Question

In which blood vessel blood flows posterior end to anterior end
A. Ventral blood vessel
B. Dorsal blood vessel
C. Sub neural blood vessel
D. Lateral esophageal vessels

Answer 1

Blood vessels are part of the circulatory system that carries blood throughout the human body. These vessels carry blood cells, nutrients and oxygen to the tissues of the body. They also remove waste and carbon dioxide from the tissues. Blood vessels are necessary for sustaining life because all tissues in the body depend on their function.

Complete answer:
Option A Ventral blood vessel: Ventral blood vessels are located below the gastrointestinal tract and above the ventricular nerves. It is also a long blood vessel that goes from the second to the last segment of the body. It is the main blood vessel of earthworms. Blood does not flow from posterior end to the anterior end.
Hence option A is not correct.
Option B Dorsal blood vessel: The dorsal blood vessel is the largest blood vessel in the body of earthworms. It is the thickest blood vessel that has narrowed muscle walls. It is visible as a dark line from the thin, semi-transparent body wall. The blood flows from posterior end to anterior end in the dorsal blood vessel.
Hence option B is the correct answer.
Option C Sub neural blood vessel: It extends from the posterior end to the midline of the abdomen, below the ventricular nerve. It is a non-muscle, valveless collecting vessel. It receives a pair of small branches in each segment that collect blood from the abdominal wall of the body and the ventricular nerve. Blood in this vessel flows from the anterior to posterior end.
Hence option C is not correct.
Option D Lateral esophageal vessels: It is a pair of large blood vessels located on each ventral side of the gut for the first thirteen segments. They collect blood from the alimentary canal of the first thirteen segments. In these vessels, blood circulates from the anterior end to the posterior end.
Hence option D is not correct.

Therefore, Option B. Dorsal blood vessel is the correct answer

Note:
The circulatory system of earthworms is of the closed type, as blood circulates only through blood vessels. The vascular system of Pheretima posthuma consists of a complex vascular system through which blood circulates continuously. The blood of earthworms is red due to the presence of soluble hemoglobin in plasma, unlike other vertebrates where hemoglobin is present in red blood cells.