in yolk-sac endodermal epithelium at 12 days , the product was identified on receptor areas at the free surface of the epithelium , in a system of endocytosed clathrin-coated vesicles , or endosomes , within a closely related apical canalicular system , and stored in subapical vacuoles .
C0014609
epithelium
C1516036
the free surface of