Gas Exchange in Humans Flashcards
Features of Gas Exchange Surface
Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster
Function of Cartilage
Rings of cartilage surround the trachea (and bronchi)
The function of the cartilage is to support the airways and keep them open during breathing
If they were not present then the sides could collapse inwards when the air pressure inside the tubes drops
Volume & Pressure Changes in the Lungs
The diaphragm is a thin sheet of muscle that separates the chest cavity from the abdomen; it is ultimately responsible for controlling ventilation in the lungs
When the diaphragm contracts it flattens and this increases the volume of the chest cavity (thorax), which consequently leads to a decrease in air pressure inside the lungs relative to outside the body, drawing air in.
When the diaphragm relaxes it moves upwards back into its domed shape and this decreases the volume of the chest cavity (thorax), which consequently leads to an increase in air pressure inside the lungs relative to outside the body, forcing air out
The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)
During inhalation the external set of intercostal muscles contract to pull the ribs up and out:
This also increases the volume of the chest cavity (thorax), decreasing air pressure, drawing air in
During exhalation, the external set of intercostal muscles relax so the ribs drop down and in:
This decreases the volume of the chest cavity (thorax) increasing air pressure, forcing air out
Explain the Link Between Physical Activity & Breathing
Frequency and depth of breathing increase when exercising
This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with the energy demand
If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid
After exercise has finished, the lactic acid that has built up in muscles needs to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions
It can only be removed by combining it with oxygen - this is known as ‘repaying the oxygen debt’
This can be tested by seeing how long it takes after exercise for the breathing rate and depth to return to normal - the longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid
