Question

The pineal body is considered as:
(a) An endocrine gland
(b) An organ concerned with voluntary actions
(c) An organ concerned with vision
(d) A vestige of the third eye and endocrine gland

Answer 1

Hint: Pineal body or what is also called the Pineal gland, is present at the roof of the epithalamus in the diencephalon region of the forebrain. Hormones secreted by this gland are known to control the sleep cycles.

Complete Answer:
The pineal gland is an endocrine type of gland found in all vertebrate brains. It is ectodermal in origin and is present behind the third cerebral ventricle, tucked in a groove where the two halves of the thalamus join. The name of the gland comes from its particular shape of a pine cone. It is present on the dorsal side of the diencephalon. In the embryonic stage, the gland is found attached at the brow spot, in between the two eyes.
In mammals, the pineal gland secretes a hormone called melatonin. This hormone affects the sleep-wake cycles. When the light is bright, this hormone gets degraded which signals the brain that it is night time and when the light is dim it gets accumulated in high concentration and hence keeping the brain aware that it is night time.
This also influences the metabolism, pigmentation that is the color of skin and the menstrual cycle of women. It has a great role in the capability of defence.

So, the correct answer is ‘A vestige of the third eye and endocrine gland’.

Note:
Nearly all vertebrates possess pineal gland except hagfish and lancet. However, lamprey which is also evolutionarily very closely related to mammals has a pineal gland. In reptiles, the pineal gland is photo-sensitive and is present in the form of a parietal or pineal eye. In these animals, it serves the function of regulation of the diurnal cycle.