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shape. The seminal vesicles are more intimately related to the wall of the bladder than to that of the rectum. Their superior ends are, as we have seen, separated from the rectum by a portion of the recto-vesical pouch of peritoneum, and lower down the septum of fascia which intervenes between the vesiculæ seminales and the rectum is denser than that which separates them from the bladder.
Each vesicula seminalis is in reality a tube bent in a tortuous manner on itself, and if the dense connective tissue which envelops it is 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 variable number of short tortuous branches come off it at different levels. The blind end of the tube usually lies at the superior and lateral extremity of the seminal vesicle, but in some cases the tubular vesicle is so bent upon itself that the blind terminal part lies against the side of the issuing duct. The development of the vesiculæ seminales shows that they are to be regarded as diverticula of the ductus deferentes, from which they originally arise as small pouches.
The dense tissue in which the seminal vesicles are embedded contains much unstriped muscle tissue, which sweeps round in the side wall of the ecto-vesical pouch. Inferiorly this tissue is attached to the capsule of the prostate. The large veins coming from the prostatic and vesical plexuses are closely related to the seminal vesicles.
FIG. 1013. THE URINARY BLADDER, PROSTATE, AND SEMINAL VESICLE VIEWED FROM THE SIDE. Drawn from specimens hardened in situ.
In A the bladder contained but a small amount of fluid; in B the quantity was somewhat greater.
Structure of the Ductus Deferens and of the Vesicula Seminalis.Except near its termination, where it is dilated to form the ampulla, the ductus deferens is a thick-walled tube with relatively a very small lumen. The hard cord-like sensation which the ductus 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 tunica muscularis, and an inner tunica mucosa. The thickness of the wall is due to the great development of the middle or muscular coat, which is composed of an intermediate layer of circularly and an inner and outer layer of longitudinally directed unstriped muscular fibres. Of these layers the middle one is by far the thickest, and forms the chief part of the thickness of the wall of the ductus deferens. The mucous membrane of the duct exhibits a number of slight longitudinal folds and possesses a ciliated epithelium. The ampulla, or terminal part, possesses a much thinner wall, and, as the surface of its mucous membrane has a number of ridges separating depressed areas, lining of this part of the tube presents a pitted or honeycombed 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 it the same coats are to be recognised as in the ductus deferens, but the muscular layer is much thinner, and the strata composing it less regularly arranged.
The seminal vesicles are not present in all mammals, and in those in which they do occur their relative size and form vary much. Among the carnivora, marsupials, and some other groups of mammals, the seminal vesicles do not occur; in some other animals, such, for instance, as the hedgehog, they are relatively of enormous size.
Vessels and Nerves of the Ductus Deferens and of the Vesicula Seminalis.-The ductus deferens receives its arterial supply from the superior or inferior vesical artery. The artery to the duct accompanies that structure, supplying it as far as the testis, where it ends by anastomosing with branches of the internal spermatic artery. The vesicula seminalis is supplied by the inferior vesical artery. The nerves of the ductus deferens and vesicula seminalis are derived from the hypogastric plexus. In lower animals the nerves for the seminal vesicles are derived from the nerve roots of the second, third, and fourth lumbar nerves.
DESCENT OF THE TESTIS.
The peculiar course pursued by the ductus deferens in the adult, and the manner in which it is related to the anterior abdominal wall, are rendered clear by a study of the arrangement of the parts in the fœtus. The testes until nearly the end of intra-uterine life are placed in the abdominal cavity. Lying at first on the posterior wall of the abdomen at the level of the upper two lumbar vertebræ, and just below the level assumed at this time by the permanent kidney, the testis is held in place by a fold of peritoneum or mesentery, called the mesorchium. As growth goes on the testis is found to occupy a lower level in the abdominal cavity; in the third month it lies in the iliac fossa, and in the seventh it is situated near the abdominal inguinal ring. Meanwhile a blind pouch or diverticulum of the peritoneal membrane, termed the processus vaginalis peritonæi, has grown downwards and inwards through the anterior
abdominal wall towards the deferens
scrotum, deriving as it goes a covering from each of the layers of the abdominal wall through which it passes. The testis with its
mesorchium. enters the
diverticulum of the ab
dominal cavity, and de- FIG. 1014.-VIEW LOOKING FROM ABOVE INTO THE PELVIS AND LOWER
scends within it until the scrotum is reached. At a later stage, the connexion between the part of the processus vaginalis that lies
PART OF THE ABDOMINAL CAVITY IN A FETUS OF ABOUT THE
On the left side, which represents a slightly more advanced condition than
in the scrotum and the peritoneal lining of the abdomen becomes lost by the obliteration of the upper part of the pouch. Thus the part of the processus vaginalis that persists in the scrotum becomes the parietal portion of the tunica vaginalis; while the visceral part of that membrane is the primitive peritoneal covering of the testis and epididymis (Figs. 1014 and 1015).
