Ventilation + gas exchange in the lungs Flashcards
Inspiration
Breathing in
What is ventilation
The movement of air in and out of lungs (breathing)
Expiration
Breathing out
What controls ventilation
Movement of muscles:
The diaphragm
The external intercostal muscles
(The internal intercostal muscles in forced expiration)
Inspiration: movement of muscles
The diaphragm contacts and flattens (moving downwards)
The external intercostal muscles contract, moving the rib cage upwards and outwards
Inspiration: effect of thoracic cavity volume
It increases
INspiration INcrease in thoracic cavity volume
Effect of increasing thoracic cavity volume
The pressure of gases inside the thoracic cavity decreases, below atmospheric pressure
How does air move into the lungs in inspiration?
Down a PRESSURE gradient from the trachea forced into the thoracic cavity and lungs
What do internal intercostal muscles do in inspiration?
Remain RELAXED
Is inspiration an active process?
Yes: requires energy for diaphragm and external intercostal muscles to CONTRACT
Expiration: movement of muscles
The diaphragm relaxes and curves by pulling upwards
The external intercostal muscles relax causing the rib cage to move downwards and inwards
Expiration: effect on thoracic cavity volume
Decreases due to movement of muscles moving in
Effect of decreasing thoracic cavity volume in expiration?
The pressure of gases increase inside the thoracic cavity above atmospheric pressure
How does air move out the lungs in expiration?
The air pressure inside the lungs has increased above atmospheric pressure so air moves out down a PRESSURE gradient from lungs to trachea out through mouth
What do internal intercostal muscles do in NORMAL expiration?
Still relaxed
Is normal expiration a passive process?
Yes because requires no contraction of muscles
Forced expiration
When you breathe out all the air you can from your lungs
Forced expiration muscle movement
The diaphragm and external intercostal muscles are relaxed again to decrease thoracic cavity
But internal intercostal muscles will contract to decrease thoracic cavity even more by moving rib cage further in to force more air out
Movement of internal and external intercostal muscles in forced expiration
Internal = contracts
External = relaxed
So ANTAGONISTIC
Where is the site of gas exchange in the lungs?
Alveoli:
What are alveoli?
Millions of microscopic air sacks contacted to the bronchioles
Movement of gases in alveoli?
Oxygen from the alveoli into the blood (oxygenates blood(
Carbon dioxide from the deoxygenated blood into the alveoli out the body
Structure of alveoli
Alveolar epithelium around the air space = thin layer of flat cells for a short diffusion distance
Connected to capillary endothelium (wall) of thin layer of flat cells
Elastin to help it recoil after movement of gases
Oxygen in alveoli
Diffuses into blood from alveoli across 2 layers: first the alveolar epithelium then capillary endothelium
Carbon dioxide in alveoli
Diffuses out of the blood into the alveoli: first the capillary endothelium then alveolar epithelium
How do gases move in the alveoli
Down their concentration gradient not pressure
Route of oxygen summary
Trachea
Bronchi
Bronchioles
Alveoli
Alveolar epithelium
Capillary endothelium
Blood
Route of carbon dioxide summary
Blood
Capillary endothelium
Alveolar epithelium
Alveoli
Bronchiole
Bronchi
Trachea
Factors affecting rate of diffusion of gases in the alveoli
Thin exchange surface
A large surface area
A steep concentration gradient
Thin exchange surface area: alveoli
Because both the alveolar epithelium and capillary endothelium are 1 cell thick
A large surface area: alveoli
Millions of alveoli (large surface area for exchange)
A steep concentration gradient: alveoli
Of oxygen and carbon dioxide: maintained by the flow of blood in capillaries to remove O2 rich blood (more diffuses in) and supplies CO2 rich blood (more diffuses out)
Ventilation to supply more O2 and remove CO2
