Anatomy of the Duodenum, Pancreas and Spleen G. Skladzien, M.D. Fall 2007

Lecture objectives

• Understand the anatomic locations and relations of the duodenum, pancreas and spleen, the common blood supplies, innervation, venous, and lymphatic drainage

• Become familiar with clinical implications of the above anatomy that are based on the relations of the organs

Segments of the Duodenum

• 1st portion – superior, named duodenal bulb, on the left side of midline at level of L1, has no concentric folds, anterior wall exposed to peritoneal cavity, posterior wall overlies pancreas

• 2nd portion – descending, runs along Rt side of L2 L3 , joins with pancreatic and common bile ducts, wraps around head of pancreas

• 3rd portion – horizontal duodenum, crosses anterior to IVC, Aorta and behind Superior mesenteric artery at approx L3 L4 vertebral level

• 4th portion – ascending, passes to Left of aorta and joins jejunum

Blood supply of Duodenum and Pancreas

• Pancreatico duodenal a. anterior and posterior branch off of gastroduodenal a

• Arcade of vessels supply both duodenum and head of pancreas

• Same vessels also communicate with superior mesenteric artery

• This represents an anastomosis between the 2 major aortic branches through which collateral circulation occurs

Duodenal bulb- smooth NO circular folds

Post bulbar duodenum – plicae circulares Latin. circular folds

Functions of Duodenum

• Mixing of gastric content with enzymes from pancreas and bile

• Gastric acid is neutralized by pancreatic/biliary secretions

• Absorption of electrolytes and nutrients

Duodenum: common pathology: petic ulcer disease, commonly 2^o to H. pylori

Functions of pancreas

• Exocrine – production of enzymes which lyse protein, CHO, nucleic acids, fats thereby assisting absorption in small bowel – enzymes enter 2^nd portion of duodenum via pancreatic duct at major duodenal papilla

• Endocrine – intravascular release of insulin and glucagon (as well as others) from Islets of Langerhans (not derived from endoderm) which regulate glucose metabolism

Innervation of duodenum pancreas and spleen

• Parasympathetic – vagal fibers, stimulates peristalsis, secretion

• Sympathetic – by way of fibers from celiac ganglia, inhibits peristalsis promotes vasoconstriction

• Visceral pain is referred to epigastrium, many inflammatory or hemorrhagic processes will cause peritonitis or retro-peritonitis which irritates somatic nerve endings

biliary and pancreatic ducts
gallbladder, relation to duodenum

Important features: anterior view

• Note that the duodenum and pancreas wrap around SMA –due to midgut rotation

• the SMA crosses anterior to the 3^rd portion of duodenum

• The duodenal bulb rest on the pancreas – ulcers and tumors of the distal stomach or duodenum can invade pancreas

Important features: posterior view

• Note the portal vein forming posterior to the pancreas

• Note the common bile duct passing posterior to pancreatic head – tumors of the pancreatic head often present as “silent”/painless jaundice

• Pancreatic head tumors invade vital unresectable structures early in course

Variations of anatomy of Hepatico-pancreatic Ampulla

Hepatico-Pancreatic Ampulla

Arterial supply and venous drainage of the pancreas and spleen

Lymphatic drainage of the distal pancreas and spleen

Innervation of the distal pancreas and spleen

Spleen

• Large lymphoid organ (NOT lymph node) develops in dorsal mesentery of stomach

• Derives blood supply from splenic a. from celiac axis

• Venous return via splenic vn. drains into portal vn.

• Intraperitoneal – most of surface covered by peritoneum

• Located in LUQ –posterior to mid axillary line

• Normal sized spleen not palpable in adult

posterior

Splenic surfaces

Spleen is in contact with stomach, Lt kidney, Lt colic flexure, and diaphragm

Hilum is single area of entry of vessels, nerves, and lymphatics

Spleen: function

• Removes old or diseased red blood cells, white cells and platelets

• Site of origin of many antibody producing lymphocytes “B” cells

• Large macrophage population filters bacteria, fungi, parasites & viruses

Spleen

• Organ has pulp-like consistency and bleeds profusely when traumatized

• Hemorrhage from lacerated capsule or fracture spleen can be massive and life threatening necessitating surgical repair/removal

• Most common iatrogenic injury is in conjunction with Lt colonic and gastric surgery due to capsular tear from traction

• Trend is for conservative/non-operative repair in hemodynamically stable patients

Does the spleen move with respiration?

