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cinguished, and are found to bear the same relation to one another as in the dried hough this may be obscured by foldings or rugæ. The aperture may be slit-like or

sloping or funnel-shaped edges; the frenula are not so prominent at times; but re projects much more abruptly into the cavity of the cæcum than in the distended imen.

PERITONCUM

LONGITUDINAL MUSC. FIBRES

CIRCULAR

MUCOUS MEMBRANE

ILEUM

VILLI

CAECUM

re of the Valvula Coli.- Each labium of the valve is formed of an ll the coats of the gut, except the peritoneum and the longitudinal muscular consequently consists of two layers of mucous membrane, with the subthe circular muscular fibres between, all of ntinuous with those of the ileum on the one che large intestine on the other. The surface um turned towards the small intestine is

villi, and conforms in the structure of its zbrane to that of the ileum ; whilst the brane of the opposite surface resembles the of the large bowel. ed specimen the superior labium usually projects che cavity of the cæcum than the inferior, so ture appears to be placed between the edge of gment and the inferior surface of the superior. ittle doubt that the efficiency of the valvula

due to the oblique manner in which the ileum ginates the large intestine; this oblique passage he case of the ureter piercing the wall of the 1 probably be sufficient to prevent a return of tents. In the great majority of cases, when in n the body, the ileum is perfectly protected from although when the parts are removed, and then

Fig. 953. DIAGRAMMATIC SECTION h fluid, this fluid often passes through the valve, THROUGH THE JUNCTION OF THE

e small intestine. Still, the efficiency of such a ILEUM WITH THE CÆCUM, TO SHOW when the parts are deprived of their natural THE FORMATION OF THE VALLot be relied upon.

VULA COLI. the segments of the valve, as seen in the dried ries considerably; they are sometimes very imperfect; and even the absence of

recorded. But here again there is danger of falling into error, through examining er such artificial conditions. Cæcum.-Three chief types of cæcum may be distinguished—the fætal type, conical

nearly symmetrical, with the inferior end gradually passing into the vermiform infantile, in which the passage from the cum to the vermiform process becomes the lateral wall more prominent, and the whole sac more asymmetrical; and the loprm, as described above, which is the condition found in 93 or 94 per cent. of adults. re.-Nothing in the arrangement of the mucous and submucous coats calls notice. The tæniæ or longitudinal bands of the muscular coat all spring se of the vermiform process (Fig. 954); the anterior runs up on the front, ne main prominence of the cæcum; the postero-lateral runs up behind this

whilst the postero-medial passes directly upwards behind the ileum (Fig. ongitudinal fibres on the superior aspect of the ileum partly join the postero; those on the anterior and posterior aspects join the circular fibres of the

is coat has, in connexion with it, certain folds and fossæ which are described

sus Vermiformis (Fig. 954). — The vermiform process (O.T. appendix, m appendix) is a worm-like tubular segment which springs from the posterior part of the cæcum about 1 to 14 inches (2.5 to 3.75 cm.) below al orifice. From that point it generally runs in one of three chief direcly—(1) over the brim, into the pelvis; (2) upwards behind the cæcum; rds and medially, thus pointing towards the spleen; each of which has lered to be the normal position by one or more observers. In the first uations it is quite evident as it hangs over the pelvic brim; in order in the second, the cæcum must be turned upwards; whilst, in the third lies behind the end of the ileum and its mesentery, and these must in order to display it. In addition to the positions just mentioned, it

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has been found in almost every possible situation in the abdomen which its length and the extent of its mesentery would allow it to attain. In every case the anterior tania of the cæcum, which is always distinct, offers the surest guide to the vermiform process, and its base can be located with certainty by following this tænia to the back of the cæcum (Fig. 954).

Its size is almost as variable as its position. Taking the average of numerous measurements, its length may be given as about 34 inches (92 mm., Berry), and its breadth as 7 inch (6 mm., Berry). On the other hand, it has been found as long as 9 inches (230 mm.), and as short as į inch (18 mm.). Even its absence has been recorded (Fawcett), but this must be looked upon as an extremely rare

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Its lumen or cavity is variable in its development, and is found to be totally or partially occluded in at least one-fourth of all adult and old bodies examined. This is looked upon as a sign of degeneracy in the process of gradual obliteration, which it is by many considered to be undergoing, in the human species. It opens into the cavity of the cæcum on its medial, or medial and posterior aspect

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Fig. 954.—THE BLOOD-SUPPLY OF THE CÆCUM AND VERMIFORM PROCESS.
The illustration to the left gives a front view ; in that to the right the cæcum is viewed from behind. In the

latter the artery of the process, and three tæniæ coli springing from the base of the vermiform process
should be specially noted. (Modified from Jonnesco).

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(Fig. 952), at a point 1 to 1} inches (2-5 to 3-8 cm.) below, and somewhat posterior to the ileo-cæcal orifice. These are the relative positions of the two orifices, as seen from the interior of the cæcum; viewed from the exterior, the base of the vermiform process is within inch of the lower border of the ileum. This apparent difference is due to the fact that the ileum adheres to the medial side of the cæcum for a distance of nearly 1 inch before it opens into it.

