The elasmobranch fishes (1934) The elasmobranch fishes . elasmobranchfish03dani Year: 1934 126 THE ELASMOBRANCH FISHES observed that the folds are far apart anteriorly and very much closer together posteriorly. The valve is formed as an ingrowth into the intestine and extends from the duodenum throughout the large intestine to the region where the opening of the rectal gland enters the intestine posteriorly. This fold is con- siderably broader than the diameter of the intestine and is thrown into a series of cones having their apices pointing anteriorly. The surface of the valve, if seen unde
The elasmobranch fishes (1934) The elasmobranch fishes . elasmobranchfish03dani Year: 1934 126 THE ELASMOBRANCH FISHES observed that the folds are far apart anteriorly and very much closer together posteriorly. The valve is formed as an ingrowth into the intestine and extends from the duodenum throughout the large intestine to the region where the opening of the rectal gland enters the intestine posteriorly. This fold is con- siderably broader than the diameter of the intestine and is thrown into a series of cones having their apices pointing anteriorly. The surface of the valve, if seen under the microscope, shows numerous finger-like villi which serve for the absorption of digested food. Colon and Rectum The part of the large intestine immediately following the valve is known as the colon (co., fig. 120). It is a muscular segment and superficially appears as slightly bulbous. Its lining, together with that of the part succeeding it, the rectum (re), is thrown into longitudinal folds. In the most posterior part, however, the walls of the rectum are smoother. The line of demarcation be- tween the colon and the rectum is formed by a lumen from the rectal or digitiform gland. EECTAL GLAND The rectal or digitiform gland (, fig. 120 and fig. 124) in Heptanchus is a finger-like structure which is composed of multitudes of gland cells and which empties by a central lumen into the in- testine. It is so arranged, however, that the lumen does not enter immediately at the point at which it reaches the intestine, but passes sharply for- ward and downward emptying on a level with the terminus of the spiral valve. CLOACA Fig. 124. Sagittal section through rectal gland, Hep- tanchus. (From Howes.) CO., colon; fd., fold of spi- ral intestine; lu., lumen of The rectum empties into an enlarged room, the gland; re, rectum. , i • i • t -, ^.^ ,i cloaca, which is lined with a smooth mucous mem- brane (see fig. 252, facing p. 290). Into the anterior part of the cloaca empty
Size: 1298px × 1541px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
