Surgery MCQs Q42

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ANATOMY • GI SURGERY

During an appendectomy, a surgical trainee is asked about the anatomy of the vermiform appendix, including its blood supply and structural layers.

Which of the following statements is correct?

A Embryologically elongates as rapidly as the rest of colon

B Longitudinal layer is continuation of the teniae coli

C Average length is 5 cm

D Tip is at a constant location

E Supplied by branches of inferior mesenteric artery

The correct answer is Longitudinal layer is continuation of the teniae coli.

Decoding the Stem

1

CLUE "Anatomy of appendix"

TRANSLATION Identify the specific anatomical constant among variable features.

Detailed Explanation

✅ Correct Option (Teniae Coli Convergence): The base of the appendix is found where the three teniae coli (longitudinal muscle bands) of the cecum converge. At the appendix itself, these bands fuse to form a complete, continuous longitudinal muscle layer. This is a critical surgical landmark used to locate the appendix.

❌ Why other options are incorrect:

→ Elongation: The appendix does not elongate as rapidly as the rest of the colon; it remains a narrow, worm-like vestigial structure.

→ Length: The average length is approximately 9 cm, though it ranges from 2 cm to over 20 cm.

→ Tip Location: The tip is highly variable (Retrocecal 65%, Pelvic 30%, etc.). Only the base is constant relative to the cecum.

→ Blood Supply: It is supplied by the appendicular artery, a branch of the ileocolic artery, which originates from the Superior Mesenteric Artery (SMA), as the appendix is a midgut structure.

🧠 High-Yield Pearls

✔ Teniae coli converge at the base – the most reliable way to find the appendix surgically.

✔ Retrocecal (65%) is the most common position.

✔ Appendicular Artery is an end artery – obstruction leads to rapid gangrene.

Integrated Clinical Questions

1. Most common position of appendix?

→ Retrocecal (65-70%).

2. Why appendix is prone to gangrene?

→ Because the appendicular artery is an end-artery with no collateral circulation.

3. Classic pain migration in appendicitis?

→ Periumbilical (T10 dermatome) → Right Iliac Fossa (Local parietal peritoneal irritation).

4. Surface landmark?

→ McBurney’s point (1/3 of the way along a line from ASIS to umbilicus).

5. Embryological origin?

→ Midgut (supplied by SMA).

⚡ Exam Pearls

• • Teniae coli = Key surgical landmark to identify the base.
• • Tip position = Variable (Common MCQ trap).
• • Blood supply = SMA (Midgut), NOT IMA (Hindgut).
• • Length = ~9 cm (average), not 5 cm.

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