Mucosal endocrine secretion

At least 15 types of mucosal endocrine cells have been identified histologically in the walls of the gut. The cells contain a range of substances (including 5-HT, gastrin, cholecystokinin, secretin, somatostatin, gastric inhibitory polypeptide, motilin, neurotensin and glucagon) which have local paracrine or true endocrine function. In many instances, it can be shown histologically that nerve fibres come into close contact with such cells, and it is probable that they play a role in endocrine secretion. Certainly, in the case of the enterochromaffin cells, which contain 5-HT, stimulation of adrenergic fibres can cause degranulation of the cells. One of the peptides, motilin, is secreted during the migrating motor complex described in Section 9.5.8, and this secretion is blocked by atropine.

Myoepithelial cells

Acinus

\ Intercalated dud

Striated duct

Fig. 9.26 A salivary acinus showing the possible sites of action of the autonomic nerves. (1) The primary endothelial secretory cells, (2) the tubular cells that can modify the primary secretion, (3) the capillaries supplying the acinus, (4) the myoepithelial cells.

Acinus

\ Intercalated dud

Striated duct

Fig. 9.26 A salivary acinus showing the possible sites of action of the autonomic nerves. (1) The primary endothelial secretory cells, (2) the tubular cells that can modify the primary secretion, (3) the capillaries supplying the acinus, (4) the myoepithelial cells.

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