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9

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-Ensherah Mokheemer

-Shatha Al-Jaberi

محمد المحتسب-

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Small intestine

Small intestine has three regions:

• The duodenum ()االثني عشر

• The jejunum

• The ileum

Duodenum:

-c-shaped

-The concavity is backward to the

left.

-At the concavity of the

duodenum we have head of

pancreas.

-It is 10 inches in length which

equals 25 cm.

-It is divided into 4 parts:

part 2 inches st1

3 inches, vertical nd2

4 inches, horizontal rd3

1 inch th4

-Duodenum embryologically is

divided into upper half and lower

half:

*The upper part is from the

foregut and thus the blood

supply for it is from the celiac trunk. Whereas the lower half is

from the midgut and thus the blood supply is from the superior

mesenteric artery.

- It is important because it receives the opening of the bile and

pancreatic ducts.

Pyloric sphincter

Bile Duct

Pancreatic duct

Duodenum

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*common bile duct comes from the liver and gallbladder and the

pancreatic duct comes from the pancreas.

*Both ducts unite and enter the duodenum through an opening called

major duodenal papilla. There is an accessory pancreatic duct which

opens in the duodenum 1 inch above the major duodenal papilla

through an opening called minor duodenal papilla.

*The duct, which results from the joining of the pancreatic duct with the

common bile duct, has a sphincter called sphincter of Oddi (circular

smooth muscle), as the ducts move from medial to lateral and at the site

of their entry a bulge is formed which is called ampulla of Vater.

*So, we have 3 important terms:

1) The bulge on the medial side is called ampulla of vater.

2) The sphincter which is the sphincter

of Oddi.

3) The opening in the duodenum which

is the major duodenal papilla .

-Most of the duodenum is retroperitoneal (behind the peritoneum)

except the 1st inch & last inch.

*The 1st inch because it has the lesser omentum on its upper border, the

greater omentum on its lower border, and the lesser sac posterior to it.

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*Last inch because after it comes the jejunum which is covered by

mesentery.

-The bile comes from the bile salt in the liver through the right hepatic

duct and left hepatic duct, they both join to form the common hepatic

duct. The common hepatic duct along with the Cystic duct, which comes

from the gallbladder, unite at the ampulla forming the common bile

duct, which eventually will join the pancreatic duct forming a duct which

will open into the duodenal through the major duodenal opening(#4).

And there is a smaller duct which comes from the pancreas called

accessory pancreatic duct which enters the duodenum through the

minor duodenum opening(#5).

-The major duodenal opening is in the 2nd part of the duodenum.

-There is a variation between individuals related to the major duodenal

duct: what normally happens is that the common bile duct and the

pancreatic duct unite at the ampulla to form a single duct with a single

sphincter entering the duodenal through the major duodenal opening. In

some abnormal cases the common bile duct and the pancreatic duct do

not unite, and they enter the duodenal as two separate ducts each has

its own sphincter and opening, in some other cases the common bile

duct and the pancreatic duct unite before the ampulla forming

hepatopancreatic duct.

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-The bile which comes from the liver goes to the gallbladder, the

gallbladder reabsorbs water from the bile concentrating it (about 20

time). When there is secretion of bile the sphincter of Oddi is closed so

bile goes back to the gall bladder to be concentrated, and when

digestion is needed the sphincter opens and the concentrated bile goes

to the duodenum to help in the digestion especially fats. When the

gallbladder is surgically removed “Cholecystectomy” the secreted bile is

diluted so the patient is asked after the surgery to eat small meals with

low amount of fat.

- The duodenum is situated in the epigastric and umbilical regions.

-The pancreas is composed of 5 parts:

Tail (in close proximity with the spleen), Body,

Neck, Head, Unicate process.

**Behind the neck the superior

mesenteric vein and the splenic vein

meet to form the hepatic portal vein.

**The splenic artery is on the upper

border of pancreas.

**The superior mesenteric vein behind the body of the pancreas is on

the lateral side of the artery.

-The spleen has 2 surfaces one is visceral and the other is costal it is on

the ribs (9, 10, 11), so fracture in these ribs will cause rupturing in the

spleen.

The First part of the duodenal:

-it is 2 inches in length, in the 1st inch duodenal ulcers occur.

-It begins from the pyloduodenal junction at the level of transpyloric line

(on the level of L1), Runs upward and backward at the level of the 1st

lumbar vertebra 1 inch to the right.

Relations of 1st part of duodenum:

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❖ Anteriorly: Ascends upward backward to the liver, reaching the

neck of gallbladder so the right lobe will be anterior and above (so

the gallbladder and the right lobe will both be anterior to it).

❖ Superiorly: The epiploic foramen

❖ Posteriorly: The lesser omentum, gastroduodenal Artery (from the

common hepatic artery), the bile duct, portal vein and Inferior

vena cava.

**The gastroduodenal artery is a branch from common hepatic

artery, after passing behind the 1st part of the duodenum the

gastroduodenal artery gives the right gastroepiploic artery and

the superior pancreaticoduodenal artery. The superior

pancreaticoduodenal artery supplies blood to the upper half of

duodenum (because it comes from the celiac trunk) and pancreas.

