![]() It is located posterior to the third ventricle and encloses the small, cerebrospinal fluid-filled pineal recess of the third ventricle which projects into the stalk of the gland. It is located in the quadrigeminal cistern. It is situated between the laterally positioned thalamic bodies, and posterior to the habenular commissure. It normally lies in a depression between the two superior colliculi. It is attached to the rest of the brain by a pineal stalk. It is reddish-gray in colour and about the size of a grain of rice (5–8 mm) in humans. The pineal gland is a pine cone-shaped (hence the name), unpaired midline brain structure. The word pineal, from Latin pinea ( pine-cone), was first used in the late 17th century to refer to the cone shape of the brain gland. In the mid-20th century, the real biological role as a neuroendocrine organ was established. In the 17th century, René Descartes revived the mystical purpose and described the gland as the "principal seat of the soul". He gave the name konario, meaning cone or pinecone, which during Renaissance was translated to Latin as pinealis. could not find any functional role and regarded the gland as a structural support for the brain tissue. Reconstruction of the biological evolution pattern suggests that the pineal gland was originally a kind of atrophied photoreceptor that developed into a neuroendocrine organ.Īncient Greeks were the first to notice the pineal gland and believed it to be a valve, a guardian for the flow of pneuma. In some species of amphibians and reptiles, the gland is linked to a light-sensing organ, variously called the parietal eye, the pineal eye or the third eye. ![]() The hagfish, considered as a primitive vertebrate, has a rudimentary structure regarded as the "pineal equivalent" in the dorsal diencephalon. ![]() The pineal gland is present in almost all vertebrates, but is absent in protochordates in which there is a simple pineal homologue. It is one of the neuroendocrine secretory circumventricular organs in which capillaries are mostly permeable to solutes in the blood. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. The shape of the gland resembles a pine cone, which gives it its name. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The pineal gland (also known as the pineal body, conarium, or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. ![]()
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