DIGESTIVE SYSTEM

Alimentary canal is straight tube running throughout the length of the body the whole of the alimentary canal is not uniform in diameterand the nature of the digestive wall is aldi different in different regions there fere it can be diveded inro the following parts .
Mouth is a crescentric aperture ventrl to the prostomium ditiuated in thefirstsegment or peristomium or buccal segmint.Buccal chamber mouth leds into a cavity called bucca; cvity or buccal chmber it is a short thinwalled chamber and extinds from first segment to the middle of the 3rd segment During movement earth buccal chamber with the help of muscular stramds wjoch[ass baclwards and forwards from the outer walls of the buccal chamber and the pharync to the body wall.
Pharynx.Buccl cavity leads into the pharynx which is a pearshaped wide swollen and muscular chamber it is continued slightly beyond the fourth segment buccal cavity is clearly separated from the pharynx by a groove in which dorsally a ceret ral ganglion is situated pharyngeal cavity is narroe and dorsoventrally compressed due to the presence of larg thick mass known pharyngeal mass or pharyngeal bulb which swpresses the phryngeal roof pharyngeal mass is made up of darkly stained irregular glandular cells or chromophil cells and muscle fibres.the glandular cells produce a salivary secretion which is poured into the cavity of the pharynx by means ofchannels of the pharyngeal mass the lateral phryngeal walls are pushed inside to form a horizontal shelf on ech side the two shelves thus divide the phryngeal cavity into a dorsal or salivary chamber and ventral or conducting chamber