Anatomy of the Intestines Flashcards
Is the duodenum mobile?
No
Where is the duodenum, in relation to the peritoneum?
- The proximal first segment is intraperitoneal
- The rest is secondarily retroperitoneal
Are the jejenum and ileum mobile?
Yes
Are the ascending and descending colon mobile?
No
Where are the ascending and descending colon, in relation to the peritoneum?
Secondarily retroperitoneal
Does the caecum have a mesentery?
No
What is the caecum commonly bound to?
The lateral abdominal wall
What is the caecum commonly bound to the lateral abdominal wall by?
A fold of peritoneum
What is the transverse colons mesentery called?
The transverse mesocolon
What is the transverse mesocolon adhered to?
The posterior wall of the omental bursa
How does the lumen diameter of the small intestine differ from the large intestine?
It is smaller
Describe the longitudinal muscle in the small intestine
Continuous layer
Describe the longitudinal muscle in the large intestine
Reduced to three bands- teniae coli
Does the small intestine have fatty tags?
No
Does the large intestine have fatty tags?
Yes, attached to its wall
What are the fatty tags of the large intestine called?
Appendices epiploicae
How does the wall of the small and large intestine differ?
- Small is smooth
- Large is sacculated
What does the saculated wall of the large intestine form?
Haustra
Describe the mucous membrane of the small intestine
Permanent folds
What are the mucous membrane folds of the small intestine called?
Plicae circulares
Describe the mucous membrane of the large intestine
Incomplete folds may be present
Describe the lymphoid tissue in the small intestine
Peyer’s patches
Describe the lymphoid tissue in the large intestine
None
How does the duodenum compare to the other sections of the small intestine?
- Shortest
- Widest
- Most fixed
How long is the duodenum?
25cm
What course does the duodenum persue?
A C-shaped course around the head of the pancreas
Where does the duodenum begin?
At the pylorus, on the right side
Where does the duodenum end?
At the duodenojejenal flexure (junction), on the left side
Where does the duodenojejunal junction occur?
At approximately the level of the L2 vertebrae, 2-3cm left of the midline
What does the duodenojejunal junction usually take the form of?
An acute angle
What is most of the duodenum fixed to?
The structures on the posterior abdominal wall
What fixes most of the duodenum to the posterior abdominal wall?
Peritoneum
What is the duodenum considered to be, with regards to the peritoneum?
Partly retroperitoneal
Label this diagram

- A - Liver
- B - Gallbladder
- C - Pylorus
- D - Duodenum
- E - Right colic flexure
- F - Duodenojejunal junction
- G - Ascending colon
- H - Stomach
- I - Pancreas
- J - Left colic flexure
- K - Transverse colon
- L - Jejenum
What parts is the duodenum considered to be divisible into?
- Superior part
- Descending part
- Inferior part
- Ascending part
How long is the superior part of the duodenum?
5cm
Where does the superior part of the duodenum lie?
Anterolateral to the body of the L1 vertebra
How long is the descending part of the duodenum?
7-10cm
Where does the descending part of the duodenum run?
Along the rght sides of L1-L3 vertebrae
How long is the inferior part of the duodenum?
6-8cm
Where does the inferior part of the duodenum cross?
The L3 vertebrae
How long is the ascending part of duodenum?
5cm
Where does the ascending part of the duodenum begin?
At the level of the L3 vertebra
What course does the ascending part of the duodenum take?
Rises superiorly as far as the superior border of the L2 vertebra
Label this diagram

