Exchange of Materials in Humans

Exchange in the Lungs.

We need a constant supply of oxygen.

When you breathe in:

•  
  • Ribs = move UP and OUT
  • Diaphragm = flattens
  • Air = goes into lungs

When you breathe out:

•  
  • Ribs = move DOWN and IN
  • Diaphragm = returns to domed shape
  • Air = moves out of lungs

Alveoli

The alveoli are adapted to make gas exchange more efficient.

In the alveoli, oxygen goes into the blood and carbon dioxide moves out of the blood.

• Moist surface.
• Spherical shape = large surface area.
• Very thin alveolos walls for easy diffusion.
• Good blood supply maintains concentration gradient.

Exchange in the Gut.

Food is broken down in the gut and then goes to the small intestine.

It enters the blood stream theough diffusion.

Villi line the small intestine to increase diffusion:

• Villi have a large surface area.
• Villi have a rich blood supply to maintain a high concentration gradient.
• Villi's cell walls are one cell thick as a short distance for diffusion.