【aldosterone】
hormone active in osmoregulation; a mineral corticoid produced by the adrenal cortex; stimulates reabsorption of Na＋ and secretion of K+

【alimentary canal】
an organ centrally involved in the human digestive system

【allantois】
the extra-embryonic membrane of birds, reptiles, and mammals that serves as an area of gaseous exchange and as a site for the storage of noxious excretion products