adjective
ventral
VEN-trul/ˈventrəl/
Relating to the belly or underside of the body.
The frog's pale ventral surface covers its underside.

Etymology
The belly root makes ventral a directional anatomical term: it identifies the body's belly side, opposite the back, rather than only the belly itself.
In context
on the other hand the middle and lower or ventral parts of their eye are sensitive to a wider range of wavelengths
More examples
- The snake's ventral scales help it grip the ground.
- In humans, the navel lies on the ventral side.
- The ray's mouth sits on its ventral surface.
Forms
ventrally adverb — On or toward the belly side.