- A - Hepatic portal vein
- B - Hepatic artery
- C - Bile duct
- D - Ampulla (duodenal cap)
- E - Supraduodenal artery
- F - Pylorus of stomach
- G - Gastroduodenal artery
- H - Anterior superior pancreaticduodenal artery
- I - Right gastro-epiploic artery
- J - Superior mesenteric vein and artery
- K - Anterior inferior pancreatico-duodenal artery
- L - Right colic artery and vein
- M - Ileocolic vein and artery
- N - Mesentery (cut edge)
- O - Middle colic artery
- P - Duodenojejunal junction
- Q - Pancreas
- R - Spleen
- S - Splenic vessels
- T - Oesophageal branches
- U - Left gastric artery and veins
- V - Lymph nodes
What is the duodenal cap/ampulla?
The first 2cm of the superior part of the duodenum
Where is the ampulla found?
Immediately distal to the pylorus
Does the ampulla have a mesentery?
Yes
Is the ampulla mobile?
Yes
Is the ampulla retroperitoneal?
No
What is the ampulla a common site of?
Ulceration
Why is the ampulla a common site of ulceration?
Because it is immediately distal to the pylorus
What can be a complication of an ampulla ulcer?
If the ulcer erodes backwards through the gastroduodenal artery, blood loss can be severe
What does the superior part of duodenum ascend from?
The pylorus
What is the superior part of the duodenum overlapped by?
The liver and gallbladder
Describe the relationship between the superior part of the duodenum and peritoneum?
- Peritoneum covers its anterior aspects
- It is bare of peritoneum posteriorly (exept for duodenal cap)
What does the the proximal part of the superior part of the duodenum have attached superiorly?
The hepatoduodenal ligament
What is the hepatoduodenal ligament part of?
The lesser omentum
What does the proximal part of the superior part of the duodenum have attached inferiorly?
The greater omentum
Where does the descending part of the duodenum run?
Inferiorly, curving around the head of the pancreas
What enters the descending part of the duodenum?
The bile and main pancreatic ducts
How do the bile and main pancreatic ducts enter the descending part of the duodenum?
Via the Ampulla of Vater
Where does the Ampulla of Vater enter the descending part of the duodenum?
Its posteromedial wall
Describe the relationship between the descending part of the duodenum and the peritoneum?
- It is entirely retroperitoneal
- The anterior surface of its proximal and distal thirds is covered with peritoneum
- The peritoneum reflects in its middle third
What is formed when the peritoneum reflects in the middle third of the descending part of the duodenum?
The double-layered mesentery of the transverse colon, the transverse mesocolon
How does the inferior part of the duodenum run?
Transversely right to left
What does the inferior part of the duodenum pass over?
The IVC, aorta, and L3 vertebra
What crosses the inferior part of the duodenum?
- The superior mesenteric artery and vein
- The root of the mesentery of the jejenum and ileum
Describe the relationship between the inferior part of the duodenum and the peritoneum
Is is completely covered in peritoneum apart from where structures cross it
What is the inferior part of the duodenum seperated from the vertebral column by?
- Right psoas major
- IVC
- Aorta
- Right testicular/ovarian vessels
Where does the ascending part of the duodenum run?
Superiorly, and along the left side of the aorta to reach the inferior border of the body of the pancreas
What happens to the ascending part of the duodenum when it reaches the inferior border of the body of the pancreas?
It curves anteriorly to join the jejenum at the duodenojejunal flexure
What is the ascending part of the duodenum spported by at the duodenojejunal flexure?
The attachment of a suspensory muscle of the duodenum (Ligament of Treitz)
What is the result of the contraction of the suspensory muscle of the duodenum?
It widens the flexure, facilitating movement
Where does the jejunum begin?
At the duodenojejenal flexure
What happens at the duodenojejunal flexure?
The digestive tract resumes an intraperitoneal course
Where does the ileum end?
The ileocaecal junction
How long are the jejunum and ileum together?
6-7m
What proportion of the intraperitoneal section of the small intestine is jejenum?
~2/5
What proportion of the intraperitoneal section of the small intestine is ileum?
3/5
Where does most of the jejeum lie?
In the left upper quadrant (LUQ) of the infracolic compartment
Where does most of the ileum lie?
In the right lower quadrant (RLQ)
Where does the terminal ileum usually lie?
In the pelvis
What happens to the terminal ileum in the pelvis?
It ascends, ending in the medial aspect of the cecum
What is the mesentery?
A fan-shaped fold of peritoneum
What does the mesentery do?
Attaches the jejenum and ileum to the posterior abdominal wall
What is found between the two layers of the mesentery?
- The superior mesenteric vessels
- Lymph nodes
- Variable amount of fat
- Autonomic nerves
What does the root of the mesentery cross?
- Ascending and inferior parts of duodenum
- Abdominal aorta
- IVC
- Right ureter
- Right psoas major
- Right testicular/ovarian vessels
Label this diagram

