Membership of the Royal College of Surgeons (MRCS) Applied Surgical Anatomy Flashcards

24 sample cards from the Applied Surgical Anatomy deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. At what vertebral level does the spinal cord terminate in adults, and why is this important for lumbar puncture?

   The conus medullaris ends at approximately L1/L2 in adults (lower, ~L3, in neonates). Lumbar puncture is therefore performed at L3/L4 or L4/L5 (level of the supracristal/Tuffier's line between the iliac crests) to avoid the cord, entering the lumbar cistern containing the cauda equina.

2. Describe the roots, trunks, divisions, cords and terminal branches of the brachial plexus.

   Roots C5-T1 unite into trunks (upper C5-6, middle C7, lower C8-T1); each trunk splits into anterior and posterior divisions; divisions form cords (lateral, posterior, medial) named by their relation to the axillary artery; cords give the terminal branches: musculocutaneous, axillary, radial, median, ulnar. Mnemonic: 'Read That Damn Cadaver Book'.

3. Explain the lesions of Erb's palsy and Klumpke's palsy in terms of nerve roots and deformity.

   Erb's palsy (upper trunk, C5-C6, from excessive head-shoulder separation) gives the 'waiter's tip' position: arm adducted, internally rotated, forearm pronated. Klumpke's palsy (lower trunk, C8-T1, from forced abduction) gives a 'claw hand' from intrinsic muscle loss and may produce Horner's syndrome via T1.

4. Which nerve is at risk in a surgical neck of humerus fracture or shoulder dislocation, and what is the deficit?

   The axillary nerve (C5-C6), which winds around the surgical neck through the quadrangular space. Injury causes deltoid paralysis (weak abduction) and a patch of sensory loss over the 'regimental badge' area of the lateral upper arm.

5. Describe the typical site of injury, motor and sensory deficits of a radial nerve lesion in the radial groove.

   A mid-shaft humeral fracture injures the radial nerve in the radial (spiral) groove, causing wrist drop (loss of wrist and finger extensors) with preserved triceps (its branches arise above the groove), and sensory loss over the dorsal first web space/anatomical snuffbox.

6. Compare the deformities and sensory loss of median nerve injury at the wrist versus ulnar nerve injury at the wrist.

   Median nerve at wrist: thenar wasting and 'ape hand' (loss of opposition/abduction of thumb), sensory loss over the lateral 3.5 digits palmar surface. Ulnar nerve at wrist: 'claw hand' (hyperextended MCP, flexed IP of ring/little fingers), wasting of hypothenar and interossei, sensory loss over the medial 1.5 digits. Ulnar claw is paradoxically worse with distal (wrist) lesions than proximal ('ulnar paradox').

7. Name the four muscles of the rotator cuff and their actions.

   Supraspinatus (initiates abduction), Infraspinatus (lateral/external rotation), Teres minor (lateral rotation), Subscapularis (medial/internal rotation). Mnemonic SITS. They stabilise the glenohumeral joint; supraspinatus tendon is the most commonly torn/impinged.

8. What are the boundaries and contents of the femoral triangle?

   Boundaries: inguinal ligament (superiorly), medial border of sartorius (laterally), medial border of adductor longus (medially); floor formed by iliopsoas and pectineus. Contents from lateral to medial: Femoral Nerve, Artery, Vein, Empty space (femoral canal/lymphatics) — mnemonic NAVEL (the femoral nerve lies OUTSIDE the femoral sheath).

9. Describe the femoral canal, the femoral ring, and why femoral hernias are prone to strangulation.

   The femoral canal is the medial-most compartment of the femoral sheath, containing lymphatics and a node (Cloquet's). Its upper opening, the femoral ring, is bounded by the inguinal ligament (anterior), lacunar ligament (medial), pectineal ligament (posterior) and femoral vein (lateral). Because the lacunar ligament is sharp and unyielding, femoral hernias passing through this narrow ring readily strangulate. A femoral hernia lies below and lateral to the pubic tubercle, an inguinal hernia above and medial.

10. What are the boundaries and contents of the popliteal fossa?

    Boundaries: biceps femoris (superolateral), semimembranosus/semitendinosus (superomedial), the two heads of gastrocnemius (inferiorly). Contents (deep to superficial): popliteal artery (deepest, against the femur), popliteal vein, tibial nerve, and common fibular (peroneal) nerve laterally; also the small saphenous vein and popliteal nodes.

11. Which nerve is at risk around the neck of the fibula, and what deficit results from its injury?

    The common fibular (peroneal) nerve winds around the neck of the fibula superficially, vulnerable to fracture, tight casts or compression. Injury causes foot drop (loss of dorsiflexion and eversion) and sensory loss over the dorsum of the foot and lateral leg, producing a high-stepping gait.

12. Name the boundaries of the cubital fossa and its contents from medial to lateral.

    Boundaries: an imaginary line between the humeral epicondyles (superiorly), pronator teres (medially), brachioradialis (laterally), with floor of brachialis/supinator and roof of bicipital aponeurosis. Contents from medial to lateral: Median nerve, brachial Artery, biceps Tendon ('My Aunt's Tea' or MAT-RN with radial nerve under brachioradialis laterally).

