6.8- EXCHANGE OF GASES IN THE LUNGS

Question 1

What is the site of gas exchange in mammals?

Answer 1

epithelium of alveoli

Question 2

What are the alveoli?

Answer 2

minute air sacs some 100-300μm in diameter + situated in lungs

Question 3

What must be maintained to ensure there’s constant supply of oxygen to body?

Answer 3

diffusion gradient must be maintained at alveolar surface

Question 4

What must there be to maintain a diffusion gradient?

Answer 4

movement of both environmental medium (e.g. air) + internal medium (e.g. blood)

Question 5

Why can the alveoli be easily damaged?

Answer 5

they’re thin

Question 6

As the alveoli are easily damage where are they often located?

Answer 6

inside organism for protection

Question 7

Why do organisms have some means of moving external medium over exchange surface e.g. lungs?

Answer 7

diffusion alone not fast enough to maintain adequate transfer of oxygen + CO2 along trachea, bronchi + bronchioles

Question 8

What is breathing basically a form of?

Answer 8

mass transport

Question 9

Approximately how many alveoli are there in the human lung?

Answer 9

about 300 million

Question 10

What is the total surface area of the lungs?

Answer 10

70m^2

Question 11

What is each alveolus lined with?

Answer 11

epithelial cells only 0.05μm to 0.3μm thick

Question 12

What is around each alveolus?

Answer 12

network of pulmonary capillaries, so narrow (7-10μm) than red blood cells flattened against thin capillary walls to squeeze through

Question 13

What is the walls of the network of pulmonary capillaries around each alveolus like?

Answer 13

walls that are only single layer of cells thick (0.04-0.2μm)

Question 14

How quick is the diffusion of gases between the alveoli and the blood?

Answer 14

rapid

Question 15

Why is the diffusion of gases between the alveoli and the blood rapid: red blood cells?

Answer 15

red blood cells slowed as they pass through pulmonary capillaries, allowing more time for diffusion

Question 16

Why is the diffusion of gases between the alveoli and the blood rapid: distance?

Answer 16

distance between alveolar air + red blood cells reduced as red blood cells flattened against capillary walls

Question 17

Why is the diffusion of gases between the alveoli and the blood rapid: walls of alveoli + capillaries

Answer 17

walls of alveoli + capillaries very thin + so distance over which diffusion happens is very short

Question 18

Why is the diffusion of gases between the alveoli and the blood rapid: surface area?

Answer 18

alveoli + pulmonary capillaries have very large total SA

Question 19

Why is the diffusion of gases between the alveoli and the blood rapid: breathing movements?

Answer 19

breathing movements constantly ventilates lungs, + action of heart constantly circulates blood around alveoli
together, these ensure that steep concentration gradient of gases to be exchanged maintained

Question 20

Why is the diffusion of gases between the alveoli and the blood rapid: blood flow?

Answer 20

blood flow through pulmonary capillaries maintains concentration gradient