Foregut, midgut, and hindgut Flashcards
The foregut gets its blood supply from which artery?
Which vertebral level is this artery?
Coeliac trunk – T12
The midgut gets its blood supply from which artery?
Which vertebral level is this artery?
Superior mesenteric artery – L1
The hindgut gets its blood supply from which artery?
Which vertebral level is this artery?
Inferior mesenteric artery – L3
What are the boundaries of the foregut?
Lower oesophagus to the 2nd part of the duodenum / major duodenal papilla
What are the boundaries of the midgut?
2nd part of the duodenum to 2/3rd of the way across the transverse colon
What are the boundaries of the hindgut?
2/3rd of the way across the transverse colon to the upper anal canal
The upper oesophageal sphincter is at which vertebral level?
C6/7
Describe the types of muscle that make up the oesophagus, in terms of voluntary and automatic.
Skeletal muscle (voluntary) forms the upper 1/3rd and smooth muscle (automatic) forms the lower 2/3rd.
An ultrasound probe can be inserted into the oesophagus to view which chamber of the heart?
Left atrium
Describe how the vagus nerve travels into the abdomen with the oesophagus.
It wraps around the oesophagus as it splits into an anterior (left) vagal trunk and posterior (right) vagal trunk
What is the vertebral level of the oesophageal hiatus?
T11-12
Which structure forms the lower oesophageal sphincter?
Right crus of the diaphragm
What are the 3 main branches of the coeliac trunk?
Common hepatic
Left gastric
Splenic
Which 2 arteries does the common hepatic artery branch into?
Proper hepatic + gastroduodenal
Which artery branches off the proper hepatic artery?
Right gastric
Which 2 arteries does the gastroduodenal artery branch into?
Superior pancreaticoduodenal + right gastroepiploic
The left gastric artery gives off which branches?
Oesophageal branches
The splenic artery branches into which 2 structures?
Short gastric arteries + left gastroepiploic
The fundus of the stomach is supplied by which arteries?
Short gastric arteries
The gastroduodenal artery passes directly behind what?
What does this make the gastroduodenal artery susceptible to damage from?
1st part of the duodenum – a duodenal ulcer which erodes through the wall and into the artery
Describe the duodenum in terms of its peritoneal covering.
Retroperitoneal except for the 1st part
The duodenum spans which vertebral levels?
L1 – L3
Which structure holds up the duodeno-jejunal flexure?
Ligament of Treitz
The ligament of Treitz can be used as a marker to distinguish between what?
Upper and lower GI bleeds
Describe the blood supply to the duodenum.
Anterior and posterior superior pancreaticoduodenal arteries from the gastroduodenal artery
Anterior and posterior inferior pancreaticoduodenal arteries from the SMA.
If an aneurysm in the SMA was compressing the duodenum, which surgical procedure could be carried out to mobilise and reposition the duodenum?
What is this procedure known as?
Cut the ligament of Treitz
Strong’s procedure
Describe if each omentum develops from the dorsal or ventral mesentery.
Greater omentum – dorsal mesentery
Lesser omentum – ventral mesentery
What 3 things are found in the free lower edge of the lesser omentum, within the hepatoduodenal ligament?
Common bile duct
Hepatic artery
Portal vein
From which artery does the appendicular artery branch off?
Ileocolic artery
Which artery connects many of the distal portions of the SMA arteries?
Marginal artery
Describe the jejunum in terms of arterial arcades, vasa recta length, lumen size, and wall thickness.
Few arterial arcades
Long vasa recta
Wide lumen
Thick wall
Describe the ileum in terms of arterial arcades, vasa recta length, lumen size, and wall thickness.
Lots of arterial arcades
Short vasa recta
Smaller lumen
Thinner wall
Describe the peritoneal covering of the caecum.
Mostly intraperitoneal
Describe the peritoneal covering of the appendix.
Intraperitoneal
Describe the pain felt with appendicitis and why this happens.
Pain at the umbilicus which then moves to the right iliac fossa.
This is because early visceral pain is felt at the umbilicus since the appendix is a midgut structure, but later stage somatic pain is felt as the appendix inflames nearby parietal peritoneum in the right iliac fossa – McBurney’s point.
What is intussusception?
Proximal segment of bowel telescopes into an adjacent distal segment, dragging the mesentery with it
In which area of the bowel does intussusception typically occur?
Ileocaecal junction
What causes the formation of a Meckel’s diverticulum?
The vitelline duct fails to disappear and a remnant (diverticulum) of tissue remains attached to the ileum
Which section of the gut tube is prone to twisting on itself, and what is this pathology called?
Sigmoid colon – volvulus
What sign can be seen on imaging that suggests a colorectal adenocarcinoma?
Apple core sign
How can infections spread from under the diaphragm to the pelvic cavity and vice versa?
Via the paracolic gutters
What is the deepest and most superior part of the right paracolic gutter?
Hepatorenal recess
What are the 3 main branches of the IMA?
Left colic
Sigmoidal
Superior rectal
What is a watershed area?
A tissue that receives dual blood supply from the most distal branches of arteries
Where is the watershed area in the GI tract? What name is given to this area and what is it at risk of if something were to compromise either or both of its blood supplies?
The junction between the midgut and hindgut – 2/3rd way across transverse colon – known as Griffith’s point, and is at risk of ischaemia if either blood supply is compromised.
Describe lymphatic drainage from the GI tract.
Cisterna chyli - thoracic duct - left supraclavicular nodes - left subclavian vein
Which bony landmark signifies the transition from rectum to anal canal?
Tip of the coccyx
Which nerve innervates the external anal sphincter?
Pudendal nerve
In the anal canal, what does the pectinate line signify?
A change in nervous innervation
What is the innervation of the anal canal below the pectinate line?
Inferior rectal nerve
Describe the blood supply to the rectum.
Superior rectal artery from the IMA
Middle and inferior rectal arteries from the internal iliac artery
What are porto-systemic anastomoses?
Connections between veins that drain to the liver (via the portal vein) and veins that drain to the heart (via the IVC)
The inferior mesenteric vein drains into where?
Splenic vein
Give the 3 key areas of porto-systemic anastomoses.
Lower oesophagus
Upper anal canal
Umbilical region on anterior abdominal wall
If the liver became cirrhotic, given that the upper anal canal is an area of porto-systemic anastomoses, what pathology could this result in?
Anorectal varices
What is the commonly reported position of haemorrhoids?
3, 7 & 11 o’clock
Why is a tumour in the descending colon likely to present with symptoms sooner than a tumour in the ascending colon?
Stool in the descending colon is firmer and the lumen is narrower
The portal vein is formed by the union of what?
SMV + splenic vein
