(i) They are fine breathing tubes in the tracheal system of insects.
(ii) They are the ultimate branches of trachea.
(iii) Tracheoles lie freely in the body cavity.
(iv) The finer tracheoles contains a fluid.
(v) Theya communicate directly with the tissues fluid.
(vi) They exchange gases with the tissue fluid.
(i) They are the breathing tubes in the lungs of higher vertebrates.
(ii) They are the branches of smaller bronchi.
(iii) Bronchioles occur inside lungs.
(iv) Finer bronchioles and alveoli are devoid of any fluid.
(v) Bronchioles ultimately open into alveolar sacs. There is no direct connection with the tissue fluid.
(vi) They exchange gases with the blood capillaries present on the walls of alveoli.