TABLE OF CONTENTS
Vomiting (Emesis) in Animals
Vomiting (emesis) in animals is the spasmodic and forceful ejection of stomach contents through the dilated esophagus and out of the mouth.
Vomiting is very rare in horses due to the presence of a well-developed and powerful cardiac sphincter and the distant position of the stomach from the abdominal walls.
In carnivores and omnivores, vomiting is common. Herbivores and rodents never vomit.
The vomiting center is located in the lateral reticular formation of the medulla and is stimulated by afferent impulses from the pharynx, stomach, duodenum, heart, and uterus.
In other non-vomiting species, the vomiting center may be absent or rudimentary.
The cranial nerves (V, VII, IX, X, and XII) supply the upper gastrointestinal tract, while spinal nerves control the diaphragm and abdominal muscles, making them the efferent nerves involved in the reflex act of vomiting.
Act of Vomiting (Emesis)
The act of vomiting (Emesis) consists of four phases:
- Esophageal dilatation
- Gastric emptying
- Gastric reflux
- Esophageal collapse
After a deep involuntary inspiration, the glottis and nasopharynx are closed by the elevation of the soft palate. This is followed by the relaxation of the esophagus, gastroesophageal junction, and the body of the stomach, along with a strong pyloric contraction.
The intrathoracic pressure increases due to the contraction of the diaphragm and abdominal muscles. Additional pressure exerted by the abdominal muscles and diaphragm forces the stomach contents into the mouth through the relaxed esophagus.
A massive antiperistaltic wave originates from the small intestine, causing reflux into the stomach.