tubulovesicle

tu·bu·lo·ves·icle (too″bu-lo-vesґĭ-kəl) a saclike membranous inclusion of nonsecreting parietal cell cytoplasm that contains the hydrogen pump mechanism. Upon stimulation of acid secretion, the tubulovesicles coalesce to form canaliculi with elongated microvilli, which have the greater surface area conducive to rapid secretion.