Describe the circulatory system of an earthworm.

(N/A) $\rightarrow$ The circulatory system of an earthworm is of the closed type,consisting of blood vessels,capillaries,and hearts.
$\rightarrow$ The blood is red,and haemoglobin is dissolved in the blood plasma.
$\rightarrow$ Blood glands are present on the $4^{th}$,$5^{th}$,and $6^{th}$ segments. They produce blood cells and haemoglobin,which is dissolved in the blood plasma. Blood cells are phagocytic in nature.
$\rightarrow$ Due to the closed circulatory system,the blood circulates only within blood capillaries,blood vessels,and hearts.
$\rightarrow$ Due to rhythmic contractions,blood circulates in only one direction. Smaller blood vessels supply the gut,nerve cord,and the body wall.
$\rightarrow$ Respiratory system:
$\rightarrow$ Earthworms lack specialised breathing devices. Respiratory exchange occurs through the moist body surface into their bloodstream. The blood flow picks up $O_{2}$ from there.