826 A MANUAL OF ANATOMY 



Ureter. — ^This is the excretory duct of the kidney, and it has the 

 form of a cylindrical tube, like a goose-quill, its colour being a dull 

 white. Its length varies from 12 to 16 inches, and its diameter is 

 about i inch. At its lower extremity it opens into the bladder, 

 and at the hilum of the kidney it presents a dilatation called the 

 pelvis of the kidney, which is funnel-shaped, being wide above and 

 narrow below. The pelvis is flattened from before backwards, and 

 lies partly in the sinus and partly outside the hilum, its direction 

 being downwards and inwards. It breaks up into two or three 

 primary divisions within the sinus, and these again form secondary 

 divisions, the resulting tubes being called ealices or infundibula, 

 which vary in number from 7 to 13. The number of ealices 

 thus falls short of the number of Malpighian pyramids (8 to 18), 

 the explanation being that one calix grasps two papillae or even 

 three. The ealices embrace the papillae of the Malpighian pyramids, 

 which thus project into them, and they receive the urine as it oozes 

 through the pores on the apices of the papillae, these pores being 

 the openings of the excretory tubes or ducts of Bellini. The 

 interspaces between the ealices in the sinus are occupied by the 

 branches of the renal bloodvessels and by fat. 



Structure of the Ureter. — The ureter is a thick-walled muscular 

 tube, lined with mucous membrane, and it consists of three coats — 

 external or fibrous, middle or nmscular, and internal or mucous. 

 The fibrous coat is composed of fibrous tissue, very compactly 

 arranged, and it contains the bloodvessels and nerves, which here 

 subdivide. The muscular coat is composed of plain muscular tissue, 

 which is disposed in three layers — otiter longitudinal, middle circular, 

 and internal longitudinal. The outer longitudinal layer is best 

 marked in the lower half of the ureter, where it forms a continuous 

 investment. In the upper half of the tube its bundles are some- 

 what scattered. The mucous coat superiorly is continued over 

 the papillae of the Malpighian pyramids, and inferiorly becomes 

 continuous with the mucous membrane of the bladder. It is 

 covered by stratified transitional epithelium, the cells being ar- 

 ranged in four layers. In the most superficial layer (nearest the 

 lumen of the tube) the cells are cubical, and present depressions on 

 their deep surfaces, which receive the round ends of the pyriform 

 cells of the layer beneath. In the second layer the cells are pyriform, 

 the round superficial ends being capped by the cubical cells of the 

 first layer, and the narrow deep ends projecting between the deeper 

 cells. In the third and fourth layers the cells are round or oval. 

 The mucous membrane is thrown into longitudinal folds, and the 

 lumen of the tube, which is of small size, presents under the micro- 

 scope a branched appearance in cross section. 



Blood-supply — Arteries. — ^The ureter receives branches from the 

 renal, spermatic (ovarian in the female), common iliac, and superior 

 vesical, arteries. 



The veins terminate in the vessels corresponding to these 

 arteries. 