Often a small fibrous band-the "ligamentum vaginale "-may be found in the adult passing through the inguinal canal and joining the peritoneum superiorly in the region of the abdominal inguinal ring. Sometimes this band is connected below with the tunica vaginalis, but more often it does not reach so far downwards. When present it represents the obliterated portion of the processus vaginalis, and is therefore known as the rudimentum processus vaginalis.
In other rare cases the processus vaginalis may persist after birth as a channel freely open to the abdominal cavity above, or the passage, becoming closed at intervals, may give rise to one or more cysts within the coverings of the spermatic funiculus.
It sometimes happens that the descent of the testis is arrested, and then, either failing to enter the processus vaginalis, the testis remains within the abdominal cavity; or entering the processus vaginalis, it fails to reach the scrotum, and lies in the inguinal canal. The term "cryptorchism" is frequently applied to such cases.
In connexion with the descent of the testis a remarkable cord-like structure-the gubernaculum testis [Hunter] must be mentioned. The gubernaculum arises for the most part within a peritoneal fold which, at an early time in the development of the foetus, may be seen stretching from the inguinal region to the Wolffian duct (future duct of the testis) and inferior end of the mesonephros or primitive kidney. This peritoneal
fold, termed the plica inguinalis (or plica inguino-mesonephrica), is joined from above by a less marked fold (the plica testis inferior) which extends downwards from the inferior end of the testis, which, at this time, is situated in the abdomen close to the inner aspect of the mesonephros. Within both these folds smooth muscular and fibrous tissue arises and gives origin to a continuous band, or ligament-the gubernaculum testis. The gubernaculum is, therefore, to be regarded as originally composed of two portions -a part developed within the plica inguinalis, and a part formed within the plica testis inferior. It is interesting to note that in the female the representatives of these two parts
of the gubernaculum remain separate throughout life, and constitute the round ligament of the uterus and the ligament of the ovary. The gubernaculum, when it is at its greatest development (about the sixth month), is rounded and cord-like, and is attached above to the lower end of the testis, while inferiorly it is fixed near the inguinal region. In the lower part of its course it is closely related to, and is partly covered by, the peritoneum of the processus vaginalis. Striped muscular fibres are present in the lower part of the gubernaculum, and have their origin from the muscles of the inguinal part of the anterior abdominal wall. As the testis
enters the processus vaginalis the gubernaculum atrophies, but at birth a short part of the gubernaculum may still be found passing downwards towards the inferior part of the scrotum and lying below the level of the tunica vaginalis. It is considered by some anatomists that the movement downwards of the testis may be partly due to a pull caused by the shrinking of the gubernaculum as it atrophies.
In some mammals, such as the elephant, the testes remain permanently within the abdominal cavity; while in others, such as the rabbit and the hedgehog, the peritoneal pouches remain widely open throughout life, and the testes are periodically withdrawn into the abdomen.
FUNICULUS SPERMATICUS (SPERMATIC CORD).
External spermatic fascia
The testis in its course downwards through the abdominal wall into the scrotum takes with it its duct-the ductus deferens-blood and lymph vessels, and nerves of supply. All these lie together in the inguinal canal as they traverse the abdominal wall, and when they leave the canal by the subcutaneous inguinal ring they extend downwards to the posterior border of the testis. The ductus deferens. the spermatic vessels, and the nerves and lymph vessels of the testis, loosely connected together, form the funiculus spermaticus, or spermatic cord. At the abdominal inguinal ring its constituent parts separate from one another, and the funiculus may therefore be considered to extend from the abdominal inguinal ring to the posterior border of the testis. The structures which form the spermatic cord are enclosed within a number of coverings derived from the layers of the anterior abdominal wall, and these, when the constituents of FIG. the cord reach the posterior border of the testis, surround the tunica vaginalis, and so form a part of the wall of the scrotum. The sheaths or coverings of the cord derived from the abdominal wall are three number, and are named external spermatic fascia, fascia cremasterica, and internal spermatic fascia. The external spermatic fascia is the most superficial of the three sheaths, and is derived from the aponeurosis of the external oblique muscle
1016.-TRANSVERSE SECTION OF THE FUN!
CULUS SPERMATICUS, OR SPERMATIC CORE
with which it is continuous round the margins of the subcutaneous inguinal ring. The fascia cremasterica consists partly of muscular fibres derived from the lower part of the internal oblique muscle, and partly of delicate connective tissue. The muscular fibres constitute the cremaster muscle and, passing down over the funiculus, form a series of loops round the testis and tunica vaginalis. The internal spermatic fascia is derived from the fascia transversalis of the abdomen. It passes downwards as a continuous sheath over the cord, and encloses its various structures, together with a certain amount of areolar tissue derived from the subperitoneal tissue of the abdominal wall and some smooth muscle fibres.
In addition to the structures enumerated above, the artery to the ductus deferens, the external spermatic (O.T. cremasteric) artery, and the genital branch (n. spermaticus externus) of the genito-femoral nerve, accompany the structures forming the funiculus spermaticus.
