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Pineal Gland

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Pineal gland



 
 
The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis or the "third eye") is a small endocrine
Endocrine system

The endocrine system is a system of small organs that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, human development , and tissue and also plays a part in determining Mood ....
 gland in the vertebrate brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
. It produces melatonin
Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae....
, a hormone that affects the modulation of wake/sleep patterns and photoperiodic (seasonal) functions. It is shaped like a tiny pine cone (hence its name), and is located near to the center of the brain, between the two hemisphere
Cerebral hemisphere

A cerebral hemisphere is defined as one of the two regions of the brain that are delineated by the body's Anatomical_position#Median_and_sagittal_plane, ....
s, tucked in a groove where the two rounded thalamic bodies
Thalamus

The thalamus is a pair and symmetric part of the brain. It constitutes the main part of the diencephalon....
 join.






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The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis or the "third eye") is a small endocrine
Endocrine system

The endocrine system is a system of small organs that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, human development , and tissue and also plays a part in determining Mood ....
 gland in the vertebrate brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
. It produces melatonin
Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae....
, a hormone that affects the modulation of wake/sleep patterns and photoperiodic (seasonal) functions. It is shaped like a tiny pine cone (hence its name), and is located near to the center of the brain, between the two hemisphere
Cerebral hemisphere

A cerebral hemisphere is defined as one of the two regions of the brain that are delineated by the body's Anatomical_position#Median_and_sagittal_plane, ....
s, tucked in a groove where the two rounded thalamic bodies
Thalamus

The thalamus is a pair and symmetric part of the brain. It constitutes the main part of the diencephalon....
 join. Unlike much of the rest of the brain, the pineal gland is not isolated from the body by the blood-brain barrier
Blood-brain barrier

The blood-brain barrier is a metabolic or cellular structure in the central nervous system that restricts the passage of various chemical substances and microscopic objects between the bloodstream and the neural tissue itself, while still allowing the passage of substances essential to metabolism function ....
 system.

Location

The pineal gland is reddish-gray and about the size of a pea
Pea

A pea is most commonly the small spherical seed or the seed-pod of the legume Pisum sativum. Each pod contains several peas. Although treated as a vegetable in cooking, it is botanically a fruit....
 (8 mm in humans), located just rostro-dorsal to the superior colliculus
Superior colliculus

The optic tectum or simply tectum is a paired structure that forms a major component of the vertebrate midbrain. In mammals this structure is more commonly called the superior colliculus , but even in mammals, the adjective tectal is commonly used....
 and behind and beneath the stria medullaris
Stria medullaris

The stria medullaris, also known as stria medullaris thalami, is a fiber bundle containing Efferent nerve fibers from the septal nuclei, lateral preoptico-hypothalamic region, and anterior thalamic nuclei to the habenula....
, between the laterally positioned thalamic bodies. It is part of the epithalamus
Epithalamus

The epithalamus is a Dorsum posterior segment of the diencephalon which includes the habenula, the stria medullaris and the pineal body. Its function is the connection between the limbic system to other parts of the brain....
.

The pineal gland is a midline structure, and is often seen in plain skull
Skull

The skull is a bone structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
 X-ray
X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequency in the range 30 Hertz to 30 Hertz and energies in the range 120 Electron volt to 120 keV....
s, as it is often calcified
Calcification

Calcification is the process in which the mineral calcium builds up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification....
. Calcification is typically due to intake of the fluoride found in water and toothpaste.

Structure and composition

The pineal body consists in humans of a lobular parenchyma
Parenchyma

Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, from Greek language parenkhuma, visceral flesh, from parenkhein, to pour in beside : para-, beside + en-, in + khein, to pour....
 of pinealocytes surrounded by connective tissue
Connective tissue

Connective tissue is a form of fibrous biological tissue.It is one of the four types of tissue in traditional classifications .Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content....
 spaces. The gland's surface is covered by a pial capsule.

The pineal gland consists mainly of pinealocytes, but four other cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 types have been identified.

