GI Tract Flashcards
Where does the oesophagus originate and terminate, and what levels are these?
Originate - cricoid cartilage C6
Terminate - cardiac orifice T11
Where does the oesophagus pass through the diaphragm?
T10 - oesophageal hiatus
What kind of sphincter is the LOS?
A physiological sphincter, formed by four phenomena:
- oesophagus enters the stomach at an acute angle
- positive intra-abdominal pressure
- folds of mucosa aid in occluding the lumen
- right crus of diaphragm has a ‘pinch-cock’ effect
Where does the foregut, midgut and hindgut start and end?
Foregut: stomach - duodenum proximal to 2nd part of duodenum (includes liver, gall bladder, pancreas and spleen)
Midgut: 2nd part of duodenum - distal 1/3rd of transverse colon
Highgut: distal 1/3rd of transverse colon - proximal anus
What is the main arterial supply to the foregut, midgut and hindgut?
Foregut - coeliac trunk
Midgut - superior mesenteric artery
Hindgut - inferior mesenteric artery
What are there 3 divisions of the coeliac trunk?
What level is the coeliac trunk?
Left gastric artery
Splenic artery
Common hepatic artery
Level of L1
At what level does the superior mesenteric artery arise?
Inferior of L1
At what level does the inferior mesenteric artery arise?
Inferior border of L3
Where do all the veins from the gut drain into?
What are the two veins that converge to make this vein?
Hepatic portal vein
Made by the meeting of: splenic vein and superior mesenteric vein
What is the lymphatic drainage of the different embryological structures in the gut:
Foregut - coeliac nodes
Midgut - superior mesenteric nodes
Hindgut - inferior mesenteric nodes
All these nodes drain into the intestinal trunk, which empties into the cysterna chyli at the end of the thoracic duct. The thoracic duct then drains into the venous system at the left subclavian vein
What is the autonomic sympathetic supply of the foregut?
Preganglionic fibres originate from T5-T9
Nerve fibres are carried in the greater splanchnic nerve
Fibres synapse at the coeliac ganglion
What is the autonomic sympathetic supply of the midgut?
Preganglionic nerve fibres arise from T10-T11
Nerve fibres are conveyed in the lesser splanchnic nerve
Fibres synpase at the superior mesenteric ganglion
What is the autonomic sympathetic supply of the hindgut?
Preganglionic fibres arise from T12-L1
Nerve fibres are conveyed in the lumbar splanchnic nerve
Fibres synapse at the inferior mesenteric ganglion
Where does referred pain from abdominal viscera perceived for the specific regions?
Foregut structures - epigastric region
Midgut structures - umbilical region
Hindgut structures - hypogastric region
What regions of the abdomen does the stomach lie in?
Epigastric, umbilical, left hypochondriac
What are the four main regions of the stomach?
Cardia
Fundus
Body
Pylorus
What is the cardial notch?
The superior angle created when the oesophagus enters the stomach
What is the angular incisure
A bend on the lesser curvature
What 2 things attach to the greater curvature of the stomach?
The gastrosplenic ligament
The greater omentum
What is the blood supply of the greater curvature of the stomach?
Short gastric arteries - supplies the fundus
Left gastro-omental artery - supplies the upper greater curvature
Right gastro-omental artery - supplies the lower greater curvature
What 2 things attach to the lesser curvature of the stomach?
Hepatogastric ligament
Lesser omentum
What is the blood supply of the lesser curvature of the stomach
Left gastric artery (branch of coeliac trunk) - supplies upper lesser curvature
Right gastric artery (branch of common hepatic artery) - supplies lower lesser curvature
What are the three muscular layers of the stomach?
Outer longitudinal
Middle circular
Inner Oblique muscle
What is the interior structure of the stomach composed of and what is their function?
Gastric folds - known as rugae.
They provide elasticity to the stomach, allowing it to expand and increase in volume without increasing in pressure
When does the common hepatic artery become the hepatic artery proper?
Once it has given off the gastroduodenal artery
From what branches do the right and left gastroepiploic arteries arise?
Right gastroepiploic - gastroduodenal artery
Left gastroepiploic - splenic artery
Where do the veins draining the stomach drain into?
Right and left gastric veins - drain into the hepatic portal vein
Short gastric vein, right and left gastroepiploic veins - drain into the superior mesenteric vein (which then drains into the hepatic portal vein)
Name the three parts of the small intestine in order
Duodenum
Jejeunum
Ileum
What are the 4 parts of the duodenum and what level are they found at?
Superior (L1)
Descending (L1-L3)
Inferior (L3)
Ascending (L3-L2)
What is the most common site for ulceration in the duodenum?
Superior part
What is the first part of the duodenum clinically referred as?
The duodenal cap
Which part of the duodenum contains the major and minor duodenal papilla?
Second part (descending part)
What enters the duodenum at the major and minor duodenal papilla’?
Major duodenal papilla - bile and pancreatic duct
Minor duodenal papilla - accessory pancreatic duct
Which part of the duodenum does the transition from the foregut to the midgut occur?
2nd part (descending)
Just below the major duodenal papilla
What is the longest section of the duodenum?
3rd part (inferior/horizontal)
What structure is located at the duodejujunal flexure?
