Pineal Gland
Pineal gland
The pineal gland is a small, pinecone-shaped gland of the endocrine system. A
structure of the diencephalon of the brain, the pineal gland produces the
hormone melatonin. Melatonin influences sexual development and sleep-wake
cycles. its composed of cells called pinealocytes and cells of the nervous system
called glial cells.
The pineal gland connects the endocrine system with the nervous system in that it
converts nerve signals from the sympathetic system of the peripheral nervous
system into hormone signals. Over time, calcium deposits build-up in the pineal
and its accumulation can lead to calcification in the elderly.
Location
The pineal gland is present in the epithalamus between the two hemispheres
tucked in the groove of the thalamus join. This gland develops from brain
section diencephalon and located behind the third cerebral ventricle,
bathed in cerebrospinal fluid.
As a part of epithalamus, it lies laterally positioned thalamic bodies and
behind the habenular commissure. It is also found near to the corpora
quadrigemina in the quadrigeminal cistern.
Structure
Outward growth of the third ventricle, this gland rests between the posterior
aspects of the thalami. It is attached to either half of the brain superiorly by
Habenular commissure and inferiorly by posterior commissure.
The Habenular commissure is part of the superior
lamina, while the posterior commissure is a part
of the inferior lamina of the pineal stalk. The
space between the laminae is known as a
pineal recess, which communicates anteriorly
with the hypothalamic sulcus and the third
ventricle.
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Histology
The pineal gland has two types of cells pinealocytes and glial cells.
• Pinealocytes produce melatonin hormone.
• Glial cells are supporting brain cells that help neurons and transmit
information to other cells through neurons.
Function
The pineal gland is involved in several functions of the body including:
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Secretion of the hormone melatonin • Influences sexual development
Regulation of endocrine functions
• Influences immune system function
Causes sleepiness
• Antioxidant activity
Conversion of nervous system signals to endocrine signals
Clinical significance
Calcification
typical in young adults and has been observed in children as young as two
years of age. The internal secretions of the pineal gland inhibit the
development of the reproductive glands because when it is severely
damaged in children, development of the sexual organs and the skeleton
are accelerated. Pineal gland calcification is detrimental to its ability to
synthesize melatonin
Tumors
Tumors of the pineal gland are called pinealomas. These tumors are rare and
50% to 70% are germinomas that arise from sequestered embryonic germ
cells.
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References
1. “Pineal (as an adjective)”. Online Etymology Dictionary, Douglas
Harper. 2018. Retrieved 27 October 2018.
2. Macchi MM, Bruce JN (2004). “Human pineal physiology and functional
significance of melatonin”. Frontiers in Neuroendocrinology.
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