Question

Hormone melatonin is secreted by
A. Adrenal
B. Thymus
C. Pituitary
D. Pineal

Answer 1

Hint: The endocrine system is considered as a control system of ductless glands that secrete hormones within specific organs from the hypothalamus of the brain to all the organs. The endocrine system is responsible for the release of hormones by providing an electrochemical connection to control and coordinate bodily functions, its metabolism, energy level, reproduction, growth and development.

Complete answer:
The secretion of hormones act as “messengers,” and are carried to different cells in the body by the bloodstream, which interpret the messages and stimulate a response in cells in order to act on them.
A. Adrenal gland is located on the upper side of each kidney which consists of two parts namely outer adrenal cortex and inner adrenal medulla. Adrenal cortex secrete the hormones of mineralocorticoids, glucocorticoids and sexocorticoids while adrenal medulla produces adrenaline (epinephrine) and nor-adrenaline (nor-epinephrine) hormones. The secretion of hormones in the adrenal gland helps to maintain blood pressure as well as regulate body metabolism.
B. Thymus gland is present in the upper part of the chest i.e. located on the dorsal side of heart. This gland produces thymosin hormone and plays an important role in the differentiation of T-lymphocytes which contribute to the development of the immune system in order to fight infections and destroy abnormal cells.
C. Pituitary gland is considered as the master gland and also called as Hypophysis. The pituitary gland is found attached to the hypothalamus which is located at the base of the forebrain. It controls the activity of other endocrine glands and secretes many hormones such as growth hormone, prolactin, follicle stimulating hormone, thyroid stimulating hormone, luteinizing hormone etc.
D. Pineal gland is a small, rounded and reddish brown pea shaped gland which is present in the middle of the brain. This gland secretes the melatonin hormone and serotonin hormone.

Hence, the correct answer is option (D).

Note: Pancreas is an elongated organ which is located behind the stomach across the back of abdomen and plays an important role in the process of digestion and secretion of hormones such as insulin and glucagon which regulates the level of blood glucose level. This gland can be classified as an endocrine (ductless) gland as well as an exocrine (ducted) gland because it contains exocrine cells that create digestive enzymes and exocrine cells to release hormones.