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TAP Block Muscle Layer Anatomy — FRCA Final MCQ

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EasyRegional AnaesthesiaTAP Block Muscle Layer AnatomyFRCA Final

A 40-year-old man (ASA II) is having a right inguinal hernia repair. The surgeon performs a TAP block under ultrasound guidance. On ultrasound, the three abdominal wall muscle layers from superficial to deep are:

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Correct answer: D — External oblique, internal oblique, transversus abdominis

On ultrasound imaging of the lateral abdominal wall (between the costal margin and iliac crest, in the mid-axillary line), three muscle layers are visible from superficial to deep: external oblique (most superficial), internal oblique (middle), and transversus abdominis (deepest, overlying the peritoneum). The TAP block targets the fascial plane between the internal oblique and transversus abdominis muscles, where the thoracolumbar nerves (T7-L1 ventral rami) travel. The 'TAP' plane appears as a bright fascial line between these two muscles on ultrasound.

Reference: RCOA – 2023 – Regional anaesthesia: TAP block anatomy; Tran TMN – 2010 – TAP block review