1110 UROGENITAL SYSTEM. 
close to the middle line and immediately above the prostate. Inferiorly, the 
vesicle becomes constricted to form a short duct (ductus excretorius), which joins 
the outer side of the corresponding vas deferens at an acute angle to form the 
common ejaculatory duct. The inner side of each vesicle is related to the vas 
deferens, and the outer side, when the bladder is empty, lies close to the sloping 
pelvic floor. The seminal vesicle often assumes a more vertical position when 
the bladder is distended, a more horizontal one when the bladder is empty. Its 
upper end is sometimes found to be curved backwards against the side of the 
rectum. The seminal vesicles are in some cases much smaller than usual, and may 
be even less than one inch in length. They are often unsymmetrical. 
The seminal vesicles are more intimately related to the wall of the bladder than 
to that of the rectum—their upper ends are separated from the rectum by a portion 
of the recto-vesical pouch of peritoneum, while lower down the septum of fascia 
which intervenes between the vesiculz seminales and the rectum is denser than 
that which separates them from the bladder. The vesicula seminalis is in reality 
a tube bent in a tortuous manner on itself, and if the dense connective tissue which 
envelops it be taken away, the length of the tube when untwisted may be found to 
be as much as five inches. The tube is closed above, and a number of short tortuous 
branches come off it at different levels. The development of the vesiculee seminales 
shows that they are to be looked upon as diverticula of the vasa deferentia, from 
which they originally arise as small pouches. 
Superior surface 
Ureter of bladder 
Seminal 
vesicle 
y 
Seminal < 
vesicle 
Urachus 
Y Urachus 
Infero-lateral 
Lateral aspect 
of prostate 
Infero-lateral 
area of bladder 
Urethra 
aspect of 
V7 Urethra prostate 
A B 
Fic. 756.—THE BLADDER, PROSTATE, AND SEMINAL VESICLE VIEWED FROM THE SIDE. 
Drawn from specimens hardened 77 situ. 
In A the bladder contained but a small amount of fluid ; in B the quantity was somewhat greater. 
The dense tissue in which the seminal vesicles are embedded contains much unstriped muscle, 
which, sweeping round in the side wall of the recto-vesical pouch, gains an attachment to the 
fascia in front of the sacrum. The large veins coming from the prostatic and vesical plexuses are 
closely related to the seminal vesicles. 
Structure of the Vas Deferens and Vesicula Seminalis.—KExcept near its 
termination, where it is dilated to form the ampulla, the vas deferens is a thick- 
walled tube with relatively a very small lumen. The hard cord-like sensation which 
the vas deferens conveys to the touch is due to the thickness and toughness of its 
wall, which is composed of three layers—an outer fibrous (tunica adventitia), an 
intermediate muscular (tunica muscularis), and an inner mucous coat (tunica mucosa). 
The thickness of the wall is due to the great development of the middle or muscular 
coat, which is composed of an inner layer of circularly and an outer layer of 
longitudinally directed unstriped muscular fibres. Near the beginning of the vas 
there is an inner longitudinal layer also. The mucous membrane of the vas 
exhibits a few longitudinal folds. The ampulla, or terminal part, possesses much 
thinner walls, and, as the surface of its mucous membrane has a number of ridges 
separating depressed areas, the lining of the tube presents a pitted or honey- 
combed appearance. The wall of the vesicula seminalis resembles that of the 
ampulla in being thin, and in having a mucous lining with uneven honeycomb-like 
ridges and depressions. In the wall of the seminal vesicle the same coats are_to 
be recognised as in the vas, but the muscular stratum is much thinner. 
