Organ System of Earthworm

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Circulatory system of earthworm: Closed circulatory system consisting of heart, blood vessels and capillaries with the blood completely confined to blood vessels and the heart. The 4-6 segments comprise blood glands which secrete blood which is carried by the haemoglobin and dissolved in the blood plasma. The blood vessels supply the gut, nerve cord and the body wall through smaller contractions of the heart. Blood cells are capable of phagocytosis. Exchange of gases occurs through moist body surface into blood stream, thus making them to come over the surface from time to time.

 

Excretory system in earthworm: Segmentally arranged coiled tubules called nephridia are the excretory organs of the earthworm. Nephridia function to regulate the volume and composition of body fluids. The structure of nephridium has a funnel that collects the excess fluids that is connected to a tubular part which throws out the wastes through a pore to the surface of the body wall into the digestive tube.

Three types of nephridia is seen – (i) Septal nephridia – present on both sides of the body from the 15th segment to the segment before the intestine opens up, (ii) integumentary nephridia – is seen attached to the body wall after the buccal cavity (segment 3) until the segment that opens to the body surface, (iii) Pharyngeal nephridia – are the three paired tufts present in the 4th, 5th and the 6th segment of the body.

 

Nervous system of earthworm: The ganglia are arranged in each segment on the ventral pair nerve cord. The nerve cord begins in the 3rd and 4th segment, bifurcating and encircling pharynx region, later joining the cerebral ganglia to form a ring on the dorsal side. This nervous system ring is responsible for integrating sensory inputs and commands the muscular responses of the body.

At the anterior end of the earthworm’s body, sensory organs for light, touch and taste are present. Light sensitiveness and vibrations of the ground help the earthworm’s bodily activities. Chemoreceptors are specialized taste receptors present in the mouth of the earthworm.

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