Question

Describe the heart of calotes.

Answer 1

In Calotes, the circulatory circuit is double. There are pulmonary or lesser circulation and systemic or greater circulation. Pulmonary circulation is conducted by the pulmonary arteries which carry deoxygenated blood to the lungs. In the lungs, the blood becomes oxygenated and returns to the left auricle by the pulmonary vein.

left auricle pours its content into the ventricle through the auriculoventricular aperture. In the greater circulation, deoxygenated blood returns to the sinus venosus by two precaval and one post­caval veins. The sinus venosus opens into the right auricle. The right auricle empties its con­tent into the ventricle.

The ventricle sends blood for circulation into the different parts of the body through the systemic and pulmonary arches. The entry and exit of blood in the ventricle are so beautifully arranged that a major quantity of oxygenated blood is always forwarded to the brain region.

As the ventricle is incompletely divided, admixture of oxygenated and deoxygenated blood occurs thrice in Calotes once in the cavum venosum, once in the dorsal aorta and another in the left ductus caroticus.

Thus, though the ventricle in Calotes is morphologi­cally incompletely divided, there is a tenden­cy for the physiological separation of the two types of blood, at least in two auricles com­pletely and in the ventricle partially. From this point, the heart of Calotes is biologically more advanced than that of Bufo.