Question

Regarding blood circulation, it may be said that in Pheretima the dorsal vessel is a

• A. Collecting vessel in first five segments and distributing vessel in other
• B. Distributing vessel in first five segments and collecting vessel on other
• C. Collecting vessel in first thirteen segments and distributing vessel in intestinal region
• D. Distributing vessel in first thirteen segments and collecting vessel in the intestinal region

Answer 1

The correct option is D Distributing vessel in first thirteen segments and collecting vessel in the intestinal region

In earthworm (Pheretima) the blood vascular system is of closed type. It is different and modified in the first thirteen segments than that of the intestinal region. There are two types of vessels- collecting blood vessels and distributing blood vessels. The dorsal blood vessel is the distributing vessel instead of the collecting vessel in the first 13 segments. Behind the 14th segment i.e intestinal region.this vessel is the main collecting vessel. Thus the correct answer is option D.