Question

The circulatory system of a rabbit differs from that of a frog in that there
A. Renal portal system in rabbit
B. Hepatic portal system in rabbit
C. Posterior vena cava in rabbit
D. Dorsal aorta in rabbit

Answer 1

Hint: Rabbit belongs to class Mammalia, while frog belongs to class Amphibia. The mammalian heart has complete four-chamber i.e. interventricular septum divides ventricle completely into two ventricular chambers. While in the frog, the heart is three-chambered, the interventricular septum forms incompletely.

Complete answer:
The heart of the rabbit is completely divided into four chambers. The upper two chambers are called auricles, while the lower two chambers are called ventricles. Upper chambers separated from each other by an intra-auricular septum into the right and left atrium similarly, the lower chambers are divided by an intra-ventricular septum into the right and ventricle septum.

The right auricle receives deoxygenated blood from different body parts by right Percival and Postcaval and the left Precaval vein and left auricle receive oxygenated blood from the heart by pulmonary veins. In the case of the frog, the upper chambers are called auricles. These chambers are also divided into left and right auricles by Intra auricular septum. The lower part is called a ventricle but it is not completely divided into two parts, because in the amphibian heart, the interventricular septum develops incompletely and results in the incomplete division of ventricle.

The heart of the frog has two additional chambers; one is sinus venous and the other is truncus arteriosus. Truncus arteriosus is also known as conus arteriosus. Sinus venosus is a triangular, thin-walled chamber attached from the dorsal surface to the heart. In the sinus venosus, the deoxygenated blood is filled and then this deoxygenated blood filled in an auricle through an opening present in sinus venosus. Truncus arteriosus arises from the ventral side of a ventricle. It is a tubular chamber present on the ventricle.

Hence, the correct answer is option C.

Note: The heart is a muscular organ and it is mesodermal in origin. The main function of the heart is to collect the deoxygenated blood from different body parts and send oxygenated blood to body parts. The heart is lined by cardiac muscles. In Pisces, the heart is of only two chambers.