Anatomy Small Intestine

• Postion of the Pancreas:

  1. Retroperitoneal except the tail.
  2. Extends from the concavity of the duodenum to the hilum of the spleen.
  3. It crosses the transpyloric plane (L1).
• The Tail of the pancreas passes in the splenicorenal (lienorenal) ligament, i.e., it is intraperitoneal and comes in contact with the hilum of the spleen.
• The head of pancreas is below, while the tail above the transpyloric plane.
• The Head

  1. Lies within the concavity of the duodenum.
  2. The uncinate process is a part of the head that extends to the left behind the superior mesenteric vessels.
• Relations:

  1.Anteriorly: Transverse colon and mesocolon

  2. Superior mesenteric blood vessels cross in front of the uncinate process.

  3.Posteriorly: Common bile duct and right renal vein
• Neck of pancreas

  Relations:

  o Anteriorly: Pyloroduodenal junction.

  o Posteriorly: Beginning of portal vein (formed by union of splenic and superior mesenteric veins).
• Blood supply of Pancreas

  Arteries and Veins (Veins drain into portal vein)

  Splenic, superior and inferior pancreaticoduodenal

  Superior pancreaticoduodenal - anterior and posterior, branches of gastroduodenal

  Inferior pancreaticoduodenal branch of superior mesenteric (anterior and posterior branches)
• Lymph nodes situated along the arterial supply. The efferent vessels drain into celiac and superior mesenteric eventually.
• Nerve supply of pancreas -

  Sympathetic, T5-T9.

  Parasympathetic: vagus.
• Pancreatic Ducts

  1. The main duct (Duct of Wirsung): Begins in the tail and runs the whole length of the gland, receiving numerous tributaries. It joins the common bile duct to form the hepatopancreatico ampulla of Vater to open in the major duodenal papilla in the middle of the second part of the duodenum. This opening is surrounded by a physiological sphincter (Sphincter of Oddi).
• Pancreatic Ducts

  Accessory pancreatic duct (Santorini): When present, drains the upper part of the head and then opens into the minor duodenal papilla a short distance above the opening of the main duct. It frequently communicates with the main duct.
• Small Intestine (6-7m) - duodenum (10 inches) , jejunum and ileum

  Retroperitoneal except the first inch
• The first part of duodenum 2 inches at the level of L1

  The first inch has hepatoduodenal ligament (lesser omentum)- portal triad

  1. Hepatic artery proper
  2. common bile duct
  3. Portal Vein
• First part of duodenum

  Anteriorly

  1. quadrate lobe
  2. neck of gallbladder

  Posteriorly

  1. Lesser sace (1st Inch only)
  2. Gastroduodenal artery
  3. Bile duct
  4. Portal Vein
  5. IVC

  Superiorly:

  1. epiploic foramen

  Inferiorly:

  1. Pancreas
• Duodenal cap/ampulla

  1. First part which is slightly dilated - intraperitoneal which is 1 inch long
  2. Most common location of duodenal ulcers as it is where the acidic chyme meets the duodenal mucosa before mixing with the alkaline secretions of the duodenum
• Duodenal cap/ampulla

  1. Except for the 1st inch which is smooth, the mucous membrane of duodenum shows circular folds, called plicae circulares
  2. The second inch of the first part "disappears" behind the peritoneum.
• Second part of duodenum (3 inches) vertically down and slightly curved (L2 and L3)

  Overlies the hilus of right kidney

  1. Anteriorly, the second part is crossed about its middle by the attachment of transverse mesocolon.
  2. It is also related to the fundus of the gall bladder and the right lobe of the liver.
  3. Medial to the second part is the head of the pancreas.
• Pancreatic Ducts

