4 gas exchange in humans

what structures are involved in the human gas exchange system?

• alveoli

• bronchioles

• bronchi

• trachea

• lungs

what does ventilation involve?

the diaphragm under the lungs and the antagonistic interaction between the external and internal intercostal muscles in the ribs

what does antagonistic mean?

when one muscle contracts, the other does the opposite

what happens to the internal intercostal muscles when the external intercostal muscles contract?

they relax

how do humans inhale (inspire)?

when the external intercostal muscles contract, the ribcage is pulled upwards and outwards. the diaphragm will contract, causing a flattened position. this provides and increased volume in the lungs, meaning there’ll be a decrease in air pressure in the lungs. this means that air moves into the lungs from the atmosphere as there’s a higher pressure in the atmosphere than in the lungs. this is because air moves down the pressure gradient

when the internal intercostal muscles contract, what happens to the external intercostal muscles?

relaxing

how do humans exhale (expire)?

when the intercostal muscles contract, the ribcage is pulled downwards and inwards. the diaphragm relaxes, causing a domed position. this provides a decreased volume in the lungs, meaning there’ll be an increase in air pressure in the lungs. this means that air moves out of the lungs to the atmosphere as there’s a lower pressure in the atmosphere compared to the lungs

once the gases are in the alveoli, where do the gases exchange?

between the epithelium and the blood

what are alveoli and how many are there in human lungs?

tiny air sacks. there are 300 million in each human lung which creates a very large surface area for gas exchange

what adaptations do the alveoli epithelium cells have?

• very thin to minimise diffusion distance

• each alveolus is surrounded by a network of capillaries to remove exchanged gases, therefore maintains a concentration gradient