MRCS Part B Revision · Anatomy
Abdominal Cavity — MRCS Part B Anatomy
By Dr Richard Miller, MBChB FRCS · Reviewed
Abdominal Cavity is a surgical anatomy station. Three of the seventeen examined stations in the MRCS Part B OSCE are surgical anatomy. The anatomy stations put a prosected specimen, a model or an image in front of you and ask you to identify structures and say what they do, what they relate to and what happens when they are injured.
What you need to know for the Abdominal Cavity station
The opened abdomen, its vessels and its peritoneal folds. The first question is the embryology, because the blood supply, the nerve supply and the position of every organ follow from it.
Embryological divisions
- Foregut — oesophagus to the second part of the duodenum at the ampulla, with liver, biliary tree, pancreas and spleen. Coeliac trunk (T12). Pain felt in the epigastrium.
- Midgut — from the ampulla to two-thirds along the transverse colon. Superior mesenteric artery (L1). Pain in the umbilical region.
- Hindgut — distal transverse colon to the upper anal canal. Inferior mesenteric artery (L3). Pain in the suprapubic region.
The abdominal aorta
It enters at T12 behind the median arcuate ligament and divides at L4 into the common iliac arteries. Its unpaired anterior branches are the coeliac trunk, superior mesenteric and inferior mesenteric arteries; its paired lateral branches the inferior phrenic, suprarenal, renal (L1–2) and gonadal (L2) arteries; its posterior branches the four lumbar arteries and the median sacral. Each common iliac divides in front of the sacro-iliac joint into an external iliac, which becomes the femoral artery under the inguinal ligament, and an internal iliac.
Internal iliac artery
The pelvic viscera (superior and inferior vesical, middle rectal, uterine and vaginal branches), the gluteal region (superior and inferior gluteal), the medial thigh (obturator), the perineum (internal pudendal) and the pelvic wall (iliolumbar and lateral sacral).
Retroperitoneal organs
Primarily: kidneys, adrenals, ureters, aorta, inferior vena cava, bladder and rectum. Secondarily, having lost their mesentery in development: the duodenum except its first part, the pancreas except the tail, and the ascending and descending colon.
Pancreas and spleen
The pancreas is supplied from both foregut and midgut: the superior pancreaticoduodenal arteries from the gastroduodenal, the inferior from the superior mesenteric, and the body and tail by branches of the splenic artery running along its upper border. The spleen lies under the left ninth to eleventh ribs with its long axis along the tenth, about 12 cm long and weighing around 150 g. Its hilum receives the splenic artery, the largest branch of the coeliac trunk, and the splenic vein joins the superior mesenteric behind the pancreatic neck to form the portal vein. The gastrosplenic ligament carries the short gastric and left gastro-epiploic vessels; the splenorenal (lienorenal) ligament carries the splenic vessels and the tail of the pancreas. Both are cut in a splenectomy, and the tail of the pancreas is the structure most easily injured.
Portosystemic anastomoses
Lower oesophagus (left gastric with azygos tributaries — varices), anal canal (superior rectal with middle and inferior rectal), umbilicus (paraumbilical veins along the ligamentum teres with the epigastric veins — caput medusae), and the bare areas of retroperitoneal organs (veins of Retzius).
Peritoneal terms
A mesentery is a double fold of peritoneum that suspends a viscus from the posterior wall and carries its vessels and nerves. An omentum is a double fold attached to the stomach: the greater omentum hangs from the greater curvature over the colon and small bowel as the “policeman of the abdomen”; the lesser omentum runs from the lesser curvature to the liver, with the portal triad in its free edge. Ascites is free fluid in the peritoneal cavity. Grey Turner's sign is flank bruising from retroperitoneal haemorrhage tracking into the subcutaneous tissue, classically in severe acute pancreatitis.
Images from this station
What are you asked at the Abdominal Cavity station?
The station runs to 19 questions over nine minutes. These are the questions as they are put to you; the model answers are in the question bank.
- Name the embryological divisions of the gut and their blood supplies
- Identify vessels 1-4
- Identify vessels 5-9
- Identify structures 10-14
- Identify structures 15-20
- Identify structures 21-22
- Identify structures 23-28
- Describe the arterial blood supply from the abdominal aorta to the pelvic brim
- What structures does the internal iliac artery supply via its branches?
- Which organs are retroperitoneal?
- What is the arterial supply to the pancreas?
- Describe the gross anatomy of the spleen
And 7 more at this station.
How is the anatomy station marked in MRCS Part B?
An anatomy station is marked out of 20, and all 20 marks go to clinical knowledge and its application. No communication, technical-skill or professionalism marks are available in an anatomy bay, which is unusual: in most other stations more than half the marks sit outside your factual knowledge.
FAQ
What does the Abdominal Cavity station ask?
It opens with "Name the embryological divisions of the gut and their blood supplies" and runs to 19 questions over nine minutes. An anatomy station is marked out of 20, and all 20 marks go to clinical knowledge and its application. No communication, technical-skill or professionalism marks are available in an anatomy bay, which is unusual: in most other stations more than half the marks sit outside your factual knowledge.
How many anatomy stations are there in MRCS Part B?
Three of the seventeen examined stations are surgical anatomy, and two more are surgical pathology. Together they make up the five Anatomy and surgical pathology stations of the Applied Knowledge component.
How are the anatomy stations marked?
Each station is marked out of 20 and all 20 marks are awarded for clinical knowledge and its application. You also receive a separate global rating of pass, borderline or fail for the station.
Are the specimens real?
Yes. Anatomy bays use prosected cadaveric specimens, models and images. Candidates report being shown photographs of specimens as well as the specimens themselves, so practise on real dissection photography rather than diagrams alone.
What happens if I get an early question wrong?
The intercollegiate guidance says that if a wrong answer would affect your performance on later questions at the same station, the examiner gives you the correct answer before moving on. One mistake does not have to cost you the whole bay.
How many stations are in the MRCS Part B OSCE?
Seventeen examined stations of nine minutes each, with a minute to read the task before each one. Two preparation stations and at least one rest station bring the circuit to about twenty, and the exam takes about three and a half hours.
What is the pass mark for MRCS Part B?
There is no published pass mark. The cut score is set separately for Applied Knowledge and Applied Skills, for each circuit, by borderline regression. Published pass rates across the 2024/25 diets ranged from 51% to 66%.
Can I fail a station and still pass?
Yes. There is no rule about how many stations you may fail: the cut score applies to your total mark in each component, so a weak station costs the marks you lost on it and strong stations elsewhere can make them back. Applied Knowledge and Applied Skills are passed separately and must both be passed at the same sitting, so a strong anatomy performance cannot rescue a weak communication one.
Dr Richard Miller, MBChB FRCS
Station summaries are reviewed against the current intercollegiate MRCS syllabus and the published marking blueprint. Guidance changes between diets: check the royal colleges' own pages before relying on a date, a fee or a threshold.
Practise this station
The question bank carries the model answer to every question above, with the rest of the anatomy stations.
More anatomy stations