The human gas exchange system

L.O to learn about osmosis and learn why it is important.

Respiration requires oxygen as a substrate and produces carbon dioxide. That means we need to get oxygen into the body and carbon dioxide out.

The main part of the human gas exchange system is the lungs, which moves air in and of the body
Air enters the lungs via the trachea (wind pipe), which then divide into bronchus and further divide into bronchioles in the lungs. At the end of the bronchioles are alveoli, which are small air sacs where the gas exchange occurs


A key point to remember when thinking about ventilation is that air moves from high pressure to low pressure. Pressure is directly related to volume. So when volume increases pressure and decreases and vice versa
During inhalation air moves in. For this to occur the pressure inside the lungs needs to be lower than outside
To ensure the pressure in the lungs is lower, the diaphragm contracts and flattens and therefore increases the volume in the lungs. Also the intercostal muscles, the muscles that surround the rib cage contract, this move the ribs up and out, therefore allowing the lungs to increase in volume even more

During exhalation air moves out of the body. For this to occur the pressure inside the lungs has to be greater than outside
To ensure the pressure in the lungs is lower, the diaphragm relaxes and moves upwards back into its original shape, the intercostal muscles also relax letting the ribs move down. Overall this makes the volume in lungs decrease and therefore the pressure increases so air moves out

DiaphragmContracts causing it to flattenRelaxes causing it to move back to its original shape
Intercostal Muscles Contract causing the ribs to move up and outRelaxes causing the ribs to move down and in
Volume of ribcage increasesdecreases
Pressure inside the chestdecreasesincreases
Movement of airAir move in to the lungsAir moves out of the lungs


Gas exchange in the lungs

The lungs are optimized to ensure that exchange happens efficiently as possible. In the lungs the two main gases that are exchanged are oxygen and carbon dioxide. Ths gas exchange across the alveoli

Gas exchange in the lungs

The alveoli are small structures within the lungs, which resemble a hollow bunch of grapes. They help to increase surface area, they have very thin walls and have a very large blood supply. All these factors help to increase the rate of diffusion

Active transport in the human body

Active transport is used in the gut when there is a low concentration of nutrient in the gut, but a high concentration in the blood.

When there is a lower concentration in the gut and the nutrients need to enter the blood then active transport allows the nutrients to travel against the concentration gradient

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