Vomiting (Emesis)
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Vomiting is the spasmodic and forceful ejection of the stomach contents to mouth through dilated oesophagus.
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Vomiting is very rare in horse due to the presence of well developed and powerful cardiac sphincter and distant position of the stomach from the abdominal walls.
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In carnivores and omnivore vomiting is common.
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Herbivores and rodent never vomit.
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The vomiting centre is located in the lateral reticular formation of the medulla which is stimulated by afferent impulses from pharynx, stomach, duodenum, heart and uterus.
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In other non-vomiters, the vomiting center may be absent or rudimentary.
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The cranial nerves 5, 7, 9, 10 and 12 to the upper gastro-intestinal tract and spinal nerves to the diaphragm and abdominal muscles are the efferent nerves involved in the reflex act of vomiting.
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Act of vomiting
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After a deep involuntary inspiration, the glottis and the nasopharynx are closed by elevation of soft palate.
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Relaxation of oesophagus, gastro-oesophageal junction and the body of the stomach followed by strong pyloric contraction.
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The intra-thoracic pressure is increased by the contraction of diaphragm and abdominal muscles.
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Additional pressure exerted by the contraction of abdominal muscles and the diaphragm, force the stomach contents into mouth through the relaxed oesophagus.
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Last modified: Friday, 30 December 2011, 7:14 AM