Suspensory muscle (ligament) of duodenum - when it contracts it widens the angle of the flexure to aid movement into the jejunum
What are the 2 main arteries that supply the duodenum and which parts do they supply
Gastroduodenal - supplies proximal to the major duodenal papilla (foregut)
Superior mesenteric - supplies distal to the major duodenal papilla (midgut)
What are the 3 branches of the gastroduodenal artery that supply the duodenum proximal to the major duodenal papilla?
Supraduodenal
Anterior superior pancreaticoduodenal
Posterior superior pancreaticoduodenal
What are the 3 branches of the superior mesenteric artery that supply the duodenum distal to the major duodenal papilla?
Anterior inferior pancreaticoduodenal
Posterior inferior pancreaticoduodenal
First jejunal branch
Where does the lymph from the duodenum drain?
Pancreatoduodenal nodes
Superior mesenteric nodes
How are the the jejunum and ileum divided into fifths?
Jejunum - proximal 2/5ths
Ileum - distal 3/5ths
What are the major differences between the jejunum and the ileum?
Jejunum is located in left upper quadrant, while the ileum is located in the right lower quadrant
Jejunum is darker (red), while the ileum is lighter (pink)
Jejunum has thicker walls, ileum has thinner walls
Jejunum has lots of plicae circulares, Ileum has few plicae circulares
Jejunum has less fat in mesentery, ileum has more fat in mesentery
What is the blood supply to the jejeunum and ileum and how does it differ?
Both are supplied by the superior mesenteric artery branches forming arcades and vasa recta
Jejunum - less arcades and longer vasa recta
Ileum - more arcades and shorter vasa recta
Is the cecum an intraperitoneal or retroperitoneal structure and why?
Intraperitoneal structure, because of its motility (not because it is is suspended by a mesentery)
What is the appendix attached to?
The cecum
It is also suspended from the terminal ileum by the mesoappendix
How does the lumen of the appendix change during age?
It is wide in young childhood, narrow in adolescence is virtually obliterated by middle age
Why are adolescents more prone to appendicitis?
Because at this age the appendix is narrow
What are teniae coli?
Three distinct strips of muscle present on the large intestine (colon) formed from the outer longitudinal fibres of the Muscularis Externa
What are epiploic appendages?
Small fat filled sacs that project from the outer wall of the colon
What are the most common positions of the appendix?
Retrocaecal (behind the cecum) - 11 o clock
Subileal (parallel with the terminal ileum) - 3 o clock
What is McBurney’s Point?
The junction of the lateral and middle 1/3rd of a line from the anterior superior iliac spine to the umbilicus
This is where the base of the appendix is, and people with appendicular problems may describe pain near this point
What is the arterial supply of the cecum and appendix?
Ileocolic artery - a branch of the superior mesenteric artery
Splits into three branches:
Anterior and posterior cecel - Supplies the cecum
Appendicular artery - supplies the appendix
Where does lymph from the cecum and appendix drain?
Upper and lower iliocolic lymph nodes
Both drain into the superior mesenteric lymph nodes
What are there distinctive features of the colon?
Haustra
Taeniae coli
Epiploic appendages
What structure is attached to the lower border of the transverse colon?
Greater omentum
What is the arterial supply to the ascending colon?
Ileocolic artery - from superior mesenteric artery
Right colic artery - from superior mesenteric artery
What is the arterial supply to the transverse colon?
Right colic artery - from superior mesenteric artery
Middle colic artery - from superior mesenteric artery
Left colic artery - from inferior mesenteric artery
What is the arterial supply to the descending colon?
Left colic artery - branch from inferior mesenteric artery
At what vertebral level does the rectum lie?
S3-S5 and the coccyx
What are the two major flexures in the rectum?
Sacral flexure - follows the curve of sacrum and coccyx
Anorectal flexure - the angle where the rectum pieces the diaphragm (formed by the pulling of the puborectalis portion of the levator ani muscle)
How do the pouches behind the rectum differ in males and females?
Males - rectovesical pouch
Females - rectouterine pouch
What is the arterial supply to the rectum?
Superior rectal artery - from inferior mesenteric artery
Middle rectal artery - from the internal iliac artery
Inferior rectal artery - from internal pudendal artery
What is the venous drainage of the rectum?
Superior rectal vein - drains into portal system
Middle and inferior rectal vein - drains into systemic venous system
(This is a site of portocaval anastomosis)
What are the 2 sphincters present in the anal canal and how are they controlled?
Internal anal sphincter - upper 2/3rds of anal canal (controlled by involuntary smooth muscle)
External anal sphincter - lower 2/3rds of anal canal (controlled voluntarily by skeletal puborectalis muscle)
What is the anorectal ring?
This is found at the junction of the rectum to the anal canal and is formed by the fusion of the internal anal sphincter, external anal sphincter and the puborectalis muscle
What is the internal structure of the anal canal
Mucosa is organised into anal columns, which are joined inferiorly by anal valves.
The anal valves form an irregular circle called the pectinate line, which divides the anus into upper and lower parts
What is the arterial supply to the anal canal?
Above pectinate line - superior rectal artery (branch of inferior mesenteric)
Below pectinate line - inferior rectal artery (branch of internal pudendal artery)