Cell type Description >- | pinealocyte
Pinealocyte

Pinealocytes are the main cell s of the pineal gland. They produce and secrete melatonin. Pinealocytes have an organelle called the synaptic ribbon; this is considered to be a specific marker for pinealocytes....
s
The pinealocytes consist of a cell body with 4-6 processes emerging. They produce and secrete melatonin
Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae....
. The pinealocytes can be stained by special silver impregnation methods. |- | interstitial cell
Interstitial cell

Interstitial cells may refer to:* Leydig cells, cells present in the male testes* A portion of the stroma of ovary* Certain cells in the pineal gland...
s
- | perivascular phagocyte
Phagocyte

Phagocytes are the cell s that protect the body by ingesting harmful foreign particles, bacteria and dead or Apoptosis cells. They are essential to fighting infections and subsequent immunity , and move through the blood and tissues of vertebrates, and the hemolymph of invertebrates....
 
- | pineal neuron
Neuron

Neurons are responsive cell in the nervous system that process and transmit information by electrochemical Signal . They are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves....
s
- | peptide
Peptide

Peptides are short polymers formed from the linking, in a defined order, of a-amino acids. The link between one amino acid residue and the next is known as an amide chemical bond or a peptide bond....
rgic neuron-like cells
In some species, neuronal-like peptidergic cells are present. These cells might have a paracrine regulatory function.


The pineal gland receives a sympathetic
Sympathetic

The word sympathetic means different things in different contexts.* In neurology and neuroscience, the sympathetic nervous system is a part of the autonomic nervous system....
 innervation from the superior cervical ganglion
Superior cervical ganglion

The superior cervical ganglion , the largest of the cervical ganglia, is placed opposite the second and third cervical vertebr?. It contains neurons that supply sympathetic nervous system innervation to the face....
. However, a parasympathetic innervation from the sphenopalatine
Sphenopalatine

Sphenopalatine can refer to:* sphenopalatine artery* sphenopalatine ganglion * sphenopalatine nerves* sphenopalatine foramen...
 and otic ganglia
Otic ganglion

The otic ganglion is a small, ovalshaped, flattened parasympathetic ganglion of a reddish-gray color, located immediately below the foramen ovale in the infratemporal fossa....
 is also present. Further, some nerve fibers penetrate into the pineal gland via the pineal stalk (central innervation). Finally, neurons in the trigeminal ganglion
Trigeminal ganglion

The trigeminal ganglion is a sensory ganglion of the trigeminal nerve which occupies a cavity in the dura mater covering the trigeminal impression near the apex of the petrous part of the temporal bone....
 innervates the gland with nerve fibers containing the neuropeptide
Neuropeptide

A neuropeptide is any of the variety of peptides found in neural tissue; e.g. endorphins, enkephalins. At present about 100 different peptides are known to be released by different populations of neurons in the mammalian brain....
, PACAP. Human follicles contain a variable quantity of gritty material, called corpora arenacea
Corpora arenacea

Corpora arenacea are calcium structures in the pineal gland and other areas of the brain such as the choroid plexus. Older organisms have numerous corpora arenacea, whose function, if any, is unknown....
 (or "acervuli", or "brain sand"). Chemical analysis shows that they are composed of calcium phosphate
Calcium phosphate

Calcium phosphate is the name given to a family of minerals containing calcium ions together with orthophosphates , metaphosphates or pyrophosphates and occasionally hydrogen or hydroxide ions....
, calcium carbonate
Calcium carbonate

Calcium carbonate is a chemical compound with the chemical formula CalciumCarbonOxygen3. It is a common substance found as Rock in all parts of the world, and is the main component of seashells, snails, and eggshells....
, magnesium phosphate
Magnesium phosphate

Magnesium phosphate is a general term for salt of magnesium and phosphate appearing in three forms:* Magnesium phosphate monobasic * Magnesium phosphate dibasic ...
, and ammonium phosphate
Ammonium phosphate

Ammonium phosphate - Molar Mass = 149.12g/mol. The normal ammonium phosphate, 3PO4, is obtained as a crystalline powder, on mixing concentrated solutions of ammonia and phosphoric acid, or on the addition of excess of ammonia to the acid phosphate 2HPO4....
. Recently, calcite deposits have been described as well. Calcium and phosphorus deposits in the pineal gland have been linked with aging.

Miscellaneous anatomy

Pinealocyte
Pinealocyte

Pinealocytes are the main cell s of the pineal gland. They produce and secrete melatonin. Pinealocytes have an organelle called the synaptic ribbon; this is considered to be a specific marker for pinealocytes....
s in many non-mammalian vertebrate
Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s have a strong resemblance to the photoreceptor
Photoreceptor

A photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eye's retina that is capable of phototransduction....
 cells of the eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
. Some evolutionary biologists believe that the vertebrate pineal cells share a common evolution
Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
ary ancestor with retinal cells.

