Earthworm Circulatory System Short Notes

In this article we will discuss about the earthworm circulatory system

Earthworm Circulatory System

• Earthworm circulatory system is closed type
• Earthworm circulatory system consists of blood vessel, heart, capillaries and blood glands
• Blood is composed of fluid plasma and colourless blood cells
• Blood is red in colour due to the presence of haemoglobin
• Haemoglobin occurs dissolved in plasma
• Circulation occurs in one direction

Main Longitudinal Blood Vessels

Dorsal vessel

• Dorsal vessel is extends through the length of the body
• Dorsal blood vessel is largest, thickest and having contractile muscular walls
• Flow of blood is from posterior to anterior
• It has a pair of valves internally which check the backward flow of blood
• It gives off branches that supply the blood to the anterior regions of the body

Ventral vessel

• Ventral vessel is found below the alimentary canal and above the ventral nerve cord
• Runs from second segment to the last segment of the body
• Ventral vessel has thin wall and lacks muscles and valves
• Flow of blood is anterior to posterior side
• It supplies the blood to ventral body wall, septal nephridia and reproductive organs

Hearts And Anterior Loop

• The hearts are contractile and surround the alimentary canal
• They are present in the segments 7th , 9th , 12th and 13th

Lateral hearts

• Pair of lateral hearts present in 7th and 9th segment
• Lateral hearts permits blood to flow downwards only
• It sends blood from dorsal vessel to ventral vessel

Lateral oesophageal hearts

• Lateral oesophageal hearts present in 12th and 13th segment
• These valves allow flow of blood to downwards only
• Sends blood from supraoesophageal and dorsal vessel to ventral vessel

Blood Gland and Circulation

Blood glands

• In the segments 4, 5, and 6 segments above pharynx are found small, red-colored the blood glands.
• These glands manufacture blood cells and hemoglobin
• In addition, these may perform excretory function in some species

Circulation of Blood

• The circulation of blood through different vessels is carried out by the peristaltic contraction of heart.
• In front of each septum, there is a pair of ring valves which direct the blood forward or backward but prevent reverse flow