Abdomen
Introduced| English | Meaning |
|---|---|
| epigastric | epigastric |
| coeliac trunk | coeliac trunk |
| superior mesenteric artery | superior mesenteric artery |
| inferior mesenteric artery | inferior mesenteric artery |
| parietal peritoneum | parietal peritoneum |
| pectinate line | pectinate line |
A map and three pipes
- The abdomen holds the digestive organs on a nine-region grid, fed by three unpaired arteries.
- The arteries' territories explain where pain is felt and where surgeons cut.
Nine regions
- Three central regions run top to bottom: epigastric 腹上区, umbilical and hypogastric. On each side are the hypochondriac, lumbar and inguinal regions.
- Four quadrants are a quicker version. Say which system you are using.
How many regions does the abdominal grid have?
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Two vertical and two horizontal lines make a 3 × 3 grid of nine regions; quadrants divide it into four.
Three arteries, three gut parts
- The coeliac trunk 腹腔干 supplies the foregut (down to the middle of the duodenum). The superior mesenteric artery 肠系膜上动脉 supplies the midgut (to two-thirds of the way along the transverse colon).
- The inferior mesenteric artery 肠系膜下动脉 supplies the hindgut, down to the upper anal canal. Veins and lymph follow the same territories.
Match each artery to its gut territory.
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One artery per embryonic gut part, and the same split explains referred pain.
Why pain is felt where it is
- Organs report pain to the spinal segments they came from in the embryo: foregut T5–9 (epigastric), midgut T10–12 (umbilical), hindgut L1–3 (hypogastric).
- Early organ pain is dull and in the midline. It becomes sharp and one-sided only when the inflamed organ touches the parietal peritoneum 壁腹膜.
Why does early appendicitis cause pain around the umbilicus?
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Visceral pain goes to the segments of embryonic origin; it moves to the right iliac fossa only when the parietal peritoneum is involved.
Worked example: three classic pains
- (Fictional cases) Appendicitis: a midgut organ, so a dull umbilical ache first, then sharp pain in the right iliac fossa once the parietal peritoneum is involved.
- Gallbladder: foregut, so epigastric ache, then right upper quadrant, and right shoulder-tip pain if the diaphragm is irritated (C3–5). Ureteric stone: pain from loin to groin.
Put the course of appendicitis pain in order.
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Visceral nerves give vague midline pain; somatic nerves in the parietal peritoneum give sharp, localised pain.
Worked example: the line that splits the anal canal
- (Fictional patient) Painless bright-red bleeding from internal haemorrhoids. The inferior mesenteric artery ends as the superior rectal artery, which supplies the canal above the pectinate line 齿状线.
- Above the line the nerves are visceral, so pain is dull or absent; below it they are somatic and very sensitive. Anatomy predicts which lesions hurt.
Why are internal haemorrhoids usually painless?
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Above the line the canal is gut-like, with visceral nerves; below it the skin-like lining has sensitive somatic nerves.
Three common slips
- Quadrants for regions. Answer in the system you were asked for.
- Forgetting drainage. Veins and lymph follow the arteries' territories, to the portal system and the matching node groups.
- Kidney pain as gut pain. Kidney and ureter pain sit in the loin and groin, not in the midline bands.
A ureteric stone typically causes pain that runs from the loin to the groin.
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The ureter's nerves enter around T11–L2, so the pain follows its course from loin to groin rather than a midline band.
Recap
- Nine regions; coeliac, superior and inferior mesenteric arteries feed foregut, midgut and hindgut.
- Gut pain is referred to T5–9, T10–12 and L1–3: epigastric, umbilical, hypogastric.
- The pectinate line splits blood supply and sensation in the anal canal.