A small opening in a membrane; a surgically constructed opening, especially one in the abdominal wall that permits the passage of waste after a colostomy or ileostomy.
One of the tiny pores in the epidermis of a leaf or stem through which gases and water vapor pass.
A mouthlike opening, such as the oral cavity of a nematode.
An artificial anus.
A membrane-bound compartment found in a cell.
A small sac or cyst or vacuole, especially one containing fluid. A blister formed in or beneath the skin, containing serum. A bleb.
(usually and especially) Such a blister that is less than 5 mm in diameter.
A small cavity formed in volcanic rock by entrapment of a gas bubble during solidification.
A small sac filled with juice, one of many constituting the pulp of a fruit such as an orange, lemon, or grapefruit.
A pocket of embryonic tissue that is the beginning of an organ.