Ventilation and Exchange at the Lungs

Question 1

Define ventilation

Answer 1

movement of air in and out of the lungs

Question 2

Define inspiration

Answer 2

(inhalation) pressure in the atmosphere is greater than in the lungs - air moves in

Question 3

Define expiration

Answer 3

(exhalation) pressure in the lungs greater than in the atmosphere - air moves out

Question 4

Describe the diaphragm

Answer 4

sheet of muscle separating thorax from abdomen

Question 5

Describe the function of internal intercostal muscles

Answer 5

contraction leads to expiration

Question 6

Describe the function of external intercostal muscles

Answer 6

contraction leads to inspiration

Question 7

Describe and explain inhalation

Answer 7

External intercostal muscles contract - internal intercostal muscles relax
Ribs pulled upwards and outwards
Diaphragm contracts and flattens
Volume of thorax increases
Pressure in lungs decreases
Atmospheric pressure greater than pulmonary pressure - air moves in to lungs

Question 8

Describe and explain exhalation

Answer 8

Internal intercostal muscles contract - external intercostal muscles relax
Ribs move downwards and inwards
Diaphragm relaxes and moves upwards
Volume of thorax decreases
Pressure in lungs increases
Pulmonary pressure greater than atmospheric pressure - air moves out of lungs

Question 9

Describe how a diffusion gradient is maintained over the surface of the alveoli

Answer 9

air movement (breathing) and movement of the blood

Question 10

Describe how the exchange surface at the lungs enables a short diffusion pathway

Answer 10

alveolar wall is one cells thick and endothelium of capillary is one cell thick

Question 11

Explain why very narrow capillaries is beneficial for efficient gas exchange

Answer 11

red blood cells are flattened against the walls - shorter distance between air and rbc
rbc’s are slowed - allows maximum time and area for diffusion