(i) Lymphocytes of blood: Produce antibodies.
(ii) Leydig cells: Secrete male sex hormone testosterone.
(iii) Guard cells: Regulate the opening and closing of stomata in leaf to facilitate transpiration and exchange of gases.
(iv) Eustachian tube: Balance air pressure on either sides of the ear drum. So that ear drum can vibrate freely.
(v) Corpus luteum: Secretes hormones oesterogen, progesterone and relaxin.