MRCS Part B Revision · Anatomy
Forearm 2 — MRCS Part B Anatomy
By Dr Richard Miller, MBChB FRCS · Reviewed
Forearm 2 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 Forearm 2 station
The anterior forearm and elbow prosection, followed by the two questions the examiners actually want: the nerve supply of the flexors, and the brachial artery's course from elbow to hand.
Muscles attaching to the medial epicondyle
The common flexor origin: pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis (its humero-ulnar head) and flexor carpi ulnaris. The ulnar nerve lies behind the epicondyle, not on it.
Deep flexors
Flexor digitorum profundus, flexor pollicis longus and pronator quadratus. Profundus alone flexes the distal interphalangeal joints; test it by holding the proximal joint straight.
Nerve supply of the flexor compartment
Median nerve: pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis. Anterior interosseous branch of the median nerve: flexor pollicis longus, the radial half of profundus, pronator quadratus. Ulnar nerve: flexor carpi ulnaris and the ulnar half of profundus. Brachioradialis is a flexor of the elbow but is a radial nerve muscle in the extensor compartment.
Cutaneous supply of the forearm
Lateral cutaneous nerve of the forearm, the continuation of the musculocutaneous nerve (C5, 6); medial cutaneous nerve of the forearm from the medial cord (C8, T1); posterior cutaneous nerve of the forearm from the radial nerve (C5–8). Dermatomes: C6 to the thumb, C7 the middle finger, C8 the little finger, T1 the medial forearm.
The brachial artery and its divisions
The brachial artery runs down the medial arm on brachialis, with the median nerve crossing it from lateral to medial, and enters the cubital fossa under the bicipital aponeurosis, where it is the pulse felt for a blood-pressure cuff. At the level of the radial neck it divides.
The radial artery passes down the lateral forearm under brachioradialis, gives a recurrent branch to the elbow anastomosis, and at the wrist lies between flexor carpi radialis and the radial border, where the pulse is taken. It then winds back through the anatomical snuffbox, pierces the first dorsal interosseous and adductor pollicis, and forms the deep palmar arch.
The ulnar artery is the larger. It gives the common interosseous artery, passes deep to pronator teres and superficialis, joins the ulnar nerve on its medial side, and crosses the wrist superficial to the flexor retinaculum through Guyon's canal, lateral to the pisiform, to form the superficial palmar arch. Allen's test checks that the two arches communicate before the radial artery is cannulated.
Axillary nerve palsy
Loss of abduction beyond the first few degrees (deltoid), weak external rotation (teres minor), and numbness over the “regimental badge” area of the upper lateral arm. Test it after any shoulder dislocation and before reducing one.
Images from this station
What are you asked at the Forearm 2 station?
The station runs to 16 questions over nine minutes. These are the questions as they are put to you; the model answers are in the question bank.
- Identify the specimen
- Identify structures 1-3
- Identify structures 4 and 5
- Identify structures 6-9
- Identify structures 10-13
- From which nerve is structure 12 a branch?
- Identify vessel 14
- Identify structures 15-17
- Identify structures 18-20
- Identify tendons 21-22
- What muscles attach to the medial epicondyle?
- What are the deep flexors of the forearm?
And 4 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 Forearm 2 station ask?
It opens with "Identify the specimen" and runs to 16 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