Pineal gland

From Self-sufficiency
Jump to: navigation, search
Pineal gland
File:Illu pituitary pineal glands.jpg
Diagram of pituitary and pineal glands in the human brain
Latin glandula pinealis
Gray's subject #276 1277
Artery superior cerebellar artery
Precursor Neural Ectoderm, Roof of Diencephalon
MeSH Pineal+gland

The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis or the "third eye") is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions.[1][2] Its shape resembles a tiny pine cone (hence its name), and it is located near the center of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join.

Location

The pineal gland is reddish-gray and about the size of a grain of rice (5–8 mm) in humans, located just rostro-dorsal to the superior colliculus and behind and beneath the stria medullaris, between the laterally positioned thalamic bodies. It is part of the epithalamus.

The pineal gland is a midline structure, and is often seen in plain skull X-rays, as it is often calcified.

Structure and composition

The pineal body consists in humans of a lobular parenchyma of pinealocytes surrounded by connective tissue spaces. The gland's surface is covered by a pial capsule.

The pineal gland consists mainly of pinealocytes, but four other cell types have been identified.

Cell type Description
Pinealocytes The pinealocytes consist of a cell body with 4-6 processes emerging. They produce and secrete melatonin. The pinealocytes can be stained by special silver impregnation methods.
Interstitial cells Interstitial cells are located between the pinealocytes.
Perivascular phagocyte Many capillaries are present in the gland, and perivascular phagocytes are located close to these blood vessels. The perivascular phagocytes are antigen presenting cells.
pineal neurons In higher vertebrates neurons are located in the pineal gland. However, these are not present in rodents.
peptidergic 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 innervation from the superior cervical ganglion. However, a parasympathetic innervation from the sphenopalatine and otic ganglia is also present. Further, some nerve fibers penetrate into the pineal gland via the pineal stalk (central innervation). Finally, neurons in the trigeminal ganglion innervate the gland with nerve fibers containing the neuropeptide, PACAP. Human follicles contain a variable quantity of gritty material, called corpora arenacea (or "acervuli", or "brain sand"). Chemical analysis shows that they are composed of calcium phosphate, calcium carbonate, magnesium phosphate, and ammonium phosphate.[3] In 2002, deposits of the calcite form of calcium carbonate were described.[4] Calcium, phosphorus[5] and fluoride[6] deposits in the pineal gland have been linked with aging.

Miscellaneous anatomy

Pinealocytes in many non-mammalian vertebrates have a strong resemblance to the photoreceptor cells of the eye. Some evolutionary biologists believe that the vertebrate pineal cells share a common evolutionary ancestor with retinal cells.[7]

In some vertebrates, exposure to light can set off a chain reaction of enzymatic events within the pineal gland that regulate circadian rhythms.[8] Some early vertebrate fossil skulls have a pineal foramen (opening). This correlates with the physiology of the modern "living fossils", the lamprey and the tuatara, and some other vertebrates that have a parietal organ or "third eye," which, in some of them, is photosensitive. The third eye represents evolution’s earlier approach to photoreception.[9] 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."[9]

Unlike much of the rest of the mammalian brain, the pineal gland is not isolated from the body by the blood-brain barrier system;[10] indeed it has profuse blood flow, second only to the kidney.[6]

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.[11]

In humans and other mammals, the light signals necessary to set circadian rhythms are sent from the eye through the retinohypothalamic system to the suprachiasmatic nuclei (SCN) and the pineal.

Function

The pineal gland was originally believed to be a "vestigial remnant" of a larger organ. As early as 1917 it was known that extract of cow pineals lightened frog skin. Dermatology professor Aaron B. Lerner and colleagues at Yale University, in the hope that a substance from the pineal might be useful in treating skin diseases, isolated and named the hormone melatonin in 1958.[12] The substance did not prove to be helpful as intended, but its discovery helped solve several mysteries such as the fact that the removal of the rat's pineal accelerated ovary growth, keeping rats in constant light decreased the weight of their pineals, and that both pinealectomy and constant light affect ovary growth to an equal extent, knowledge that gave a boost to the then new field of chronobiology.[13]

Melatonin is N-acetyl-5-methoxy-tryptamine, a derivative of the amino acid tryptophan, which also has other functions in the central nervous system. The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light.[14] Photosensitive cells in the retina detect light and directly signal the SCN, entraining its rhythm to the 24-hour cycle in nature. Fibers project from the SCN to the paraventricular nuclei (PVN), which relay the circadian signals to the spinal cord 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 disorders.

