A histology student is examining a slide of the small intestine under the microscope. Which of the following is the most common type of epithelial cell found in the crypts of Lieberkühn?

Explanation

## Crypts of Lieberkühn: Cellular Composition **Key Point:** The crypts of Lieberkühn (intestinal glands) are lined predominantly by undifferentiated columnar epithelial cells, which serve as the proliferative zone of the small intestinal mucosa. ### Histological Architecture The crypts contain a heterogeneous population of cells arranged in a specific pattern: | Cell Type | Location in Crypt | Function | Frequency | |-----------|-------------------|----------|----------| | Undifferentiated columnar cells | Lower 2/3 of crypt | Proliferation, stem cell niche | **Most common** | | Paneth cells | Base (deepest) | Antimicrobial peptides, growth factors | ~5–10% | | Enteroendocrine cells | Scattered throughout | Hormone secretion | ~1–2% | | Goblet cells | Upper portion | Mucus secretion | Increase toward villus | **High-Yield:** Undifferentiated columnar cells represent the **proliferative compartment** of the intestinal epithelium. These cells divide rapidly (every 3–5 days) and differentiate as they migrate upward toward the villus tip. ### Why Other Options Are Wrong - **Paneth cells** are specialized secretory cells found at the base of crypts; they are far less numerous than undifferentiated cells. - **Enteroendocrine cells** are scattered endocrine cells (enteroendocrine, not enterochromaffin) that are rare in crypts. - **Goblet cells** increase in frequency toward the villus and are more abundant in the upper crypt and villus epithelium, not the proliferative lower crypt. **Clinical Pearl:** The rapid turnover of crypt epithelial cells (every 3–5 days) explains why chemotherapy and radiation damage the small intestine so severely—they target rapidly dividing cells. [cite:Junqueira's Basic Histology 14e Ch 17]