In some vertebrates, exposure of the pineal to light can directly set off a chain reaction of enzymatic events which regulate circadian rhythm
Circadian rhythm

A circadian rhythm is a roughly-24-hour cycle in the biochemical, physiological or behavioural processes of living beings, including plants, animals, fungi and cyanobacteria....
s. Some early vertebrate fossil skulls have a pineal foramen
Foramen

In anatomy, a foramen is any opening....
 (opening). This corroborates with the physiology of the modern "living fossil
Living fossil

Living fossil is an informal term for any living species of organism which appears to be the same as a species otherwise only known from fossils and which has no close living relatives....
s", the lamprey
Lamprey

A lamprey is a parasitic marine animal with a toothed, funnel-like sucking mouth. While lampreys are well known for those species which bore into the flesh of other fish to hematophagy, these species make up the minority....
 and the tuatara
Tuatara

The tuatara is a reptile endemism to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia....
, and some other vertebrates which have a parietal organ
Parietal eye

A parietal eye, also known as a parietal organ or third-eye, is a part of the epithalamus present in some animal species. The eye may be photoreceptive and is usually associated with the pineal gland, regulating circadian rhythmicity and hormone production for thermoregulation....
 or "third eye" which, in some of them, is photosensitive. The third eye represents evolution’s earlier approach to photoreception. The structures of the third eye in the tuatara are homologous to the cornea, lens and retina, though the latter resembles that of an octopus rather than a vertebrate retina. The asymmetrical whole consists of the "eye" to the left and the pineal sac to the right. "In animals that have lost the parietal eye, including mammals, the pineal sac is retained and condensed into the form of the pineal gland."

Fossils seldom preserve soft anatomy. The brain of the Russian Melovatka bird, about 90 million years old, is an exception, and it shows a larger-than-expected parietal eye and pineal gland.

In humans and other mammals, the light signals necessary to set circadian rhythms are sent from the eye through the retinohypothalamic
Retinohypothalamic tract

The Retinohypothalamic tract is a photic input pathway involved in circadian rhythms. The RHT is an input pathway from the mammalian retina to the Suprachiasmatic nucleus in the brain....
 system to the suprachiasmatic nuclei
Suprachiasmatic nucleus

The suprachiasmatic nucleus, or nuclei, , a tiny region on the brain's midline in a shallow impression of the optic chiasm, is responsible for controlling endogenous circadian rhythms....
 (SCN) and the pineal.

Function

The pineal gland was originally believed to be a "vestigial remnant" of a larger organ (much as the appendix
Vermiform appendix

In human anatomy, the appendix is a blind ended tube connected to the cecum , from which it develops embryologically. The cecum is a pouch-like structure of the Colon ....
 was thought to be a vestigial digestive organ). Aaron Lerner and colleagues at Yale University
Yale University

Yale University is a private university in New Haven, Connecticut. Founded in 1701 as the Collegiate School, Yale is the Colonial Colleges institution of higher education in the United States and is a member of the Ivy League....
 discovered that melatonin, the most potent compound then known to lighten frog skin, was present in the highest concentrations in the pineal. Melatonin
Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae....
 is a derivative of the amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 tryptophan
Tryptophan

Tryptophan is one of the 20 List of standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG....
, which also has other functions in the central nervous system
Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
. The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. Photosensitive cells in the retina detect light and directly signal the suprachiasmatic nucleus
Suprachiasmatic nucleus

The suprachiasmatic nucleus, or nuclei, , a tiny region on the brain's midline in a shallow impression of the optic chiasm, is responsible for controlling endogenous circadian rhythms....
 (SCN), entraining it to the 24 hour clock. Fibers project from the SCN to the paraventricular nuclei (PVN), which relay the circadian signals to the spinal cord
Spinal cord

The spinal cord is a long, thin, tubular bundle of neuron and glia that extends from the brain. The brain and spinal cord together make up the central nervous system....
 and out via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland. The function(s) of melatonin in humans is not clear; it is commonly prescribed for the treatment of circadian rhythm sleep disorder
Circadian rhythm sleep disorder

Circadian rhythm sleep disorders are a family of sleep disorders affecting, among other things, the timing of sleep. People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs....
s.