** The bile duct after passing behind the 1st part penetrates the

head of pancreas, so it can open in the duodenum.

**portal vein behind the neck of pancreas

**Most posterior is inferior vena cava.

❖ Inferiorly: The head of pancreas.

The second part of duodenum (vertical part).

-starts from the visceral surface of the liver (the right lobe is anterior to

it), and it ends at lower border of L3 vertebrae (or between L3 and L4).

- It is 3” (3 inch) long

- halfway of it, the bile duct and the main pancreatic duct pierce the

medial wall, and then form the ampulla that opens in the major

duodenal papilla.

- Obstructive jaundice is a particular type of jaundice and occurs when

the essential flow of bile to the intestine is blocked and remains in the

bloodstream. This might be due to blocked bile ducts caused by

gallstones in the gallbladder. It is treated by a procedure called ERCP.

ERCP (Endoscopic Retrograde Cholangio-Pancreatography): The

procedure is performed by using a long, flexible, viewing instrument (a

duodenoscopy); the duodenoscope is inserted through the mouth,

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through the back of the throat, down the oesophagus, through the

stomach and into the duodenum. Once the papilla of Vater is

identified, a small plastic catheter (cannula) is passed through an open

channel of the endoscope into the opening of the papilla, and into the

bile ducts and/or the pancreatic duct and then plastic or metal stents

or tubing are inserted to relieve the obstruction of the bile ducts or

pancreatic duct ,the bile will go down the duodenum and excreted in

stool.

-can be also used to treat

pancreatic infections via

pancreatic duct

-The projection of the head of pancreas is called uncinate process it is behind the superior mesenteric vessels which originates from the Aorta behind the body of pancreas.

Relations of the second part of duodenum:

❖ Anteriorly: The gallbladder (fundus), Right lobe of the liver, Transverse colon, coils of small intestine (Especially the ileum).

❖ Posteriorly: The hilum of the right kidney along with the right Ureter which descends from it.

❖ Laterally: Right colic flexure, Ascending colon, Right lobe of the liver.

❖ Medially: Head of pancreas, Bile and pancreatic ducts.

The third part (the horizontal part):

-It is 4 inches in length.

-Above it is the pancreas, and the superior mesenteric cross it anteriorly.

-It is on the level of L3.

What we see in this figure is an

endoscopy of the duodenum we

notice that there are circular folds

of submucosa through mucosa in

the inner wall of the duodenum

they are called plicae circulars

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Relations of the third part:

❖ Anteriorly: The root of the mesentery of the small intestine (which starts from the level of L2 at one inch to the left it crosses the right sacroiliac joint, crossing the horizontal part at the level of L3), the superior mesenteric vessels contained within the mesentery, coils of jejunum ,part of the ileum.

❖ Posteriorly: The right ureter, the right psoas muscle, the inferior vena cava, the abdominal aorta.

❖ Superiorly: The head of the pancreas. ❖ Inferiorly: Coils of jejunum

The fourth part of duodenum:

-It is 1 inch in length.

- Runs upward to the left End in the duodejejunal junction at the level of the left. tolumbar vertebrae ndthe 2

- The junction (flexure) is held in position by the ligament of Treitz (landmark to the end of duodenum and beginning of jejunum, which is attached to the right crus of the diaphragm (duodenal recess).

Relation of the fourth part:

❖ Anteriorly: The beginning of the root of the mesentery - coils of the jejunum.

❖ Posteriorly: left psoas major, the sympathetic chain left margin of the aorta.

❖ Superiorly: Uncinate process of the pancreas.

Blood supply of duodenum

Upper half:(1st part +

upper1/2 of 2nd part) is

supplied by the superior

pancreaticoduodenal

artery, a branch of the

gastroduodenal artery.

-It is part of the foregut,

so it is supplied by

celiac trunk.

Lower half: (lower ½of 2nd

part +3rd +4th part) is

supplied by the inferior

pancreaticoduodenal

artery, a branch of the

superior mesenteric

artery.

-It is part of the midgut,

so it is supplied by

superior mesenteric

artery.

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** The Celiac trunk common hepatic artery gastroduodenal artery (behind first part of

deudenum) superior pancreaticoduodenal artery.

**Superior mesenteric artery inferior pancreaticoduodenal artery.

-The venous drainage of the duodenum follows the arteries (superior

pancreaticoduodenal vein for the upper half and the inferior

pancreaticoduodenal vein for the lower half). Ultimately these veins

drain into the portal system, either directly or indirectly through

the splenic or superior mesenteric vein.

* The inferior pancreaticoduodenal vein goes to the portal vein via the

superior mesenteric vein (indirectly).

*The superior pancreaticoduodenal vein goes to the portal vein directly

or indirectly via superior mesenteric vein (variation).

**Inferior mesenteric vein drains into the splenic vein or into the

junction (variation).