The pineal gland also contains the necessary precursors and enzymes for the secretion of di-methyl-tryptamine.[15].

The compound pinoline is also produced in the pineal gland; it is one of the beta-carbolines.

The human pineal gland grows in size until about 1–2 years of age, remaining stable thereafter,[16][17] although its weight increases gradually from puberty onwards.[18][19] The abundant melatonin levels in children are believed to inhibit sexual development, and pineal tumors have been linked with precocious puberty. When puberty arrives, melatonin production is reduced. Calcification of the pineal gland is typical in adults.

In animals, the pineal gland appears to play a major role in sexual development, hibernation, metabolism, and seasonal breeding. [20].

Pineal cytostructure seems to have evolutionary similarities to the retinal cells of chordates.[7] Modern birds and reptiles have been found to express the phototransducing pigment melanopsin in the pineal gland. Avian pineal glands are believed to act like the SCN in mammals.[21]

Studies on rodents suggest that the pineal gland may influence the actions of recreational drugs, such as cocaine,[22] and antidepressants, such as fluoxetine (Prozac),[23] and its hormone melatonin can protect against neurodegeneration.[24]

Metaphysics and Philosophy

The secretory activity of the pineal gland is only relatively 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 occult theories surrounding its perceived function.

René Descartes, who dedicated much time to the study of the pineal gland,[25] called it the "seat of the soul".[26] He believed that it was the point of connection between the intellect and the body.[27] The relevant quotation as to Descartes' reason for believing this is,
“My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed. The reason I believe this is that I cannot find any part of the brain, except this, which is not double. Since we see only one thing with two eyes, and hear only one voice with two ears, and in short have never more than one thought at a time, it must necessarily be the case that the impressions which enter by the two eyes or by the two ears, and so on, unite with each other in some part of the body before being considered by the soul. Now it is impossible to find any such place in the whole head except this gland; moreover it is situated in the most suitable possible place for this purpose, in the middle of all the concavities; and it is supported and surrounded by the little branches of the carotid arteries which bring the spirits into the brain.”[25] (29 January 1640, AT III:19-20, CSMK 143)
"For he [Descartes] maintained, that the soul or mind is specially united to a particular part of the brain, namely, to that part called the pineal gland, by the aid of which the mind is enabled to feel all the movements which are set going in the body, and also external objects, and which the mind by a simple act of volition can put in motion in various ways...Such is the doctrine of this illustrious philosopher (in so far as I gather it from his own words) ; it is one which, had it been less ingenious, I could hardly believe to have proceeded from so great a man. Indeed, I am lost in wonder, that a philosopher, who had stoutly asserted, that he would draw no conclusions which do not follow from self-evident premisses, and would affirm nothing which he did not clearly and distinctly perceive, and who had so often taken to task the scholastics for wishing to explain obscurities through occult qualities, could maintain a hypothesis, beside which occult qualities are commonplace. What does he understand, I ask, by the union of the mind and the body?" (Baruch de Spinoza, Ethics; part 5)[28]

The notion of a 'pineal-eye' is central to the philosophy of the French writer Georges Bataille, which is analyzed at length by literary scholar Denis Hollier in his study Against Architecture.[29] In this work Hollier discusses how Bataille uses the concept of a 'pineal-eye' as a reference to a blind-spot in Western rationality, and an organ of excess and delirium.[30] This conceptual device is explicit in his surrealist texts, The Jesuve and The Pineal Eye.[31]

In Discordianism it is maintained that the pineal gland allows one to consult with the goddess Eris.[32]

Additional images

The pineal body is labeled in these images.

  • Gray715.png

    Mesal aspect of a brain sectioned in the median sagittal plane.

  • Gray716.png

    Dissection showing the ventricles of the brain.

  • Gray719.png

    Hind- and mid-brains; postero-lateral view.

