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Score — click each question to reveal
Q1
The posterior wall of the rectus sheath below the arcuate line is formed by:
A. Transversalis fascia only (no aponeurotic posterior wall)
B. Posterior layer of internal oblique aponeurosis
C. External oblique aponeurosis
D. Transversus abdominis aponeurosis
✓ Answer: A — Transversalis fascia only
Below the arcuate line (halfway between umbilicus and pubis), ALL three aponeuroses pass anterior to rectus abdominis → the posterior rectus sheath is formed only by transversalis fascia (+ peritoneum). This makes the posterior sheath absent below the arcuate line. The arcuate line itself is the lower free edge of the posterior sheath.
⚠ Above arcuate line: posterior sheath = posterior layer of internal oblique + transversus abdominis aponeurosis. Below: only transversalis fascia. Rectus sheath haematoma below arcuate line = blood spreads freely into pelvis → larger haematoma.
Q2
Hesselbach's (inguinal) triangle is bounded by:
A. Inguinal ligament + conjoint tendon + femoral vessels
B. Inguinal ligament + rectus abdominis + inferior epigastric artery
C. Rectus abdominis + inferior epigastric + pubic crest
D. External oblique + internal oblique + transversus
✓ Answer: B — Inguinal ligament + rectus + inferior epigastric artery
Hesselbach's triangle: Lateral = inferior epigastric artery; Medial = lateral border of rectus abdominis; Inferior = inguinal ligament. Direct hernias emerge MEDIAL to the inferior epigastric artery, through this triangle. Indirect hernias emerge LATERAL to the inferior epigastric artery, through the deep inguinal ring.
⚠ Direct = medial to inferior epigastric = through Hesselbach's triangle = through posterior wall of inguinal canal. Indirect = lateral to inferior epigastric = through deep ring = congenital patent processus vaginalis. “Direct goes straight through; Indirect goes the long way round.”
Q3
The diaphragm opening at T10 transmits:
A. Aorta + thoracic duct + azygos vein
B. Inferior vena cava + right phrenic nerve
C. Oesophagus + two vagal trunks + left gastric vessels
D. Sympathetic trunks + splanchnic nerves
✓ Answer: C — Oesophagus + vagal trunks + left gastric vessels
Mnemonic I 8 (ate) 10 eggs AT 12: T8 = IVC + right phrenic nerve; T10 = Oesophagus + anterior & posterior vagal trunks + left gastric vessels; T12 = Aorta + thoracic duct + azygos vein. The oesophageal hiatus is a muscular opening (crural diaphragm) → sliding hiatus hernia (most common) passes through here.
⚠ T8 = IVC (right phrenic travels with IVC). T12 aortic hiatus is BEHIND the diaphragm (between the crura), so aorta is not truly “through” diaphragm muscle. Azygos and thoracic duct also pass at T12.
Q4
The SITS mnemonic for the rotator cuff stands for (in order of their insertions from superior to inferior):
A. Subscapularis, Infraspinatus, Teres minor, Supraspinatus
B. Supraspinatus, Infraspinatus, Subscapularis, Teres minor
C. Subscapularis, Supraspinatus, Infraspinatus, Teres minor
D. Supraspinatus, Infraspinatus, Teres minor, Subscapularis
✓ Answer: D — Supraspinatus, Infraspinatus, Teres minor, Subscapularis
SITS: Supraspinatus (greater tubercle, superior facet; abduction 0–15°, nerve: suprascapular C5), Infraspinatus (greater tubercle, middle facet; lateral rotation, nerve: suprascapular C5/6), Teres minor (greater tubercle, inferior facet; lateral rotation, nerve: axillary C5/6), Subscapularis (lesser tubercle; medial rotation, nerve: upper/lower subscapular C5–C7). Together they compress the humeral head into the glenoid (dynamic stability).
⚠ Subscapularis = MEDIAL rotator (inserts on lesser tubercle). The other three (SST) = lateral rotators + abductors on the greater tubercle. Most commonly torn: supraspinatus (impingement under coracoacromial arch).