**the portal vein is formed by the union of the superior mesenteric vein

and the splenic vein behind the neck on pancreas.

The Lymphatic drainage:

• The lymph vessels follow the arteries:

The foregut: supplied by the celiac trunk via the superior pancreaticoduodenal

vessels.

The midgut supplied by the superior mesenteric artery via the inferior

pancreaticoduodenal vessels.

The hindgut: supplied by the inferior mesenteric vessels

The superior and inferior pancreaticoduodenal veins usually drain into the superior

mesenteric vein

The inferior mesenteric vein drains into the splenic vein.

Both the splenic vein and the superior mesenteric vein form the portal vein behind the

neck of pancreas.

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o Drain upward (foregut) via pancreaticoduodenal nodes the gastroduodenal nodes the celiac nodes (around the origin of celiac trunk).

o Drain downward (midgut) via pancreaticoduodenal nodes the superior mesenteric nodes around the origin of the superior mesenteric artery.

Nerve supply of duodenum:

o Sympathetic: postganglionic fibres from the celiac ganglia and the superior mesenteric ganglia.

o Parasympathetic: From vagus nerve which synapses in the myenteric plexus in the wall of intestine.

Jejunum and Ileum:

-Both jejunum and ileum are intraperitoneal organs, present in the free edge of mesentery.

-They are 6m in length and they are mobile.

-Their main function is absorption.

-They are supplied by the superior mesenteric artery and the venous drain is the superior mesenteric vein which drains into the portal vein to the liver.

- The jejunum begins at the duodenojejunal junction, the ileum ends at the ileocecal junction.

-The ileum ends in the right iliac fossa in the cecum.

-The jejunum is the upper part and the ileum is the lower part, but it is to the right, so it can end in the cecum, and they are in the umbilical region.

**If someone has inflammation in the small intestine the pain will be in the umbilical region.

Mesentery of the small intestine:

- fan-shaped fold of peritoneum.

-Its length is about 15cm.

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-It starts ate level of the 2nd lumbar vertebra one inch to the left and it ends in the right sacroiliac joint.

Remember that the superior mesenteric artery forms arcades and vasa recta in the mesentery.

The differences between the jejunum and the ileum:

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Blood supply of Jejunum & Ileum:

Arteries:

• The arterial supply is from branches of the superior

mesenteric artery.

• The intestinal branches arise from the left side of the artery and run in the mesentery to reach the gut.

• They anastomosis with one another to form a series of arcades.

• The lowest part of the ileum is also supplied by the ileocolic artery.

Veins:

• The veins correspond to the branches of the superior mesenteric artery

• Drain into the superior mesenteric vein.

Lymphatic Drainage of jejunum & ileum

The lymphatic drainage either goes to the celiac trunk for the foregut or superior mesenteric lymph nodes for the midgut which is present round the origin of the superior mesenteric artery from the anterior abdominal wall.

**The cisterna chyli: It is a lymphatic sac present under the diaphragm along with the opening of the abdominal aorta (Basically it is present on the left side of abdominal aorta orifice in the diaphragm).

Nerve Supply of jejunum & Ileum

• The nerves are derived from

parasympathetic (vagus):

Vagus starts from the medulla oblongata in the brain and descends downward and it does not synapse in the celiac ganglia it only synapses in the myenteric plexus in the wall of the organs and it controls the secretomotor activity of glands and the motor activity of smooth muscles for peristaltic movement.

Sympathetic: Vasoconstrictor of blood vessels and contraction of sphincter (Example sphincter of Oddi). As for the sympathetic it comes from ( T6-T9) Thoracic ganglia in the chest, as it descends it synapses in the celiac or superior mesenteric or inferior mesenteric ganglia, the

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post ganglionic fibres then goes and synapse with parasympathetic (vagus) fibres forming celiac plexus or superior mesenteric plexus or inferior mesenteric plexus and they go to the wall of the organs.

The plexus mentioned above consists of sympathetic and parasympathetic fibres.

• Nerves from the superior mesenteric plexus

The last topic we are going to cover in this lecture is Congenital anomaly of small intestine:

Meckel's Diverticulum: -a congenital anomaly of the ileum, it is a remnant of vitelline (vitellointestinal duct) duct of embryo. Normally this vitelline duct should be obliterated after delivery in some abnormal cases obliteration does not occur and as result of that Meckel’s Diverticulum is formed 2 feet’s away from the ileocecal junction and it is 2 inches in length and it occurs in 2% of the people.

-The tissue present inside the diverticulum is either gastric or pancreatic tissue.

-complications that might occur are: infections and ulcers, and ulcers might perforate; peritonitis also can result from the perforation of ulcer leading to bleeding (haemorrhage).

-The clinical picture of it is similar to the appendicitis: Pain in the right iliac fossa so it may be mistaken for appendicitis.

-During surgery the surgeon finds the appendices normal looks through the small intestine and finds Meckel’s Diverticulum so they remove it and then it’s done.

The End

Sorry for any mistake

Please do not forget to refer to the slides

Good Luck