Unit 5 Question Bank
Sourcing: items tagged TMU 2021–22 come from the real final paper. Items tagged
Slide come from the TMU lecture. Items tagged Gray's are built from the textbook to cover
examinable content. Nothing here is invented; answers are verifiable against the cited page — check against
the official marking scheme where one exists.
0 / 20 answered
1The quadrangular space is bounded laterally by the ( ).
Answer: D
Laterally the surgical neck of the humerus; medially the long head of triceps; above subscapularis and teres minor with the shoulder capsule; below teres major.Snell's 10e Ch.3 · Gray's 4e p.714
2Which structures pass through the quadrangular space?
Answer: A
The axillary nerve with the posterior circumflex humeral artery and vein. The radial nerve and profunda brachii use the triangular interval; the circumflex scapular artery uses the triangular space.TMU Lecture 6 Slide 12 · Gray's 4e Fig. 7.38
3The content of the triangular space is the ( ).
Answer: B
Only the circumflex scapular artery, a branch of the subscapular artery, which contributes to the scapular anastomosis.TMU Lecture 6 Slide 12
4Supraspinatus and infraspinatus are supplied by the ( ).
Answer: C
Both take the suprascapular nerve. The axillary nerve supplies deltoid and teres minor; the subscapular nerves supply subscapularis and teres major.TMU Lecture 6 Slide 10 · Gray's 4e p.687
5Which muscle is NOT part of the rotator cuff?
Answer: D
The cuff is SITS — supraspinatus, infraspinatus, teres minor, subscapularis. Teres major is not a cuff muscle and does not blend with the joint capsule.Gray's 4e p.687, Fig. 7.9C
6Injury to the axillary nerve at the surgical neck of the humerus produces ( ).
Answer: A
Deltoid is paralysed and wastes, flattening the shoulder contour — the square shoulder — with loss of abduction and numbness over the regimental badge area.TMU Lecture 6 Slide 13
7Which structure passes through the triangular interval?
Answer: B
The triangular interval lies below teres major, between the long head of triceps medially and the humeral shaft laterally, and transmits the radial nerve and profunda brachii artery into the posterior arm.Gray's 4e Fig. 7.37, p.712
8The nerve supplying trapezius is the ( ).
Answer: C
The accessory nerve [XI] supplies trapezius and sternocleidomastoid. It is found on the deep surface of trapezius and is at risk in posterior triangle surgery.TMU Lecture 6 Slide 4
9The cephalic vein terminates by draining into the ( ).
Answer: D
It ascends in the deltopectoral groove, pierces the deep fascia and drains into the axillary vein. That groove is the standard route for pacemaker leads.TMU Lecture 6 Slide 16
10Which muscle initiates abduction of the shoulder?
Answer: A
Supraspinatus initiates the first roughly 15°, after which deltoid takes over. This is why a supraspinatus tear leaves a patient unable to start abduction though they can often hold the arm up once it is lifted for them.Gray's 4e p.687
11Which muscle forms the floor of the sheath of the erector spinae?
Answer: B
The thoracolumbar fascia has three layers: posterior and middle enclose erector spinae in its sheath, while the anterior layer lies in front of quadratus lumborum.TMU Lecture 6 Slide 7
12Teres major and subscapularis are supplied by the ( ).
Answer: C
The upper and lower subscapular nerves from the posterior cord. Note your TMU slide writes "infrascapular nerve" — a translation artefact; use subscapular, the term Gray's and Snell's use.Gray's 4e p.743, Fig. 7.56
13Above, the quadrangular space is bounded by the ( ).
Answer: D
Subscapularis and teres minor together with the capsule of the shoulder joint — which is exactly why the axillary nerve is so vulnerable in shoulder dislocation.Snell's 10e Ch.3 — Quadrangular Space
14Which muscle laterally rotates the shoulder AND is supplied by the axillary nerve?
Answer: A
Teres minor — a lateral rotator like infraspinatus, but sharing the axillary nerve with deltoid rather than the suprascapular nerve. A neat exception to test.TMU Lecture 6 Slide 10
15The circumflex scapular artery is a branch of the ( ).
Answer: B
The subscapular artery (from the third part of the axillary artery) divides into the circumflex scapular and thoracodorsal arteries.TMU Lecture 7 Slide 19–20
16Which of these is the deepest muscle of the back dissected in this lecture?
Answer: C
Order of dissection is trapezius and latissimus dorsi (superficial) → levator scapulae and rhomboids → thoracolumbar fascia and erector spinae in its sheath.TMU Lecture 6 Slides 3–6
17Subscapularis lies on the ( ) surface of the scapula.
Answer: D
Subscapularis fills the subscapular fossa on the costal (anterior) surface, against the ribs — which is why it forms part of the posterior wall of the axilla and is seen only from the front.TMU Lecture 6 Slide 9
18Loss of sensation over the 'regimental badge' area of the shoulder indicates injury to the ( ).