Sometimes the orifice of the vermiform process has a crescentic fold or valve, the valvula processus vermiformis, placed at its superior border ; but it is probably of very little functional importance, for the aperture of the process is usually so small that its cavity is not likely to be invaded by the contents of the cæcum.

The vermiform process is completely covered with peritoneum, and has a considerable mesentery, the mesenteriolum processus vermiformis (0.T. meso-appendix), which extends to its tip as a rule, and connects the process to the inferior surface of that part of the mesentery proper which goes to the inferior extremity of the ileum.

The vermiform process is relatively, to the rest of the large intestine, longer in the child at birth than in the adult, the proportion being about 1 to 16 or 17 at birth and 1 to 19 or 20 in the adult. (The difference is certainly not as great as stated by Ribbert, who makes the proportion 1 to 10 at birth and 1 to 20 in the adult.) The process attains its greatest length and diameter during adult and middle age, and atrophies slowly after that time. It is said to be slightly longer in the male than in the female.

Total occlusion of its cavity is found in 3 or 4 per cent. of bodies; it is then converted into a fibrous cord. Partial occlusion is present in 25 per cent. of all cases, and in more than 50 per cent.

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those over 60 years old, whilst it is unknown in the child. This frequency of occlusion, the ysiological atrophy which takes place after middle life, the great variations in length, and other ns of instability

, ħave been considered to point to the retrogressive character of the vermiform A vermiform process is found only in man, the higher apes, and the wombat, although in ain rodents a somewhat similar arrangement exists. În carnivorous animals the cæcum is very tly developed ; in herbivorous animals (with a simple stomach) it is, as a rule, extremely large. as been suggested that the vermiform process in man is the degenerated remains of the vorous cæcum, which has been replaced by the carnivorous form. Another and perhaps probable view regards the process as a lymph organ, having the same functions as lymph es , and, like these , undergoing degeneration after

middle life (Berry). the fætus and child, as well as in the adult with the infantile type of cæcum, the vermirocess springs from the true apex, not from the medial and posterior aspect.

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Fig. 955.–STRUCTURE OF THE VERMIFORM PROCESS. A. From a child two years old.

B. From a male, age 56. ed that the tela submucosa is almost entirely occupied by lymph nodules and patches. The uscularis niucose is very faint, and lies quite close to the bases of the intestinal glands. The al layer of muscular fibres forms a continuous sheet. ies, although reputed to find their way very easily into the vermiform process, are ere after death. On the other hand, concretions or calculi, formed of mucus, aus salts, are often present (Berry). (Fig. 955).—The tunica serosa is complete, and forms a perfect investment

The tunica muscularis, unlike that of the rest of the large intestine, has a stout layer of longitudinal fibres, which passes at the root of the process eniæ coli (Fig. 954). The layer of circular fibres is well developed. The is almost entirely occupied by large masses of lymph tissue surrounded ph spaces. Owing to the large size of these lymph nodules, the areolar aucosa is compressed against the inner surface of the muscular coat, and ed fibrous ring, which sends processes at intervals between the lymph che mucous membrane. These lymph nodules, which correspond to

nodules, have, owing to their great number, been almost completely mucosa (in which they chiefly lie in the intestine) into the submucosa. at corresponds to that of the large intestine in its general characters, lands are fewer, and irregular in their direction ; the lamina muscularis

ill-defined ; it lies just internal to the lymphoid nodules of the subliately outside the base of the intestinal glands. Some few lymph ucous coat also.

the Cæcum and Vermiform Process (Fig. 954). — These parts are y the ileo-colic artery. This gives off, near the upper angle formed by the

with the small intestine—a) an anterior ileo-cæcal artery, which passes he ileo-cæcal junction to the cæcum, and breaks up into numerous branches

part; (b) a posterior ileo-cæcal artery, similarly disposed on the back; and miform process. The last-named branch passes down behind the ileum (Fig. nesentery of the process, and running along this near its free border, sends off

the little mesentery to the process, before finally ending in it. The course he ileun is said to render it subject to pressure from fæcal masses in that ispose to an interference with the blood supply of the vermiform process, s in it.

The lymph vessels of the cæcum and vermiform process arise mainly from networks in the mucous and serous coats.

The first of these networks communicates with a lymph sinus which is found at the base of the lymph nodules in the process, and the vessels from it pierce the muscular coats, and pas in company with the blood-vessels. They are connected with mucous lymph glands found near the ileo-cæcal junction, especially on the posterior and medial aspect, in the angle between the ileum and colon.

Small isolated glands may be found lying in close contact with the medial part of the cæcum. on its anterior and posterior aspects. From these glands, the lymph stream is directed upwards and medially towards the coeliac and lumbar glands. The lymph vessels of the vermiform process may also communicate with the lymph nodes in the iliac fossa, and also, it has been stated, with the lymph vessels of the right ovary.

Cæcal Folds and Fossæ. - The peritoneum in the neighbourhood of the cæcum forms certain fossæ, of which the most interesting and important are—(a) the fosse cæcalis; (b) the recessus ileocæcalis inferior; (c) the recessus ileocæcalis superior; and (d) the recessus retrocæcalis.

