Definition of pineal in US English:


(also pineal body, pineal gland)


  • A pea-sized conical mass of tissue behind the third ventricle of the brain, secreting a hormone-like substance in some mammals.

    • ‘Melatonin is a hormone produced by the pineal gland, a small organ deep in the mammalian brain that conveys information to the rest of the brain and body about the length of light-dark cycles.’
    • ‘The pineal gland in the brain secretes melatonin, which has been linked to depression.’
    • ‘Some of these supplements, called glandulars, contain bovine brain, pituitary, pineal gland, and spinal cord, all organs where infectious prions may concentrate.’
    • ‘One theory is that it is related to the amount of melatonin in the body, a hormone secreted by the pineal gland.’
    • ‘In the human body there is a gland called the pineal gland located in the brain almost in the centre of the head.’
    • ‘Other distinct anatomic structures such as the pineal gland and third ventricle could not be identified due to autolysis.’
    • ‘The pineal gland or pineal body is a small gland in the middle of the head.’
    • ‘In addition to the latter, the following components of the epithalamus can be distinguished: the habenular commissure, the pineal body, and the posterior commissure.’
    • ‘Secreted nightly by the pineal gland, the hormone alerts birds, lizards, and mammals to approaching mating seasons and helps them keep track of hibernation deadlines.’
    • ‘Melatonin is a hormone secreted at night by the pineal gland of the brain.’
    • ‘Melatonin is produced and secreted by the pineal gland, whose activity is regulated by the suprachiasmatic nuclei.’
    • ‘Apparently, psychoactive substances stimulate the pineal gland in the brain.’
    • ‘This diurnal variation in melatonin synthesis is brought about by norepinephrine secreted by the postganglionic sympathetic nerves that innervate the pineal gland.’
    • ‘The cells of the suprachiasmatic nucleus send signals to other parts of the brain, especially the pineal gland, initiating hormonal and nerve signals that synchronize the body and the brain to the biological clock.’
    • ‘The major glands that make up the human endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes.’
    • ‘These are extremely rare benign tumours which develop from the pineal gland situated between the two halves of the brain (cerebral hemispheres).’
    • ‘A gland in the brain known as the pineal gland produces the hormone melatonin when the body is exposed to light - sunlight or artificial light.’
    • ‘The 24-hour circadian rhythm of light - dark (day-night) cycle is controlled by the hypothalamus through a neural pathway to the pineal gland.’
    • ‘Melatonin and serotonin are indoleamines derived from tryptophan which are produced by the pineal gland in vertebrates.’
    • ‘Melatonin is a hormone that is naturally secreted in the evening from the pineal gland in the brain and tells the brain it is time to sleep.’


Late 17th century: from French pinéal, from Latin pinea ‘pine cone’. The anatomical term refers to the shape of the gland.