MRCS Part B Revision · Anatomy
Humerus 1 — MRCS Part B Anatomy
By Dr Richard Miller, MBChB FRCS · Reviewed
Humerus 1 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 Humerus 1 station
A prosection of the shoulder and proximal humerus, read for the attachments that make the joint work: the rotator cuff, the coracoid muscles, the biceps, and the two spaces through which the axillary and radial nerves leave the axilla.
Siding the specimen
The head faces medially, upwards and backwards; the greater tubercle is lateral and the lesser tubercle anterior, with the intertubercular (bicipital) groove between them. Hold the bone with the head medial and the groove facing you: the specimen is then from the side on which the head sits.
The rotator cuff
- Supraspinatus — supraspinous fossa to the upper facet of the greater tubercle. Starts abduction; suprascapular nerve (C5, 6).
- Infraspinatus — infraspinous fossa to the middle facet. External rotation; suprascapular nerve.
- Teres minor — upper lateral border of the scapula to the lower facet. External rotation; axillary nerve (C5, 6).
- Subscapularis — subscapular fossa to the lesser tubercle. Internal rotation; upper and lower subscapular nerves (C5, 6).
Together they press the humeral head into the glenoid throughout movement, which is the joint's real stability; the capsule and labrum contribute far less. Supraspinatus is the tendon that tears, because it runs under the acromion and is compressed against it in abduction.
The coracoid process
Three muscles and three ligaments. Muscles: the short head of biceps and coracobrachialis from the tip (as the conjoint tendon), and pectoralis minor onto the medial border. Ligaments: coracoacromial, coracoclavicular (conoid and trapezoid) and coracohumeral.
Biceps brachii
The long head arises from the supraglenoid tubercle inside the joint and runs down the bicipital groove under the transverse humeral ligament; the short head comes from the coracoid tip. The muscle inserts on the radial tuberosity, with the bicipital aponeurosis passing medially into the deep fascia of the forearm. It supinates the forearm and flexes the elbow; musculocutaneous nerve (C5, 6).
Quadrangular and triangular spaces
- Quadrangular space — teres minor above, teres major below, long head of triceps medially, surgical neck of the humerus laterally. Transmits the axillary nerve and posterior circumflex humeral vessels.
- Lateral triangular space (triangular interval) — teres major above, long head of triceps medially, humeral shaft laterally. Transmits the radial nerve and profunda brachii artery.
- Medial triangular space — teres minor, teres major and long head of triceps; transmits the circumflex scapular artery.
Images from this station
What are you asked at the Humerus 1 station?
The station runs to 16 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 and side the above specimen
- Identify structures 1-3
- Identify structures 4-6
- Identify structures 7-9
- Identify structures 10-12
- Name the rotator cuff muscles
- What are the origins, insertions and actions of the rotator cuff muscles?
- Which muscles attach to the coracoid process?
- What are the attachments and insertion of the biceps?
- What are the borders of the quadrangular space?
- What are the boundaries of the lateral triangular space?
- Identify muscles 1 and 2
And 3 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 Humerus 1 station ask?
It opens with "Identify and side the above 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