Respiration
In most organisms, oxygen is inhaled and enters the nasal cavity, where it is filtered by cilia. It then goes down into the trachea. After the trachea, it passes through the bronchi into the lungs. Each lung has bronchioles. Inside the bronchioles, there is alveoli. The oxygen is diffused into the alveoli, going from high to low concentration. Carbon dioxide is diffused out of the alveoli, and it is exhaled. When organisms breathe, the diaphragm moves up and down.
Snail Gas Exchange
Snails have skin that water can pass through. Though this entails that snails can breathe through their skin, they constantly have to face loss of water, because the skin is also permeable to water. Snails also have gills in the mantle cavity. The gills have feathery bumps that absorb oxygen from water and diffuse carbon dioxide out into the water. The gills look like combs, and they are called ctenidia. Click here to look at the ctenidia! Most snails have two gills. [1]
Snail Gas Exchange
Snails have skin that water can pass through. Though this entails that snails can breathe through their skin, they constantly have to face loss of water, because the skin is also permeable to water. Snails also have gills in the mantle cavity. The gills have feathery bumps that absorb oxygen from water and diffuse carbon dioxide out into the water. The gills look like combs, and they are called ctenidia. Click here to look at the ctenidia! Most snails have two gills. [1]