Chap, xxx.] KIDNEY, URETER, AND BLADDER. 243 



The bundles of the arterise rectse and venae 

 rectse form severally, in the boundary layer, the 

 transparent strise mentioned on a previous page as 

 alternating with the opaque strise, these latter being 

 bundles of urinary tubules. 



At the apex of each papilla there is a network 

 of capillaries around the mouth of each duct. 



318. The outer capsule of the kidney contains a 

 network of capillary blood-vessels ; the arterial 

 branches leading into them are derived from two 

 sources : (a) from the outrunners of the interlobular 

 arteries of the cortex, and (b) from extrarenal arteries. 

 The veins lead (a) into the venae stellatse, and (b) the 

 extrarenal veins. 



The lymphatic vessels form a plexus in the capsule 

 of the kidney. They are connected with lymph 

 spaces between the urinary tubes of the cortex. 

 The large blood-vessels are surrounded by a plexus of 

 lymphatics, which take up lymph spaces between the 

 urinary tubules, both in the cortex and the boundary 

 layer. 



319. The ureter is lined with stratified transi- 

 tional epithelium. Underneath this is the mucosa, 

 a connective tissue membrane with capillary blood- 

 vessels. The submucosa is a loose connective tissue 

 Then follows a muscular coat composed of non- 

 striped muscular tissue, arranged as an inner and 

 outer longitudinal and a middle circular coat. Then 

 follows an outer limiting thin fibrous coat or adventitia. 

 In this last have been observed minute ganglia in 

 connection with the nerve branches. 



320. The bladder is similar in structure, but the 

 mucous membrane and muscular coat are veiy much 

 thicker. In the latter, which consists of non-striped 

 fibres, are distinguished an inner circular, a middle 

 oblique, and an outer longitudinal stratum. The 

 last is best developed in the fundus. 



