

Answer 3

Air forced out of the lungs in expiration (exhalation)

Question 4

Which muscles are responsible for pressure changes within the lungs?

Answer 4

• the diaphragm, a sheet of muscle separating thorax from the abdomen
• intercostal muscles that lie between the ribs
  
  • internal intercostal muscles (expiration)
  • external intercostal muscles (inspiration)

Question 5

What is inspiration?

Answer 5

Breathing in and is an active process, meaning it uses energy

Question 6

What happens to the intercostal muscles during inspiration?

Answer 6

External muscles contract, whilst internal relax.

Question 7

What happens to the ribs during inspiration?

Answer 7

Ribs are pulled up and out, increasing thorax volume

Question 8

What happens to the diaphragm during inspiration?

Answer 8

Diaphragm muscles contract, causing it to flatten, which also increases thorax volume.

Question 9

What is the result of inspiration?

Answer 9

Increased thorax volume decreases pressure in the lungs, atmospheric pressure greater than pulmonary pressure so air is forced into the lungs.

Question 10

What is expiration?

Answer 10

Breathing out. It is largely passive (does not require much energy)

Question 11

What happens to the intercostal muscles during expiration?

Answer 11

Internal muscles contract, whilst external relax.

Question 12

What happens to the ribs during expiration?

Answer 12

Ribs move downwards and inwards, decreasing volume of thorax.

Question 13

What happens to the diaphragm during expiration?

Answer 13

Diaphragm muscles relax and so its pushed up again by contents of abdomen that were compressed during inspiration. Volume of thorax therefore further decreases.

Question 14

What is the result of expiration?

Answer 14

Decreased volume in thorax increases pressure in the lungs. Pulmonary pressure is greater than atmosphere, so air is forced out of lungs.

Question 15

What is the main cause of air being forced out during normal breathing and how does it differ during strenuous activity?

Answer 15

Recoil of elastic tissue in the lungs. Muscles only play a major part during strenuous conditions such as exercise.