what is duodenal perforation?
Perforations of the duodenum occur most often with ulcers on the anterior wall of the
duodenum. Perforations occur less often with ulcers on the posterior wall. However, posterior
wall perforations may erode the gastroduodenal artery causing severe hemorrhage and extend
into the pancreas. Clinical findings: Air under the diaphragm, pain radiates to the left shoulder.
_________ THE SMALL INTESTINE __________
The small intestine extends from the pylorus to the
ileocaecal junction. It is about 6 m long. The length is
greater in males than in females, and greater in
cadavers, due to loss of tone than in the living. It is
divided into
(a) an upper, fixed part, called the
duodenum, which measures about 25 cm in length; and
(b) a lower, mobile part, forming a very long
convoluted tube. The upper two-fifths of the mobile
intestine are known as the jejunum, and the lower three-
fifths are known as the ileum. The structure of the small
intestine is adapted for digestion and absorption.
Relevant Features
1. Large surface areai^For absorptien of digested
food a very large surface area is required. This is
achieved by (a) the great length of the intestine; and
(b) the presence of circular folds of mucous membrane,
villi and microvilli./
rThe circular folds of mucous membrane, plicae circulares, or
valves of Kerkring form complete or*"T--©\ incomplete circles.
These folds are permanent, and r ^ -j are not obliterated by
distension. They begin in the (p y second part of the duodenum,
and become large ^"^> and closely set below the level of the
major duodenal papilla. They continue to be closely set in the
proximal half of the jejunum, but diminish progressively in size
and number in the distal half of the jejunum and in the proximal
half of the ileum. They are almost absent in the distal half of the
ileunOApart from increasing the surface area for absorption, the
circular folds facilitate absorption by slowing down the passage
of intestinal contents.
The intestinal villi are finger-like projections of
mucous membrane, just visible to the naked eye. They
give the surface of the intestinal mucosa a velvety
appearance. They are large and numerous in the
duodenum and jejunum, but are smaller and fewer in the
ileum. They vary in density from 10 to 40 per square
millimetre, and are about 1 to 2 mm long. They increase
the surface area of the small intestine about eight times.
villus is covered by spHayer of absorptive
columnar cells. The surface of these cells has a striated
border which is seen, under the electron microscope to
be made of microvilli)
2. Intestinal glands or crypts of Lieberkuhn: These are
simple tubular glands distributed over the entire mucous
membrane of the jejunum and ileum. They open by
small circular apertures on the surface of mucous
membrane between the villi. They secrete digestive
enzymes and mucus. The epithelial cells deep in the
crypts show a high level of mitotic activity. The
proliferated cells gradually move towards the surface, to
be shed from the tips of the villi. In this way, the
complete epithelial lining of the intestine is replaced every two to four days.
The duodenal glands or Brunner's glands lie in the
submucosa. These are small, compound tubuloacinar
glands which secrete mucus.
3. Lymphatic follicles: The mucous membrane of
the small intestine contains two types of lymphatic
follicles. The solitary lymphatic follicles are 1 to 2
mm in diameter, and are distributed throughout
the small and large intestines. The aggregated
lymphatic follicles or Peyer's patches form circular
or oval patches, varying in length from 2 to 10 cm
and containing 10 to over 200 follicles. They are
largest and most numerous in the ileum, and are
small, circular and fewer in the distal jejunum.
They are placed lengthwise along the antim'esenteric
border of the intestine. Peyer's patches are ulcerated
in typhoid fever, forming oval ulcers with their long
axes along the long axis of the bowel}
Both the solitary and aggregated lymphatic follicles
are most numerous at puberty, but thereafter diminish in
size and number, although they may persist up to old
age.
Each villus has a central lymph vessel called a lacteal.
Lymph from lacteals drains into plexuses in the walls of
the gut and from there to regional lymph nodes.
4. The arterial supply to jejunum and ileum is derived
from the jejunal and ileal branches of the superior
mesenteric artery. The vasa recta are distributed
alternately to the opposite surfaces of the gut. They run
between the serous and muscular coats, and give off
numerous branches which supply and pierce the muscular
coat and form a plexus in the submucosa. From this
plexus, minute branches pass to the glands and villi. The
anastomosis between the terminal, intestinal branches is
poor .
