3. Gas Exchange in Humans

Question 1

structure

Answer 1

trachea which splits into 2 bronchi/bronchus which branch off into bronchioles which end in small air sacs aveoli

Question 2

why humans need gas exchange

Answer 2

O2 in blood for repiration

rid of CO2 from respiration

Question 3

inspiration (breathing in

4 things

Answer 3

1. external intercostal muscles and diaphragm contract
2. ribcage upwards and outwards. diaphragm flattens
3. volume of thoracic cavity increased = lung pressure decreased (below atmospheric pressure)
4. air flows down pressure gradient into lungs
   active process, requires energy

Question 4

expiration (breathing out)

4 things

Answer 4

1. external intercostal muscles and diaphragm relax
2. ribcage downwards and inwards. diaphragm curved again
3. volume of thoracic cavity decreased = lung pressure increased (above atmospheric pressure)
4. air flows down pressure gradient out of lungs
   passive process - doesn’t require energy

Question 5

forced expiration

Answer 5

1. external intercostal muscles relax and internal intercostal muscles contract pulling rib cage further down and in
2. 2 sets of intercostal muscles antagonistic

Question 6

gas exchange in aveoli

Answer 6

1. lots of aveloi = large surface area
2. surrounded by network of capillary’s
3. O2 diffuses out of aveloi across aveolar epithelium and capillary endothelium and into haemoglobin in blood
4. CO2 diffuse into aveloi from blood and breathed out

Question 7

aveloi adaptations

Answer 7

thin exchange surface = aveolar epithelium 1 cell thick. short diffusion pathway
large number of aveoli = large surface area
steep conc gradient between aveoli and blood - maintained by flow of blood and ventilation