The compound pinoline
Pinoline

Pinoline is a methoxylated tryptoline which occurs in the pineal gland during the metabolism of melatonin. Its chemical names are 5-methoxytryptoline and 6-methoxy-1,2,3,4-tetrahydro-?-carboline....
 is also produced in the pineal gland; it is one of the beta-carboline
Beta-carboline

?-Carboline is an organic compound amine that is the prototype of a class of Chemical compound known as ?-carbolines....
s.

The human pineal gland grows in size until about 1-2 years of age, remaining stable thereafter , although its weight increases gradually from puberty onwards . It appears to play a major role in sexual development, hibernation
Hibernation

Hibernation is a state of inactivity and Metabolism depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate....
 in animals, metabolism, and seasonal breeding. The abundant melatonin levels in children is believed to inhibit sexual development, and pineal tumors have been linked with precocious puberty
Precocious puberty

Precocious puberty is an unusually early onset of puberty, the process of sexual maturation triggered by the brain or exogenous chemicals, which usually begins in late childhood and results in reproductive maturity and completion of growth....
. When puberty arrives, melatonin production is reduced. Calcification
Calcification

Calcification is the process in which the mineral calcium builds up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification....
 of the pineal gland is typical in adults.

Pineal cytostructure seems to have evolutionary similarities to the retinal cells of chordates. Modern bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s and reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s have been found to express the phototransducing pigment
Pigment

A pigment is a material that changes the color of light it Reflection as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light....
 melanopsin
Melanopsin

Melanopsin is a photopigment found in specialized photosensitive ganglion cells of the retina that are involved in the regulation of circadian rhythms, pupillary light reflex, and other non-visual responses to light....
 in the pineal gland. Avian pineal glands are believed to act like the suprachiasmatic nucleus
Suprachiasmatic nucleus

The suprachiasmatic nucleus, or nuclei, , a tiny region on the brain's midline in a shallow impression of the optic chiasm, is responsible for controlling endogenous circadian rhythms....
 in mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s.

Studies suggest that in rodents the pineal gland may influence the actions of recreational drugs, such as cocaine, and antidepressant
Antidepressant

An antidepressant is a psychiatric medication used for alleviating major depressive disorder or dysthymia. Drug groups known as MAOIs, tricyclics, and second-generation antidepressants such as SSRIs, and serotonin-norepinephrine reuptake inhibitors are particularly associated with the term....
s, such as fluoxetine (Prozac), and its hormone melatonin can protect against neurodegeneration
Neurodegeneration

BackgroundNeurodegeneration is the umbrella term for the progressive loss of structure or function of neurons, including death of neurons. Many neurodegenerative diseases including Parkinson?s, Alzheimer?s, and Huntington?s occur as a result of neurodegenerative processes....
.

Cultures, philosophies and mythologies


The secretory activity of the pineal gland has only relatively recently become understood. Historically, its location deep in the brain suggested to philosophers that it possessed particular importance. This combination led to its being a "mystery" gland with myth, superstition and metaphysical
Metaphysics

Metaphysics investigates principles of reality transcending those of any particular science. cosmology and ontology are traditional branches of metaphysics....
 theories surrounding its perceived function.

René Descartes
René Descartes

Ren? Descartes , , also known as Renatus Cartesius , was a French philosophy, mathematician, scientist, and writer who spent most of his adult life in the Dutch Republic....
, who dedicated much time to the study of the pineal gland, called it the "seat of the soul
Soul

In many religions and parts of philosophy, the soul is the immaterial part of a person. It is usually thought to consist of one's thoughts and Personality psychology, and can be synonymous with the spirit, mind or self....
". He believed that it was the point of connection between the intellect and the body.

The notion of a 'pineal-eye' is central to the philosophy of the seminal French writer Georges Bataille
Georges Bataille

Georges Bataille was a French people writer. Although subsequent philosophers have been significantly influenced by his thought, Bataille tended not to refer to himself as a philosophy....
, which is analyzed at length by literary scholar Denis Hollier in his study Against Architecture. In this work Hollier discusses how Bataille uses the concept of a 'pineal-eye' as a reference to a blind-spot in Western rationality.

Additional images


External links

- "Endocrine System: pineal gland "
  • Images of Pineal region http://rad.usuhs.edu/medpix/medpix.html?mode=image_finder&action=search&srchstr=pineal&srch_type=all#top