Principal pulsating organ which causes the flow of the blood in insect is known as:

Correct option is C

In insects, the principal circulatory organ responsible for pumping hemolymph (insect blood) is the dorsal vessel. It is a tubular, pulsatile structure running along the dorsal midline of the insect's body and plays a central role in the open circulatory system.
�� Structure and Function of the Dorsal Vessel:
· Divided into two regions:
· Heart (posterior part, located in the abdomen)
· Aorta (anterior part, located in the thorax and head)
· The heart contains valves (ostia) that regulate the one-way flow of hemolymph.
· Pulsations of the heart force hemolymph forward into the aorta, from where it is distributed throughout the body cavity (haemocoel).
· The hemolymph bathes the internal organs directly, as there are no closed blood vessels like in vertebrates.
Explanation for Each Option
(a) Dorsal and Ventral diaphragms ❌
· These are supportive muscular structures that help regulate hemolymph flow within compartments of the body cavity but do not generate the main pulse.
(b) Haemocytes ❌
· These are blood cells in hemolymph involved in immune responses and wound healing, not responsible for pumping.
(c) Dorsal vessel ✅
· Correct answer.
· The primary organ responsible for pumping hemolymph in insects.
(d) Haemocoel ❌
· The body cavity filled with hemolymph where organs are bathed, not a pumping structure.