The Surgical Dissection Of The Fifth Sixth Seventh And Eighth Layers Of The Inguinal Region And Their Connexion With Those Of The Thigh

Sources: Surgical Anatomy

When we remove the internal oblique and cremaster muscles, we expose the

transverse muscle, which may be regarded as the fifth inguinal layer, F,

Pl. 30. This muscle is similar in shape and dimensions to the internal

oblique. The connexions of both are also similar, inasmuch as they arise

from the inner edge of the crista ilii, and from the outer half of, V,

Poupart's ligament. The fleshy fibres of these two muscles vary but
br /> little in direction, and terminate at the same place--viz., the linea

semilunaris, which marks the outer border of the rectus muscle. But

whilst the fleshy parts of these three abdominal muscles, D E F, form

successive strata in the groin, their aponeurotic tendons present the

following peculiarities of arrangement in respect to the rectus muscle.

The tendon of the external oblique, d, passes altogether in front of the

rectus; that of the internal oblique is split opposite the linea

semilunaris into two layers, which enclose the rectus between them as

they pass to be inserted into the linea alba. But midway between the

navel and pubes, at the point marked G, both layers of the tendon are

found to pass in front of the rectus. The tendon of the transverse

muscle passes behind the rectus; but opposite the point G, it joins both

layers of the internal oblique tendon, and with this passes in front of

the rectus. The fibrous structure thus constituted by the union of the

tendons of the internal oblique and transverse muscles, e f, is named

the "conjoined tendon."



The conjoined tendon, f, Plates 30 and 31, appears as a continuation of

the linea semilunaris, for this latter is in itself a result of the

union of the tendons of the abdominal muscles at the external border of

the rectus. As the conjoined tendon curves so far outwards to its

insertion into the pectineal ridge of the pubic bone, as to occupy a

situation immediately behind the external ring, it thereby fortifies

this part against the occurrence of a direct protrusion of the bowel.

But the breadth, as well as the density, of this tendon varies in

several individuals, and these will accordingly be more or less liable

to the occurrence of hernia.



The arched inferior border of the transverse muscle, F, Plate 30,

expresses by its abrupt termination that some part is wanting to it; and

this appearance, together with the fact that the fibres of this part of

the muscle blend with those of the internal oblique and cremaster, and

cannot be separated except by severing the connexion, at once suggests

the idea that the cremaster is a derivation from both these muscles.



Assuming this to be the case, therefore, it follows that when the

dissector removes the cremaster from the space L h, he himself causes

this vacancy in the muscular parietes of the groin to occur, and at the

same time gives unnatural definition to the lower border of the

transverse and oblique muscles. In a dissection so conducted, the cord

is made to assume the variable positions which anatomists report it to

have in respect to the neighbouring muscles. But when we view nature as

she is, and not as fashioned by the scalpel, we never fail to find an

easy explanation of her form.



In the foetus, prior to the descent of the testicle, the cremaster

muscle does not exist. (Cloquet, op cit.) From this we infer, that those

parts of the muscles, E F, Plate 30, which at a subsequent period are

converted into a cremaster, entirely occupy the space L h. In the adult

body, where one of the testicles has been arrested in the inguinal

canal, the muscles, E F, do not present a defined arched margin, above

the vacant space L h, but are continued (as in the foetus) as low down

as the external abdominal ring. In the adult, where the testicle has

descended to the scrotum, the cremaster exists, and is serially

continuous with the muscles, E F, covering the space L h; the meaning of

which is, that the cremasteric parts of the muscles, E F, cover this

space. The name cremaster therefore must not cancel the fact that the

fibres so named are parts of the muscles, E F. Again, in the female

devoid of a cremaster, the muscles, E F, present of their full

quantities, having sustained no diminution of their bulk by the

formation of a cremaster. But when an external inguinal hernia occurs in

the female body, the bowel during its descent carries before it a

cremasteric covering at the expense of the muscles E F, just in the same

way as the testicle does in the foetus. (Cloquet.)



From the above-mentioned facts, viewed comparatively, it seems that the

following inferences may be legitimately drawn:--1st, that the space L h

does not naturally exist devoid of a muscular covering; for, in fact,

the cremaster overlies this situation; 2nd, that the name cremaster is

one given to the lower fibres of the internal oblique and transverse

muscles which cover this space; and 3rd, that to separate the

cremasteric elongation of these muscles, and then describe them as

presenting a defined arched margin, an inch or two above Poupart's

ligament, is an act as arbitrary on the part of the dissector as if he

were to subdivide these muscles still more, and, while regarding the

subdivisions as different structures, to give them names of different

signification. When once we consent to regard the cremaster as

constituted of the fibres originally proper to the muscles, E F, we then

are led to the discovery of the true relations of the cord in respect to

these muscles.



