Chronomorphology of the duodenum in man.

The aim of the present study was to investigate the possible existence of rhythmicity of some morphological structures of the duodenum [correction of jejunum] in man. The height of intestinal villi was found to vary significantly during the 24 h time span, being higher during the day than during the night, when the proportion between small and medium size villi changed (p less than 0.05). The highest mitotic activity was found at 200 and at 600, and the lowest at 1000 and 1400 (p less than 0.01). Both height and width of microvilli did not change during the 24 h span, while thickness of the glycocalyx was slightly higher during the day when compared to the night. There were no significant circadian changes of Paneth cell granularity. We conclude that circadian rhythmicity of duodenum [correction of jejunum] morphology in man is less distinct than in animals, but that significant circadian changes in some parameters do exist.