THE DUODENUM. 1019 
Paraduodenal Fossa (fossa of Landzert).—This fossa, which is best seen in the 
infant, is placed some distance to the left of the terminal part of the duodenum. It is 
produced by the inferior mesenteric vein raising up a fold of peritoneum, as it runs 
along the outer side of the fossa, and then inwards above it (see Fig. 689, where the vein, 
but not the fossa, is shown). It is limited below by a special fold (the mesenterico-meso- 
colic fold). According to Moynihan, this is the only fossa to the left of the duodenum 
capable of developing into the sac of a hernia; and when this occurs, the inferior 
mesenteric vein always lies in the anterior margin of the orifice of the sac (accompanied 
for some distance by the ascending branch of the left colic artery). 
.In addition to the above, a duodeno - jejunal fossa at the front of the duodeno- 
jejunal flexure, and five other fossx, have—perhaps unnecessarily—been described in 
this region. 
Peritoneal Relations of the Duodenum.—Whilst the relations of the peritoneum to the 
second and third portions of the duodenum are usually described as in the foregoing account, it 
should perhaps be pointed out, that it is not really the front, but the right half of the cireum- 
ference of the descending portion which has a serous coat. Similarly, it is the lower and 
anterior half of the circumference of the transverse part of the third portion which is clothed 
by peritoneum, whilst considerably more than half of the circumference of its ascending terminal 
part is covered ; for the peritoneum forms a fold running in behind this part, in addition to 
covering its left side and half its anterior aspect. 
Interior of Duodenum.—No valvul conniventes are found in the duodenum 
for an inch or two beyond the pylorus. Here they begin; at first as low, scattered, 
and irregular folds; further down, they gradually become larger, more regular, and 
more numerous ; and by the time the middle 
of the descending stage is reached they have 
attained a considerable development. In 
the lower part of the duodenum the folds 
are large, prominent, and closely set. 
On the inner aspect of the descending 
portion, about its middle—namely, 34 or 4 
inches (8°7 to 10 em.) beyond the pylorus 
—is seen a prominent papilla, on which the 
bile and pancreatic ducts open by a common 
orifice (Fig. 690). This is known as the 
bile papilla (papilla duodeni; caruncula 
major of Santorini). 
Hood-like 
valvula | 
connivens 
—— Bile papilla 
Common open- 
ing of bile and 
.. pancreatie duet 
—Frenulum 
The bile papilla is placed beneath, and protected Fic, 690.—THE BILE PAPILLA IN THE 
by, a prominent, hood-like valvula connivens, which INTERIOR OF THE DUODENUM. 
is situated immediately above it. From its lower 
margin a firm ridge of the mucous membrane (the plica longitudinalis duodeni) descends for 
a considerable distance, and acts as a frenum, which fixes the papilla and directs its apex 
somewhat downwards (Fig. 690). The papilla is prominent, and nipple or dome-shaped, and at 
its summit is placed the small orifice, which will usually admit the point of a pencil; the 
whole bears a close resemblance to the nozzle of a perfume-spray. 
Nearly an inch higher up, and invariably on the ventral side of the bile papilla (sometimes 
as much as a $ to ? inch distant), is seen a second and smaller papilla (the caruncula minor of 
Santorini), at the point of which is placed the very small orifice of the accessory pancreatic 
duct. This second papilla seems to be constantly present, although sometimes so small that it 
may easily escape detection unless carefully sought for. When well developed, it may have a 
hood-like valvula connivens and a little frenulum, like those of the bile papilla. 
Structure of the Duodenum.—tThe peritoneal coat, which is incomplete, has 
already been described in detail, in connection with each division of the duodenum. 
The muscular coat is well developed, and is pierced by the bile and pancreatic ducts, 
but otherwise calls for no special description. 
The submucosa differs from that of the rest of the small intestine, in that it con- 
tains, especially in the upper half of the duodenum, the glands of Brunner (glandule 
duodenales). These are small acinotubular glands, closely resembling the pyloric glands 
of the stomach, which lie in the submucous coat, and send their ducts through the 
Inuscularis mucose to open on the surface between Lieberkithn’s glands, or sometimes into 
these glands themselves (Fig. 684). They can be exposed by removing the peritoneal 
and muscular coats, and also some of the submucosa, when they appear as little round 
or flattened masses of a reddish gray colour, varying in size from =;'5th to ;4,th of an inch in 