5. The lymphatics (lacteals) have a circular course in
the walls of the intestine. Tuberculous ulcers and
subsequent strictures are due to involvement of these
lymphatics. Large lymphatic vessels formed at the
mesenteric border pass to the mesenteric lymph nodes.
6. The nerve supply of the small intestine is
sympathetic (T9 to Til) as well as parasympathetic
(vagus), both of which pass through the coeliac and
superior mesenteric plexuses. The nerves form the
myenteric plexus of Auefbach, containing
parasympathetic ganglia between the circular and
longitudinal muscle coats. Fibres from this plexus form
the submucous plexus of Meissner which also contains
parasympathetic ganglia. Sympathetic nerves are motor
to the sphincters and to the muscularis mucosae, and
inhibitory for peristaltic movements. The
parasympathetic nerves stimulate
peristalsis, but inhibit the sphincters. The nerve plexuses
and neurotransmitters of the gut are quite j complex.
These are now called the enteric nervous system.
7. The function of the small intestine comprises
digestion and absorption of the digested contents from
the fluid.
We will now consider the parts of the small
intestine one by one.
_______________THE DUODENUM_____________
what is duodenum?
The term duodenum is a Latin corruption of the Greek
word, dudekadaktulos, meaning twelve fingers.
Definition and Location
The duodenum is the shortest, widest and most fixed
part of the small intestine. It extends from the pylorus
to the duodenojejunal flexure. It is curved around the
head of the pancreas in the form of the letter 'C. The
duodenum lies above the level of the umbilicus,
opposite first, second and third lumbar vertebrae.
DISSECTION
Examine the C-shaped duodenum and head of
pancreas lying in its concavity . Cut
through the lower wall of the first part extending the
cut on medial wall of second and upper wall of third
part of duodenum to see its interior. Carefully look
for the longitudinal fold on the posteromedial wall
below the middle of second part. The longitudinal
fold is often covered by a circular fold containing
orifice of the major duodenal papilla draining both
the bile and pancreatic ducts. Identify and dissect the
structures related to all the four parts of the
duodenum.
Surface Marking
The duodenum is 2.5 cm wide, and lies above the
umbilicus. Its four parts are marked in the following
ways.
(a) First part : by two parallel lines 2.5 cm apart
extending from the pyloric orifice upwards and to
the right for 2.5 cm
(b) Second part : by similar lines on the right lateral
vertical plane extending from the end of the first
part downwards for 7.5 cm.
(c) Third part : by two transverse parallel lines 2.5
cm apart on the subcostal plane, extending
Location of the duodenum.
from the lower end of the second part towards the
left for 10 cm. It crosses the median plane above
the umbilicus. (d) Fourth part: by two lines
extending from the left end of the third part to the
duodenojejunal flexure which lies 1 cm below the
transpyloric plane, and 3 cm to the left of the
median plane. This part is 2.5 cm long.
length and Parts
Duodenum is 25 cm long and is divided into the i
following four parts (Fig. 20.3).
1. First or superior part, 5 cm long.
2. Second or descending part, 7.5 cm long.
3. Third or horizontal part, 10 cm long.
4. Fourth or ascending part, 2.5 cm long.
Parts of the duodenum.
Peritoneal Relations
The duodenum is mostly retroperitoneal and fixed,
except as its two ends where it is suspended by folds of
peritoneum, and is therefore, mobile. Anteriorly, the
duodenum is only partly covered with peritoneum.
Superior Part (First Part)
● The first 2 cm of the superior part is intraperitoneal and therefore has a mesentery and is
mobile; the remaining distal 3 cm of the superior part is retroperitoneal.
● Radiologists refer to the first 2 cm of the superior part of the duodenum as the duodenal cap
or bulb.
● The superior part begins at the pylorus of the stomach (gastroduodenal junction) which is
marked by the prepyloric vein.
● Posterior relationships include the common bile duct and gastroduodenal artery. The hep-
atoduodenal ligament attaches superiorly and the greater omentum attaches inferiorly.