  • Gray720.png

    Median sagittal section of brain.

References

Cite error: Invalid <references> tag; parameter "group" is allowed only.

Use <references />, or <references group="..." />

External links

TA 2-4:
musculoskeletal
Bone (Carpus · Collar bone (clavicle) · Thigh bone (femur) · Fibula · Humerus · Mandible · Metacarpus · Metatarsus · Ossicles · Patella · Phalanges · Radius · Skull (cranium) · Tarsus · Tibia · Ulna · Rib · Vertebra · Pelvis · Sternum) · Cartilage
TA 5-11:
splanchnic/
viscus
mostly
Thoracic
TA 12-16
peripheral (Artery, Vein, Lymph vessel) · Heart
primary (Bone marrow, Thymus) · secondary (Spleen, Lymph node)
N/S
Non-TA
Epithalamus
Surface
Thalamus
Surface
Hypothalamus
Surface
Autonomic zones
Posterior is diencephalon, but anterior is glandular
Subthalamus
Ventricular system:
Third ventricle
Islets of pancreas
Hypothalamic/
pituitary axes
+parathyroid
Pineal gland
ar:غدة صنوبرية

bn:পিনিয়াল গ্রন্থি bs:Epifiza bg:Епифиза ca:Glàndula pineal cs:Šišinka cy:Corffyn pineol da:Epifysen de:Zirbeldrüse dv:ޕިނިއަލް ގްލޭންޑް et:Käbinääre el:Επίφυση es:Glándula pineal eu:Guruin pineal fa:غده پینه آل fr:Glande pinéale ga:Faireog phinéalach gl:Glándula pineal ko:송과선 it:Ghiandola pineale he:בלוטת האצטרובל jv:Kelenjar pineal la:Glandula pinealis lt:Kankorėžinė liauka mk:Епифиза nl:Pijnappelklier ja:松果体 no:Konglekjertelen pl:Szyszynka pt:Glândula pineal ro:Glandă pineală ru:Шишковидное тело simple:Pineal gland sk:Šuškovité teliesko sl:Češerika fi:Käpyrauhanen sv:Tallkottkörteln th:ต่อมไพเนียล uk:Шишкоподібне тіло