(a) The fossa cæcalis (Fig. 956, B) is only occasionally present, and can be exposed by turning the cæcum and adjacent part of the ileum upwards. It is a fossa in the

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Fig. 956.—THE CÆCAL Folds and Fossa. In A, the cæcum is viewed from the front; the mesentery of the vermiform process is distinct, and is attached

above to the inferior surface of the portion of the mesentery going to the end of the ileum. In B, the cæcum is turned upwards to show a retro-cæcal fossa, which lies behind it and behind the beginning of the ascending colon.

parietal peritoneum on the posterior abdominal wall, open above, in which the lower end of the cæcum occasionally lies. It is produced by the plica cæcalis, a peritoneal fold which passes from the surface of the iliacus to the right lateral aspect of the cæcum. Two forms, lateral and medial, are described; the first lies behind the lateral part of the ascending colon, immediately above the cæcum ; the second behind its medial part. These fosse are specially interesting because, when present, they frequently lodge the vermiform pro cess (see Fig. 956, B), a condition which is said to favour the production of appendicitis.

(b and c) Recessus Ileocæcales and Plica Ileocæcalis.-If the vermiform process is drawn down, and the finger run towards the cæcum, along the inferior border of the terminal part of the ileum, its point will generally run into a fossa situated in the angle between the ileum and cæcum (Fig. 956, A), which is known as the recessus ileocecalis inferior. The fold which bounds the fossa in front is the plica ileocæcalis (0.T. the "bloodless fold of Treves"). It passes from the ileum to the front of the mesentery of the vermiform process, which forms the posterior wall of the fossa.

The plica ileocæcalis contains some unstriped muscle fibres continuous with the longitudinal muscle coat of the cæcum, and some fat especially at its free margin.

The recessus ileocæcalis inferior is bounded above by the lower end of the ileum, to the right by the cæcum, in front by the plica ileocæcalis, behind by the root of the mesenteriolum of the processus vermiformis, while it is open to the left or medially.

Similarly, if the finger is run out along the superior border of the ileum towards the cuecum, it will usually lodge in a smaller fossa, the recessus ileocæcalis superior, which is

bounded in front by a small peritoneal process, the ileo-colic fold (Fig. 956, A), containing the anterior cæcal artery.

The recessus ileocecalis superior lies at the upper margin of the opening of the ileum into the colon, and is bounded behind by the ileum, to the right by the

cæcum.

(d) Recessus Retrocæcalis.— This is an occasional recess which passes upwards between he ascending colon and the posterior abdominal wall. Its orifice looks downwards or to e left, and lies in the fossa cæcalis behind the cæcum.

COLON.

Colon Ascendens. The ascending colon begins about the level of the interercular plane, opposite the ileo-cæcal orifice, where it is continuous with the im. From there it runs upwards and somewhat posteriorly, with a slight conty to the left, until it reaches the inferior surface of the liver, where it hends rds and to the left, and passes into the right flexure of the colon (Fig. 957). s course it lies in the angle between the quadratus lumborum, and the more nent psoas major medially (Fig. 957).

is situated chiefly in the right lumbar region, but it extends slightly into pochondrium above; and, although it usually begins about the level of the bercular plane, still with a low position of the cæcum it will extend further and may occupy a considerable part of the iliac region. length is extremely variable, depending upon the extent to which the cæcum ended from the position it occupied during development, viz., in contact under surface of the liver. from 5 to 8 inches long, and it is wider and more prominent than the ng colon. It generally presents several minor curves or flexures, and nas the appearance of being pushed into a space which is too short to ate it. ons.-Anteriorly, it is usually in contact with the abdominal wall, but the tine frequently intervenes, particularly above (Fig. 957). To its medial

coils of the small bowel and the psoas major; to the lateral side is the f the abdomen. Its posterior surface, which is free from peritoneum ig. 968), is connected by areolar tissue to the iliacus muscle as far up as

the ilium, to the quadratus lumborum above that, and finally to the of the right kidney. reat majority of cases only the two sides and the anterior surface are peritoneum, the posterior surface being destitute of a serous coat (Fig. small proportion of bodies, however, the ascending colon is provided -te peritoneal coat and a mesentery, but this latter is so short that it a slight amount of movement in the gut. teral aspect of the cæcum and colon there are occasionally found 1 pockets termed recessus paracolici.

n, the ascending colon is frequently found distended with gas or faces after rt its large size and prominence as compared with the descending colon, which

i Dextra.—The right (O.T. hepatic) flexure of the colon is the

large intestine between the end of the ascending colon and the transverse colon (Figs. 947 and 957). ending colon reaches the inferior surface of the liver, it bendsmetimes obtusely-forwards and to the left on the anterior surface ey, and on reaching the front of the descending portion of the into the transverse colon.

placed between the descending duodenum medially and the in of the liver, or the side wall of the abdomen, laterally; above, the colic impression on the liver, and posteriorly it rests on the oneal relations are similar to those of the ascending colon. ersum.-This is the long and looped portion of the large intestine

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