21. GI Anatomy Flashcards
What are the 4 layers of the GI tract?
What is the foregut (boundaries, length, diameter, blood supply)?
- *1) Mucosa** - epithelium, lamina propria, muscularis mucosa
- *2) Submucosa** (BV, lymph, nerves)
- *3) Muscularis propria** - inner circular, outer longitudinal
- *4) Serosa/adventitia** - covered by visceral peritoneum
- NB: serosa = intraperitoneal organs, continuous with viscera. Adventitia = retroperitoneal structures (SAD PUCKER)* [Pic]
Mouth to 2nd part of duodenum (major duodenal papilla), 25cm long, 2cm diameter, upper and lower oesophageal sphincters, supplied by coeliac trunk T12
What is the arterial supply and venous drainage of the oesophagus?
What does the LOS do?
Arterial supply: inf thyroid, ext carotid, bronchial arteries, throacic aorta, inferior phrenic, left gastric (from coeliac trunk)
Venous drainage: inf thyroid, azygous system, gastric veins (go into portal system, so if have chronic liver disease -> cirrhosis -> portal HTN -> oesophageal varices) [Pic]
Tonic contraction of smooth muscle, together with cural diaphragm. Acts as valve/sphincter. Impairment of mechanisms can lead to achalasia (failure of fibre relaxation) and GORD
What 3 things does the stomach do?
What 3 structures form the portal triad?
What are the 3 structures drawn onto the diagram?
Is the duodenum intraperitoneal or retroperitoneal?
Stores ingested food, mechanical breakdown, chemical digestion
Common bile duct, portal vein, common hepatic artery
Top L: hepatoduodenal ligament; Top R: hepatogastric ligament; Bottom: greater omentum
First part is intraperitoneal, rest is retroperitoneal. Divided up into different parts [Pic]
Describe the foregut blood supply.
Label A-I of the liver.
Comes off coeliac trunk [Pic]
A) porta hepatis (contains portal triad)
B) cystic duct
C) bile duct
D) portal vein
E) hepatic artery proper
F) caudate loebe
G) fissure for ligamentum venosum
H) fissure for ligamentum teres
I) quadrate lobe
What borders:
a) Calot’s triangle
b) Cystohepatic triangle
and why are they important?
Label the following parts of the liver and biliary tree.
Cholecystectomy - need to tie vessels off (cystic artery) - find it by finding the triangle.
a) Cystic duct, common hepatic duct and cystic artery
b) Cystic duct, common hepatic duct and inferior surface of liver [Pic]
A) common hepatic duct
B) cystic duct
C) common bile duct
D) ampulla of vater
NB. Bile is made in canaliculi. Cystic duct is 2-way. Pancreatic duct from pancreas joins the common bile duct.
Describe the structure and function of the peritoneum.
What is its clinical relevance?
Label the diagram below.
Serous membrane, two continuous layers: parietal and visceral. Facilitates organ movement (but can twist on itself - volvulus). Insulation and contains mesentry, nerves and vessels
‘Acitve’ during organ injury/inflammation, differing nociception
A) Lesser omentum
B) Transverse mesocolon
C) Transverse colon
D) Greater sac
E) Greater omentum
F) Small intestine
G) Mesentery
H) Duodenum
I) Omental bursa
The midgut is the longest section of the gut. What are the boundries?
Describe its blood supply (originates, path).
Label the blood supply of the midgut
2nd part of duodenum to 2/3 along transverse colon
SMA: originates L1, travels inferiorly, passes anterior to uncinate process of pancreas, along with SMV, to target tissues in mesentery
A) middle colic artery
B) right colic artery
C) ileocolic artery
D) anterior cecal artery
E) posterior cecal artery
F) appendicular artery
G) ileal arteries
H) vasa recta
I) jejunal arteries
The hindgut is the shortest section of gut. What are the ‘watershed’ areas? (receives dual blood supply from the most distal branches of 2 large arteries)
What is ischaemic colitis (causes, symptoms)?
Is ischaemic colitis the same as mesenteric ischaemia?
