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Equine myenteric plexus with special reference to the pelvic flexure pacemaker. 1991

G A Burns, and J F Cummings
New York State College of Veterinary Medicine, Department of Anatomy, Cornell University, Ithaca, New York 14850.

Sellers et al. (1979, Am. J. Phys., 237: E457-E464) proposed a pelvic flexure pacemaker mechanism to account for the bidirectional contraction waves needed to both retain ingesta within the right ventral colon for cellulose digestion and terminal fermentation and to transport the digesta distad once the process has been completed. To corroborate the presence of a pelvic flexure pacemaker, we prepared whole mount samples of the tunica muscularis from 23 horses at ten sites along the large colon, cecum and jejunum. Following smooth muscle enzymatic digestion, somata of the myenteric plexus were stained with an RNA-specific agent, Cuprolinic blue. These somata were quantified at each site to establish any regional variations in neuronal density. Results indicated an increased neuronal density at the level of the pelvic flexure, especially in the region of the left dorsal colon. The increased neuronal density at the left dorsal colon compared to the other sampling sites was statistically significant (Wilcoxon signed rank test, P less than .01 at each sampling site). There was remarkable size variation (from 10-60 microns) among neurons at the individual sampling sites. However, no statistically significant size discrepancy existed between sampling sites (Friedman's rank test, P = .10). The 23 horses ranged from 6 months to 15 years of age. No age-related differences in neuronal density was discovered (Kruskal-Wallis ANOVA test, P greater than .05). Neuronal densities did not vary on the basis of sex (Wilcoxon signed pairs test, P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

UI MeSH Term Description Entries
D007583 Jejunum The middle portion of the SMALL INTESTINE, between DUODENUM and ILEUM. It represents about 2/5 of the remaining portion of the small intestine below duodenum. Jejunums
D008297 Male Males
D009197 Myenteric Plexus One of two ganglionated neural networks which together form the ENTERIC NERVOUS SYSTEM. The myenteric (Auerbach's) plexus is located between the longitudinal and circular muscle layers of the gut. Its neurons project to the circular muscle, to other myenteric ganglia, to submucosal ganglia, or directly to the epithelium, and play an important role in regulating and patterning gut motility. (From FASEB J 1989;3:127-38) Auerbach's Plexus,Auerbach Plexus,Auerbachs Plexus,Plexus, Auerbach's,Plexus, Myenteric
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D010388 Pelvis The space or compartment surrounded by the pelvic girdle (bony pelvis). It is subdivided into the greater pelvis and LESSER PELVIS. The pelvic girdle is formed by the PELVIC BONES and SACRUM. Pelvic Region,Region, Pelvic
D002432 Cecum The blind sac or outpouching area of the LARGE INTESTINE that is below the entrance of the SMALL INTESTINE. It has a worm-like extension, the vermiform APPENDIX. Cecums
D003106 Colon The segment of LARGE INTESTINE between the CECUM and the RECTUM. It includes the ASCENDING COLON; the TRANSVERSE COLON; the DESCENDING COLON; and the SIGMOID COLON. Appendix Epiploica,Taenia Coli,Omental Appendices,Omental Appendix,Appendices, Omental,Appendix, Omental
D005260 Female Females
D006736 Horses Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest. Equus caballus,Equus przewalskii,Horse, Domestic,Domestic Horse,Domestic Horses,Horse,Horses, Domestic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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