MRCS Part B Revision · Anatomy
Cortex — MRCS Part B Anatomy
By Dr Richard Miller, MBChB FRCS · Reviewed
Cortex 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 Cortex station
A hemisphere seen from the side and in section: the lobes, the sulci that bound them, and the functional areas that the examiner will ask you to point to.
Lobes and boundaries
The central sulcus separates the frontal lobe from the parietal lobe, the lateral (Sylvian) fissure separates both from the temporal lobe, and the parieto-occipital sulcus on the medial surface, with a line drawn from it to the pre-occipital notch, separates the occipital lobe. The insula lies hidden in the floor of the lateral fissure. On the medial surface the cingulate gyrus arches over the corpus callosum, and the calcarine sulcus cuts into the occipital lobe.
Functional areas
- The precentral gyrus is the primary motor cortex, arranged as an inverted homunculus with the leg on the medial surface, supplied by the anterior cerebral artery, and the face lowest, supplied by the middle cerebral.
- The postcentral gyrus is the primary somatosensory cortex, with the same arrangement.
- Broca's area in the inferior frontal gyrus of the dominant hemisphere produces speech; Wernicke's area in the posterior superior temporal gyrus understands it.
- The primary auditory cortex is on the superior temporal gyrus in the lateral fissure, the primary visual cortex either side of the calcarine sulcus, and the olfactory cortex on the uncus.
Layers
The neocortex, most of the hemisphere, has six layers of neurones; the allocortex of the hippocampus and olfactory areas has three or four. Brodmann's numbering follows the histology: area 4 is the motor strip, areas 3, 1 and 2 the sensory strip, area 17 the visual cortex, and areas 44 and 45 Broca's area.
Blood supply
The anterior cerebral artery runs over the corpus callosum and supplies the medial surface, so its occlusion weakens the opposite leg. The middle cerebral artery runs through the lateral fissure and supplies most of the lateral surface, including the face and arm areas and the speech areas, so its occlusion gives a face-and-arm weakness with dysphasia if the dominant side is affected. The posterior cerebral artery supplies the occipital lobe and the medial temporal lobe, so its occlusion gives a homonymous hemianopia.
Why it matters to a surgeon
The motor and sensory strips are the eloquent cortex that neurosurgeons map before resecting a tumour. A lesion pressing on the precentral gyrus causes focal seizures that march along the homunculus. The middle cerebral territory is where an embolus from a carotid plaque lands, which is the reason for a carotid endarterectomy.
Images from this station
What are you asked at the Cortex station?
The station runs to 15 questions over nine minutes. A prompt the station repeats — against each marker on a specimen, for instance — is listed once here; the model answers are in the question bank.
- Identify structures 1-3
- Identify structures 4 and 5
- Identify structures 6-8
- Identify structures 9-11
- Identify structures 12 and 13
- Identify structures 14-16
- Identify structures 17 and 18
- Identify structures 19 and 20
- Identify structures 21-23
- Identify structures 24 and 25
- Describe the arterial supply to the brain
- What is the important benefit of the circle of Willis?
And 2 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 Cortex station ask?
It opens with "Identify structures 1-3" and runs to 15 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