Q5
The LOAF muscles of the hand are innervated by which nerve?
A. Ulnar nerve
B. Radial nerve
C. Median nerve (recurrent branch + palmar digital branches)
D. Anterior interosseous nerve
✓ Answer: C — Median nerve
LOAF = Lateral two lumbricals (index, middle fingers), Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis (superficial head). All innervated by the median nerve — the first two via palmar digital branches, the thenar three via the recurrent (thenar) branch of the median nerve. All other intrinsic hand muscles = ulnar nerve.
⚠ “All intrinsic hand muscles are ulnar EXCEPT LOAF (median).” Opponens pollicis = opposition of thumb (median nerve). Adductor pollicis = ulnar nerve (Froment's sign tests this). FPB has dual innervation (deep head = ulnar).
Q6
Palmar interossei ADDUCT the fingers; dorsal interossei ABDUCT them. This is described by the mnemonic:
A. DABS / PADS
B. PAD / DAB
C. PALM / DORM
D. ADDS / DUCTS
✓ Answer: B — PAD / DAB
PAD = Palmar interossei ADduct; DAB = Dorsal interossei ABduct. Both groups are innervated by the deep branch of the ulnar nerve (C8, T1). Reference axis for abduction/adduction of the fingers = the middle finger. 4 dorsal interossei (abduct index, middle from both sides, ring finger); 3 palmar interossei (adduct index, ring, little toward middle finger).
⚠ All interossei + all hypothenar + adductor pollicis + medial two lumbricals = ulnar nerve. Clawing worst in ring + little fingers in ulnar palsy (“ulnar paradox” — wrist lesion claws more than elbow lesion because intrinsics of index/middle also lost).
Q7
The safe triangle for chest drain insertion is bounded by:
A. Anterior axillary line, clavicle, and mid-axillary line
B. Mid-clavicular line, 2nd intercostal space only
C. Lateral border of pectoralis major, anterior border of latissimus dorsi, and a horizontal line at the level of the nipple (5th intercostal space)
D. Posterior axillary line, 7th intercostal space, and midline
✓ Answer: C — Lateral pec major + anterior latissimus + 5th ICS horizontal line
The safe triangle for chest drain insertion: anterior = lateral border of pectoralis major; posterior = anterior border of latissimus dorsi; inferior = horizontal line at the 5th intercostal space (nipple level in males). Drain inserted in the 4th or 5th ICS, mid-axillary line, over the upper border of the rib below (to avoid the neurovascular bundle which runs in the costal groove of the rib above).
⚠ 2nd ICS mid-clavicular = needle decompression for tension pneumothorax (emergency, before definitive drain). Chest drain = safe triangle, 4th/5th ICS, mid-axillary, over the TOP of the lower rib.
Q8
The internal anal sphincter (IAS) is derived from which muscle layer and is controlled by:
A. Striated muscle; voluntary control via pudendal nerve
B. Smooth muscle (longitudinal); voluntary control
C. Striated muscle; automatic reflex via S2–S4
D. Smooth muscle (circular); involuntary control via autonomic nervous system
✓ Answer: D — Smooth muscle; autonomic (involuntary)
The IAS is a thickening of the circular smooth muscle of the rectum. It is tonically contracted at rest (responsible for ~85% of resting anal canal pressure) via sympathetic stimulation (L1–L2). It relaxes on rectal distension (recto-anal inhibitory reflex, RAIR). The EAS = striated muscle, voluntary control via inferior rectal nerve (branch of pudendal nerve, S2–S4). EAS provides the squeeze pressure and conscious continence.
⚠ IAS = involuntary = smooth muscle = autonomic. EAS = voluntary = striated = pudendal nerve. Puborectalis (levator ani) also contributes via maintaining the anorectal angle.
Q9
Which muscle is the primary motor for resisted hip abduction and stabilises the pelvis during single-leg stance (Trendelenburg's test)?
