MCQs – Anatomy 1

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High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on shoulder anatomy, brachial plexus neuroanatomy, and key surgical landmarks. The single most important clinical trade-off is distinguishing static versus dynamic shoulder stabilizers, which guides management of instability and nerve injury localization. Exam questions often force a choice between upper trunk versus root-level brachial plexus lesions based on nerve origin (e.g., suprascapular vs long thoracic nerve). While classic anatomy remains foundational, modern practice increasingly emphasizes functional nerve testing and intraoperative nerve monitoring to refine diagnosis and surgical planning.

High-Yield Decision Matrix

Active Recall Q&A

Shoulder Stabilizers & Spaces

Q: What are the static stabilizers of the shoulder?
A: Capsuloligamentous structures, articular surfaces, and negative intra-articular pressure.
Related Pearl: Negative intra-articular pressure creates a suction effect critical for glenohumeral joint stability.

Q: What are the dynamic stabilizers of the shoulder?
A: Rotator cuff muscles, biceps tendon, and deltoid muscle.
Related Pearl: Dynamic stabilizers provide active control during shoulder motion, preventing dislocation.

Q: What anatomical structures define the quadrangular space?
A: Teres minor, teres major, long head of triceps, and humeral shaft.
Related Pearl: The axillary nerve and posterior circumflex humeral artery pass through this space, making it vulnerable in shoulder injuries.

Q: What nerve and artery pass through the quadrangular space?
A: Axillary nerve and posterior circumflex humeral artery.
Related Pearl: Injury here can cause deltoid paralysis and lateral shoulder numbness.

Q: What is the superior border of the quadrangular space anteriorly?
A: Subscapularis muscle (not teres minor).
Related Pearl: This is a common exam trap; the anterior border differs from the posterior.

Q: What structures pass through the triangular interval?
A: Radial nerve and profunda brachii artery.
Related Pearl: The triangular interval is not a true space but a passageway for these structures.

Q: What muscles border the triangular space?
A: Teres minor, teres major, and long head of triceps.
Related Pearl: The circumflex scapular artery passes through this space.

Brachial Plexus & Innervation

Q: Which spinal nerve roots primarily innervate the rotator cuff?
A: C5 and C6 roots.
Related Pearl: Rotator cuff muscle testing helps localize lesions to upper brachial plexus.

Q: Where is the omohyoid muscle located relative to the anterior scalene?
A: Anterior to the anterior scalene muscle.
Related Pearl: The anterior scalene lies anterior to the brachial plexus, important for surgical approaches.

Q: From which part of the brachial plexus do the suprascapular and nerve to subclavius arise?
A: Upper trunk.
Related Pearl: Lesions at the upper trunk affect these nerves and their muscles.

Q: From which part of the brachial plexus do the long thoracic and dorsal scapular nerves arise?
A: Roots of the brachial plexus.
Related Pearl: Identifying these nerves helps differentiate pre-ganglionic from post-ganglionic plexus injuries.

Q: What characterizes acute brachial neuritis?
A: Acute severe pain onset that decreases over weeks, patchy neurologic findings in C5-T1 distribution, with motor weakness predominating over sensory changes.
Related Pearl: Consider this diagnosis when plexus symptoms are patchy and confusing.

Elbow, Graft, and Cord Syndromes

Q: How does the elbow medial collateral ligament behave in flexion?
A: Both anterior and posterior bands, as well as the capsule, are tight in flexion.
Related Pearl: This tightness stabilizes the elbow against valgus stress during flexion.

Q: Which nerves are most at risk during posterior iliac crest bone graft harvesting?
A: Cluneal nerves, especially more than 8 cm from the posterior superior iliac spine (PSIS).
Related Pearl: Injury can cause sensory deficits over the buttock.

Q: What are the sensory and motor findings in anterior cord syndrome?
A: Loss of motor function and temperature/pain sensation; dorsal columns remain intact.
Related Pearl: Caused by anterior spinal artery or vertebral artery insufficiency.

