Surgical Anatomy Part 36

E. The spine of the ischium, cut.

F. The horizontal pubic ramus, cut.

G. The summit of the bladder covered by the peritonaeum; G *, its side, not covered by the membrane.

H H. The recto-vesical peritonaeal pouch,

I. The vas deferens.

K. The ureter.

L. The vesicula seminalis.

M, N, O, P, Q, R, S, T, U, refer to the same parts as in Plate 48.

V. The prostate.

W. The lower part of the r.e.c.t.u.m.

X. The deep perinaeal fascia.

[Ill.u.s.tration: Abdomen, showing bone, blood vessels and other internal organs.]

Plate 49

COMMENTARY ON PLATES 50 & 51.

THE SURGICAL DISSECTION OF THE SUPERFICIAL STRUCTURES OF THE MALE PERINAEUM.

The median line of the body is marked as the situation where the opposite halves unite and const.i.tute a perfect symmetrical figure. Every structure--superficial as well as deep--which occupies the median line is either single, by the union of halves, or dual, by the cleavage and part.i.tion of halves. The two sides of the body being absolutely similar, the median line at which they unite is therefore common to both. Union along the median line is an occlusion taking place by the junction of sides; and every hiatus or opening, whether normal or abnormal, which happens at this line, signifies an omission in the process of central union. The s.e.xual peculiarities are the results of the operation of this law, and all forms which are anomalous to either s.e.x, may be interpreted as gradations in the same process of development; a few of these latter occasionally come under the notice of the surgeon.

The region which extends from the umbilicus to the point of the coccyx is marked upon the cutaneous surface by a central raphe dividing the hypogastrium, the p.e.n.i.s, the s.c.r.o.t.u.m, and the perinaeum respectively into equal and similar sides. The umbilicus is a cicatrix formed after the metamorphosis of a median foetal structure--the placental cord, &c.

In the normal form, the meatus urinarius and the a.n.u.s coincide with the line of the median raphe, and signify omissions at stated intervals along the line of central union. When between these intervals the process of union happens likewise to be arrested, malformations are the result; and of these the following are examples:--Extrusion of the bladder at the hypogastrium is caused by a congenital hiatus at the lower part of the linea alba, which is in the median line; Epispadias, which is an urethral opening on the dorsum of the p.e.n.i.s; and Hypospadias, which is a similar opening on its under surface, are of the same nature--namely, omissions in median union. Hermaphrodism may be interpreted simply as a structural defect, compared to the normal form of the male, and as a structural excess compared to that of the female.

Spina bifida is a congenital malformation or hiatus in union along the median line of the sacrum or loins. As the process of union along the median line may err by a defect or omission, so may it, on the other hand, err by an excess of fulfilment, as, for example, when the urethra, the v.a.g.i.n.a, or the a.n.u.s are found to be imperforate. As the median line of union thus seems to influence the form of the hypogastrium, the genitals, and the perinaeum, the dissection of these parts has been conducted accordingly.

By removing the skin and subjacent adipose membrane from the hypogastrium, we expose the superficial fascia. This membrane, E E E*, Fig. 1, Plate 50, is, in the middle line, adherent to B, the linea alba, and thereby contributes to form the central depression which extends from the navel to the p.u.b.es. The adipose tissue, which in some subjects acc.u.mulates on either side of the linea alba, renders this depression more marked in them. At the folds of the groin the fascia is found adherent to Poupart's ligament, and this also accounts for the depressions in both these localities. From the central linea alba to which the fascia adheres, outwards on either side to the folds of both groins, the membrane forms two distinct sacs, which droop down in front, so as to invest the t.e.s.t.i.c.l.es, E**, and p.e.n.i.s in a manner similar to that of the skin covering these parts. As the two sacs of the superficial fascia join each other at the line B, coinciding with the linea alba, they form by that union the suspensory ligament of the p.e.n.i.s, which is a structure precisely median.

The superficial fascia having invested the t.e.s.t.i.c.l.es each in a distinct sac, the adjacent sides of both these sacs, by joining together, form the median septum scroti, E, Fig. 2, Plate 50. In the perinaeum, Fig. 1, Plate 51, the fascia, A, may be traced from the back of the s.c.r.o.t.u.m to the a.n.u.s. In this region the membrane is found to adhere laterally to the rami of the ischium and p.u.b.es; whilst along the median perinaeal line the two sacs of which the membrane is composed unite, as in the s.c.r.o.t.u.m, and form an imperfect septum. In front of the a.n.u.s, beneath the sphincter ani, the fascia degenerates into cellular membrane, one layer of which is spread over the adipose tissue in the ischio-rectal s.p.a.ce, whilst its deeper and stronger layer unites with the deep perinaeal fascia, and by this connexion separates the urethral from the a.n.a.l s.p.a.ces. The superficial fascia of the hypogastrium, the s.c.r.o.t.u.m, and the perinaeum forming a continuous membrane, and being adherent to the several parts above noticed, may be regarded as a general double sac, which isolates the inguino-perinaeal region from the femoral and a.n.a.l regions, and hence it happens that when the urethra becomes ruptured, the urine which is extravasated in the perinaeum, is allowed to pa.s.s over the s.c.r.o.t.u.m and the abdomen, involving these parts in consequent inflammation, whilst the thighs and a.n.a.l s.p.a.ce are exempt. The tunicae v.a.g.i.n.ales, which form the immediate coverings of the t.e.s.t.i.c.l.es, cannot be entered by the urine, as they are distinct sacs originally protruded from the abdomen. It is in consequence of the imperfect state of the inguino-perinaeal septum of the fascia, that urine effused into one of the sacs is allowed to enter the other.