A. Gluteus medius
B. Piriformis
C. Tensor fasciae latae
D. Gluteus maximus
✓ Answer: A — Gluteus medius
Gluteus medius (and minimus): abductors of the hip; stabilise the pelvis during the stance phase so the opposite side doesn't drop. Trendelenburg's sign: positive when the pelvis drops on the non-weight-bearing side → indicates weakness of the weight-bearing hip abductors (gluteus medius). Causes: superior gluteal nerve injury, hip pain, femoral neck fracture. Gluteus maximus = extension + lateral rotation (stairs, rising from chair).
⚠ Trendelenburg sign: pelvis drops on the opposite side to the weak gluteus medius. The patient leans toward the weak side (Trendelenburg gait = “waddling”). Superior gluteal nerve (L4–S1) supplies gluteus medius, minimus, and TFL.
Q10
All muscles of the soft palate are supplied by the vagus nerve (CN X) via the pharyngeal plexus EXCEPT:
A. Levator veli palatini
B. Tensor veli palatini (CN V3 — medial pterygoid nerve)
C. Musculus uvulae
D. Palatoglossus
✓ Answer: B — Tensor veli palatini (CN V3)
All soft palate muscles = CN X via pharyngeal plexus (accessory nerve fibres carried by vagus), EXCEPT tensor veli palatini = CN V3 (medial pterygoid nerve, branch of mandibular division). Tensor veli palatini opens the Eustachian tube during swallowing. This is a classic anatomy MCQ. “All palate = vagus, except the TENSOR = trigeminal.”
⚠ Gag reflex: afferent = CN IX (glossopharyngeal); efferent = CN X (vagus). Palatal movement on saying “Aah” = CN X. Unilateral CN X palsy → uvula deviates to the healthy side.
Q11
The inguinal canal in males contains (complete list):
A. Spermatic cord only
B. Ilioinguinal nerve only (spermatic cord is in the scrotum)
C. Spermatic cord + ilioinguinal nerve + genital branch of genitofemoral nerve
D. Spermatic cord + femoral nerve
✓ Answer: C — Spermatic cord + ilioinguinal nerve + genital branch of GFN
Male inguinal canal contents: (1) Spermatic cord (vas deferens + testicular artery + pampiniform plexus + lymphatics + genital branch of genitofemoral nerve + autonomic fibres + cremasteric artery + artery to vas); (2) Ilioinguinal nerve (enters through the canal, exits through the superficial ring); (3) The genital branch of the genitofemoral nerve (enters with the deep ring, runs with spermatic cord → cremaster muscle). In females: round ligament of the uterus replaces the spermatic cord.
⚠ The iliohypogastric nerve does NOT enter the inguinal canal. The femoral nerve passes under the inguinal ligament in the femoral sheath, lateral to the canal. Ilioinguinal nerve enters through the wall of the canal, not the deep ring.
Q12
Guyon's canal at the wrist transmits the:
A. Median nerve and radial artery
B. Median nerve and ulnar artery
C. Radial nerve and radial artery
D. Ulnar nerve and ulnar artery
✓ Answer: D — Ulnar nerve and ulnar artery
Guyon's canal (ulnar tunnel): between the pisiform (medial) and hook of hamate (lateral), covered by the palmar carpal ligament. Transmits: ulnar nerve + ulnar artery. Compression (cyclist's palsy, hook of hamate fracture) → ulnar nerve palsy at wrist → weakness of all intrinsic muscles EXCEPT LOAF, loss of sensation ulnar 1.5 digits (palmar & dorsal), hypothenar wasting, clawing ring + little finger.
⚠ Distinguish: carpal tunnel = median nerve + 9 tendons (no ulnar nerve/artery). Guyon's canal = ulnar nerve + ulnar artery only (no tendons). Both pass through the wrist but are separate canals.
