Anatomy study note · Abdomen

Jejunum and ileum

The mobile small intestine, about 6 m long, from the duodenojejunal flexure to the ileocaecal junction. The jejunum is the upper two-fifths and the ileum the rest, with a gradual change between them.

Key points

• Jejunum: wide, thick, red, few arcades, long vasa recta.
• Ileum: thinner, many arcades, short vasa recta, Peyer patches.
• Both supplied by the SMA; drain to the SMV.
• Pain → umbilicus (T9–T11).
• Pre-arterial midgut segment; returns in the 3rd month.
• Exomphalos: loop fails to return.
• Peyer patches: ileum.
• Villi + crypts of Lieberkühn; Paneth cells make lysozyme.

The full note in the atlas also covers

Features · Blood supply · Nerve supply · Lymph drainage · Histology · Development · Clinical notes

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 7, PDF pp. 855–860
• Inderbir Singh’s Human Embryology, ch. 13, PDF pp. 182, 184–186, 193–194; ch. 14, PDF p. 224
• BRS Cell Biology & Histology, 7th ed., ch. 16, PDF pp. 293–296, 295

More from the abdomen

• Kidney
• Large intestine
• Linea alba
• Liver
• Lumbar plexus
• Pancreas
• Peritoneum
• Portal vein
• Psoas major
• Pyramidalis
• Quadratus lumborum
• Rectus abdominis

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