Plicae circulares
Summary
Plicae circulares (valves of Kerckring) are permanent circular mucosal-submucosal folds of the small intestine that increase absorptive surface area. They are most prominent in the jejunum and key for radiographic identification of the small bowel.
Detail
The small intestine amplifies its surface area in three layers: plicae circulares (mucosa + submucosa, gross folds), villi (mucosal projections), and microvilli (the brush border of enterocytes), collectively expanding surface area ~600-fold. Plicae are absent in the proximal duodenum, tall and densely packed in the jejunum (the boards buzzword 'tall and stacked plicae'), and become shorter and sparser in the ileum where Peyer's patches dominate. On abdominal X-ray, plicae circulares produce the complete 'stack of coins' appearance crossing the entire lumen of the small bowel, distinguishing it from haustra of the colon which only cross part of the lumen. Loss of plicae and villi (e.g., celiac disease) causes malabsorption, classically affecting the duodenum and proximal jejunum.
Sources
- First Aid for USMLE Step 1 2024
- Junqueira's Basic Histology
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