Body
Medicinal leech is a segmented word related to earthworm. Both circular and longitudinal muscles make up leeches and they contain a true digestive system with a separate anus and mouth. The body consists of a posterior and anterior sucker which each have a specific function. Leeches have cylindrical, flattened bodies divided into thirty- three or thirty-four segments ( Sawyer 1986). The dorsal side is a dark brown to black color, bearing six longitudinal, reddish or brown strips. Medicinal leech have five pairs of eyes. In regards to external features, leeches lack setae, septa and parapodia which function in locomotion. They instead move by swimming or looping involving attachment to a substance using its posterior sucker. Medicinal leeches also have a clitellum which is a thickened glandular section of the body wall that secretes a viscid sac in which eggs are deposited. Located in the diagram above it is present about 2 cm behind the anterior end of the body.
Suckers
One characteristic of the Class Hirundinea that separates them from earthworms is their possession of an anterior and posterior sucker. The posterior sucker or rear suction cup helps it move and cling to a host but the reason why medicinal leeches are such an interests to doctors is because of their anterior sucker which houses three sharp teeth. Leeches are able to feed for 30 minutes to 6 hours or more, taking in several times its body weight. Another important part of the anterior sucker is the leech saliva. The saliva of leech contains about 100 pharmacologically active substances like Hirudin, hyaluronnidase, vasodilators, anesthetics, antibacterial, and collagenase (Lone, Ahmad, Anwar, Habib and Iman 1:31-35 ). These substances are injected into human body while sucking of the blood. Furthermore, the proteins in leech salvia helps to numb pain and reduces swelling which was one of major forms of therapy during the Civil War.