Q13
The deep inguinal ring is located in the:
A. Midpoint of the inguinal ligament, in the transversalis fascia
B. Medial third of the inguinal ligament, in the external oblique aponeurosis
C. Lateral third of the inguinal ligament, in the internal oblique muscle
D. Pubic tubercle, in the external oblique aponeurosis
✓ Answer: A — Midpoint of inguinal ligament, in transversalis fascia
The deep inguinal ring is a defect in the transversalis fascia, located at the midpoint of the inguinal ligament (halfway between ASIS and pubic tubercle), about 1.25 cm above the ligament. Lateral to the inferior epigastric artery. The superficial inguinal ring is in the external oblique aponeurosis, just above and lateral to the pubic tubercle.
⚠ Deep ring test: press on the deep ring (midpoint of inguinal ligament) and ask patient to cough → if hernia controlled = indirect; if not controlled = direct (comes through Hesselbach's triangle, medial to deep ring).
Q14
Volkmann's ischaemic contracture of the forearm results from:
A. Rupture of the flexor tendons during supracondylar fracture
B. Untreated anterior compartment syndrome of the forearm causing flexor muscle fibrosis
C. Radial nerve palsy causing extensor weakness
D. Compression of the median nerve in the carpal tunnel
✓ Answer: B — Untreated forearm compartment syndrome → flexor fibrosis
Volkmann's ischaemic contracture: complication of untreated acute compartment syndrome of the anterior compartment of the forearm (most commonly after supracondylar fracture in children). Ischaemia → necrosis → fibrosis of FDS, FDP, FPL → fixed flexion deformity of wrist + fingers with extension of the IPJs when wrist is flexed. Classic posture: flexed wrist, flexed MCPJs, hyperextended IPJs (intrinsic-minus hand).
⚠ Volkmann's = forearm. Prevention = prompt fasciotomy. The 6 Ps apply: pain on passive extension of fingers is the most reliable early warning sign. Do NOT apply a tight cast → monitor carefully.
Q15
Which muscle opposes the action of the rotator cuff in stabilising the glenohumeral joint by pulling the humeral head inferiorly?
A. Coracobrachialis
B. Biceps brachii short head
C. Deltoid (when paralysed, inferior subluxation occurs)
D. Long head of triceps
✓ Answer: C — Deltoid (inferior subluxation when paralysed)
The deltoid muscle (axillary nerve, C5/6) is the most powerful abductor of the shoulder. When it is paralysed (e.g. axillary nerve injury after shoulder dislocation or surgical neck fracture), the humeral head is not adequately supported → inferior subluxation of the glenohumeral joint (visible step-down beneath the acromion). The rotator cuff compresses the head; the deltoid supports it from below during abduction.
⚠ Axillary nerve injury: “regimental badge” area sensory loss (over deltoid insertion lateral arm) + deltoid paralysis → flattened shoulder + inferior subluxation.
Q16
The pelvic diaphragm (floor) is formed by which muscle group?
A. Obturator internus + piriformis
B. Transversus perinei profundus only
C. Ischiocavernosus + bulbospongiosus
D. Levator ani (puborectalis + pubococcygeus + iliococcygeus) + coccygeus
✓ Answer: D — Levator ani + coccygeus
The pelvic diaphragm = levator ani (puborectalis + pubococcygeus + iliococcygeus) + coccygeus. Levator ani: origin = pubic body + tendinous arch + ischial spine; insertion = perineal body, anococcygeal raphe, coccyx. Innervation: nerve to levator ani (S3/4 directly) + perineal branch of S4. Functions: supports pelvic organs, aids defaecation/parturition, maintains anorectal angle (puborectalis), urinary continence.
⚠ Obturator internus and piriformis form the WALLS of the pelvis (not the floor). Ischiocavernosus and bulbospongiosus = superficial perineal pouch (perineal muscles, below the pelvic floor). Transversus perinei = deeper perineal muscles.
Q17
The quadriceps femoris group is innervated by the femoral nerve (L2–L4). Which of the following is NOT a part of this group?
