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smooth muscular fibres, which is continued upwards and backwards on the sides of the urethra to form a part of the "sphincter vesica." At a lower level striped muscular tissue, which is continuous with the deep part of the sphincter urethræ membranacea muscle, occupies a position in front of the urethral canal.
The muscular tissue of the prostate is to be regarded as the thickened muscular layer of the wall of the urethra, broken up and invaded by the prostatic glands which arise and are developed from the lining layer of the canal during embryonic life.
In old age the prostate frequently undergoes a hypertrophy, which may affect chiefly the glandular tissue, or the entire organ. Not infrequently calcareous concretions are found embedded in the prostate.
Vessels and Nerves of the Prostate. The prostate receives its blood-supply from branches of the hæmorrhoidal and inferior vesical arteries, while the large plexus of veins-plexus pudendalis -which surrounds it, and into which the veins of the penis open, communicates with the vesical plexus, and drains into the hypogastric veins. In old people the veins of the prostate usually become much enlarged.
The nerves of the prostate are derived from the hypogastric plexus.
The bulbo-urethral glands (O.T. glands of Cowper) are a pair of small bodies placed in relation to the second, or membranous, part of the urethra. They are each about the size of a pea, and are of a yellowish-brown colour. Situated in the space between the two fascia of the urogenital diaphragm, they lie below the level of the apex of the prostate, and above that of the bulbus urethre (Figs. 1024 and 1026). Each gland is made up of a number of closely applied lobes or lobules, and is of the compound racemose type. The ductules of the gland unite to form a single ductus excretorius, which pierces the bulbus urethra, and, after a relatively long course, ends by opening into the cavernous portion of the urethra by a minute aperture. The secreting acini are lined with columnar epithelium.
The glands receive their arterial supply from the artery to the bulb.
The urethra in the male is a channel of about eight inches in length leading from the bladder to the external urethral orifice at the extremity of the glans penis. The canal serves not only for the passage of urine, but it also affords an exit for the seminal products, which enter by the ejaculatory ducts, and for the secretion of the prostatic and bulbo-urethral glands. In addition, numerous minute glandulæ urethrales pour their secretion into the urethra.
As it passes from the internal urethral orifice, to its external opening, the urethra describes a somewhat shaped course, and it is customary to divide it into certain sections, which have received distinctive names. The first part of the urethra lies within the pelvic cavity, and has a somewhat vertical course as it traverses the prostate. Turning more forwards, the urethra passes below the pubic arch, and pierces the fibrous layers which form the pelvic wall in this region. Leaving the pelvis minor, the canal enters the bulbus urethre, where the latter is attached to the fascia inferior of the urogenital diaphragm, and throughout the rest of its course it lies in the erectile tissue of the corpus caver nosum urethræ and of the glans penis. The part of the urethra which lies embedded in the prostate is called the pars prostatica, or prostatic portion; the short part which pierces the pelvic wall is called the pars membranacea, or membranous portion, and the part surrounded by the corpus cavernosum urethra receives the name of pars cavernosa, or cavernous portion. Of these three sections of the urethra the cavernous portion is much the longest, and the membranous is the shortest.
Pars Prostatica Urethræ Virilis.-The prostatic part of the male urethra descends through the prostate from the base towards the apex, describing a slight curve which is concave forwards. It is about one inch in length,
FIG. 1024.-DISSECTION OF THE MALE PELVIC ORGANS AND OF THE PENIS,
The dorsal vein of the penis and the pudendal venous plexus are coloured blue.
and is narrower above and below than in its middle portion, which is, indeed, the widest part of the whole urethral canal. Except while fluid is passing, the canal is collapsed, and the mucous membrane of the anterior and posterior walls is in contact, and thrown into a series of longitudinal folds. When distended, the middle, or widest part of the canal, may normally have a diameter
of about one-third of an inch. The posterior wall, often termed the "floor" the prostatic urethra, presents a distinct median ridge or elevation called th crista urethralis (Fig. 1026). This projects forwards into the urethra to su an extent that the canal in transverse section presents a somewhat crescenti outline. In the depressions, or grooves, on each side of the crista urethral
FIG. 1025.-ADULT MALE PELVIS IN MEDIAN SECTION.
