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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

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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

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