On removing the transverse muscle, we expose the inguinal part of the

transversalis fascia--the sixth inguinal layer, L h, Plate 30--K k,

Plate 31. This fascia or membrane affords a general lining to the

abdominal walls, in some parts of which it presents of a denser and

stronger texture than in others. It is stretched over the abdomen

between the muscles and the peritonaeum. The fascia iliaca, the fascia

pelvica, and the fascia transversalis, are only regional divisions of

the one general membrane. On viewing this fascia in its totality, I find

it to exhibit many features in common with those other fibrous

structures which envelope serous cavities. The transversalis fascia

supports externally the peritonaeum, in the same way as the dura mater

supports the arachnoid membrane, or as the pleural fascia supports the

serous pleura. While the serous membranes form completely shut sacs, the

fibrous membranes which lie external to those sacs are pierced by the

vessels which course between them and the serous membranes, and afford

sheaths or envelopes for these vessels in their passage from the

interior to the external parts. The sheath, H h, Plates 30 and 31, which

surrounds the spermatic vessels, and the sheath, R, Plate 31, which

envelopes the crural vessels, are elongations of the fascia

transversalis.



In the groin, the transversalis fascia, K k, Plate 31, presents, in

general, so dense a texture as to offer considerable resistance to

visceral pressure. Here it is stretched between the transverse muscle,

F, Plate 31, and the peritonaeum, I. It adheres to the external surface

of the peritonaeum, and to the internal surface of the transverse

muscle, by means of an intervening cellular tissue. It is connected

below to Poupart's ligament, along the line of which it joins the fascia

iliaca. It lines the lower posterior aspect of the rectus muscle, where

this is devoid of its sheath; and it is incorporated with f, the

conjoined tendon, thereby fencing the external abdominal ring.

Immediately above the middle of Poupart's ligament, this membrane, at

the point marked h, Plate 30, is pouched into a canal-shaped elongation,

which invests the spermatic vessels as far as the testicle in the

scrotum; and to this elongation is given the names "fascia spermatica

interna" (Cooper), "fascia infundibuliform" (Cloquet). The same part,

when it encloses an external oblique hernia, is named "fascia propria."

The neck or inlet of this funnel-shaped canal is oval, and named the

"internal abdominal ring." As this ring looks towards the interior of

the abdomen, and forms the entrance of the funnel-shaped canal, it

cannot of course be seen from before until we slit open this canal.

Compare the parts marked H h in Plates 30 and 31.



The inguinal and iliac portions of the fascia transversalis join along

the line of Poupart's ligament, A C. The iliac vessels, in their passage

to the thigh, encounter the fascia at the middle third of the crural

arch formed by the ligament, and take an investment (the sheath, R) from

the fascia. The fore part of this sheath is mentioned as formed by the

fascia transversalis--the back part by the fascia iliaca; but these

distinctions are merely nominal, and it is therefore unnecessary to

dwell upon them. The sheath of the femoral vessels is also

funnel-shaped, and surrounds them on all sides. Its broad entrance lies

beneath the middle of Poupart's ligament. Several septa are met with in

its interior. These serve to separate the femoral vessels from each

other. The femoral vein, O, Plate 30, is separated from the falciform

margin, S s, of the saphenous opening by one of these septa. Between

this septum and the falx an interval occurs, and through it the crural

hernia usually descends. These parts will be more particularly noticed

when considering the anatomy of crural hernia.



Beneath the fascia transversalis is found the subserous cellular

membrane, which serves as a connecting medium between the fascia and the

peritonaeum. This cellular membrane may be considered as the seventh

inguinal layer. It is described by Scarpa (sull' Ernie) as forming an

investment for the spermatic vessels inside the sheath, where it is

copious, especially in old inguinal hernia. It is also sometimes mixed

with fatty tissue. In it is found embedded the infantile cord--the

remains of the upper part of the peritoneal tunica vaginalis--a

structure which will be considered in connexion with congenital herniae.