Like all the other structures which join on either side of the median line, the p.e.n.i.s appears as a symmetrical organ, D D, Fig. 2, Plate 50.

While viewed in section, its two corpora cavernosa are seen to unite anteriorly, and by this union to form a septum "pectiniforme;"

posteriorly they remain distinct and lateral, F F, Fig. 2, Plate 51, being attached to the ischio-pubic rami as the crura p.e.n.i.s. The urethra, B, Fig. 2, Plate 50, is also composed of two sides, united along the median line, but forming between them a ca.n.a.l by the cleavage and part.i.tion of the urethral septum. All the other structures of the perinaeum will be seen to be either double and lateral, or single and median, according as they stand apart from, or approach, or occupy the central line.

The perinaeum, Figs. 1, 2, Plate 51, is that s.p.a.ce which is bounded above by the arch of the p.u.b.es, behind by C, the os coccygis, and the lower borders of, I I, the glutaei muscles and sacro-sciatic ligaments, and laterally by D D, the ischiatic tuberosities. The osseous boundaries can be felt through the integuments. Between the back of the s.c.r.o.t.u.m and the a.n.u.s the perinaeum swells on both sides of the raphe, A B, Fig. 3, Plate 50, and a.s.sumes a form corresponding with the bag of the superficial fascia which encloses the structures connected with the urethra. The a.n.u.s is centrally situated in the depression formed between D D, the ischiatic tuberosities, and the double folds of the nates.

The perinaeum, Fig. 3, Plate 50, is, for surgical purposes, described as divisible into two s.p.a.ces (anterior and posterior) by a transverse line drawn from one tuber ischii, D, to the other, D, and crossing in front of the a.n.u.s. The anterior s.p.a.ce, A D D, contains the urethra; the posterior s.p.a.ce, D D C, contains the r.e.c.t.u.m. The central raphe, A B C, traverses both these s.p.a.ces. The anterior or urethral s.p.a.ce is (while viewed in reference to its osseous boundaries) triangular in shape, the apex being formed by the pubic symphysis beneath A, whilst two lines drawn from A to D D, would coincide with the ischio-pubic rami which form its sides. The raphe in the anterior s.p.a.ce indicates the central position of the urethra, as may be ascertained by pa.s.sing a sound into the bladder, when the shaft of the instrument will be felt prominently between the points A B. Behind the point B, the sound or staff sinks deeper in the perinaeum as it follows the curve of the urethra towards the bladder, and becomes overlaid by the bulb, &c.

The ischiatic tuberosities, D D, Fig. 3, Plate 50, are, in all subjects, sufficiently prominent to be felt through the integuments, &c.; and the line which, when drawn from one to the other, serves to divide the two perinaeal s.p.a.ces, forms the base of the anterior one. In well-formed subjects, the anterior s.p.a.ce is equiangular, the base being equal to each side; but according as the tuberosities approach the median line, the base becomes narrowed, and the triangle is thereby rendered acute.

These circ.u.mstances influence the direction in which the first incision in the lateral operation of lithotomy should be made. When the tuberosity of the left ischium stands well apart from the perinaeal centre, the line of incision, B E, Fig. 3, Plate 50, is carried obliquely from above downwards and outwards; but in cases where the tuberosity approaches the centre, the incision must necessarily be made more vertical. The posterior perinaeal s.p.a.ce may be described on the surface by two lines drawn from D D, the ischiatic tuberosities, to C, the point of the coccyx, whilst the transverse line between D and D bounds it above.

By removing the integument and superficial fascia, we expose the superficial vessels and nerves, together with the muscles in the neighbourhood of the urethra and the a.n.u.s. The accelerator urinae, E, Fig. 2, Plate 51, which embraces the urethra, and the sphincter ani, B C, which surrounds the a.n.u.s, H, occupy the median line, and are divided each into halves by a central tendon, E B C, which traverses the perinaeum from before backwards, to the point of the coccyx. On either side of the a.n.u.s, in the ischio-rectal s.p.a.ce, D D, Fig. 1, Plate 51, is found a considerable quant.i.ty of granular adipose tissue, traversed by the inferior haemorrhoidal arteries and nerves-branches of the pudic artery and nerve.