The scrotum, in which the testes are placed, varies much in appearance in different subjects, and even in the same individual at different times. As the
FIG. 1017.-DISSECTION TO SHOW THE FUNICULUS SPERMATICUS AS IT ISSUES FROM THE SUBCUTANEOUS INGUINAL RING. On the right-hand side of the figure the funiculus has been cut across, and the structures composing it are seen in section. On the left-hand side of the figure the external oblique muscle has been removed.
result of cold or of exercise, the wall of the scrotum becomes contracted and firm, and the skin covering it wrinkled; at other times the wall may be relaxed and flaccid, the scrotum then assuming the appearance of a pendulous bag. The left side of the scrotum reaches to a lower level than the right, in correspondence with the lower level of the testis on that side of the body. The skin covering the scrotum is of a darker colour than the general skin of the body, and is covered with hair. It is marked in the median plane by the raphe scroti, which is continued backwards towards the anus, and forwards on to the inferior, or urethral, surface of the penis. The difference in the appearance of the scrotum at different times is due to the amount of contraction or relaxation of a layer of
muscular fibres, constituting the tunica dartos, situated in the superficial fascia When this muscular layer is contracted, the scrotum becomes smaller and somewhat globular, and the skin is thrown into folds or wrinkles called ruga; wher it is relaxed, the scrotum is flaccid and pendulous, and the skin becomes more smooth and even. The layer of fascia which contains the smooth muscle fibres can be shown to be continuous superiorly with the superficial fascia of the penis. and with the deep layer of the superficial fascia of the abdomen, and to be attached laterally to the bones forming the pubic arch. The muscle fibres are arranged in a thick layer of interlacing bundles, and many of the deeper fibres are continued into the septum scroti, which divides the scrotum into two cavities, one for each testis. The wall of each of these cavities is formed by the corresponding tunica vaginalis, infundibuliform fascia, fascia cremasterica, and intercolumnar fascia; while the skin, the superficial fascia, and the superficial part of the dartos muscle form coverings which are common to the whole scrotum, and enclose both cavities. The layer of tissue immediately beneath the dartos tunic is made up of exceedingly loose and easily stretched areolar connective tissue, and in it, as throughout in the superficial fascia of the scrotum, there is an entire absence of fat.
The scrotum in the foetus contains no cavity, but, like the labia majora in the female, it composed entirely of vascular connective tissue.
Vessels and Nerves of the Scrotum. The scrotum receives its vascular supply from the posterior scrotal branches of the perineal divisions of the internal pudendal arteries, which rea it from behind, and from the external pudendal branches of the femoral artery, which reach its upper and anterior part.
The nerves of the scrotum are derived on each side from the posterior scrotal branches of the perineal division of the pudendal nerve, from the perineal branch of the posterior cutane nerve of the thigh, and from the ilio-inguinal nerve. The branches from the pudendal and posterior cutaneous nerves reach the scrotum from behind, while the ilio-inguinal supplies s upper and anterior part. The nerve fibres for the dartos muscle fibres are believed to have the origin from the hypogastric plexus.
The penis is composed chiefly of erectile tissue, and is traversed by the cana. of the urethra. The surface nearest to which the canal of the urethra lies called the facies urethralis, or urethral surface; the opposite and more extensive aspect is the dorsum penis. The erectile tissue is for the most part dispose in three longitudinal columns, which in the body of the organ are placed side by side, while at the root of the penis they separate from one another, and become attached to the fascia inferior of the urogenital diaphragm and to the pubic and Two of these masses of erectile tissue, placed one on each side of the median plane and forming the dorsum and sides of the penis, are called the corpora cavernosa penis, while the third, which is called the corpus cavernosum urethra (O.T. corps spongiosum), is situated in the median plane near the urethral surface. The corp cavernosum urethra is the part of the penis which is traversed by the urethra and it is considerably smaller than the corpora cavernosa penis, which form the chief bulk of the organ.
In the corpus penis, or body of the penis, each corpus cavernosum penis is place close to the median plane, and presents a rounded surface, except where it is flattened by contact with its fellow of the opposite side. The corpora caver penis are separated on the anterior or dorsal surface by a shallow groove, and ot the posterior or urethral aspect by a deeper and wider furrow, in which lies the corps cavernosum urethra (Fig. 1018). Towards the distal end of the penis the corps cavernosum urethra appears to expand, and, spreading towards the dorsal surface the organ, it forms a kind of conical cap, the glans penis, which covers over the bla rounded termination of the corpora cavernosa penis. The prominent margin the glans, called the corona glandis, projects dorsally and laterally beyond ** extremities of the corpora cavernosa penis. The glans is traversed by the term part of the urethra, which ends near the summit of the glans in a slit-like open called the orificium urethræ externum, or external urethral orifice. The un corpora cavernosa penis end in a blunt conical extremity, the apex of which