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1-موضوعات
عامة
2-أشعارى
3-مختارات شعرية و قصصية
4-مقالات أدبية
5-مقالات تاريخية و سياسية
6-شخصيات
7-إسلاميات
8-عروض الكتب
9-القسم الطبى
10-طب الأسنان
11-مدوناتى الخاصة
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The duodenum, jejunum and ileum make up the small intestine. We have already
discussed the duodenum.
Jejunum and Ileum
The jejunum and ileum is slung from the posterior abdominal wall by
the mesentery of the small intestines and,
therefore, is extremely mobile. The mesentery of the small intestine
arises from the root of the mesentery which
extends from the duodenojejunal flexure to the ileocecal junction.
The jejunum is about 2.5m (8ft) long and
passes imperceptibly into the ileum, which is
about 4m (12ft) long. this part of the small intestine occupies a central
position in the abdominal cavity, below the liver and the stomach, and
behind the transverse mesocolon, the
transverse colon and the
greater omentum. The lowest coils of the intestine lie in the
pelvic cavity. The purple dotted line
in the lower image is an arbitrary line that can be used to separate the
jejunum which is to the upward left of the line and the ileum which is to
the downward and right of the line. |
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Blood Supply to Ileum and Jejunum
The ileum and jejunum are supplied by the
superior mesenteric artery and its intestinal branches.
The branches are rather special in that small arcades are formed and from
the arcades, the straight vessels,
vasa recta arise and supply the intestine.
These straight vessels are end arteries and if they should be occluded,
the part of the intestine supplied by them will die.
One way to tell the ileum from the jejunum, other than by general
location, is that there are more layers of arcades before the vasa recta
are given off, in the ileum. |
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Liver
The liver is the largest gland of the body. It normally weighs about 1.5kg.
The sharp inferior border of the liver does not normally extend below the
right costal margin. If it does, it is enlarged. In order to free the liver
for study, you must cut the falciform ligament, superior and inferior parts of
the coronary ligament, the right and left triangular ligaments, the lesser
omentum and the structures in its free margin (common bile duct, proper
hepatic artery and portal vein) and the hepatic veins at the point where they
empty into the inferior vena cava.
This is an anterior view of the liver. You should identify the:
 | right lobe |
| cut edge of the falciform ligament |
| left lobe |
| diverging cut edges of the superior part of the
coronary ligament |
| fundus of the gall bladder |
|
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This an image of the visceral surface of the liver. Make sure you can
orient yourself properly. Check out to see where the fundus of the gall
bladder is located. Identify the following structures:
| right lobe |
| fundus of the gall bladder |
| cystic duct |
| portal vein |
| hepatic arteries |
| common bile duct |
| quadrate lobe |
| ligamentum teres |
| left lobe |
| ligamentum venosum and its groove |
| caudate lobe |
| groove for the inferior vena cava and the cut hepatic veins within
it |
| porta hepatis outline in yellow. The area where the arteries, ducts
and portal vein enter and leave the liver. |
|
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Finally we take a look at the superior aspect of the liver. This part
of the liver is separated from the heart by the domes of the diaphragm. In
this image, the anterior (diaphragmatic) surface of the liver is upward
and the visceral surface is downward on the page. This aspect allows you
to identify the:
| right lobe |
| cut edge of the falciform ligament |
| the cut edges of the superior and inferior parts of the
coronary ligament |
| the left triangular ligament |
| the right triangular ligament |
| bare area of the liver (where there is
no peritoneum covering the liver |
| groove for the inferior vena cava and
the hepatic veins |
| caudate lobe of the liver more or less
wrapping around the groove of the inferior vena cava |
|
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Separation of the four lobes of the liver:
| right sagittal fossa - groove for inferior vena cava and gall
bladder |
| left sagittal fissure - contains the ligamentum venosum and round
ligament of liver |
| transverse fissure (also porta hepatis) - bile ducts, portal vein,
hepatic arteries |
|
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| Relationship of the visceral aspect of the liver to other abdominal
viscera. |
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Biliary System
The biliary system is made up of the ducts arising in the liver, the
gall bladder and its duct and the common bile duct. Starting in the liver,
the small biliary ducts converge to form the larger
right and left hepatic ducts. These, in
turn, join to form the common hepatic duct
which joins with the cystic duct to form the
common bile duct. Remember, when we studied
the duodenum, that the common bile duct joins the major pancreatic duct to
empty into the ampulla which then empties into the second part (descending
part) of the duodenum.
