title: [Preciseness of the ultrastructural order in the tunic of the small intestine].
abstract: The muscular cost of ileum of man was observed both at light and electron microscopes. Four muscular layers could be identified. The first layer appears as an innermost layer of circular muscle. The second layer is the circular one. The third layer occupies the region between circular and longitudinal muscle layers. The fourth layer is the longitudinal one. The structure of both circular and longitudinal layers is like that described for other mammals. The first and the third layers show a very special structure; moreover, interstitial cells of Cajal are found inside the first layer and in the connective tissue lying between the first and second layer. In the third layer two types of smooth muscle cells are present: one types shows a typical structure; the second type, which was never described before, is very peculiar and because of its similarity with interstitial cells of Cajal has been considered of the same nature. Nerve bundles are mainly concentrated between the first and second layers and in the region between circular and longitudinal layers (the third layer), where is localised the myenteric plexus. All these findings are discussed in an attempt to correlate the contractile activities of ileum of man with the structure of its muscular coat.
mesh_terms: D006801:Humans; D007082:Ileum / Q000648:ultrastructure*; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000166:cytology / Q000648:ultrastructure*
vernacular_title: Precisazioni di ordine ultrastrutturale sulla tunica del tenue dell'uomo.