Experimental and Cytological Studies on the Function of the Urinary Bladder Epithelium

Abstract

The author studied cytologically on the urinary bladder epithelium of nine normal dogs. The transitional epithelium of the urinary bladder is composed of two epithelial layers; the first one consists of large superficial cells (Deckzellen) and the second of the pseudostratified columnar epithelium, where the nuclei of the epithelial cells are ordinarily arranged in three rows. Therefore the second layer consists of the prismatic cells of the first, second and third rows. The number of row of the epithelial cells in the second layer varies, however, from one to five according to different conditions. The large superficial. cells have various sizes and shapes; the convex free surface is provided with a crusta, while the basal surface provides the thin projections between the sujacent cells, but they never reach the connective tissue. The epithelial cells of the second pseudostratified layer are all prismatic in shape, and their basal ends are connected with the underlying connective tissue. The cells of the third or innermost row are called the basal cells.The GOLGI apparatus is well developed in the superficial cells and in the cells of the first row of the second layer, where the apparatus has a netlike structure and is situated in the para- and infranuclear regions of the cytoplasm and embraces the nuclei from the downside. The development of the apparatus becomes gradually weak towards the second and third or basal row, and the apparatus is usually found in the supranuclear region of the basal cells.The mitochondria in the epithelial cells of the urinary bladder are usually filamentous or rod-like in shape, and have frequently the swellings at their ends. They are distributed almost equally in the cytoplasm and arranged in various portions of the cytoplasm nearly parallel to the perpendicular axis of the epithelium. The epithelial cells of the urinary bladder of the dog contain a large amount of the stainable and fat granules. The amount of these granules is generally largest in the superficial cells, they decrease, however, gradually towards the innermost row. The stainable and fat granules occur simultaneously in some locations of the cytoplasm; the majority of them is found together in the GOLGI-field. In this study the author could not obtain the findings which indicate the discharge of the granules from the superficial cells into the bladder lumen. In some cases, however, the author found that the considerable amount of the granules may leave the epithelial cells into the connective tissue and flow into the blood streams. Concerning the origin of the stainable granules, the author supports the following opinion; they are derived at first from the swellings at the ends of the mitochondria and grow gradually to the large partly stained granules. The latter contain fat substance and finally convert into the fat granules.Glycogen in the epithelium of the urinary bladder of the dog was demonstrated by the periodic acid-SCHIFF reaction. The superficial cells generally contain a considerable amount of it, which decreases gradually toward the cells of the innermost row, so that it finally disappears in the basal cells. On the contrary, ribonucleic acid (RNA) which is most abundant in the basal cells decreases gradually towards the outermost row and finally disappears in the superficial cells: The distributive states of glycogen and RNA in the epithelium of the dog's urinary bladder are inversely situated.