  1. The posteromedial wall of the second part of the duodenum receives at about its middle the common opening of the common bile duct and the main pancreatic duct that unite to form a common ampulla (hepatopancreatic ampulla of Vater) that opens on the summit of the major duodenal papilla.
• 1. If an accessory pancreatic duct is present, it opens separately into the second part of the duodenum on the minor duodenal papilla located short distance above the hepatopancreatic ampulla.
• Accessory Pancreatic Duct - Santorini

  Stone Impaction -> infected bile -> Pancreas

  2 duodenal papilla - minor and major
• Third part of duodenum (4 inches)

  Horizontally to the left corssing the midline

  Posterior: relations (right and left): right psoas muscle, ureter, IVC and aorta

  Anteriorly (left third) it is corssed by root of the mesentery - superior mesenteric vessels

  Superiorly: 3rd part in contact with inferior border of head of pancreas
• Fourth part of body is 1 inch

  Turns obliquely upward on the left psoas muscles

  Posteriorly - related to the left margin of aorta to the right is the lumbar vertebral column

  Anteriorly and to the left are coils of jejunum

  The duodenojejunal flexure is fixed in its position by a peritoneal fold (ligament of Treitz), which is attached to the right crus of the diaphragm.
• Jejunum and Ileum - 6m

  Upper 2/5th is the jejnum

  Lower 3/5th is the ileum

  Connected to the posterior abdominal wall through mesentery which allows greater rnge of mobility
• Root of mesentery

  It runs obliquely downward from the left to the right at an angle of about 45o. It begins at the duodenojejunal junction at the level of L2 and terminates at the level of the right sacroiliac joint.

  This attachment is 6 inches (15 cm) long.
• Root of Mesentry

  Intestinal border is 6m

  Length is 15cm

  Depth is 20cm

  Crosses 3rd of part of the duodenum where the superior mesenteric vessels or their numerous branches or tributaries enter between its two layers, and then continues downward
• Root of Mesentery

  3rd part of duodenum

  Aorta and IVC

  Right psoas muscle, ureter and gonadal vessels
• In the living the jejunum can be distinguished from the ileum by the following features:

  1. Generally, the jejunum tends to stay in peritoneal cavity superiorly and to the left, the ileum inferiorly and to the right.
  2. The jejunum is wider bored, thicker walled, and redder than the ileum. The jejunal wall is thicker because the permanent foldings of the mucus membrane (plica circulares) are larger, more numerous, and closely set in the jejunum
• The jejunum mesenteric vessels form only one or two arcades (loops), with long and infrequent branches passing to the intestinal wall. The ileum receives numerous short terminal vessels that arise from a series of 3 or 4 or even more arcades. The "windows" between the arterial loops are called lunettes.
• At the jejunal end of the mesentery, the fat is deposited near the root and is scanty near the intestinal wall. Following the ileum distally, more of fat is found within the mesentery so that it extends from the root to the intestinal wall, more and more obscuring the arterial loops.
• Aggregations of lymphoid tissue (Peyer’s patches) are present in the mucous membrane of the lower ileum along the antimesenteric border.
• The jejunum and ileum in their entire length have (unlike the large intestine) a complete muscular coat, composed of two complete layers: the external (outer) longitudinal layer and the internal (inner) circular layer.
• Meckle´s DIverticulum

  Remnant of vitellointestinal duct, connecting primitive gut to yolk sac (4th week). It Disappears at (7th week).

  It is an outpouching of the terminal ileum, within two (2) feet from the ileocecal junction on the antimesenteric border.
• Meckel's diverticulum

  1. Disappear 2. fibrous cord 3. Cyst 4. Sinus 5. fistula
• Common Hepatic Artery

  1. Hepatic Artery Proper - Right and left hepatic and the left hepatic gives right gastric artery
  2. gastroduodenal Artery - Right gastroepiploic artery, Anterior superior pancreaticoduodenal, Posterior superior pancreaticoduodenal
• Blood supply to intestines

  Superior mesenteric artery (L1) branches off to inferior pancreaticoduodenal and 12-15 jejunal and ileal arteries