The first part begins at the pylorus, and passes
backwards, upwards and to the right to meet the second
part at the superior duodenal flexure. Its relations are as
follows.
Peritoneal Relations
1. The proximal 2.5 cm is movable. It is attached to
the lesser omentum above, and to the greater
omentum below.
2. The distal 2.5 cm is fixed. It is retroperitoneal. It is
covered with peritoneum only on its anterior
aspect.
Visceral Relations
Anteriorly: Quadrate lobe of liver, and gall bladder
Posteriorly. Gastroduodenal artery, bile duct and
portal vein .
Superiorly : Epiploic foramen .
Interiorly : Head and neck of the pancreas.
Descending Part (Second Part)
● The descending part is retroperitoneal and receives the common bile duct and main pancre-
atic duct on its posterior/medial wall at the hepatopancreatic ampulla (ampulla of Vater).
Course
This part is about 7.5 cm long. It begins at the superior
duodenal flexure, passes downwards to reach the lower
border of the third lumbar vertebra, where it curves
towards the left at the inferior duodenal flexure, to
become continuous with the third part. Its relations are as
follows.
Peritoneal Relations
It is retroperitoneal and fixed. Its anterior surface is
covered with peritoneum, except near the middle,
where it is directly related to the colon.
Visceral Relations
Anteriorly : (a) Right lobe of the liver; (b) transverse
colon, (c) root of the transverse mesocolon, anffl (d)
small intestine .
Posteriorly: (a) Anterior surface of the right kidney
near the medial border, (b) right renal vessels, (c) right
edge of the inferior vena cava, (d) right psoas major
.
Medially : (a) Head of the pancreas and (b) the bile
duct .
Laterally : Right colic flexure .
The interior of the second part of the duodenum
shows the following special features.
1. The major duodenal papilla is an elevation present
posteromedially, 8 to 10 cm distal to the pylorus. The
hepatopancreatic ampulla opens at the summit of the
papilla.
2. The minor duodenal papilla is present 6 to 8 cm
distal to the pylorus, and presents the opening of the
accessory pancreatic duct .
Horizontal Part (Third Part)
● The horizontal part is retroperitoneal and runs horizontally across the L3 vertebra
between the superior mesenteric artery anteriorly and the aorta and inferior vena cava (IVC)
posteriorly.
● In severe abdominal injuries, this part of the duodenum may be crushed against the L3 vertebra.
Course
This part is about 10 cm long. It begins at the ! inferior
duodenal flexure, on the right side of the lower border
of the third lumbar vertebra. It passes almost
horizontally and slightly upwards in front of the
inferior vena cava, and ends by joining the fourth part
in front of the abdominal aorta. Its relations are as
follows .
Peritoneal Relations
It is retroperitoneal and fixed. Its anterior surface is
covered with peritoneum, except in the median plane,
where it is crossed by the superior mesenteric vessels
and by the root of the mesentery.
Visceral Relations
Anteriorly : (a) Superior mesenteric vessels and
(b) root of mesentery (Fig. 20.6A).
Posteriorly: (a) Right ureter, (b) right psoas major,
(c) right testicular or ovarian vessels, (d) inferior
vena cava, and (e) abdominal aorta with origin of
inferior msenteric artery.
Superiorly : Head of the pancreas with uncinate
process .
Inferiorly : Coils of jejunum.
Ascending Part (Fourth Part)
● The ascending part is intraperitoneal and ascends to meet the jejunum at the duodenojejunal junc-
tion which occurs approximately at the L2 vertebral level about 2 to 3 cm to the left of the midline.
● This junction usually forms an acute angle which is called the duodenojejunal flexure which
is supported by the ligament of Treitz (represents the cranial end of the dorsal mesentery).
● The ligament of Treitz serves as the anatomical landmark for the distinction between upper and
lower gastrointestinal (GI) tract bleeds.
Course
This part is 2.5 cm long. It runs upwards on or
immediately to the left of the aorta, up to the upper
border of the second lumbar vertebra, where it turns
forwards to become continuous with the jejunum at the
duodenojejunal flexure. Its relations are as follows.