Splenic flexure - superior and inferior mesenteric artery watershed area. Also inferior mesenteric and hypogastric watershed area. [Pic]
Colon inflammation due to ischaemia (reduced perfusion all around - splenic felxure furthest from SMA and IMA so gets least perfusion). Caused by global low flow states: heart failure, MI, sepsis, haemorrhage/thromboembolism. Symptoms: abdo pain, bloody diarrhoea
No.
Differentiate between ischaemic colitis and mesenteric ischaemia in terms of:
a) symptom onset (time-wise)
b) cause
c) blood supply loss
d) presenting symptoms
e) management
Ischaemic colitis: inflammation and injury of large intestine resulting from inadequate blood supply
Mesenteric ischaemia: injury of small intestine due to inadequate blood supply. Can be acute or chronic. Worse outcome than IC
[Pic]
What are the organs found in the areas indicated, and conditions that may cause pain in those areas?
Case 1
17yo male, fit and well, 24h constant stomach ache, no hunger, no D + V, T 37.4, obs otherwise normal. Sent home. Returned 24h later with sharper pain that moved towards groin, T 37.9, HR 98, BP 125/77, bloods: WCC 15.4, CRP 170. O/E localised RIF tenderness and guarding. Admitted, kept NBM
What would you suspect and thus do?
[Pic]
Appendicitis - laparoscopic appendicectomy
Differentiate between somatic pain and visceral pain.
What is referred pain?
Somatic pain: i.e. cutaneous, ‘pricking, stabbing, burning’, sensitive to burning and cutting, high density of innervation, well localised sensation of pain
Visceral: ‘dullness, vagueness, fullness’, sensitive to ischaemia, inflammation, distension, less sensitive to direct mechanical trauma, low density of innervation, therefore poorly localised pain
Misinterpretation of signals at higher centres, stimuli from area of low density innervation (viscera), processed as being from an area of high density innervation (skin, dermatome)
Explain how referred pain is felt in appendicitis.
What is biliary colic?
What is biliary disease?
Obstruction of appendix by faecolith -> appendix swollen and inflamed -> inflammation stimulates visceral afferents initially (mesoappendix) -> vague pain at umbilicus -> condition worsens (larger, more inflammed), stimulates somatic afferents in parietal peritoneum -> pain migrates to RIF
Gallstones symptomatic with cystic duct obstruction or if passed into the CBD. RUQ pain +/- radiation to back/shoulder +/- N&V, episodes last 12-24h. Pain often after fatty meal
Stone lodged in GB neck, causes sustained contraction, organ inflammation - longer duration of sx, localised peritonism, evidence of inflammatory response -> CHOLECYSTITIS (tx = IV abx)
What is Murphy’s sign?
What happens if the stonne lodged in the CBD causes 2o infection? What is Charcot’s triad?
What happens if the stone were to move distally towards the ampulla, and blocks the main pancreatic duct? What would you see clinically?
Palpate under R costal margin (RUQ), ask pt to inhale deeply, inflamed GB comes into contact with parietal peritoneum, pain stops further inhalation. Only +ve if same manoeuvre on LHS doesn’t elicit painful response
- *(Ascending) cholangitis**.
- *RUQ pain**, jaundice, pyrexia/rigors
Reflux of bile into pancreas, autodigestion, inflammatory reaction = acute pancreatitis. Clinically: epigastric pain radiating to back (sitting forward may relieve), vomiting, SIRS, ARDS. Cullens/Grey Turners signs [Pic]
What is peritonitis?
How is it treated?
List the retroperitoneal structures (SAD PUCKERS).
Inflammation of peritoneum. Peritoneal cavity = large pace, can facilitate the spread of inflammatory/infective process. Many substances can irritate the parietal peritonem e.g. pus, blood, bile (causes local guarding, rigidity etc.), if cause is pronounced/severe (e.g. perforated viscus - duodenum, appendix etc.) -> large release of contents -> generalised peritoneal abdomen (‘rigid - board-like’)
IV rehydration and correct electrolyte disturbances. IV abx. Laparotomy for drainage and lavage.
Suprarenal glands, Aorta/IVC, Duodenum (2nd and 3rd parts), Pancreas, Ureters, Colon (ascending, descending), Kidneys, (o)Esophagus, Rectum
