tube-shaped structure, tube - (anatomy) any hollow cylindrical body structure

microtubule - a microscopically small tubule

nephron, uriniferous tubule - any of the small tubules that are the excretory units of the vertebrate kidney

seminiferous tubule - any of the numerous long convoluted tubules in the testis which are the sites where spermatozoa mature

vasa efferentia - the several highly convoluted tubules that lead from the rete testis to the vas deferens and form the head of the epididymis

trachea - one of the tubules forming the respiratory system of most insects and many arachnids