13. Describe the blood supply to the femoral head and the surgical significance of femoral neck fractures.

    Mainly from the medial and lateral circumflex femoral arteries (forming a retinacular anastomosis on the neck), with a small contribution from the artery of the ligamentum teres. An intracapsular (subcapital) femoral neck fracture disrupts the retinacular vessels, risking avascular necrosis of the head — hence such fractures in the elderly are often treated with arthroplasty rather than fixation.

14. Explain the difference between a synovial joint and the typical posterior surgical approach to the hip.

    A synovial (diarthrodial) joint has a fluid-filled cavity, articular (hyaline) cartilage, a fibrous capsule lined by synovium, and supporting ligaments. The posterior (Moore/Southern) approach to the hip splits gluteus maximus and detaches the short external rotators, risking injury to the sciatic nerve which lies just posterior to the joint.

15. What are the meningeal layers and the potential spaces relevant to intracranial haemorrhage?

    From outer to inner: dura mater, arachnoid mater, pia mater. Extradural (epidural) haematoma lies between bone and dura (classically arterial, middle meningeal artery, biconvex on CT). Subdural haematoma lies between dura and arachnoid (bridging veins, crescentic). Subarachnoid haemorrhage lies in the CSF-filled subarachnoid space (often aneurysmal).

16. Trace the flow of cerebrospinal fluid from production to absorption.

    CSF is produced by the choroid plexus of the lateral ventricles, flows through the interventricular foramina (of Monro) to the third ventricle, through the cerebral aqueduct (of Sylvius) to the fourth ventricle, exits via the median (Magendie) and lateral (Luschka) apertures into the subarachnoid space, and is absorbed into the dural venous sinuses through arachnoid granulations.

17. Describe the blood supply of the brain and the components of the circle of Willis.

    Anterior circulation: internal carotid arteries. Posterior circulation: vertebral arteries joining to form the basilar artery. The circle of Willis is formed by: anterior communicating artery, two anterior cerebral arteries, two internal carotids, two posterior communicating arteries and two posterior cerebral arteries, providing collateral flow.

18. Compare the sympathetic and parasympathetic nervous systems in terms of outflow, ganglia location and neurotransmitters.

    Sympathetic ('fight or flight'): thoracolumbar outflow (T1-L2), short preganglionic/long postganglionic fibres, ganglia near the cord (paravertebral chain/prevertebral), postganglionic transmitter usually noradrenaline. Parasympathetic ('rest and digest'): craniosacral outflow (CN III, VII, IX, X and S2-4), long preganglionic/short postganglionic fibres, ganglia near/in the target organ, transmitter acetylcholine throughout.

19. Which cranial nerves carry parasympathetic fibres and to which ganglia/targets do they relay?

    CN III to the ciliary ganglion (pupillary constrictor/ciliary muscle); CN VII to the pterygopalatine ganglion (lacrimal, nasal glands) and submandibular ganglion (submandibular/sublingual glands); CN IX to the otic ganglion (parotid); CN X provides parasympathetic supply to thoracic and abdominal viscera up to the splenic flexure (relaying in walls of the organs).

20. Explain the embryological basis and clinical features of Meckel's diverticulum using the 'rule of 2s'.

    Meckel's diverticulum is a persistent remnant of the vitellointestinal (omphalomesenteric) duct. Rule of 2s: ~2% of the population, ~2 feet (60 cm) proximal to the ileocaecal valve, ~2 inches long, often presents before age 2, twice as common in males, and contains 2 types of ectopic mucosa (gastric and pancreatic). It is a true diverticulum (all bowel layers).

21. Describe the embryological rotation of the midgut and how malrotation predisposes to volvulus.

    The midgut herniates into the umbilical cord at ~6 weeks, rotates a total of 270 degrees anticlockwise around the superior mesenteric artery, and returns to the abdomen by ~10 weeks. Incomplete rotation leaves a narrow mesenteric base and abnormal peritoneal (Ladd's) bands, predisposing to midgut volvulus and duodenal obstruction.

22. What is the embryological origin of the thyroglossal duct and the clinical features of a thyroglossal cyst?

    The thyroid develops at the foramen caecum of the tongue and descends along the thyroglossal duct, passing close to (often through) the developing hyoid bone. A persistent duct remnant forms a midline thyroglossal cyst that classically moves upward on swallowing and on protrusion of the tongue; surgical removal (Sistrunk procedure) requires excising the central body of the hyoid.

23. Define McBurney's point and other key abdominal surface markings used clinically.

    McBurney's point: two-thirds along a line from the umbilicus to the right ASIS (surface marking of the appendix base). The transpyloric plane of Addison (L1) marks the pylorus, neck of pancreas, fundus of gallbladder, and origin of the SMA. The fundus of the gallbladder lies where the right lateral border of rectus meets the costal margin (tip of 9th costal cartilage).

24. What are the surface landmarks for the lung borders and pleural reflections, and why does the pleura extend into the neck?

    The lung's lower border crosses ribs 6 (midclavicular), 8 (midaxillary) and 10 (paravertebral), while the parietal pleura extends two ribs lower (8, 10, 12). The cervical pleura/lung apex rises ~2.5 cm above the medial third of the clavicle, so a supraclavicular stab or central line attempt can cause a pneumothorax.

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