Gas Exchange in Humans Flashcards
Breathing mechanism that causes air to fill in the lungs
- Diaphragm (muscle) contracts and external intercostal muscles contract
- Causing pressure to decrease
- Air moves down a pressure gradient
Process of gas exchange structures
Nose/ mouth -> Trachea -> bronchi -> broncioles -> alveoli
Alveoli adaptations
Large surface area = lots of them
Rich blood supply = maintains conc gradient
Short diffusion path = one cell thick
Moist
Advantage of alveoli being moist
O2 dissolves
Easier for oxygen to diffuse into capillary and enter bloodstream
Advantage of rich blood supply
Maintains conc gradient
Constantly has low concentration of oxygen so O2 can constantly be diffusing into capillary and binds to haemoglobin
Inspiration process
1) External intercostal muscles contract, internal intercostal muscles relax
2) Ribs move up and out, increasing volume of thorax
3) Diaphragm muscles contract, increasing volume of thorax
4) Pressure in thorax is reduced
5) Atmospheric pressure greater than pulmonary pressure, forcing air in lungs
Expiration process
1) Internal intercostal muscles contract, external intercostal muscles relax
2) Ribs move down and in, decreasing volume of thorax
3) Diaphragm muscles relax and pushed up (by contents of abdomen)
4) Reducing thorax volume, increasing thorax pressure
5) Pulmonary pressure greater than atmosphere, air forced out
Why is diffusion between alveoli and blood fast
Diffusion:
-Red blood cells slow as they pass through capillaries = more diffusion time
-Distance is short between alveoli air and red blood cells when blood cells flatten against capillary walls
-Walls of alveoli and capillaries are thin = short diffusion
- alveoli and capillaries have large SA
Maintains steep concentration gradient
- Breathing movements keep lungs ventilated constantly, heart constantly circulates blood around alveoli
- Blood flow through capillaries
What does the alveoli do
Exchanges oxygen and CO2 to and from capillaries in lungs
Process of exchange between CO2 and O2
Simple diffusion
from high to low concentration
How does simple diffusion occur
Alveoli has high O2 conc and low CO2 conc
Capillaries has high CO2 conc and low O2 conc
simple diffusion = high to low
So CO2 moves into alveoli and out of alveoli into capillary
Advantage of thin alveoli walls
Short diffusion distance to capillary network
Extensive capillary network advantage
Short diffusion distance
Constant flow, oxygenated blood constantly brought away from alveoli and deoxygenated blood brought to them
Maintaining conc gradient
What is ventilation definition
Mass flow of gases
What does ventilation do
continuous flow of blood in capillaries, ensuring always higher concentation of O2 in alveoli than in blood