- A - Duodenum
- B - Duodenojejunal junction
- C - Ileocecal junction
- D - Cecum
- E - Appendix
What colour is the jejenum?
Deeper red
What colour is the ileum?
Paler pink
What is the diameter of the jejunum?
2-4cm
What is the diameter of the ileum?
2-3cm
How does the wall of the jejenum and ileum differ?
- Jejenum wall is thick and heavy
- Ileum wall is thin and light
Does the jejenum or ileum have greater vascularity?
Jejenum
How do the vasa recta in the jejenum and ileum differ?
- Long in jejenum
- Short in ileum
Describe the arcades of the jejunum
A few large loops
Describe the arcades in the ileum
Many short loops
Does the jejunum or ileum have more fat in the mesentery?
Ileum
Describe the circulae folds in the jejunum?
- Large
- Tall
- Closely packed
Describe the circulae folds in the ileum
- Low
- Sparse
- Absent in distal part
How many Peyer’s patches are in the jejenum?
Few
How many Peyers patches are in the ileum?
Many
What is the intestinal adult derivative of the foregut?
Duodenum (proximal to bile duct)
What is the intestinal adult derivative of the midgut?
- Duodenum (distal to bile duct)
- Jejunum/ileum
- Cecum/ascending colon
- Proximal 2/3 transverse colon
What is the intestinal adult derivative of the hindgut?
- Distal 1/3 transverse colon
- Descending/sigmoid colon
- Rectum/upper anal canal
What is the blood supply to the intestinal adult derivates of the foregut?
Celiac trunk
What is the blood supply to the intestinal adult derivates of the midgut?
Superior mesenteric artery and vein
What is the blood supply to the intestinal adult derivates of the hindgut?
Inferior mesenteric artery and vein
What is the duodenum dervied from?
Both midgut and foregut
- Proximal to bile duct, duodenum derived from foregut
- Distal to bile duct, derived from midgut
What is the blood supply to the duodenum proximal to the bile duct?
From the coeliac trunk, via the gastroduodenal artery and its branch the superior pancreaticoduodenal artery
Coeliac trunk -> Gastroduodenal -> Superior pancreaticoduodenal
What is the duodenum distal to the bile duct derived from?
The midgut
What is the blood supply of the duodenum distal to the bile duct?
From the superior mesenteric artery, through its branch the inferior pancreaticoduodenal artery
Abdominal aorta -> SMA -> Inferior Pancreaticoduodenal
Where do the pancreaticoduodenal arteries lie?
In a curve between the duodenum and the head of the pancreas
What do the veins of the duodenum follow?
The arteries
What do the veins of duodenum drain into?
The hepatic portal vein
- Some directly
- Some through the superior mesenteric and splenic veins
Label this diagram

- A - Right gastric artery
- B - Common hepatic artery
- C - Right gastro-omental artery
- D - Gastroduodenal artery
- E - Superior pancreaticoduodenal artery
- F - Posterior superior pancreaticoduodenal artery
- G - Anterior superior pancreaticoduodenal artery
- H - Duodenum
- I - Posterior inferior pancreaticoduodenal artery
- J - Anterior inferior pancreaticoduodenal artery
- K - Superior mesenteric artery
- L - Inferior pancreaticoduodenal artery
- M - Pancreas
- N - Splenic artery
- O - Left gastro-omental artery
- P - Spleen
- Q - Short gastric artery
- R - Left gastric artery
- S - Celiac trunk
What are the jejunum and ileum derived from embryological?
Midgut
What is the result of the jejunum and ileum both being derived from the midgut?
With regard to the arteries
Their blood supply is derived from the superior mesenteric artery, via the jejunal and ileal arteries
What does the jejunal artery arise from?
Abdominal aorta -> SMA
What does the ileal artery arise from?
Abdominal aorta -> SMA
Where does the SMA usually arise from the abdominal aorta?
At the level of the L1 vertebra, approx. 1cm inferior to the celiac trunk
Where does the superior mesenteric artery run?
Between the layers of the mesentery
How many branches does the superior mesenteric artery send to the jejunum and ileum?
15-18
What happens to the branches of the SMA sent to the jejunum and ileum?
These arteries unite to form loops or arches called arterial arcades
What do the arterial arcades give rise to?
Straight arteries called vasa recta
Label this diagram

- A - Hepatic portal vein
- B - Common hepatic artery
- C - Gastroduodenal artery
- D - Right gastro-omental artery
- E - Duodenum
F - Ileocolic artery - G - Ileal branch
- H - Cecum
- I - Appendix
- J - Celiac trunk
- K - Pancreas
- L - Superior mesenteric artery (SMA)
M - Superior mesenteric vein - N - Jejunum
- O - Jejunal arteries
- P - Arterial arcades
- Q - Ileal arteries
- R - Vasa recta (straight arteries)
- S - Ileum
Label this diagram