The urinary bladder is empty and firmly contracted. The urethra is opened up in its entire length. the numerous ducts of the prostatic glands open by minute apertures. Some few ducts from the middle part of the gland open nearer the median plane, on the sides of the urethral crest. On the summit of the crista urethralis is a slit-like opening which leads backwards and upwards for a distance of about a quarter of an inch, as a blind pouch, in the substance of the prostate. This little cavity is known as the utriculus prostaticus, and represents the fused posterior ends of the Müllerian ducts, from which the uterus and vagina of the female are developed. The term uterus masculinus is therefore some times applied to this little pouch. On each side of the mouth of the utricle is the much more minute opening of the ejaculatory duct. When traced upwards towards the bladder, the urethral crest, diminishing in height, becomes indistinct.
but in it can often be traced as a slight median ridge as far as the uvula vesica. When followed in the opposite direction the ridge becomes less marked, and can be followed on the urethral wall into the membranous portion of the canal, where it divides into a pair of inconspicuous folds or elevations, which gradually fade out into the urethral wall (Fig. 1026).
The curvature and, to a less degree, the length of the prostatic urethra depends upon the amount of distension of the bladder and of the rectum (compare Figs. 989 and 990).
Pars Membranacea Urethræ.-The second, or membranous portion, of the
FIG. 1026.-DISSECTION SHOWING THE TRIGONUM VESICE AND THE POSTERIOR WALL OR FLOOR OF THE URETHRA IN ITS PROSTATIC, MEMBRANOUS, AND THE PROXIMAL PART OF ITS CAVERNOUS SUBDIVISIONS. The canal has been opened up by removing its anterior and upper wall.
urethra leads downwards and forwards from the apex of the prostate to the bulbus urethra, and is the shortest and narrowest of the three subdivisions of the canal, its length being somewhat less than half an inch. It begins at the superior fascia of the urogenital diaphragm, a layer of pelvic fascia which lies above the sphincter urethræ membranacea muscle. Here it is continuous with the prostatic portion of the urethra. It ends, having pierced the inferior fascia of the urogenital diaphragm, by becoming continuous with the cavernous portion of the urethra. Placed in front of the anal canal, it lies about one inch behind and below the arcuate ligament of the pubis (O.T. sub-pubic ligament). It is surrounded by fibres of the sphincter urethræ membranacea muscle, and behind it, on each side of the median plane, lies the bulbo-urethral gland. The posterior part of the bulbus
of about one-third of an inch. The posterior wall, often termed the "floor" of the prostatic urethra, presents a distinct median ridge or elevation called the crista urethralis (Fig. 1026). This projects forwards into the urethra to such i an extent that the canal in transverse section presents a somewhat crescentic outline. In the depressions, or grooves, on each side of the crista urethral
Caverrons porn on of rethra Bulb of tretira
F: 1025 -ADULT MALE PELVIS IN MEDIAN SECTION.
pty ani srmly, stracted. The urethra is opened up in its entire length.
the numerous ducts of the prostatic glands open by minute apertures. Some few ducts from the middle part of the gland open nearer the median plane, or the sides of the urethral crest. On the summit of the crista urethralis is a slit-like opening which leads backwards and upwards for a distance o about a quarter of an inch, as a blind pouch, in the substance of the prostate This little cavity is known as the utriculus prostaticus, and represents the fused posterior ends of the Mullerian duets, from which the uterus and vagina of the female are developed. The term uterus masculinus is therefore sometimes applied to this little pouch. On each side of the mouth of the utricle is the much more minute opening of the ejaculatory duct. When traced upwards towards the ladder, the urethral crest, diminishing in height, becomes indistinct