A. Sartorius
B. Rectus femoris
C. Vastus medialis
D. Vastus intermedius
✓ Answer: A — Sartorius is NOT part of quadriceps
Quadriceps = rectus femoris + vastus medialis + vastus lateralis + vastus intermedius (four heads). All unite in the quadriceps tendon, encase the patella, and continue as the patellar ligament to the tibial tuberosity. Sartorius (L2/L3, femoral nerve) is a separate muscle of the anterior thigh — it crosses to the medial side (ASIS → medial tibia) and forms part of the pes anserinus with gracilis + semitendinosus.
⚠ The patella is a sesamoid bone within the quadriceps tendon. Rectus femoris = only quad head that crosses the hip (AIIS origin) → flexes the hip + extends the knee.
Q18
The sternocleidomastoid (SCM) muscle, acting alone on one side, produces:
A. Ipsilateral lateral flexion + ipsilateral rotation of the head
B. Ipsilateral lateral flexion + contralateral rotation of the head
C. Contralateral lateral flexion + ipsilateral rotation
D. Pure extension of the neck
✓ Answer: B — Ipsilateral tilt + contralateral rotation
Unilateral SCM: lateral flexion (tilt) toward the SAME side + rotation of chin toward the OPPOSITE side. Bilateral SCM: flexes the neck (brings head forward). Torticollis (wry neck) = fibrosis/spasm of one SCM → persistent ipsilateral tilt + contralateral chin rotation. Innervation: accessory nerve (CN XI) (motor) + C2/C3 (sensory). SCM divides the neck into anterior and posterior triangles.
⚠ Congenital torticollis = fibrous nodule in SCM at birth (from birth trauma/ischaemia). Treatment: physiotherapy, release if persists >1 year. Atlantoaxial rotatory subluxation also causes torticollis (Grisel's syndrome after pharyngitis).
Q19
The most commonly torn rotator cuff tendon is:
A. Subscapularis
B. Infraspinatus
C. Supraspinatus
D. Teres minor
✓ Answer: C — Supraspinatus
Supraspinatus is the most commonly torn rotator cuff tendon (>90% of cuff tears). Its tendon passes through the subacromial space under the coracoacromial arch → impingement between the greater tuberosity and the acromion in 60–120° arc of abduction (“painful arc syndrome”). Tests: Empty can test (Jobe's test): arm at 90° abduction, 30° forward flexion (scapular plane), thumb pointing down → resistance → pain/weakness = supraspinatus tear. Drop arm test: unable to maintain 90° abduction.
⚠ “Critical zone” of supraspinatus tendon = relatively avascular area 1 cm from its insertion → degenerative tears here with age. Full-thickness tears → MRI diagnosis → arthroscopic repair.
Q20
The posterior wall of the inguinal canal is formed primarily by:
A. Internal oblique muscle
B. External oblique aponeurosis
C. Inguinal ligament
D. Transversalis fascia (+ conjoint tendon medially)
✓ Answer: D — Transversalis fascia + conjoint tendon medially
Inguinal canal walls: Anterior = external oblique aponeurosis (+ internal oblique laterally); Posterior = transversalis fascia throughout + conjoint tendon (IA + TA) medially; Roof = arching fibres of internal oblique + transversus abdominis; Floor = inguinal ligament + lacunar ligament medially. Direct hernias push through the posterior wall (transversalis fascia) medial to the inferior epigastric artery.
⚠ Bassini repair = reconstruction of the posterior wall using conjoint tendon. Lichtenstein = mesh repair without disturbing conjoint tendon. Inguinal ligament = FLOOR (inferior wall), not posterior wall.
D1Hesselbach's (Inguinal) Triangle+
A triangle on the posterior surface of the anterior abdominal wall bounded by: lateral = inferior epigastric artery; medial = lateral border of rectus abdominis; inferior = inguinal ligament. The floor is the transversalis fascia, reinforced medially by the conjoint tendon. Direct inguinal hernias protrude through this triangle (medial to the inferior epigastric artery) through a weakness in the transversalis fascia. They are acquired, rarely strangulate, and typically reduce easily with supine position.
