In amphibians, gas exchange always occurs across
1. Bucco pharyngeal cavity
2. Cutaneous respiration (through skin)
3. Pharyngeal respiration
Physiology of cutaneous respiration in frog
It occurs all the time. When frog is on water or on land, on dormancy, cutaneous respiration takes place. Oxygen first dissolves in water covering the skin. This then diffuses through epidermis into the blood vessel.
Carbon dioxide diffuses in reverse direction. The blood is passed to different parts of body.
Justification for cutaneous respiration in frog
1. Skin is thin, moist, devoid of scales.
2.It is richly supplied by blood capillaries.
3. Secretion of mucus in mucus gland keeps skin moist.
4. Frog in regular interval enters water to keep its skin moist.