The retroperitoneum Flashcards
List the primary retro-peritoneal structures
Abdominal aorta and its branches Inferior vena cava and its tributaries Kidneys & ureters Adrenal glands Nerves (lumbar plexus & sympathetic trunk
What is meant by primary retroperitoneal structures
These structures developed outside the parietal peritoneum. They never had a mesentery.
List the secondary retroperitoneal structures and explain why they are secondary
Duodenum (except the first part) *
Pancreas (tail is INTRAperitoneal) *
Colon (ascending and descending only)*
- These organs originally had a mesentery, then became secondarily retroperitoneal when the mesentery fused with the body wall
Are any retroperitoneal structures found on the anterior abdominal wall
No- they are found on the posterior abdominal wall
Therefore we access the body posteriorly to perform biopsies of these organs
What is the first superimposed structure
the duodenum
Describe the first part of the duodenum
Superior
Extends from pyloric orifice to neck of gallbladder
Just to the right of L1
Passes anteriorly to bile duct, gastroduodenal artery, portal vein and IVC
5cm long
Why is the first part of the duodenum important clinically
Referred to as the ampulla or duodenal cap
Most duodenal ulcers occur in this part of the duodenum
Describe the second part of the duodenum
Right of midline extends from neck of gall bladder to the lower border of L3
Anterior surface is crossed by the transverse colon
Posterior to it is the right kidney
Medially is the head of the pancreas
This part contains the major duodenal papilla- entrance for bile and pancreatic ducts
Also contains minor duodenal papilla- entrance for accessory pancreatic duct
7-10cm
Where is the junction between the foregut and midgut found
Just below the major duodenal papilla
Describe the 3rd part of the duodenum
The inferior part- crosses the IVC, the aorta and vertebral column
It is crossed anteriorly by the superior mesenteric artery and vein
6-8cm
Describe the 4th part of the duodenum
Ascending
Passes upward on or to the left of the aorta to approximately the upper border of L2 and terminates at the duodenojejunal flexure
5cm
Describe the superimposed structures
Duodenum, pancreas and spleen are superimposed on the ‘background’ structures. All are retroperitoneal except the spleen and the tail of the pancreas.
What type of organ is the pancreas
Exocrine and endocrine gland
It is therefore a secretory organ
Describe the relations of the pancreas
It extends across from the posterior abdominal wall from the duodenum, on the right, to the spleen on the left
Lies mostly posterior to the stomach
Describe the head of the pancreas
Lies within C-shaped concavity of the duodenum
anterior to IVC
Describe the uncinate process
Projects from the lower part of the head
Passes posterior to the superior mesenteric vessels
But passes anterior to the IVC
Describe the neck of the pancreas
Anterior to the superior mesenteric vessels and IVC
Posterior to the neck is where the superior mesenteric vein and splenic vein join to form the portal vein
Describe the body of the pancreas
Elongate and extends from neck to tail
extends to the left side across the aorta to left kidney
Describe the tail of the pancreas
Passes between layers of the splenorenal ligament
kidney to spleen in dorsal foregut mesentery (lieno-renal or spleno-renal ligament)
Describe the pancreatic duct
Begins at tail
After entering the head it moves inferiorly and in the lower part of the head it joins the bile duct
This joining forms the hepatopancreatic ampulla (Ampulla of Vater), which enters the descending part of the duodenum at the major duodenal papilla
Surrounding the ampulla of vater is the sphincter of oddi- a collection of smooth muscle
Describe the accessory pancreatic duct
Empties into the duodenum just above the major duodenal papilla in the minor duodenal papilla
Presence of two ducts reflects the embryological origin of the pancreas
Describe the embryogenesis of the pancreas
Derived from buds growing into dorsal and ventral foregut mesenteries
At the foregut/midgut junction the septum transversum generates 2 pancreatic buds (dorsal and ventral endoderm) which will fuse to form the pancreas. The dorsal bud arises first and generates most of the pancreas. The ventral bud arises beside the bile duct and forms only part of the head and uncinate process of the pancreas.
Dorsal swings to the ventral