THE UROGENITAL SYSTEM 89 



Note the elongated flattened gland lying against the con- 

 cave surface of the vesicular gland. Find its duct and 

 trace it to the anterior end of the urethra. Find also the 

 pair of small glands (probably the ampullar y glands), 

 each of which encircles the ductus deferens near its en- 

 trance into the urethra. 



The prostate gland comprises two regions. One attaches 

 to the dorsal and lateral surfaces of the proximal end of 

 the urethra, and to the dorsal side of the vesicular gland. 

 The other region consists of two prominent lobes lying 

 ventral to the urinary bladder, to which they are attached. 

 The lobes are also fastened to the adjacent body wall. 

 Dissect away the tough external tunic of connective tissue, 

 and note that both parts of the gland are a mass of tubules. 

 The prostatic secretion in man dilutes and lends bulk to 

 the seminal fluid. It has been suggested that in rodents 

 the secretion assists the locomotion of the sperm cells, 

 and also nourishes them. 



The urinary bladder is an oval sac attached to the dorsal 

 surface of the ventral part of the prostate gland. The 

 bladder narrows proximally to the neck, which joins the 

 ductus deferentia to form the urethra. Each ureter, or 

 urinary drainage tube of the kidney, joins the correspond- 

 ing side of the bladder near the neck. Urine entering the 

 bladder through the ureters, is stored there temporarily, 

 then flows through the neck into the urethra, which con- 

 veys it to the outside. The urethra also carries the sper- 

 matic fluid during copulation. 



The descent of the testis carries the ductus deferens ven- 

 tral to the ureter. This accounts for the way these tubes 

 loop around each other in the adult. 



A mesentery in the sagittal plane connects the bladder 

 and posterior part of the prostate gland with the ventral 

 body wall. 



