Vomiting (Emesis) in animals
Vomiting is the spasmodic and forceful ejection of the stomach contents to mouth through dilated oesophagus.
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.
In carnivores and omnivore vomiting is common.
Herbivores and rodent never vomit.
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.
In other non-vomiters, the vomiting center may be absent or rudimentary.
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.
- Act of vomiting is composed of four phases-
- Oesophageal dilatation
- Gastric emptying
- Gastric reflux
- Oesophageal collapse
After a deep involuntary inspiration, the glottis and the nasopharynx are closed by elevation of soft palate. Relaxation of oesophagus, gastro-oesophageal junction and the body of the stomach followed by strong pyloric contraction.
The intra-thoracic pressure is increased by the contraction of diaphragm and abdominal muscles. Additional pressure exerted by the contraction of abdominal muscles and the diaphragm, force the stomach contents into mouth through the relaxed oesophagus.
Massive antiperistalsis originates from the small intestine which reflux into the stomach.