Peritoneal Relations
It is mostly retroperitoneal, and covered with peritoneum
only anteriorly. The terminal part is suspended by the
uppermost part of the mesentery, and is mobile.
Visceral Relations
Anteriorly : (a) Transverse colon, (b) transverse
mesocolon, (c) lesser sac, and (d) stomach.
(Posteriorly : (a) Left sympathetic chain, (b) left psoas
major, (c) left renal vessels, (d) left testicular vessels,
and (e) inferior mesenteric vein
To the right: Attachment of the upper part of the root
of the mesentery .
To the left: (a) Left kidney and (b) left ureter.
Superiorly : Body of pancreas.
It is made up of : (a) Striped muscle fibres in its upper
part, (b) elastic fibres in its middle part, and (c) plain
muscle fibres in its lower part.
Normally its contraction increases the angle of the
duodenojejunal flexure. Sometimes it is attached only to
the flexure, and then its contraction may narrow the
angle of the flexure, causing partial obstruction of the
gut.
Arterial Supply
The arterial supply of the duodenum is from the following.
● Supraduodenal artery which supplies the upper portion of the duodenum (abdominal aorta →
celiac trunk → common hepatic artery → gastroduodenal artery → supraduodenal artery).
● Anterior and posterior superior pancreaticoduodenal arteries (abdominal aorta → celiac
trunk → common hepatic artery → gastroduodenal artery → anterior and posterior superior pancre-
aticoduodenal arteries).
● Anterior and posterior inferior pancreaticoduodenal arteries (abdominal aorta → superior
mesenteric artery → anterior and posterior inferior pancreaticoduodenal arteries).
The duodenum develops partly from the foregut and
partly from the midgut. The opening of the bile duct into
the second part of the duodenum represents the junction
of the foregut and the midgut. Upto the level of the
opening, the duodenum is supplied by the superior
pancreaticoduodenal artery, and below it by the inferior
pancreaticoduodenal artery .
The first part of the duodenum receives additional
supply from:
(a) The right gastric artery;
(b) the supraduodenal artery of Wilkie, which is usually a branch of the hepatic artery;
(c) the retroduodenal
branches of the gastroduodenal artery; and
(d) some branches from the right gastroepiploic artery.
Venous Drainage
The venous drainage of the duodenum is to the following.
● Anterior and posterior superior pancreaticoduodenal veins (anterior and posterior superior
pancreaticoduodenal veins → portal vein → hepatic sinusoids → central veins → hepatic veins →
inferior vena cava).
● Anterior and posterior inferior pancreaticoduodenal veins (anterior and posterior inferior pan-
creaticoduodenal veins → superior mesenteric vein → portal vein → hepatic sinusoids → central
veins → hepatic veins → inferior vena cava).
The veins of the duodenum drain into the splenic,
superior mesenteric and portal veins.
Lymphatic Drainage
Most of the lymph vessels from the duodenum end in
the pancreaticoduodenal nodes present along the inside
of the curve of the duodenum, i.e. at the junction of the
pancreas and the duodenum. From here the lymph
passes partly to the hepatic nodes, and through them to
the coeliac nodes; and partly to the superior mesenteric
nodes and ultimately via intestinal lymph trunk into the
cisterna chyli. Some vessels from the first part of the
duodenum drain into the pyloric nodes, and through
them to the hepatic nodes. Some vessels drain into the
hepatic nodes directly. All the lymph reaching the
hepatic nodes drains into the coeliac nodes.
Nerve Supply
Sympathetic nerves from thoracic ninth and tenth
spinal segments and parasympathetic nerves from the
vagus, pass through the coeliac plexus and reach the
duodenum along its arteries.
I
HISTOLOGY
[Mucous membrane: Shows evaginations in the form
of villi and invaginations to form crypts ofLieberkuhn.
Lining of villi is of columnar cells with microvilli.
Muscularis mucosae comprises two layers.
Submucosa is full of mucus secreting Brunner's
glands.) The muscularis externa comprises outer
longituainal and inner circular layer of muscle fibres.
Outermost layer is mostly connective tissue.
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