By removing the subserous cellular tissue, we lay bare the peritonaeum,

which forms the eighth layer of the inguinal region. Upon it the

epigastric and spermatic vessels are seen to rest. These vessels course

between the fascia transversalis and the peritonaeum. The internal ring

which is formed in the fascia, K h, may be now seen to be closed by the

peritonaeum, I. The inguinal canal, therefore, does not, in the normal

state of these parts, communicate with the general serous cavity; and

here it must be evident that before the bowel, which is situated

immediately behind the peritonaeum, I, can be received into the canal, H

h, it must either rupture that membrane, or elongate it in the form of a

sac.



The exact position which the epigastric, L, Plate 31, and spermatic

vessels, M, bear in respect to the internal ring, is a point of chief

importance in the surgical anatomy of the groin; for the various forms

of herniae which protrude through this part have an intimate relation to

these vessels. The epigastric artery, in general, arises from the

external iliac, close above the middle of Poupart's ligament, and

ascends the inguinal wall in an oblique course towards the navel. It

applies itself to the inner border of the internal ring, and here it is

crossed on its outer side by the spermatic vessels, as these are about

to enter the inguinal canal.



The inguinal canal is the natural channel through which the spermatic

vessels traverse the groin on their way to the testicle in the scrotum.

In the remarks which have been already made respecting the several

layers of structures found in the groin, I endeavoured to realize the

idea of an inguinal canal as consisting of elongations of these layers

invaginated the one within the other, the outermost layer being the

integument of the groin elongated into the scrotal skin, whilst the

innermost layer consisted of the transversalis fascia elongated into the

fascia spermatica interna, or sheath. The peritonaeum, which forms the

eighth layer of the groin, was seen to be drawn across the internal ring

of this canal above in such a way as to close it completely, whilst all

the other layers, seven in number, were described as being continued

over the spermatic vessels in the form of funnel-shaped investments, as

far down as the testicle.



With the ideas of an inguinal canal thus naturally constituted, I need

not hesitate to assert that the form, the extent, and the boundaries of

the inguinal canal, as given by the descriptive anatomist, are purely

conventional, and do not exist until after dissection; for which reason,

and also because the form and condition of these parts so described and

dissected do not appear absolutely to correspond in any two individuals,

I omit to mention the scale of measurements drawn up by some eminent

surgeons, with the object of determining the precise relative position

of the several parts of the inguinal region.



The existence of an inguinal canal consisting, as I have described it,

of funnel-shaped elongations from the several inguinal layers continued

over the cord as far as the testicle, renders the adult male especially

liable to hernial protrusions at this part. The oblique direction of the

canal is, in some measure, a safeguard against these accidents; but this

obliquity is not of the same degree in all bodies, and hence some are

naturally more prone to herniae than others.





DESCRIPTION OF THE FIGURES OF PLATES 30 & 31.



PLATE 30.



A. The anterior superior iliac spine.



B. The umbilicus.



C. The spine of the pubis.



D. The external oblique muscle; d, its tendon. .



E. The internal oblique muscle; e, its tendon.



F. The transverse muscle; f, its tendon, forming, with e, the conjoined

tendon.



G. The rectus muscle enclosed in its sheath.



H. The fascia spermatica interna covering the cord; h, its funnel-shaped

extremity.



I, K, L, M. See Plate 31.



N. The femoral artery; n, its profunda branch.



O. The femoral vein.



P. The saphena vein.



Q. The sartorius muscle.



R. The sheath of the femoral vessels.



S. The falciform margin of the saphenous opening.



T. The anterior crural nerve.



U. The pubic portion of the fascia lata.



V. The iliac portion attached to Poupart's ligament.



W. The lower part of the iliacus muscle.














PLATE 31.



A. The anterior superior iliac spine.



B. The umbilicus.



C. The spine of the pubis.



D. The external oblique muscle; d, its tendon; d*, the external ring.



E. The internal oblique muscle.



F. The transverse muscle; f, its tendon; forming, with e, the conjoined

tendon.



G. The rectus muscle laid bare.



H h. The fascia spermatica interna laid open above and below d*, the

external ring.



I. The peritonaeum closing the internal ring.



K. The fascia transversalis; k, its pubic part.



L. The epigastric artery and veins.



M. The spermatic artery, veins, and vas deferens bending round the

epigastric artery at the internal ring; m, the same vessels below

the external ring.



N. The femoral artery; n, its profunda branch.



O. The femoral vein, joined by--



P. The saphena vein.



Q. The sartorius muscle.



R. The sheath of the femoral vessels.



S S. The falciform margin of the saphenous opening,



T. The anterior crural nerve.



U. The pubic part of the fascia lata.



V. The iliac part of the fascia lata.



W. The lower part of the iliacus muscle.