The Leech
The leech starts its digestive system with the jaws, three blades set at an angle to each other. In feeding they slice their way through the skin of the host, leaving a Y-shaped incision. Behind the blades is the mouth, located ventrally at the anterior end of the body. It leads successively into the pharynx, then the esophagus, the crop, the gizzard, and the intestinum (tissue between the pulmonary alveoli and the bloodstream), which ends at the posterior sucker. The crop is a distension of the alimentary canal that functions as an expandable storage compartment. In the crop, some blood-sucking species of leech can store up to five times the body mass of blood. Then the leech produces an anticoagulant that prevents the stored blood from clotting, plus other agents that inhibit microbial decay of the blood.
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