Small Intestine - Anatomy Flashcards
Where does the SI extend to and from?
From the pylorus of the stomach to the ileocaecal junction where it meets the LI at the ileocaecal valve
What are the 3 parts of the SI?
Duodenum, jejunum, ileum
Where does the duodenum run to and from?
From the pylorus of the stomach to the duodenojejunal junction.
Describe the first section (superior) of the duodenum
It ascends upwards from the pylorus of the stomach, and is connected to the liver by the hepatoduodenal ligament
The first part of the duodenum is intraperitoneal, with the remained being retroperitoneal (only covered anteriorly)
Describe the second section (descending) of the duodenum
Curves inferiorly around the head of the pancreas. It lies posteriorly to the transverse colon, and anterior to the right kidney.
What is the descending duodenum marked by internally?
The major duodenal papilla
What is the major duodenal papilla?
The opening at which bile and pancreatic secretions to enter from the ampulla of Vater (hepatopancreatic ampulla).
Describe the third section (inferior) of the duodenum?
Travels laterally to the left, crossing over the inferior vena cava and aorta. It is located inferiorly to the pancreas, and posteriorly to the superior mesenteric artery and vein
Describe the fourth section (ascending) of the duodenum?
After the duodenum crosses the aorta, it ascends and curves anteriorly to join the jejunum
Where does the duodenum meet the jejunum?
At the duodenojejunal flexure (sharp turn)
What is located at the duodenojejunal flexure?
The suspensory ligament of the duodenum / ligament of treitz
Piece of peritoneum (causing duodenum to ascend slightly)
What is a duodenal ulcer?
The erosion of the mucosa in the duodenum. It may also be described as a peptic ulcer (although this term can also be used to refer to ulcerations in the stomach)
Where are duodenal ulcers likely to occur?
In the superior portion of the duodenum.
What can the duodenum be divided into?
4 parts:
- Superior
- Descending
- Inferior
- Ascending
Together these parts form a ‘C’ shape, and which wraps around the head of the pancreas.
How are the jejunum and ileum attached to the posterior abdominal wall?
A mesentery
Where does the ileum end?
At the ileocaecal junction.
What is function of ileocaecal valve?
It can prevent reflux of material back into the ileum
Where is the jejunum/ileum located?
Upper left quadrant / lower right quadrant
Describe the wall of the jejunum/ileum
Thick / thin
Describe the vasa recta (straight arteries) of the jejunum/ileum
Longer / shorter
Describe the arcades (arterial loops) of the jejunum/ileum
Less arcades / more arcades
Describe the colour of the jejunum/ileum
Red / pink
What is the section of the duodenum proximal to the major duodenal papilla supplied by?
The gastroduodenal artery (branch of the coeliac trunk).
What is the section of the duodenum distal to the major duodenal papilla supplied by?
Supplied by the inferior pancreaticoduodenal artery (branch of superior mesenteric artery).
Why is the transition from proximal to distal to the major duodenal papilla important?
It marks the change from the embryological foregut to midgut
Where do the veins of the duodenum drain into?
The hepatic portal vein
Where is lymphatic drainage of the duodenum to?
The pancreatoduodenal and superior mesenteric nodes.
Where is the arterial supply to the jejunum and ileum from?
The superior mesenteric artery.
Where does the SMA arise from the aorta?
At level L1, immediately inferior to the coeliac trunk
What does the SMA branch into?
It moves in between layers of mesentery, splitting into approximately 20 branches. These branches anastomose to form loops, called arcades.
What arises from the arcades?
Long and straight arteries arise, called vasa recta.
What is venous drainage of the jejunum and ileum via?
The superior mesenteric vein
What does the SMV unite with?
The splenic vein at the neck of the pancreas to form the hepatic portal vein.
Where is lymphatic drainage of the jejunum and ileum into?
The superior mesenteric nodes.