Gray's Anatomy 4e · Unit 04
D2Rotator Cuff+
A group of four muscles and their tendons that encircle and stabilise the glenohumeral joint by compressing the humeral head into the shallow glenoid cavity. Mnemonic: SITS — Supraspinatus (suprascapular nerve, abduction + cuff compression), Infraspinatus (suprascapular nerve, lateral rotation), Teres minor (axillary nerve, lateral rotation), Subscapularis (subscapular nerves, medial rotation). The tendon of supraspinatus is most commonly torn due to impingement under the coracoacromial arch. Together the cuff muscles provide the critical “force couple” with the deltoid for full abduction.
Gray's Anatomy 4e · Unit 04
D3Safe Triangle for Chest Drain+
The anatomically safe zone for intercostal chest drain insertion, minimising risk of injury to lung, diaphragm, liver, spleen, and neurovascular bundle. Borders: anterior = lateral border of pectoralis major; posterior = anterior border of latissimus dorsi; inferior = a horizontal line at the level of the nipple (5th intercostal space in males). The drain is inserted in the 4th or 5th ICS, mid-axillary line, over the UPPER border of the lower rib (to avoid the intercostal neurovascular bundle running in the costal groove of the rib above). This is BTS (British Thoracic Society) recommended site.
Gray's Anatomy 4e · Unit 04
D4Arcuate Line of the Rectus Sheath+
A curved line approximately halfway between the umbilicus and the pubic symphysis that marks the lower free edge of the posterior layer of the rectus sheath. Above: posterior sheath = posterior lamina of internal oblique + transversus abdominis aponeurosis. Below: all aponeuroses pass anterior to rectus → no posterior sheath → only transversalis fascia separates rectus from peritoneum. Clinically: rectus sheath haematoma below the arcuate line can spread freely into the extraperitoneal space and pelvis, producing a larger haematoma that may mimic an acute abdomen.
Gray's Anatomy 4e · Unit 04
D5Thenar Eminence+
The muscular mound at the base of the thumb on the palm, formed by three thenar muscles: abductor pollicis brevis (most superficial), flexor pollicis brevis (intermediate), and opponens pollicis (deepest, produces opposition). All three are innervated by the recurrent (thenar) branch of the median nerve, which arises just distal to the flexor retinaculum and hooks back around its distal border. Wasting of the thenar eminence = carpal tunnel syndrome (late sign) or proximal median nerve lesion. Deep head of FPB is ulnar nerve.
Gray's Anatomy 4e · Unit 04
D6Pelvic Diaphragm+
The muscular floor of the pelvis, forming a hammock-shaped sheet that supports the pelvic viscera and maintains continence. Formed by: levator ani (puborectalis + pubococcygeus + iliococcygeus) + coccygeus. Levator ani origin: inner surface of pubic body (pubis) + tendinous arch of levator ani (thickened obturator fascia) + ischial spine. Insertion: perineal body, coccyx, anococcygeal raphe. Nerve supply: nerve to levator ani (direct branches from S3/4) + perineal branch of pudendal nerve. Functions: support pelvic organs, resist raised intra-abdominal pressure, urinary/faecal continence, maintain anorectal angle (puborectalis), aid in parturition.
Gray's Anatomy 4e · Unit 04
Essay 1
Describe the inguinal canal: its four walls, the deep and superficial rings, and the contents in males and females. How do you distinguish indirect from direct inguinal hernia clinically?
8 marks
Four walls of the inguinal canal
- Anterior wall: external oblique aponeurosis throughout; internal oblique reinforces laterally
- Posterior wall: transversalis fascia throughout; conjoint tendon (IA + TA) reinforces medially
- Roof (superior wall): arching fibres of internal oblique + transversus abdominis
- Floor (inferior wall): inguinal ligament + lacunar ligament medially
Rings
- Deep inguinal ring: opening in transversalis fascia, midpoint of inguinal ligament, 1.25 cm above ligament, lateral to inferior epigastric artery
- Superficial inguinal ring: V-shaped defect in external oblique aponeurosis, above and lateral to pubic tubercle
Contents — Male
Spermatic cord: (1) vas deferens, (2) testicular artery, (3) pampiniform venous plexus, (4) cremasteric artery, (5) artery to vas, (6) lymphatics, (7) sympathetic fibres, (8) genital branch of genitofemoral nerve. Plus the ilioinguinal nerve (lies on spermatic cord, not within).