The gall bladder receives bile from the liver
by way of the common hepatic duct into the cystic duct. The gall bladder
stores and concentrates its contents and also excretes its bile back
through the cystic duct to join the common hepatic duct to become the
common bile duct which then carries the bile into the duodenum.
The location of the tip of the fundus can be approximated on the surface
of the abdomen at the point where the lateral edge of the rectus abdominis
crosses the cartilage of the 9th rib. |
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List of Items to Know
Liver
| right lobe |
| left lobe |
| quadrate lobe |
| caudate lobe |
| falciform ligament
 | ligamentum teres of liver |
|
| coronary ligament
| right triangular ligament |
| left triangular ligament |
|
| porta hepatis
| common hepatic duct |
| portal vein |
| proper hepatic artery
 | left hepatic |
| right hepatic
| cystic |
|
|
| gall bladder
| fundus |
| cystic duct |
|
| ligamentum venosum or groove for the ligament |
|
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Celiac Trunk
| common hepatic artery
| proper hepatic artery
| left hepatic |
| right hepatic
| cystic artery |
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Structures of the Posterior Abdomen
Peritoneum
After the gastrointestinal tract is removed, what you have left in the
posterior abdomen are the cut edges of the peritoneum and the remaining
peritoneum that covers the "retroperitoneal" structures.
It is worth while to take a look at this type of image to appreciate just
how the various mesenteries are reflected from the posterior abdominal
wall as well as the diaphragm.
Identify the:
| coronary ligament and its triangular parts
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| cut edges of the transverse mesocolon
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| area where the ascending colon used to
be |
| cut edges of the sigmoid mesocolon |
| space where descending colon used to be
|
| root of the mesentery |
| duodenojejunal flexure |
|
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Retroperitoneal Structures of the Abdomen
After the mesentery has been cleaned from the posterior abdominal
wall, you can see the true retroperitoneal structures of the abdomen.
These are the great vessels and their branches, sympathetics, kidneys and
their ureters, and suprarenal glands.
You should be able to see the following structures:
| inferior vena cava (IVC)
| testicular (or ovarian) |
|
| aorta
| celiac trunk |
| superior mesenteric artery |
| inferior mesenteric artery |
| external iliac |
| internal iliac |
| testicular (or ovarian) |
|
| lumbar sympathetic chain |
| celiac ganglia |
| kidney
| ureter |
|
| suprarenal gland |
|
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Structure of the Kidney
When the kidney is opened, you can see the following structures:
| cortex |
| medulla
| renal columns |
| renal pyramid |
|
| interlobar arteries |
| renal papilla |
| minor calyx |
| major calyx |
| renal pelvis |
| ureter |
|
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Muscles and Nerves of the Posterior Abdominal Wall
Finally, with the kidneys and their related structures removed, you
can see the muscles that make up the posterior abdominal wall and the
branches of the the lower thoracic and lumbar nerves.
