Morphometric study of the guinea pig small intestine during development

The mucosal surface area of the guinea pig duodenum, jejunum, and ileum was determined during development, in three age groups: 1-day-old and 2- and 12-week-old animals. The morphometric analysis was performed at three magnification levels. The nominal surface area was determined at the macroscopic level, from intestinal length and perimeter. Villus and microvillus amplification factors were estimated at light-microscopic and transmission electron-microscopic levels, respectively. We found: (1) an increase in the nominal surface area that is maximal in the ileum (7.7-fold); (2) an increase in the villus amplification factor in the duodenum (1.4-fold) and a decline in the jejunum and ileum (0.8-fold), although in the jejunum villus dimensions rise; and (3) a similar increase in the microvillus amplification factor in the three segments (1.1- to 1.4-fold). In conclusion, the total mucosal surface area increased from day 1 to week 12, by 3-fold in the duodenum and jejunum and by 8-fold in the ileum. Regionally, the jejunum shows the largest mucosal surface area, followed by the ileum, and, finally, the duodenum.