Dorsal blood vessel

• It is the principal blood-conducting organ in insects which remains closed at the posterior end and opens anteriorlyintoo the head.
• It is divided into an anterior aorta and a posterior heart extending throughout the length of the body.

1. Aorta: It is the anterior part of the dorsal blood vessel and functions as a principal artery. It is present in the thoracic region and opens into the head near the brain. Its attachment with the heart posteriorly is marked by an aortic valve. Anteriorly sometimes it gets divided into 2 or more cephalic arteries in the head.

2. Heart: It is the posterior part of the orsal blood vessel extending up to the terminal end of the abdomen. The heart remains in position with the help of alary muscles that are attached to the tergum of the abdomen on one side and to the dorsal diaphragm on another side.

• The heart consists of several chambers marked by constrictions and the presence of an opening called the incurrent ‘ostia’ which allows the entry of blood fromthe pericardial sinus into the heart.
• The number of oOstiadepends upon the number of heart chambers which will be usually 9. The walls of the heart also consist of muscles. HThe heartmainly functions as the pumping organ into the aorta.