Small intestine
It is approximately 1.5 cm in diameter in newborns after 35 weeks of gestational age, and 2.5–3 cm (1 inch) in diameter in adults. On abdominal X-rays, the small intestine is considered to be abnormally dilated when the diameter exceeds 3 cm. On CT scans, a diameter of over 2.5 cm is considered abnormally dilated. The surface area of the human small intestinal mucosa, due to enlargement caused by folds, villi and microvilli, averages 30 square meters.
Small intestine (Chinese medicine)
Transporting point of SI: Urinary Bladder 27. Conception vessel – anterior midline from perineum to lower lip. This is also the Alarm point for the SI which is called "Gateway to the Source"(guan yuan). Governing vessel is from perineum, to spine to crown of head down to upper lip.