![INSIDE THE WORM, FROM FRONT TO BACKThe worm's alimentary canal (or gut) is the central feature of its body cavity. And w...](https://img3.voofla.com/300/476/718455263004760.jpg)
01/24/2023
INSIDE THE WORM, FROM FRONT TO BACK
The worm's alimentary canal (or gut) is the central feature of its body cavity. And why not? The worm is, after all, mainly an eating and composting machine. It eats its own weight in earth, minerals, and organic matter each day, and this job requires an impressive digestive system. The alimentary canal lies in the center of the body cavity. Its wall is comprised of three layers: the interior, which is a mucous layer; the middle, composed of strong muscle fibers and blood vessels; and the outer layer, which is protective.
The canal is basically a tube that runs clear through the length of the worm, from the mouth to the a**s. Different parts of the canal somewhat different purposes, ever, and so scientists have given different names to these parts. Just behind the mouth is the buccal cavity, the cheek pouch of the worm. It is in this region, extending only to the first or second anterior segment, where the taste cells are located. No one knows whether a worm can spit out food it doesn't like, but it certainly can stop eating distasteful food once the food reaches the buccal cavity.
Behind the buccal cavity is the pharynx, which connects the mouth to the esophagus. The pharynx extends to about the sixth segment, and is used as a kind of suction pump, drawing in food from the mouth.
The esophagus opens from the pharynx and leads to the crop and the gizzard. The crop feeds food back to the gizzard, which, with the aid of powerful muscular contractions, grinds up the food for further digestion. The sand and other mineral particles that the worm consumes act as grinding stones in the gizzard.
Behind the gizzard, which ends at about the twentieth segment in most common species, begins the intestine. It is here, as in our own bodies, that most of the digestion and absorption of the worm's food takes place. There are many folds in the inner wall of the intestine, which give the food greatest chance to be fully absorbed.
Between the intestine and the body wall are five pairs of vessels that scientists call, for lack of a better name, "hearts. Although they do not resemble mammalian hearts, their function is much the same. They direct the flow of blood through the worm's body. The worm has only two major blood vessels, one dorsal (topside) and the other ventral (bottom side). There are many minor vessels and capillaries that carry blood to all parts of the body.
The respiratory system of the worm is very rudimentary. There are no lungs or other such apparatus, but oxygen is received through the body wall, where it is taken up by the blood and circulated throughout the worm’s body.
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