Epithalamus

Pineal Gland (Epiphysis Cerebri)

Pineal gland is situated between the 2 superior colliculi below the splenium of corpus callosum and it is a midline cone shaped reddish gray structure (only 3 mm X 5 mm in size) inhabiting the vertical groove. It projects back from the posterior wall of the 3rd ventricle, below the splenium of the corpus callosum. It’s a stalk which splits into 2 laminae. The ventral (or inferior) lamina continues with all the posterior commissure and the dorsal (or superior) lamina continues with the habenular commissure. The extension of the cavity of the 3rd ventricle between the 2 laminae is referred to as pineal recess.

Structure and Functions

The pineal gland is a neuroendocrine gland and is composed of parenchymal cells, referred to as pinealocytes and neuroglial cells. The pinealocytes secrete a hormone named melatonin. The calcium phosphates and carbonates are deposited in the gland with age in the creation of multilaminar corpuscles referred to as corpora arenacea or brain sand. They are generally viewed as miniature shadows in radiographs of the skull. A displaced calcified pineal gland signifies a space-occupying lesion inside the brain.

Pineal secretions consisting of melatonin have an inhibitory effect on different endocrine glands and gonads.

Unique Features

Pineal gland is the only part of the brain that has no nerve tissue in it.

It’s the only part of the brain that is supplied by a nerve (nervus conarii) which originates from outside the brain from superior cervical sympathetic ganglion in the neck.