Question

Sinus venosus of the frog is formed by the union of

• A. Two precavals and two post cavals
• B. One precaval and two post cavals
• C. One precaval and one post caval
• D. Two precavals and one post caval

Answer 1

The correct option is D

Two precavals and one post caval

The correct option is option D.

The explanation for the correct option:

1. The sinus venosus, an expanded area located between the vena cava and the right atrium, serves as the pacemaker in amphibians like the frog.
2. It is triangular-shaped and is present on the dorsal side of the heart.
3. It is formed by the union of three main vena cava.
4. They are the two precavals and one post caval.
5. It receives deoxygenated blood from the superior vena cava( precaval) and inferior vena cava (post caval) and opens into the right auricle.

Final Answer:

Sinus venosus is formed by two precavals and one post caval.