Table 1.

Characteristics of the Normal Human Intestinal Epithelium

Characteristic	Small intestine	Colon	Ref
Size	• Diameter: 2–3 cm • Length: 500 cm	• Diameter: 4–5 cm • Length: 150 cm	[82]
Flow/Transit Time	• Mean transit time: 84 min • Rate: 0.7–3.0 mL/min	• Mean transit time: 11–14 h • Intermittent flow • Mass movement: ~1 /d	[83–86]
Contractions	Postprandial: • Contraction frequency: 3/s • Contraction amplitude: 20–24 mm Hg Interdigestive: • Contraction Frequency: 0–10/s • Contraction Amplitude: 0–30 mmHg	Subject to circadian variation • Low-amplitude (<50 mmHg): ~ 61/day • High-amplitude: (>100 mmHg): ~ 5 /day	[86–88]
Epithelial Architecture	• Crypt depth: 132–141 μm • Crypt diameter: 49–50 μm • Villous height: 567–640 μm • Villous diameter: 157–160 μm • Villous/crypt numbers: 1.4–2.3	• Crypt depth: 433 μm • Crypt diameter: 74 μm	[89–91]
Cell Lifetime	• Stem cells: long-lived • Absorptive enterocytes: 3–5 d • Paneth cells: 20 d	• Stem cells: long-lived • Absorptive enterocytes: 3–5 d	[92–94]
Mucus Layer(s)	• One Layer: 50 – 450 μm	• Outer Layer: 300 – 700 μm • One Layer: 50 – 450 μm	[13–15, 17, 95]