You should be able to point out the:
| diaphragm
| right and left parts of the diaphragm
|
| right crus |
| left crus |
| medial arcuate ligament arches over
the sympathetic trunk as it enters the abdomen and the upper fibers of
the psoas muscle. |
| lateral arcuate ligament arches over
the free tip of the twelfth rib and the subcostal nerve (T12) |
| median arcuate ligament arches over
the aorta and the cysterna chyli (a lymphatic sac that continues into
the thorax as the thoracic duct. |
|
| quadratus lumborum |
| psoas major |
| psoas minor (frequently absent) |
| iliacus |
| nerves
| sympathetic trunk |
| hypogastric plexus |
| T12 - subcostal |
| L1
| iliohypogastric |
| ilioinguinal |
|
| genitofemoral - lies on top of the
psoas major muscle |
| lateral femoral cutaneous |
| femoral - lateral to the psoas major
|
| obturator - medial to the psoas major
|
|
|
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Openings of the Diaphragm
The diaphragm has several structures passing through it and these openings
are found at different vertebral levels as follows:
| opening for inferior vena cava -
T8 |
| esophageal hiatus - T10
|
| aortic hiatus - T12
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Lumbosacral Plexus
The nerves of the posterior abdominal wall are branches of the
lumbosacral plexus. This plexus is shown in the adjacent image.
You should be able to identify the roots of the plexus:
L1 gives rise to the iliohypogastric and
ilioinguinal nerves.
L1 + L2 gives rise to the genitofemoral
nerve
L2 + L3 gives rise to the lateral femoral
cutaneous
L2 + L3 + L4 give rise to the femoral
and obturator nerves
L4 + L5 give rise to the lumbosacral trunk
which joins sacral nerves to form the sacral plexus.
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Arteries and Veins of the Posterior Abdomen
Immediately after the aorta enters the abdomen under the median
arcuate ligament, it gives rise to its first paired branches, the
inferior phrenic arteries.
You can break up the branches of the aorta into paired and unpaired
branches. The unpaired branches are:
| celiac trunk
| splenic - pancreas, spleen, fundus of
stomach, left part of greater curvature of stomach |
| left gastric - esophagus, lesser
curvature of the stomach |
| common hepatic - liver, gall bladder,
right side of lesser curvature of stomach, pancreas, duodenum, right
side of greater curvature of stomach |
|
| superior mesenteric - pancreas,
duodenum, jejunum, ileum, ascending colon, transverse colon |
| inferior mesenteric - descending colon,
sigmoid colon, upper rectum |
| median sacral |
|
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The paired branches supply the organs and muscular walls of the
abdomen as well as pelvic structures and the lower limb. They are:
| inferior phrenic
| superior phrenic |
|
| middle suprarenal |
| renal
| inferior phrenic |
|
| lumbar |
| common iliacs
| external iliac
| deep circumflex iliac |
| inferior epigastric |
|
| internal iliac - studied with pelvis
|
|
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The veins all drain into the inferior vena cava and thus
back to the heart. The major veins are:
| external iliac |
| internal iliac |
| common iliac |
| lumbar veins |
| left renal vein
| left testicular or ovarian vein |
| suprarenal vein |
|
| right renal vein
| suprarenal vein |
|
| hepatic veins |
| inferior vena cava |
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Duodenum
The duodenum, into which the stomach opens, is about 25 cm long, C-shaped
and begins at the pyloric sphincter. It is almost entirely retroperitoneal and
is the most fixed part of the small intestine.
The duodenum is described as having four parts:
- Part one, superior part (SD)
- Part two, descending part (DD)
- Part three, horizontal part (HD)
- part four, ascending part (AD)
The fourth part of the duodenum terminates at the duodenojejunal
flexure DJF with the jejunum.
The ligament of Treitz is a musculofibrous
band that extends from the upper aspect of the ascending part of the
duodenum to the right crus of the diaphragm and tissue around the celiac
artery.
|
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Blood Supply of the Duodenum
| superior pancreaticoduodenal
| anterior and posterior branches |
|
| inferior pancreaticoduodenal
| anterior and posterior branches |
Most duodenal ulcers occur within 5 cm of the pylorus and most frequently
on the anterior wall.
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The Celiac Trunk
The abdominal viscera and associated organs are supplied by three branches
of the abdominal aorta. These are unpaired branches that, for the most part,
arise from the anterior part of the aorta. The first of these branches is the
celiac trunk (or artery).