Cervical Anatomy & Quadriplegia

Q: Where are the superior and inferior thyroid arteries located relative to cervical vertebrae?
A: Superior thyroid artery at C4-5; inferior thyroid artery at C6-7.
Related Pearl: Important landmarks during anterior cervical spine surgery to avoid vascular injury.

Q: What is lost in a C6 quadriplegic patient regarding finger flexion?
A: No function in flexor digitorum superficialis (FDS).
Related Pearl: FDS function is critical for finger flexion; its loss impairs grip.

Q: What is the order of innervation for tendon transfers in tetraplegic hand reconstruction?
A: 1) Deltoid (C4,5), 2) Biceps, 3) Brachioradialis, 4) ECRL, 5) ECRB, 6) Pronator teres, 7) FCR, 8) Finger extensors, 9) Thumb extensors, 10) Partial digital flexors, 11) Intrinsics.
Related Pearl: Prioritize stronger proximal muscles for transfer to restore distal function.

Q: Which muscles are innervated at C5?
A: (Unspecified in notes; typically deltoid and biceps begin at C5/6).
Related Pearl: C5 alone is often incomplete; C5/6 roots are critical for shoulder abduction.

Q: Which muscles are innervated at C5/6?
A: Deltoid.
Related Pearl: Deltoid function is a key marker for C5/6 integrity.

Q: Which muscles are innervated at C6?
A: Deltoid, biceps, brachioradialis, ECRL, ECRB, pronator teres.
Related Pearl: C6 level is critical for elbow flexion and wrist extension.

Q: Which muscles are innervated at C7?
A: Deltoid, biceps, brachioradialis, ECRL, ECRB, pronator teres, FCR, triceps.
Related Pearl: Triceps function is a hallmark of C7 integrity.

Q: Which muscles are innervated at C8?
A: All C7 muscles plus finger extensors, thumb extensors, finger flexors.
Related Pearl: C8 controls finger movements essential for hand function.

Q: Which muscles are innervated at T1?
A: All above plus intrinsic hand muscles.
Related Pearl: T1 innervation is critical for fine motor control of the hand.

Spinal Cord & Knee Approaches

Q: Where does the spinal cord terminate embryologically and at birth?
A: Embryologically at L3/4; at full term neonate at L1.
Related Pearl: Cord ascends during development; lumbar puncture levels differ in neonates vs adults.

Q: What are the landmarks for the posterior approach to the knee?
A: Medial sural cutaneous nerve and small saphenous vein.
Related Pearl: Avoiding these structures prevents sensory loss and hematoma.

Q: Describe the Bruser lateral approach to the knee.
A: Maximal knee flexion with a transverse incision over the lateral meniscus; risks injury to lateral inferior geniculate artery.
Related Pearl: Vascular injury can cause postoperative bleeding and compromise meniscal repair.

Q: Which ACL insertion is biomechanically stronger?
A: Femoral insertion.
Related Pearl: Femoral side fixation is critical in ACL reconstruction for graft stability.

Miscellaneous

Q: What forms the outer wall of a myelomeningocele?
A: Epidermis.
Related Pearl: The skin covering is often thin and prone to rupture, risking infection.

Q: Where is the supraclavicular block performed?
A: Between the anterior and middle scalene muscles.
Related Pearl: The brachial plexus emerges between these muscles, making this an effective block site.

Q: What nerves are lost if the pectoralis major is completely paralyzed after neck trauma?
A: All five nerves from C5-T1, including lateral and medial pectoral nerves.
Related Pearl: Clavicular head mainly innervated by C5-C6; sternocostal head by C7-T1.

Q: What is the anatomical relationship of the subclavian vein to the artery?
A: The subclavian vein lies anterior to the subclavian artery.
Related Pearl: This is critical for safe central venous catheter placement.

Q: What causes Horner’s syndrome in the context of brachial plexus injury?
A: First rib fracture, T1 root avulsion, or stellate ganglion disruption.
Related Pearl: Injury to white rami communicantes alone does not cause Horner’s syndrome.

Q: Where is the artery of Adamkiewicz usually located?
A: Left side, between T9 and L2 vertebral levels.
Related Pearl: Injury to this artery during thoracoabdominal surgery can cause spinal cord ischemia.

