Changes in the mucosal surface area of the small gut of rats of different ages.

Changes in the mucosal surface area of the small intestine of the ageing male Wistar rat were investigated. The results show that the mucosal surface area (Ma) and, even more, the mucosal area per unit serosal area (Ra) diminishes along the length of the small intestine (excluding the duodenum) in the young rat. In adults, however, there is relative constancy of these parameters along the small intestine. The serosal circumference (Sc) of the intestinal segments investigated increased considerably with advancing age.