Large Intestine
The large intestine extends from the ileocecal junction to the anus
and is about 1.5m long. On the surface, you can identify bands of
longitudinal muscle fibers called taeniae coli,
each about 5mm wide. There are three bands and they start at the base of
the appendix and extend from the cecum to the rectum. Along the sides of
the taeniae, you will find tags of peritoneum filled with fat, called
epiploic appendages (or appendices
epiploicae). The sacculations, called haustra,
are characteristic features of the large intestine, and distinguish it
from the rest of the intestinal tract.
The large intestine consists of the following parts:
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum Not seen in diagram.
- anal canal Not seen in diagram.
- anus Not seen in diagram.
There are two flexures associated with the colon:
- right colic flexure or hepatic flexure
- left colic flexure or splenic flexure
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The cecum is about 6cm long and is a blind
cul-de-sac which lies in the right
iliac fossa. It is the part of the colon below the opening of the ileum
into the colon. The cecum lies immediately behind the abdominal wall and
greater omentum. There is frequently a peritoneal recess behind the cecum
called the retrocecal recess and the appendix
is sometimes hiding within this recess and may extend as far superiorly as
the liver.
Hanging off the cecum is the vermiform appendix
which opens into the cecum about 2cm below the ileocecal opening. The
average length of the appendix is about 10cm and may lie in different
positions. It has its own mesentery called the
mesoappendix which carries the appendicular artery.
If the cecum is opened, you can identify the opening of the ileum into the
cecum. This opening is surrounded by thickened muscle which forms the
iliocolic valve. In this image, you can see
the first part of the ascending colon with its
semilunar folds. |
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Arterial Supply of the Colon
| The colon is supplied by branches of the superior
mesenteric and inferior mesenteric
arteries.
|
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Venous Drainage of the Gastrointestinal Tract
The venous drainage of the gastrointestinal tract, from the lower esophagus
to the upper rectum is by way of the portal venous system. This system also
drains the spleen and pancreas.
The portal vein is usually described as being formed by the splenic
and superior mesenteric veins. The inferior mesenteric vein then joins the
splenic vein. However, there are variations to this pattern and might
exist. Two of these are that the inferior mesenteric vein may join at the
junction of the splenic with the superior mesenteric or the inferior
mesenteric veins may join the superior mesenteric vein before it merges
with the splenic. Identify the:
| superior rectal vein |
| inferior mesenteric vein |
| splenic vein |
| superior mesenteric vein |
| esophageal veins |
| left gastric vein |
| portal vein |
The numbered stars represent the areas where the portal venous system
anastomoses with the caval venous system and are clinically important in
portal or caval hypertension.
- esophageal plexus - caval drainage into
azygos veins, portal drainage into the left gastric vein
- rectal plexus - caval drainage into
middle and inferior rectal veins and then into the pudendal and internal
iliac veins back to inferior vena cava, portal drainage into the
superior rectal, the inferior mesenteric and the splenic
- paraumbilical veins - caval drainage
downward to the superficial inferior epigastric vein to the femoral
vein, to the external iliac, to the inferior vena cava, upward to the
thoracoepigastric vein, the lateral thoracic vein, subclavian vein,
superior vena cava, portal drainage through the paraumbilical vein to
the portal vein.
|
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Clinical Consideration
Portal obstruction. In cases of liver disease
where the portal blood can no longer pass through the liver, the blood will
try to get back to the heart any way it can and this usually involves the
superior or inferior venae cavae. One possible cause of liver disease is
chronic alcoholism. When the liver becomes impassable, it will pass
backwards through the portal vein into the left gastric, paraumbilical or
superior rectal. At each of these sites, the veins become enlarged and will
result in other clinical signs and symptoms.
In case of the esophageal plexus (*1),
esophageal varices will develop and massive hemorrhage may occur resulting
in death.
In case of the rectal plexus (*2), hemorrhoids
occur, resulting in pain and bleeding.
In case of the paraumbilical veins (*3), visible
signs of venous enlargement and tortuosity occur on the abdomen and these
are referred to the caput medusae.
Caval blockage. In cases where tumors or other
pathologies compress the vena cava, the blood will utilize the above
connections to return blood to the heart but this time through the caval
system.
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