Question

18. Frogs have very poor lung development. What other systems and tissues must the frog use to aid with breathing and how do these tissues/systems work with the lungs to perform respiration?

Answer 1

The systems or tissues frogs use in addition to lungs for respiration are

1) Gills

2) skin

3) mouth

4) lungs

Gills:
All frogs go through a process called metamorphosis, in which they mature from their larval, or tadpole, stage into adult frogs. One of the hallmarks of this process for most frog species is the transition from having gills to having functional lungs. A newly hatched tadpole's gills are external. These gills take in oxygen when water passes over them. As the tadpole matures, the gills are absorbed by the body and become an internal part of the tadpole's anatomy.

Lungs
Once mature, frogs lose their gills and are able to bring oxygen into their bodies through functioning, though comparatively underdeveloped, lungs. Frogs rely on their lungs to breathe when they are active and need more oxygen than skin respiration alone can provide. Unlike mammals that draw air continuously into their lungs, frogs only breathe through lungs when necessary. Because they lack a diaphragm to help regulate the pressure in their lungs, frogs must use their throats, nostrils and mouths together to bring in and expel gases.

Skin
Though they have functional lungs, much of a frog’s respiration occurs through the skin. A frog’s moist skin is thin and marbled with blood vessels and capillaries close to the surface. The moisture on the skin dissolves oxygen from the air and water surrounding the frog and transmits it into the blood. Though moist skin is essential for this process, frogs are not limited to skin respiration only when under water. Glands in the frog’s skin produce mucus that keeps the skin moist and allows for respiration even on dry land.

Mouth
Frogs have an additional surface for respiration other than their skin -- the moist lining of the mouth. When the frog's mouth is not submerged completely in water, this respiratory lining is in constant use, bringing oxygen into the bloodstream from the surrounding air and diffusing excess carbon dioxide back into the environment.

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