Contents — Female
Round ligament of the uterus (homologue of gubernaculum) + ilioinguinal nerve. No spermatic cord.
Indirect vs Direct hernia
- Indirect: enters through deep ring (lateral to inferior epigastric artery), passes through entire canal, exits superficial ring into scrotum. Covered by all three layers of spermatic cord coverings. Controlled by occluding the deep ring. Younger patients, congenital (patent processus vaginalis). Risk of strangulation higher.
- Direct: pushes through posterior wall (Hesselbach's triangle), medial to inferior epigastric artery. NOT controlled by occluding deep ring. Older patients, acquired (weakness). Rarely strangulates. Reduces spontaneously in supine position.
Marking (8 marks): All four walls named correctly (2) · Deep ring location (0.5) · Superficial ring location (0.5) · Spermatic cord contents (3 key structures) (1.5) · Female content (0.5) · Indirect vs direct distinction: IEA relationship + deep ring test (2)
Essay 2
Describe the diaphragm: its attachments, the three major openings (with vertebral levels and structures passing through each), and its nerve supply. What is a hiatus hernia?
8 marks
Attachments
- Sternal part: two slips from xiphoid process
- Costal part: inner surfaces of lower 6 ribs (7th–12th) and costal cartilages
- Lumbar part: medial and lateral arcuate ligaments + right crus (L1–L3) + left crus (L1–L2)
- Central tendon: fibrous centre into which muscle fibres insert
Three major openings (I 8 10 AT 12)
- T8 — Caval opening (in central tendon): IVC + right phrenic nerve + lymphatics
- T10 — Oesophageal hiatus (muscular, in right crus): oesophagus + anterior & posterior vagal trunks + left gastric vessels
- T12 — Aortic hiatus (behind diaphragm, between crura): descending aorta + thoracic duct + azygos vein
Nerve supply
- Motor: phrenic nerve (C3, C4, C5 — “C3, 4, 5 keeps the diaphragm alive”) bilaterally
- Sensory: central tendon = phrenic nerve; peripheral = lower 6 intercostal nerves
Hiatus hernia
- Sliding (Type I) = ~95%: GOJ + part of stomach herniate into chest through oesophageal hiatus. Associated with GORD. Reduces when supine.
- Para-oesophageal (Type II/III): fundus herniates alongside oesophagus; GOJ remains in abdomen. Risk of gastric volvulus, strangulation.
Marking (8 marks): Sternal + costal + lumbar attachments (1.5) · T8 opening + contents (1.5) · T10 opening + contents (1.5) · T12 opening + contents (1.5) · Phrenic nerve C3,4,5 (1) · Hiatus hernia types (1)
Essay 3
Describe the rotator cuff: the four muscles (origin, insertion, action, nerve supply), and the clinical presentation and investigations for supraspinatus tear.
8 marks
SITS — four rotator cuff muscles
- Supraspinatus: Origin = supraspinous fossa; Insertion = superior facet of greater tubercle; Action = abduction (0–15°), humeral head depression; Nerve = suprascapular (C4–C6)
- Infraspinatus: Origin = infraspinous fossa; Insertion = middle facet of greater tubercle; Action = lateral rotation; Nerve = suprascapular (C5–C6)
- Teres minor: Origin = lateral border of scapula; Insertion = inferior facet of greater tubercle; Action = lateral rotation; Nerve = axillary (C5–C6)
- Subscapularis: Origin = subscapular fossa; Insertion = lesser tubercle; Action = medial rotation, adduction; Nerve = upper + lower subscapular (C5–C7)
Supraspinatus tear — clinical features
- Painful arc: 60–120° abduction (impingement under coracoacromial arch)
- Unable to initiate abduction from 0° (supraspinatus initiates first 15°)
- Drop arm test positive: inability to maintain 90° abduction against gravity
- Empty can (Jobe's) test: pain/weakness in scapular plane with thumb pointing down
- Chronic: cuff tear arthropathy with superior migration of humeral head on X-ray
Investigations
- X-ray: normal or superior head migration; acromial spur
- Ultrasound: first-line dynamic assessment of cuff tendons
- MRI: gold standard for full-thickness vs partial-thickness tear, extent, retraction
- MR arthrogram: for labral tears / SLAP lesions if also needed
Marking (8 marks): Each of 4 muscles with correct insertion facet + nerve (4) · Painful arc (1) · Drop arm test (1) · Empty can test (1) · Investigations: US + MRI (1)
Essay 4
Describe the muscles of the pelvic floor (levator ani group). What is the role of puborectalis in faecal continence? What happens when it is damaged?