- A - Jejunum
- B - Windows
- C - Vasa recta
- D - Arterial arcades
Label this diagram

- A - Ileum
- B - Enroaching fat
- C - Vasa recta
- D - Arterial arcades
What does the large intestine consist of?
- Caecum
- Appendix
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
How can the large intestine be distinguished from the small intestine?
- Omental appendices
- Teniae coli
- Haustra
- Diameter
What are omental appendices?
Small, fatty, omentum like projections
What are teniae coli?
Three distinct longitudinal bands of muscle
Where do teniae coli begin?
At the appendix
How does the teniae coli begin at the appendix?
The appendixes longitudinal muscle splits into 3 bands
Where do teniae coli run?
The length of the large intestine
What happens to the teniae coli to terminate them?
Merge together again at the rectosigmoid junction into a continuous layer around the rectum
What are haustra?
Sacculations of the wall of the colon between teniae
How does the diameter of the large intestine differ to that of the small?
It is much larger
Label this diagram

- A - Right colic flexure
- B - Omental appendices
- C - Ascending colon
- D - Mesocolic tenia coli
- E - Ascending branch of ileocolic artery
- F - Anterior and posterior cecal branches of ileocolic artery
- G - Cecum
- H - Mesoappendix
- I - Appendicular artery
- J - Appendix
- K - Ileocolic artery
- L - Ileal branch of ileocolic artery
- M - Ileocecal recess and fold
- mi - Superior
- mii - inferior
- N - Transverse colon
- O - Omental tenia coli
- P - Semilunar folds
- Q - Haustra
- R - Left colic flexure
- S - Descending colon
- T - Free tenia coli
- U - Sigmoid colon
- V - Long omental appendices
- W - Rectum
- X - Anal canal
What is the caecum?
The first part of the large intestine
What is the caecum continuous with?
The ascending colon
What is the caecum continuous with?
The ascending colon
How could the caecum be described?
As a blind intestinal pouch
How big is the caecum?
Approx. 7.5cm in both length and breadth
Where does the caecum lie?
In the iliac fossa of the right lower quadrant of the abdomen, inferior to the junction of the terminal ileum and caecum (ileocaecal junction)
Is the caecum palpable through the anterolateral abdominal wall?
Under some circumstances
Under what circumstances is the caecum palpable through the anterolateral abdominal wall?
If distended with faeces or gas
How close is the caecum to the inguinal ligament?
Usually lies within 2.5cm of it
What is the relationship between the caecum and the peritoneum?
It is almost entirely enveloped by peritoneum
Is the caecum mobile?
Yes
Does the caecum have mesentery?
No
What is the result of the relative freedom of the caecum?
It can be displaced from the iliac fossa
What is the caecum commonly bound to?
The lateral abdominal wall
What is the caecum commonly bound to the lateral abdominal wall by?
One or more cecal folds of peritoneum
Label this diagram

- A - Cecal folds
- B - Ileal papilla
- C - Ileal orifice
- D - Ileum
- E - Opening of appendix
- F - Cecum
What is the appendix?
A blind intestinal diverticulum
How big is the appendix?
6-10cm
What does the appendix contain?
Masses of lymphoid tissue
What does the appendix arise from?
The posteromedial aspect of the caecum inferior to the ileocecal junction
Where does the appendix sit in relation to the caecum?
Usually retrocaecal, but its position is variable
Does the appendix have a mesentery?
Yes, the mesoappendix
Describe the mesoappendix
A short, triangular mesentery
What is the mesoappendix derived from?
The posterior side of the mesentery of the terminal ileum
What does the mesoappendix attached to?
The caecum and proximal part of the appendix
What is the caecum derived from embryologically?
Midgut
What is the result of the caecum being midgut derived?
With regards to its arterial supply
It receives its blood supply from the SMA, by way of the ileocolic artery
What is the ileocolic artery?
SMA terminal branch
What is the appendix derived from embryologically?
Midgut
What is the result of the appendix being midgut derived?
With respect to the arterial supply
It receives its blood supply from the SMA, by way of the appendicular artery
What is the venous drainage from the caecum and appendix?
Flows through a through a tributary of the SMV, the ileocolic vein
Label this diagram

- A - Superior mesenteric artery
- B - Middle colic artery
- C - Right colic artery
- D - Ileocolic artery
- E - Cecum
- F - Appendicular artery
- G - Appendix
- H - Superior rectal artery
Label this diagram

