Cutaneous respiration

Cutaneous respiration is gas exchange across an animal’s skin or other outer body surface. It supplies oxygen and removes carbon dioxide by diffusion between the body and its environment.

Diffusion: The net movement of particles from higher concentration to lower concentration. Oxygen and carbon dioxide cross the body surface down their concentration gradients.
Partial pressure: The pressure contributed by one gas in a mixture of gases. Differences in oxygen and carbon dioxide partial pressures drive exchange across the skin.
Earthworm: A segmented annelid that exchanges gases across its moist body surface. Earthworms depend on skin exchange rather than lungs or gills.
Pulmonary respiration: Gas exchange between air and blood in lungs. Lungs provide an internal respiratory surface, unlike exchange across the outer body.
Fick's law of diffusion: A relationship describing how diffusion rate depends on surface area, distance, and concentration difference. It explains why efficient skin exchange needs a large area and a short diffusion path.
Oxygen: A reactive chemical element that many organisms use in aerobic metabolism. Cutaneous uptake supplies oxygen for cellular energy production.
Amphibian respiration: Gas exchange in amphibians through the skin, lungs, and lining of the mouth. Many amphibians combine cutaneous uptake with other respiratory routes.
Branchial respiration: Gas exchange through gills, usually in water. Gills are specialized respiratory organs that increase exchange area beyond the skin.
Skin permeability: The capacity of skin to allow substances to pass through it. Gas exchange depends on the outer surface allowing oxygen and carbon dioxide to cross.
Carbon dioxide: A colorless gas produced by cellular respiration and used by plants in photosynthesis. Cutaneous exchange removes this metabolic waste gas from the body.

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