zh:松果體
  1. ↑ Macchi M, Bruce J (2004). "Human pineal physiology and functional significance of melatonin". Front Neuroendocrinol. 25 (3-4): 177–95. doi:10.1016/j.yfrne.2004.08.001. PMID 15589268. 
  2. ↑ Arendt J, Skene DJ (2005). "Melatonin as a chronobiotic". Sleep Med Rev. 9 (1): 25–39. doi:10.1016/j.smrv.2004.05.002. PMID 15649736. Exogenous melatonin has acute sleepiness-inducing and temperature-lowering effects during 'biological daytime', and when suitably timed (it is most effective around dusk and dawn) it will shift the phase of the human circadian clock (sleep, endogenous melatonin, core body temperature, cortisol) to earlier (advance phase shift) or later (delay phase shift) times. 
  3. ↑ Bocchi G, Valdre G (1993). "Physical, chemical, and mineralogical characterization of carbonate-hydroxyapatite concretions of the human pineal gland". J Inorg Biochem. 49 (3): 209–20. doi:10.1016/0162-0134(93)80006-U. PMID 8381851. 
  4. ↑ Baconnier S, Lang S, Polomska M, Hilczer B, Berkovic G, Meshulam G (2002). "Calcite microcrystals in the pineal gland of the human brain: first physical and chemical studies". Bioelectromagnetics. 23 (7): 488–95. doi:10.1002/bem.10053. PMID 12224052. 
  5. ↑ "IngentaConnect High Accumulation of Calcium and Phosphorus in the Pineal Bodies". Ingentaconnect.com. 2006-06-16. Retrieved 2009-07-06. 
  6. ↑ 6.0 6.1 Luke, Jennifer. "Fluoride Deposition in the Aged Human Pineal Gland". Caries Res. 2991 (35): 125–28. Retrieved 2009-05-20. 
  7. ↑ 7.0 7.1 Klein D (2004). "The 2004 Aschoff/Pittendrigh lecture: Theory of the origin of the pineal gland--a tale of conflict and resolution". J Biol Rhythms. 19 (4): 264–79. doi:10.1177/0748730404267340. PMID 15245646. 
  8. ↑ Moore RY, Heller A, Wurtman RJ, Axelrod J. Visual pathway mediating pineal response to environmental light. Science 1967;155(759):220–3. PMID 6015532
  9. ↑ 9.0 9.1 Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  10. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  11. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  12. ↑ Lerner AB, Case JD, Takahashi Y (1960). "Isolation of melatonin and 5-methoxyindole-3-acetic acid from bovine pineal glands". J Biol Chem. 235: 1992–7. PMID 14415935. 
  13. ↑ Coates, Paul M. (2005). Encyclopedia of Dietary Supplements. Marc R. Blackman, Gordon M. Cragg, Mark Levine, Joel Moss, Jeffrey D. White. CRC Press. p. 457. ISBN 0824755049. Retrieved 2009-03-31. 
  14. ↑ Axelrod J (1970). "The pineal gland". Endeavour. 29 (108): 144–8. PMID 4195878. 
  15. ↑ Strassman, R. DMT: The Spirit Molecule, p56
  16. ↑ Lack of pineal growth during childhood. Schmidt F, Penka B, Trauner M, Reinsperger L, Ranner G, Ebner F, Waldhauser F. J Clin Endocrinol Metab. 1995 Apr;80(4):1221-5.
  17. ↑ Development of the pineal gland: measurement with MR. Sumida M, Barkovich AJ, Newton TH. AJNR Am J Neuroradiol. 1996 Feb;17(2):233-6.
  18. ↑ Tapp E, Huxley M. The weight and degree of calcification of the pineal gland. J Pathol 1971;105:31–39
  19. ↑ Tapp E, Huxley M. The histological appearance of the human pineal gland from puberty to old age. J Pathol 1972;108:137–144
  20. ↑ Strassman
  21. ↑ Natesan A, Geetha L, Zatz M (2002). "Rhythm and soul in the avian pineal". Cell Tissue Res. 309 (1): 35–45. doi:10.1007/s00441-002-0571-6. PMID 12111535. 
  22. ↑ Uz T, Akhisaroglu M, Ahmed R, Manev H (2003). "The pineal gland is critical for circadian Period1 expression in the striatum and for circadian cocaine sensitization in mice". Neuropsychopharmacology. 28 (12): 2117–23. doi:10.1038/sj.npp.1300254. PMID 12865893. 
  23. ↑ Uz T, Dimitrijevic N, Akhisaroglu M, Imbesi M, Kurtuncu M, Manev H (2004). "The pineal gland and anxiogenic-like action of fluoxetine in mice". Neuroreport. 15 (4): 691–4. doi:10.1097/00001756-200403220-00023. PMID 15094477. 
  24. ↑ Manev H, Uz T, Kharlamov A, Joo J (1996). "Increased brain damage after stroke or excitotoxic seizures in melatonin-deficient rats". FASEB J. 10 (13): 1546–51. PMID 8940301. 
  25. ↑ 25.0 25.1 Descartes and the Pineal Gland (Stanford Encyclopedia of Philosophy)
  26. ↑ Descartes R. Treatise of Man. New York: Prometheus Books; 2003. ISBN 1-59102-090-5
  27. ↑ Descartes R. "The Passions of the Soul" excerpted from "Philosophy of the Mind", Chalmers, D. New York: Oxford University Press, Inc.; 2002. ISBN 978-0-19-514581-6
  28. ↑ http://en.wikisource.org/wiki/Ethics_%28Spinoza%29/Part_5
  29. ↑ Hollier, D, Against Architecture: The Writings of Georges Bataille, trans. Betsy Wing, MIT, 1989.
  30. ↑ Ibid, p.129
  31. ↑ Bataille, G, Visions of Excess: Selected Writings, 1927-1939 (Theory and History of Literature, Vol 14), trans. Allan Stoekl et al., Manchester University Press, 1985
  32. ↑ [1]Principia Discordia
Retrieved from "http://ssf.f15ijp.com/wiki/index.php?title=Pineal_gland&oldid=18782"