6 marks
Levator ani — three parts
- Puborectalis: Origin = posterior surface of pubic body; loops behind the anorectal junction (not inserting into coccyx); forms the anorectal sling maintaining the anorectal angle (~80–90°). Tonic contraction = continence. Relaxation = straightening of angle during defaecation.
- Pubococcygeus: Pubic body → anococcygeal raphe + coccyx. Supports bladder, vagina, rectum.
- Iliococcygeus: Tendinous arch → coccyx. Broadest part; like a hammock.
Nerve supply
Nerve to levator ani (S3/S4 direct branches from sacral plexus on superior/pelvic surface) + perineal branch of pudendal nerve (inferior surface).
Puborectalis in faecal continence
Puborectalis maintains the anorectal angle at ~90° by its sling-like tonic pull, creating a mechanical valve. During defaecation, puborectalis relaxes (angle straightens to ~130°). The internal anal sphincter provides resting pressure; the external anal sphincter provides voluntary squeeze. All three act together for continence.
Damage consequences
- Puborectalis denervation/damage (obstetric injury, sphincterotomy) → loss of anorectal angle → faecal incontinence
- Levator ani damage in childbirth → pelvic organ prolapse (cystocoele, rectocoele, uterine prolapse)
Marking (6 marks): Three parts of levator ani named (1.5) · Puborectalis sling concept + anorectal angle (2) · Nerve supply (1) · Consequence of damage (1.5)
Essay 5
Describe the intrinsic muscles of the hand that are supplied by the median nerve. What are the signs of median nerve palsy at the wrist?
6 marks
Median nerve intrinsic muscles (LOAF)
- Lateral two lumbricals (1st and 2nd): arise from radial side of FDP tendons of index and middle fingers; insert into extensor expansion; flex MCPJs + extend IPJs. Nerve: palmar digital branches of median nerve.
- Opponens pollicis: deepest thenar muscle; origin = flexor retinaculum + trapezium; insertion = radial border of 1st metacarpal shaft. Action: opposition (rotation + flexion + medial rotation of 1st metacarpal). Key for pinch.
- Abductor pollicis brevis: most superficial; abducts thumb at MCPj in palmar plane.
- Flexor pollicis brevis: superficial head = median nerve; deep head = ulnar nerve. Flexes thumb at MCPJ.
Signs of median nerve palsy at the wrist (CTS / wrist laceration)
- Sensory loss: palmar surface of radial 3½ digits (thumb, index, middle, radial half of ring) + dorsal fingertips
- Thenar wasting: opponens + APB + FPB atrophy → flat thenar eminence
- Loss of opposition: cannot bring thumb to face little finger pad-to-pad (ape hand deformity)
- Weak pinch: cannot form the “OK” circle (if AIN also involved)
- LOAF wasting; ring/little clawing NOT severe (FDP to ring/little = ulnar; lateral 2 lumbricals lost but medial 2 intact)
Marking (6 marks): All 4 LOAF muscles named with function (2.5) · Opponens pollicis action described (0.5) · Sensory distribution (1) · Thenar wasting + ape hand (1) · Loss of opposition (1)