In front of the a.n.u.s are seen two small muscles (transversae perinaei), G G, Fig. 2, Plate 51, each arising from the tuber ischii of its own side, and the two becoming inserted into, B, the central tendon. These transverse muscles serve to mark the boundary between the anterior and posterior perinaeal s.p.a.ces. Behind each muscle is found a small artery, crossing to the median line. The left transverse muscle and artery are always divided in the lateral operation of lithotomy. On the outer sides of the anterior perinaeal s.p.a.ce are seen the erectores p.e.n.i.s muscles, F F, overlaying the crura p.e.n.i.s. Between each muscle and the accelerator urinae, the superficialis perinaei artery and nerve course forwards to the s.c.r.o.t.u.m, &c.

The perinaeal muscles having been brought fully into view, Plate 52, Fig. 1, their symmetrical arrangement on both sides of the median line at once strikes the attention. On either side of the anterior s.p.a.ce appears a small angular interval, L, formed between B, the accelerator urinae, D, the erector p.e.n.i.s, and E, the transverse muscle. Along the surface of this interval, the superficial perinaeal artery and nerve are seen to pa.s.s forwards; and deep in it, beneath these, may also be observed, L, the artery of the bulb, arising from the pudic, and crossing inwards, under cover of the anterior layer of the membrane named the deep perinaeal fascia. The first incision in the lateral operation of lithotomy is commenced over the inferior inner angle of this interval.

The muscles occupying the anterior perinaeal s.p.a.ce require to be removed, Fig. 1, Plate 53, in order to expose the urethra, B M, the crus p.e.n.i.s, D, and the deep perinaeal fascia. The fascia will be now seen stretched across the subpubic triangular s.p.a.ce, reaching from one ischio-pubic ramus to the other, whilst by its lower border, corresponding with the line of the transversae perinaei muscles, it becomes continuous with the superficial fascia, in the manner before described. The deep perinaeal fascia (triangular ligament) encloses between its two layers, C E, on either side of the urethra, the pudic artery, the artery of the bulb, Cowper's glands, and some muscular fibres occasionally to be met with, to which the name "Compressor urethrae" has been a.s.signed. At this stage of the dissection, as the princ.i.p.al vessels and parts composed of erectile tissue are now in view, their relative situations should be well noticed, so as to avoid wounding them in the several cutting operations required to be performed in their vicinity.

Along the median line (marked by the raphe) from the s.c.r.o.t.u.m to the coccyx, and close to this line on either side, the vessels are unimportant as to size. The urethra lies along the middle line in the anterior perinaeal s.p.a.ce; the r.e.c.t.u.m occupies the middle in the posterior s.p.a.ce. When either of these parts specially requires to be incised--the urethra for impa.s.sable stricture, &c., and the lower part of the r.e.c.t.u.m for fistula in ano--the operation may be performed without fear of inducing dangerous arterial haemorrhage. With the object of preserving from injury these important parts, deep incisions at, or approaching to, the middle line must be avoided. The outer (ischio-pubic) boundary of the perinaeum is the line along which the pudic artery pa.s.ses. The anterior half of this boundary supports also the crus p.e.n.i.s; hence, therefore, in order to avoid these, all deep incisions should be made parallel to, but removed to a proper distance from this situation. The structures placed at the middle line, B M F, Fig. 2, Plate 52, and those in connexion with the left perinaeal boundary, D G L, require (in order to insure the safety of these parts) that the line of incision necessary to gain access to the neck of the bladder in lithotomy should be made through the left side of the perinaeum from a point midway between M, the bulb, and D, crus p.e.n.i.s above, to a point, K, midway between the a.n.u.s, F, and tuber ischii, G, below. As the upper end of this incision is commenced over the situation of the superficial perinaeal artery and the artery of the bulb, the knife at this place should only divide the skin and superficial fascia.

The lower end, K, just clears the outer side of the dilated lower part of the r.e.c.t.u.m. The middle of the incision is over the left lobe of the prostate gland and neck of the bladder, which parts, together with the membranous portion of the urethra, are still concealed by the deep perinaeal fascia, the structures between its layers, and the anterior fibres of K, the levator ani muscle. The incision, if made in due reference to the relative situation of the parts above noticed, will leave them untouched; but when the pudic artery, or some one of its branches, deviates from its ordinary course and crosses the line of incision, a serious haemorrhage will ensue, despite the anatomical knowledge of the most experienced operator. When it is requisite to divide the superficial and deep sphincter ani as in the operation for complete fistula in ano, if the incision be made transversely in the ischio-rectal fossa, the haemorrhoidal arteries and nerves converging towards the a.n.u.s will be the more likely to escape being wounded.

DESCRIPTION OF THE FIGURES OF PLATES 50 & 51.

PLATE 50.

FIGURE 1.

A. The umbilicus.

B. The linea alba.

C. The suspensory ligament of the p.e.n.i.s.

D D. The two corpora cavernosa p.e.n.i.s.

E E**. The hypogastric and scrotal superficial fascia.

F F. The spermatic cords.

FIGURE 2.

A. The umbilicus.

B. The urethra.

C*. The tunica v.a.g.i.n.alis; c, the t.e.s.t.i.c.l.e invested by the tunic.

D D. The corpora cavernosa seen in section.

E. The scrotal raphe and septum scroti.

FIGURE 3.