Gas Exchange - Humans

Question 1

Lungs

Answer 1

air => mouth => trachea => bronchi => bronchioles => alveoli => capillaries

Question 2

Inspiration

Answer 2

external intercostal and diaphragm muscles contract
ribcage moves upwards and outwards
diaphragm contracts and flattens
thoracic cavity volume increases
lung pressure decreases
air moves down pressure gradient from air to lungs
ACTIVE process

Question 3

Expiration

Answer 3

external intercostal and diaphragm muscles relax
ribcage moves downwards and inwards
diaphragm relaxes and domes
thoracic cavity volume decreases
lung pressure increases
air moves down pressure gradient from lungs to air
PASSIVE process

Question 4

Forced Expiration

Answer 4

external intercostal relax
internal intercostal contrace
ribcage pulled further down and in
intercostal muscles movement is antagonistic (opposing)

Question 5

Alveoli

Answer 5

where gaseous exchange happens
made up of alveolar epithelium
Many alveoli - big SA for exchanging O2 and CO2
thin exchange surface - one cell thick - short diffusion pathway
steep conc grad maintained by flow of blood and ventilation
surrounded by capillaries network
O2 diffuses out of alveoli across alveolar epithelium and capillary endothelium into Hb in blood
CO2 diffuses into alveoli from blood and is expired