a smooth sac within the cell, formed by or fused with coated vesicles that shed their clathrin, in which ligands are separated from their receptors and from which the receptors are returned to the cell surface.
Main Entry: en·do·some Pronunciation: 'en-d&-"sOm Function: noun : a conspicuous body other than a chromatin granule that occurs within thenuclear membrane of a vesicular protozoan nucleus and is either a karyosome or a nucleolus
[en-duh-sohm] 
dəˌsoʊm