Anatomic/clinical importance of relationships of duodenum and pancreas

• Duodenum must also be removed when head of pancreas is removed for neoplasia

• Both are susceptible to blunt and penetrating abdominal trauma

• Blunt trauma may cause rupture of duodenum or fracture of pancreas due to pressure against spine

• When traumatized, duodenum, bile duct, and pancreas may release digestive enzymes into retroperitoneal tissues and cause life threatening septic shock syndromes

Anatomic/clinical importance of relationships of duodenum and pancreas

• Both are retroperitoneal except for anterior wall of duodenal bulb and small area of transverse duodenal wall

• Both share a common blood supply – pancreaticoduodenal arteries and veins

• pancreaticoduodenal arteries are an anastomosis between celiac trunk and superior mesenteric vessels - major arterial branches of aorta

Anatomic/clinical importance of relationships of pancreas and spleen

• Trauma to the spleen may also involve the tail of the pancreas

• Surgical removal of the spleen may endanger the tail of the pancreas

• Pancreatitis may result in thrombosis of the splenic vein, portal vein as well as compression of the duodenum or stomach

Anatomy of the Liver, Bile Ducts and Gallbladder

Lecture objectives

• Understand the gross structure of the liver and how it relates to its microscopic structure and function

• Understand the concept of the portal triad

• Know the lobes of the liver and the planes that divide them

• Become familiar with the gross anatomy of the gall bladder and biliary ducts and the common sites of mechanical obstruction

Micro architecture of the liver

Biliary anatomy

Attachments of the liver

• Coronary ligament- dome of Rt and medial Lt lobe to diaphragm

• Left triangular ligament – lt lateral segment to diaphragm

• Right triangular ligament- lateral aspect of Rt lobe to diaphragm

• Falciform ligament + round ligament (obliterated umbilical vein) –divides medial segments of Lt lobe from lateral segment

• Lesser omentum to stomach – forms part of the anterior wall of the lesser sac, is continuous medially with hepatoduodenal ligament

• Hepatoduodenal ligament – contains portal triad - common bile duct , hepatic a a branch of the celiac axis, portal vn leads into the hilum of the liver, all blood flow, innervation, lymphatics and bile pass through this structure

Attachments of the liver

Coronary ligament and perihepatic spaces

Porta Hepatis

• Hepatic portal vein - 70% blood flow to liver

• Hepatic artery – 30% blood flow-oxygenated

• Common bile duct

• Lymphatic vessels

• Hepatic nerve plexus

Functions of the liver > 200 known biochemical processes occur in liver, major ones are:

• Glucose storage as glycogen

• Gluconeogenesis

• Production of bile – detergent properties assist in fat absorption in intestine

• Lipoprotein and cholesterol synthesis

• Plasma protein and coagulation factor synthesis

• Macrophages clear bacteria and other foreign organisms from blood

• Conversion of ammonia to urea

• Removal of heme breakdown products from blood

• Drug metabolism

Lesser omentum and portal triad

Lobulation of liver

Hepatic veins drain directly into inferior vena cava

Lobulation and segmentation of the liver

• Surgical resection of the liver often performed for trauma or tumor, either primary or metastatic

• Understanding of the lobar and segmental anatomy allows removal of up to 75% of liver mass

• Liver is only organ capable of regeneration

Lymphatics of liver

The gallbladder

• Forms as a blind pouch off of common bile duct only cystic allows inflow or outflow

• Blood supply is cystic a., a branch of the Rt hepatic a.

• Venous drainage into liver and hepatoduodenal ligament – becomes markedly dilated in portal HTN

• Innervation via vagus – stimulates contraction (along with enteral hormones)

• Afferent nerves follow branches of sympathetics from celiac ganglion

Lymphatics of gallbladder and major bile ducts

Innervation of liver and gallbladder

Common clinical problems: hepatobiliary tract

• Gallstones

• Fatty liver (hepatic steatosis)

• Cirrhosis

• Liver metastases

cholelithiasis

• 2 types of stones, cholesterol and bilirubinate

• Stones cause blockage at narrow points in duct system

• Cystic duct obstruction causes cholecystitis

• Common bile duct obstruction > obstructive jaundice + possible gallstone pancreatitis

Portal-systemic collaterals

NO VALVES IN PORTAL VEIN

Does the liver move with respiration?

Does the gallbladder move with respiration?