- A - Ileocolic vein
- B - Right colic vein
- C - Middle colic vein
- D - Superior mesenteric vein
- E - Hepatic portal vein
- F - Inferior mesenteric vein
- G - Left colic vein
- H - Sigmoid and recto-sigmoid veins
What are the parts of the colon?
- Ascending
- Transverse
- Descending
- Sigmoid
Where does the ascending colon pass?
Superiorly on the right side of the abdominal cavity, from the caecum to the right lobe of the liver
What happens to the ascending colon at the right lobe of the liver?
It turns to the left at the right colic flexure (hepatic flexure)
Where does the right colic flexure lie?
Deep to the 9th and 10th ribs
What is the right colic flexure overlapped by?
The inferior part of the liver
Is the caecum or the ascending colon narrower?
The ascending colon
What is the relationship between the ascending colon and the peritoneum?
- It is secondarily retroperitoneal along the right side of the posterior abdominal wall
- Covered by peritoneum anteriorly and on its sides
How is the ascending colon seperated from the anterolateral abdominal wall?
By the greater omentum
What % of people have a short mesentery of the ascending colon?
25%
What is the right paracolic gutter?
A deep vertical groove lined with parietal peritoneum in the ascending colon
Where does the right paracolic gutter lie?
Between the lateral aspect of the ascending colon and the adjacent abdominal wall
How does the transverse colon differ from the other parts of the colon?
- Longest
- Most mobile
How does the transverse colon cross the abdomen?
From the right to left colic flexures (splenic flexure)
What happens to the transverse colon at the left colic flexure?
It turns inferior before becoming the descending colon
How does the left colic flexure differ from the right colic flexure?
- More superior
- More acute
- Less mobile
Where does the left colic flexure lie?
Anterior to inferior part of the left kidney
What is the left colic flexure attached to?
The diaphragm
How is the left colic flexure attached to the diaphragm?
Through the phrenocolic ligament
Does the transverse colon have a mesentery?
Yes, the transverse mesocolon
What course does the transverse colon and its mesentery take?
Loops down, often inferior to the level of the iliac crests
What is the mesentery adherent to or fused with?
The posterior wall of the omental bursa
Where does the root of the transverse mesocolon lie?
Along the inferior border of the pancreas
What is the transverse mesocolon continuous with?
The parietal peritoneum posteriorly
Is the transverse colon freely moveable?
Yes
What is the result of the transverse colon being freely movable?
The transverse colon is variable in position
What position does the transverse colon usually take?
Hangs down to the level of the umbilicus (L3), but in tall, thin people, it may extend down into the pelvis
What is the relationship between the descending colon and the mesentery?
- It is secondarily retroperitoneal
- Covered by peritoneum anteriorly and laterally
What is the result of the peritoneal covering of the posterior descending colon?
Binds it to the posterior abdominal wall
Where is the descending colon found?
Between the left colic flexure and the left iliac fossa
What happens to the descending colon at the left iliac fossa?
It is continuous with the sigmoid colon
Where does the descending colon pass as it descends?
Anterior to the lateral border of the left kidney
What % of people have a short mesentery of the descending colon?
33%
What is the left paracolic gutter?
A deep vertical groove lined with parietal peritoneum in the descending colon
Where does the left paracolic gutter lie?
Between the lateral aspect of the ascending colon and the adjacent abdominal wall
What is the sigmoid colon characterised by?
Its S-shaped loop of variable length
What does the sigmoid colon link?
The descending colon and the rectum
Where does the sigmoid colon run?
From the iliac fossa to the S3 vertebrae
What indicates the rectosigmoid junction?
The terminatiation of the teniae coli
Where do the teniae coli terminate?
Approx. 15cm from the anus
Does the sigmoid colon have a mesentery?
Yes, usually long
What is the result of the sigmoid colons long mesentery?
It has considerable mobility, especially its middle part
What can the mobility of the sigmoid colon lead to?
Volvulus of the sigmoid colon
What does the root of the sigmoid mesocolon have?
An inverted V-shaped attachment
Where does the attachment of the sigmoid mesocolon extend?
Medially and superiorly along the external iliac vessels to the anterior aspect of the sacrum
What is found posterior to the apex of the root of the sigmoid mesocolon?
The left ureter and division of the left common iliac artery
What is the relationship between the left ureter and the divison of the left common iliac artery that lies posterior to the apex of the root of the sigmoid mesocolon?
Lie retroperitoneally