Circulatory system of amphioxus

Circulatory system of amphioxus

The circulatory system of amphioxus is close type. The blood is colourless because absence of respirative pigment and carpuscles. It's main function to transport the food and excretory material. The heart is absent. So all blood vessels are muscular and contractile. The endothecial lining absent all blood vessels and present only in dorsal aorta. There are no difference between arteries veins. The main vessels and there branches are as follow.

Sinus Velosus

It is small present just below the posterior end of pharynx. The blood from different part of body collected by sinus Velosus.

Ventral Aorta

It is large and longitudinal. It runs in the wall of pharynx below the endostyle so the name also given as sub-endostyler aorta. Due to contraction of wall the blood flow anterior side. This artrism open into efferent branchial artrism. Each efferent vessels break into small capilary network.

Dorsal Aorta

There are two longitudinal right and left lateral dosrsal aorta present dorso lateral side of pharynx. It continues anterior internal carotid aurtory which supply the blood in oral hood. The dorsal aorta unite behind the pharynx into median dorsal aorta and runs between intestine and Notochord enters into caudal autostray. It supply the blood into intestine through several intestinal artrism.

Sub-Intestinal veins 

The blood from tail is collected by caudal veins and form intestine by I testinsl veins. These join a small sub- intestinal veins present below the intestine the blood flow anteriorly by it.

Hepatic portal system

The Sub-Intestinal veins continue as Hepatic portal veins present in midgut divertucullum which breaks in capilary network from midgut divertucullum the blood is collected by hepatic veins. Hepatic portal system first time discovered in Branchiostoma.

Cardinal veins

The ventral and lateral region of body is collected by anterior and posterior Cardinal veins. Behind the pharynx. It unite in common Cardinal veins.

Parietal veins

The blood from dorsal body is collective by pair of parietal veins. It runs above the intestine and join with sinus Velosus.

Course of circulation

The blood flow anterior in parietal, sub intestinal Cardinal veins and ventral aorta. It flow posterior by lateral and median dorsal auroty. The course of circulation shown as follows: