Median eminence

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Median eminence
HypothalamicNuclei.PNG
Median eminence is 'ME', at bottom-center, in light-green
Details
Identifiers
Latin eminentia mediana hypothalami
MeSH D008473
NeuroNames 402
NeuroLex ID birnlex_925
TA98 A14.1.08.409
TA2 5784
FMA 74634
Anatomical terms of neuroanatomy

The median eminence is generally defined as the portion of the ventral hypothalamus from which the portal vessels arise. [1] The median eminence is a small swelling on the tuber cinereum, posterior to and on top of the pituitary stalk; it lies in the area roughly bounded on its posterolateral region by the cerebral peduncles, and on its anterolateral region by the optic chiasm.

As one of the seven areas of the brain devoid of a blood–brain barrier, [2] the median eminence is a circumventricular organ having permeable capillaries. [3] [4] [5] [6] Its main function is as a gateway for release of hypothalamic hormones, [7] although it does share contiguous perivascular spaces with the adjacent hypothalamic arcuate nucleus, indicating a potential sensory role. [4] [8]

Physiology

The median eminence is a part of the hypothalamus from which regulatory hormones are released. [2] [7] It is integral to the hypophyseal portal system, which connects the hypothalamus with the pituitary gland. The pars nervosa (part of the posterior pituitary gland) is continuous with the median eminence via the infundibular stalk. Parvocellular neurosecretory cells from the hypothalamus terminate in the median eminence. [9]

The median eminence is the structure where secretions of the hypothalamus (releasing and inhibiting hormones) regulatory hormones, known as "hypophysiotropic hormones") collect before entering the portal system emptying into the general circulation. [2] [7] Such hypophysiotropic hormones include: CRF (corticotropin-releasing factor), GnRH (gonadotropin-releasing hormone), TRH (thyrotropin-releasing hormone), GHRH (growth hormone-releasing hormone), and DA (dopamine). [7] These hypophysiotropic hormones stimulate or inhibit the release of hormones from the anterior pituitary. [7] Further, anatomical evidence exists for bidirectional communication between the median eminence and the arcuate and ventromedial nucleus of the hypothalamus. [4] [8]

References

  1. ↑ Barrett, Kim E. (2019). Ganong's Review of Medical Physiology. Susan M. Barman, Heddwen L. Brooks, Jason X.-J. Yuan, William F. Preceded by: Ganong (26th ed.). [New York]. p. 303. ISBN   9781260122404. OCLC   1076268769.{{cite book}}: CS1 maint: location missing publisher (link)
  2. 1 2 3 Gross PM, Weindl A (December 1987). "Peering through the windows of the brain". Journal of Cerebral Blood Flow and Metabolism. 7 (6): 663–72. doi: 10.1038/jcbfm.1987.120 . PMID   2891718.
  3. ↑ Scott DE, Pepe GJ (July 1987). "The fetal baboon median eminence as a circumventricular organ: I. Transmission electron microscopy". Brain Research Bulletin. 19 (1): 87–94. doi:10.1016/0361-9230(87)90170-5. PMID   3651843. S2CID   26399150.
  4. 1 2 3 Gross PM (1992). "Chapter 31: Circumventricular organ capillaries". Circumventricular Organs and Brain Fluid Environment - Molecular and Functional Aspects. Progress in Brain Research. Vol. 91. pp. 219–33. doi:10.1016/S0079-6123(08)62338-9. ISBN   9780444814197. PMID   1410407.
  5. ↑ Johnson AK, Gross PM (May 1993). "Sensory circumventricular organs and brain homeostatic pathways". FASEB Journal. 7 (8): 678–86. doi: 10.1096/fasebj.7.8.8500693 . PMID   8500693. S2CID   13339562.
  6. ↑ Ganong WF (2000). "Circumventricular organs: definition and role in the regulation of endocrine and autonomic function". Clinical and Experimental Pharmacology & Physiology. 27 (5–6): 422–7. doi:10.1046/j.1440-1681.2000.03259.x. PMID   10831247. S2CID   23652492.
  7. 1 2 3 4 5 Palkovits M (1984). "Neuropeptides in the hypothalamo-hypophyseal system: lateral retrochiasmatic area as a common gate for neuronal fibers towards the median eminence". Peptides. 5 (Suppl 1): 35–9. doi:10.1016/0196-9781(84)90262-6. PMID   6148739. S2CID   3877865.
  8. 1 2 Shaver SW, Pang JJ, Wainman DS, Wall KM, Gross PM (March 1992). "Morphology and function of capillary networks in subregions of the rat tuber cinereum". Cell and Tissue Research. 267 (3): 437–48. doi:10.1007/BF00319366. PMID   1571958. S2CID   27789146.
  9. ↑ Hall, John E. (2021). Guyton and Hall Textbook of Medical Physiology. Michael E. Hall (14th ed.). Philadelphia, PA. pp. 931–932. ISBN   978-0-323-59712-8. OCLC   1129099861.{{cite book}}: CS1 maint: location missing publisher (link)
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