Question

In the truncus arteriosus of frogs, synangium is separated from pylangium by which valve?
A. Spiral valve
B. Distal row of semilunar valves
C. Proximal row of semilunar valves
D. Secondary septum

Answer 1

Hint: Frog belongs to class Amphibia of Kingdom Animalia. It has a three-chambered heart. It is a muscular organ situated in between the two lungs and is located in the anterior part of the body cavity.

Complete answer: In frogs, the truncus arteriosus is a tube-shaped structure that arises from the right side of the ventricle. The walls of these structures are muscular and thick. At the anterior end of these structures, there is a division into two trunks. Out of these, the elongated portion that remains undivided is the phylangium, whereas the end part of the divided trunk is known as the synangium. These structures are separated by a proximal row of semilunar valves. The truncus arteriosus is one of the two additional chambers present in the frog’s heart.
A. Spiral valves in amphibians are present within the truncus arteriosus. It functions differently for oxygenated and deoxygenated blood. It is not the point of separation of synangium and phylangium.
B. The distal row of semilunar valves is not involved in the separation of synangium and phylangium in amphibians.
D. The secondary septum is not the structure involved in the separation of synangium and phylangium. Therefore, the correct answer is option C.

Note: Other than the two atria and one ventricle and truncus arteriosus, the additional chamber in a frog’s heart is the sinus venosus. It is located on the dorsal heart surface. It is a wide chamber that opens to the right auricle.