Q: What nerves arise from the medial cord of the brachial plexus?
A: Axillary, radial, upper and lower subscapular, and thoracodorsal nerves.
Related Pearl: Medial cord injuries affect multiple shoulder and arm muscles.

Classic Clinical Notes

• Static stabilizers of the shoulder: capsuloligamentous, articular surfaces, and the negative intra-articular pressure components. Dynamic stabilizers include the rotator cuff, biceps tendon, deltoid.

• Quadrangular space: teres minor, teres major, long head triceps, humeral shaft – axillary nerve and posterior circumflex humeral artery (at the front, you don’t see teres minor – the superior border is subscap).

• Triangular interval: not really a space per se – radial nerve and profundi brachii.

• Triangular space: teres minor, teres major, long head of triceps – circumflex scapular goes through it.

• Rotator cuff is basically C5/6.

• The omohyoid muscles lies anterior to anterior scalene muscle (which lies anterior to the brachial plexus).

• The suprascapular nerve and nerve to subclavius come off of the upper trunk.

• The long thoracic nerve and dorsal scapular nerve come off the roots (look for them to tell you if the brachial plexus lesion is pre or post-ganglionic).

• Acute brachial neuritis is characterized by acute onset of severe pain, which decreases dramatically over several weeks. Etiology unknown. Present with patchy neurologic findings in C5-T1 distribution. Motor weakness predominates over sensory change. Consider this diagnosis if the clinical picture is abit confusing, with various parts of the plexus affected.

• The elbow MCL – both the anterior and posterior bands are tight in flexion; the capsule is also tight in flexion.

• The nerves most apt to get bagged when doing posterior iliac crest grafting – cluneal (more than 8 cm from PSIS);

• Anterior vertebral artery insufficiency – anterior cord syndrome: motor and temp/pain sensation; dorsal columns intact.

• The superior thyroid artery may get in your way doing a C4-5 approach; the inferior thyroid artery is more around the C6-7 region.

• C6 quad: no function in FDS.

• Tendon transfers for tetraplegic hand – the order of innervation goes:

first: deltoid (C4,5), then biceps

1. brachioradialis
2. ECRL
3. ECRB
4. Pronator teres
5. FCR
6. finger extensors
7. thumb extensors
8. partial digital flexors
9. intrinsics

• C5 – ?

• C5/6 – deltoid

• C6 – deltoid, biceps, brachioradialis, ECRL, ECRB, pronator

• C7 – deltoid, biceps, brachioradialis, ECRL, ECRB, pronator, FCR, triceps

• C8 – deltoid, biceps, brachioradialis, ECRL, ECRB, pronator, FCR, triceps, finger extension, thumb extension, finger flexion

• T1 – all of the above plus intrinsics.

• The spinal cord begins embrylogically down at around L3/4, but by full term neonate it is at L1.

• Landmark for the posterior approach of the knee – medial sural cutaneous nerve and small saphenous vein.

• The Bruser lateral approach to the knee – flex the knee maximally and make a transverse incision over the lateral meniscus; endangers the lateral inferior geniculate artery.

• The tibial and femoral insertions of the ACL – the femoral is stronger (??).

• Outer wall of a myelomeningocele: epidermis.

• The supraclavicular block for the brachial plexus would be performed between the anterior and middle scalene muscles (the plexus comes out from between the two.)

• If you get stabbed in the neck and lose pec major completely – you’ve lost all 5 nerves (C5-T1). The lateral pectoral nerve comes off the lateral cord, the medial from the medial cord. The clavicular head of pec major is mainly innervated by C5 and C6 in particular. The sternocostal head is mainly C7 and C7, and some T1.

• The subclavian vein is anterior to the artery.

• Horner’s syndrome – myosis, ptosis, anhidrosis – from first rib fracture, T1 root avulsion, stellate ganglion disruption. An injury to the white rami communicantis of T1 does not cause a Horners.

• Artery of Adamkowitz – Left T9-L2 in most cases.

• Medial cord, brachial plexus – gives off axillary and radial nerves, and the upper and lower subscapular nerves, and the thoracodorsal nerve.

Last Updated on January 25, 2026 by Christian Veillette