Answer: A
The axillary nerve supplies the skin over the lower part of deltoid. Testing this patch is the standard check before and after reducing a dislocated shoulder.TMU Lecture 6 Slide 13 · Snell's 10e Ch.3
19The medial border of the quadrangular space is formed by the ( ).
Answer: B
The long head of triceps runs vertically and closes the medial side of both the quadrangular and triangular gaps — it is the vertical bar of the cross that creates them.Snell's 10e Ch.3
20Which nerve is at risk when operating in the posterior triangle of the neck?
Answer: C
The accessory nerve crosses the posterior triangle superficially before reaching trapezius. Injury causes trapezius wasting, shoulder droop and difficulty raising the arm above the head.TMU Lecture 6 Slide 4 · Gray's 4e p.1013
1 Quadrangular space — TMU 2021–22 · 3′+
An intermuscular space immediately below the glenohumeral joint.
Above: subscapularis and teres minor with the capsule of the shoulder joint.
Below: teres major.
Medially: long head of triceps brachii.
Laterally: surgical neck of the humerus.
Contents: axillary nerve · posterior circumflex humeral artery and vein.Snell's 10e Ch.3 · Gray's 4e p.714
Above: subscapularis and teres minor with the capsule of the shoulder joint.
Below: teres major.
Medially: long head of triceps brachii.
Laterally: surgical neck of the humerus.
Contents: axillary nerve · posterior circumflex humeral artery and vein.Snell's 10e Ch.3 · Gray's 4e p.714
2 Triangular space — 3′+
A smaller space medial to the quadrangular space.
Above: teres minor. Below: teres major. Laterally: long head of triceps.
Content: circumflex scapular artery.TMU Lecture 6 Slide 12
Above: teres minor. Below: teres major. Laterally: long head of triceps.
Content: circumflex scapular artery.TMU Lecture 6 Slide 12
3 Triangular interval — 3′+
The gap below teres major.
Above: teres major. Medially: long head of triceps. Laterally: shaft of the humerus.
Contents: radial nerve and profunda brachii (deep brachial) artery, passing into the posterior compartment of the arm.Gray's 4e Fig. 7.37, p.712
Above: teres major. Medially: long head of triceps. Laterally: shaft of the humerus.
Contents: radial nerve and profunda brachii (deep brachial) artery, passing into the posterior compartment of the arm.Gray's 4e Fig. 7.37, p.712
4 Rotator cuff — 2′+
The four muscles whose tendons blend with the capsule of the shoulder joint and hold the head of the humerus in the shallow glenoid cavity: supraspinatus, infraspinatus, teres minor and subscapularis (SITS).
Supraspinatus is the most frequently torn, because it passes through a narrow subacromial gap and its blood supply is poorest near its insertion.Gray's 4e p.687
Supraspinatus is the most frequently torn, because it passes through a narrow subacromial gap and its blood supply is poorest near its insertion.Gray's 4e p.687
5 Deltopectoral groove — 2′+
The groove between the deltoid and pectoralis major muscles, containing the cephalic vein as it ascends to pierce the deep fascia and join the axillary vein.
A reliable surface landmark, used as an access route for pacemaker leads and central venous catheters.TMU Lecture 6 Slide 16
A reliable surface landmark, used as an access route for pacemaker leads and central venous catheters.TMU Lecture 6 Slide 16
6 Axillary nerve — 3′+
A branch of the posterior cord of the brachial plexus (C5, C6). It passes backwards through the quadrangular space with the posterior circumflex humeral vessels and winds round the surgical neck of the humerus.
Supplies: deltoid and teres minor, plus skin over the lower deltoid.
Injury: fracture of the surgical neck or shoulder dislocation → square shoulder, loss of abduction, regimental-badge numbness.TMU Lecture 6 Slide 13
Supplies: deltoid and teres minor, plus skin over the lower deltoid.
Injury: fracture of the surgical neck or shoulder dislocation → square shoulder, loss of abduction, regimental-badge numbness.TMU Lecture 6 Slide 13
1
Draw and describe the boundaries and contents of the quadrangular and triangular spaces.
8′
Set as homework in TMU Lecture 6 — expect it as a drawing question.
How the spaces are formed
Behind the shoulder the two teres muscles run horizontally toward the humerus and the long head of triceps runs vertically, crossing them. The gaps between these muscles and the humerus form the two spaces.
Quadrangular space
- Above: subscapularis and teres minor, with the capsule of the shoulder joint
- Below: teres major
- Medially: long head of triceps brachii
- Laterally: surgical neck of the humerus
- Contents: axillary nerve; posterior circumflex humeral artery and vein
Triangular space
- Above: teres minor
- Below: teres major
- Laterally: long head of triceps brachii
- Content: circumflex scapular artery
Clinical importance
The axillary nerve lies against the surgical neck of the humerus in the quadrangular space, so a fracture there or an anterior shoulder dislocation paralyses deltoid — producing a square shoulder and loss of abduction.
