Haustrum

Example:The sac in the bladder stores urine before excretion.

Definition:A pouch or sac within a bodily organ or structure, serving a storage or functional purpose.

Example:The pouch in the stomach is used for temporary storage of food before digestion begins.

Definition:A sac-like outpouching or fold in the wall of a body cavity or canal, often used for storing or collecting substances.