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Explain about the digestive system in earthworm?
The digestive/excretory system of an earthworm is very simple. In short, food goes in one end and comes out the other. Nephridia, which are analogous with human kidneys, are found in pairs in every segment except for the first three and the last one (Musurca). Although some water is reabsorbed by the blood, the remainder is excreted through the ventral pores, or nephridia. Digestion, on the other hand, is similar to that of human beings except an earthworm has a crop and a gizzard. With the help of the pharyngeal muscles on either side of the pharynx, a worm actually sucks in its food. From the pharynx, the food moves to the esophagus and then into the crop for storage until the rest of the tract is clear. From there the food moves to the gizzard where the soil is ground up with little stones, releasing organic matter. Nutrients are absorbed by the worm when the food passes through its intestine, which ends with the anus (Loretto).

An earthworm’s digestive system consists of a mouth,a pharynx, an esophagus, a crop, a gizzard and an intestine.

1.Mouth: The first section of the earthworm, the anterior end or head, consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl.

2. Pharynx:Food particles pass from the worm’s mouth to its pharynx where the food is lubricated by mucus secretions. The food is very slimy now, which makes it easier to pass along to the esophagus.

3. Oesophagus: This is where the slimy food is mixed with calcium carbonate. Calcium carbonate is the same kind of chemical found in medication, such as TUMS, which is used for heartburn. Calcium carbonate is a base, which is a type of chemical that neutralize acids. Decaying food (a worms favorite food) forms acids but the calcium carbonate neutralizes this acid.

4. Crop: Food passes from the esophagus to the crop, which is a temporary food storage area. In the crop the food gets mixed together. This mixture then moves into the gizzard.

5. Gizzard: Earthworms do not have teeth to grind their food, but the muscles of their gizzard churns and mixes the food. Since earthworms eat dirt, the sand grains grind against the food tearing it into smaller and smaller parts. Glands in the walls of the gizzard add enzymes, which are chemicals that aid in the breakdown of chemicals in the food. When the food has been churned and mixed so that it looks like thick paste, it is moved in the intestine.

6.Intestine: The thick paste of food continues to be digested in the intestine, where there are friendly bacteria that eat the food mixture. As the bacteria digest the food, the bacteria use what it needs and the rest is waster for the bacteria. This waste contains the nutrients that the earthworm’s body needs. A very important job of these friendly bacteria is that they prepare the nutrients in a form that can be absorbed into the small blood vessels lining the intestine. The blood carries the nutrients to all parts of the earthworm’s body.


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