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The enteric nervous system (ENS) is a subdivision of the Peripheral Nervous System, that directly controls the gastrointestinal system.
It is derived from neural crest.12
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Function
It is capable of autonomous functions3 such as the coordination of reflexes, although it receives considerable innervation from the autonomic nervous system and thus is often considered a part of it. Its study is the focus of neurogastroenterology.
It can be damaged by ischemia.4
Transplantation has been described as a theoretical possibility.5
Anatomy
It has as many as one hundred million neurons, one thousandth of the number of neurons in the brain, and considerably more than the number of neurons in the spinal cordcitation needed. The enteric nervous system is embedded in the lining of the gastrointestinal system.
The neurons of the ENS are collected into two types of ganglia: myenteric (Auerbach's) and submucosal (Meissner's) plexuses.6 Myenteric plexuses are located between the inner and outer layers of the muscularis externa, while submucosal plexuses are located in the submucosa.
Complexity
The enteric nervous system has been described as a "second brain".7 There are several reasons for this. The enteric nervous system can operate autonomously. It normally communicates with the CNS through the parasympathetic (eg, via the vagus nerve) and sympathetic (eg, via the prevertebral ganglia) nervous systems. However, vertebrate studies show that when the vagus nerve is severed, the enteric nervous system continues to function.
In vertebrates the enteric nervous system includes efferent neurons, afferent neurons, and interneurons, all of which make the enteric nervous system capable of carrying reflexes and acting as an integrating center in the absence of CNS input. The sensory neurons report on mechanical and chemical conditions. Through intestinal muscles, the motor neurons control peristalsis and churning of intestinal contents. Other neurons control the secretion of enzymes. The enteric nervous system also makes use of more than 30 neurotransmitters, most of which are identical to the ones found in CNS, such as acetylcholine, dopamine, and serotonin. The enteric nervous system has the capacity to alter its response depending on such factors as bulk and nutrient composition. In addition, ENS contains support cells which are similar to astroglia of the brain and a diffusion barrier around the capillaries surrounding ganglia which is similar to the blood-brain barrier of cerebral blood vessels.8
References
- ^ Barlow AJ, Wallace AS, Thapar N, Burns AJ (May 2008). "Critical numbers of neural crest cells are required in the pathways from the neural tube to the foregut to ensure complete enteric nervous system formation". Development 135 (9): 1681–91. doi:. PMID 18385256. http://dev.biologists.org/cgi/pmidlookup?view=long&pmid=18385256.
- ^ Burns AJ, Thapar N (October 2006). "Advances in ontogeny of the enteric nervous system". Neurogastroenterol. Motil. 18 (10): 876–87. doi:. PMID 16961690. http://dx.doi.org/10.1111/j.1365-2982.2006.00806.x.
- ^ enteric nervous system at Dorland's Medical Dictionary
- ^ Linhares GK, Martins JL, Fontanezzi F, Patrício Fdos R, Montero EF (2007). "Do lesions of the enteric nervous system occur following intestinal ischemia/reperfusion?". Acta Cir Bras 22 (2): 120–4. PMID 17375218. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-86502007000200008&lng=en&nrm=iso&tlng=en.
- ^ Gershon MD (April 2007). "Transplanting the enteric nervous system: a step closer to treatment for aganglionosis". Gut 56 (4): 459–61. doi:. PMID 17369379. http://gut.bmj.com/cgi/pmidlookup?view=long&pmid=17369379.
- ^ "The Enteric Nervous System". Retrieved on 2008-11-29.
- ^ Gershon MD (July 1999). "The enteric nervous system: a second brain". Hosp Pract (Minneap) 34 (7): 31–2, 35–8, 41–2 passim. PMID 10418549.
- ^ Silverthorn, Dee U.(2007)."Human Physiology". Pearson Education, Inc., San Francisco, CA 94111.
External links
Additional images
 The myenteric plexus from the rabbit. X 50. |
 The plexus of the submucosa from the rabbit. X 50. |
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