The exchange of gases is vital for our survival, gaseous exchange happens in thelungs, in the alveoli. For effective gaseous exchange a large surface area is needed to ensure an efficient gas exchange area, this is why the alveoli are tiny sacs bunched together to increase the area so that more gases can be diffused. The body would have to work harder to increase the oxygen intake and its supply of oxygen to the muscles if the surface area was smaller.
The thinner the cell wall the quicker diffusion can take place, the alveoli are made up of flattened epithelial cells making them only one cell thick, the capillaries are also only one cell thick, with the distance between the alveoli and capillaries being so thin it allows the gases to reach their destination quicker, letting oxygen diffuse into the blood and bind with the haemoglobin, making oxy-haemoglobin and then get transported around the body, carbon dioxide can diffuse back into the alveoli as a waste product ready to be exhaled. If the diffusion area were thicker this process would take longer.
The area needs to be moist, as gases need to be in solution to diffuse across a membrane, oxygen and carbon dioxide dissolve in this membrane. This makes it easier for the transportation as water can diffuse in and out of the alveoli. If the area weren’t moist the alveoli would dry out making diffusion harder. The water also contains a soapy surfactant, which reduces its surface tension and stops the alveoli collapsing. (Wright, 2007)
A steep concentration gradient of the gases needs to be maintained. Gases will always move from a high concentration to a low concentration, in a constant strive for equilibrium. This gradient is maintained by blood flow on one side carrying oxygen away quickly and by airflow on the other side. Oxygen can diffuse down its concentration gradient from the air to the blood, and carbon dioxide can diffuse down its concentration gradient from the blood to the air. (Wright, 2007
No comments:
Post a Comment