Morphology of Frog

The frog's body is streamlined for swimming, flattened dorso-ventrally, and divided into just two regions - head and trunk - with no neck and no tail in the adult. Smooth, slimy, loosely attached skin, dark green above and pale below, covers the whole animal. The roughly triangular head bears a wide, anteriorly placed mouth, external nostrils on the snout, and large eyes protected by a thin lower eyelid, a thick immovable upper eyelid, and a transparent nictitating membrane that shields the eye underwater; a pair of tympanic membranes just behind the eyes serve as external ear drums, since frogs lack any external ear structure. The trunk carries short, stumpy forelimbs (used mainly to absorb the shock of landing after a jump) and long, powerful hind limbs ending in five webbed toes plus a small sixth toe, adaptations for both leaping and swimming; at rest the hind limb folds into a Z-shape. A single cloacal aperture at the rear of the trunk, between the hind limbs, is the shared opening for the digestive, excretory and reproductive syst …