||"When calculating the enlargement of the small intestinal
area due to villi, [researchers] averaged the diameter of this part of
the intestine to 2.5 cm. The surface enlargements due to
villi and microvilli in the small intestine were averaged to
6.5 and 13 times, respectively. It follows that the calculated
area of the small intestine will be
ASi [Area Small intestine]=291×2.5×p×1.57×6.5×13×10^-4=30m^2. For the large intestine, [researchers] calculated the macroscopic
surface area from data published by Khashab et al.
[ref 25]. [They] averaged the length to 190cm and the
diameter to 4.8cm. The surface enlargement due
to microvilli was averaged to 6.5 times. Thus,
ALi [Area Large intestine]=190×4.8×p×1×1×6.5×10^-4=1.9m^2. It follows that the total surface area in vivo of the
human digestive tract, including the relatively small surfaces of oral cavity (197cm^2), the esophagus
(235cm^2), and the stomach (500cm^2), was
~32m^2 (Figure 5)."