Marking guide: quadrangular boundaries 3 · quadrangular contents 1.5 · triangular boundaries 1.5 · triangular content 1 · one clinical point 1.
2
Summarise the scapular muscles with their functions and nerve supply.
8′
Set as homework in TMU Lecture 6.
| Muscle | Action | Nerve |
|---|---|---|
| Deltoid | Abducts the shoulder | Axillary nerve |
| Supraspinatus | Initiates abduction (first ~15°) | Suprascapular nerve |
| Infraspinatus | Lateral rotation | Suprascapular nerve |
| Teres minor | Lateral rotation | Axillary nerve |
| Teres major | Adduction, medial rotation, extension | Lower subscapular nerve |
| Subscapularis | Adduction, medial rotation | Upper and lower subscapular nerves |
Grouping worth stating
Two abduct (deltoid, supraspinatus); two rotate laterally (infraspinatus, teres minor); two rotate medially and adduct (teres major, subscapularis). Four of them — supraspinatus, infraspinatus, teres minor, subscapularis — form the rotator cuff.
Note: the TMU slide writes "infrascapular nerve" for teres major and subscapularis; the accepted term is subscapular nerve.
Marking guide: six muscles named 2 · actions 3 · nerves 2 · rotator cuff identified 1.
3
Describe the axillary nerve and the consequences of its injury.
6′
Origin and course
- Arises from the posterior cord of the brachial plexus (C5, C6)
- Passes backwards through the quadrangular space with the posterior circumflex humeral artery
- Winds round the surgical neck of the humerus, deep to deltoid
- Divides into anterior and posterior terminal branches
Distribution
- Motor: deltoid and teres minor
- Sensory: skin over the lower part of deltoid (upper lateral cutaneous nerve of the arm)
- Articular: a branch to the shoulder joint
Injury
- Causes: fracture of the surgical neck of the humerus; anterior dislocation of the shoulder; badly placed intramuscular injection into deltoid
- Motor loss: deltoid paralysis and wasting → loss of abduction beyond the first few degrees; the shoulder contour flattens into a square shoulder
- Sensory loss: the regimental badge area over the lower deltoid
Testing that patch of skin is the routine check before and after reducing a dislocated shoulder.
Marking guide: origin 1 · course through quadrangular space 1 · relation to surgical neck 1 · motor supply 1 · square shoulder 1 · sensory area 1.
4
Describe the rotator cuff. Why is supraspinatus the muscle most often torn?
6′
Composition
Four muscles whose tendons blend with the capsule of the shoulder joint and hold the humeral head in the glenoid cavity — Supraspinatus, Infraspinatus, Teres minor and Subscapularis.
| Muscle | Action | Nerve |
|---|---|---|
| Supraspinatus | Initiates abduction | Suprascapular |
| Infraspinatus | Lateral rotation | Suprascapular |
| Teres minor | Lateral rotation | Axillary |
| Subscapularis | Medial rotation | Upper and lower subscapular |
Why the cuff exists
The glenoid cavity is very shallow relative to the humeral head. The shoulder trades bony stability for range of movement, and the cuff supplies the stability that the socket does not.
Why supraspinatus fails first
- Its tendon passes through a narrow gap between the head of the humerus below and the acromion above, so every abduction drags it through that space
- Its blood supply is poorest close to its insertion
- The result is degeneration, impingement and eventually rupture
Clinically the patient cannot initiate abduction but can often maintain it if the arm is passively lifted, because deltoid can continue what supraspinatus had to begin.
Marking guide: four muscles 2 · nerve supply 1 · function of the cuff 1 · anatomical reason for supraspinatus tears 1.5 · clinical sign 0.5.
5
Compare the triangular space, the quadrangular space and the triangular interval.
6′
| Gap | Boundaries | Contents |
|---|---|---|
| Triangular space | Above: teres minor · Below: teres major · Lateral: long head of triceps | Circumflex scapular artery |
| Quadrangular space | Above: subscapularis + teres minor + capsule · Below: teres major · Medial: long head of triceps · Lateral: surgical neck of humerus | Axillary nerve · posterior circumflex humeral vessels |
| Triangular interval | Above: teres major · Medial: long head of triceps · Lateral: shaft of humerus | Radial nerve · profunda brachii artery |
How to keep them apart
The long head of triceps is the vertical divider. Medial to it is the triangular space; lateral to it and above teres major is the quadrangular space; below teres major is the triangular interval.
Clinical relevance
Each gap carries a nerve or vessel that can be injured there: the axillary nerve at the surgical neck (square shoulder) and the radial nerve as it enters the spiral groove (wrist drop).
Marking guide: three gaps correctly distinguished 3 · contents 2 · organising principle or clinical point 1.