top of page


Study guide:


  • Vomiting (emesis):  Forceful oral expulsion of gastric contents associated with contraction of the abdominal and chest wall musculature, frequently preceded by nausea and abdominal pain.

  • Nausea: The unpleasant sensation of the imminent need to vomit, usually referred to the throat or epigastrium; a sensation that may or may not ultimately lead to the act of vomiting.

  • Regurgitation: The act by which food is brought back into the mouth without the abdominal and diaphragmatic muscular activitythat characterizes vomiting.

  • Retching: Spasmodic respiratory movements against a closed glottis with contractions of the abdominal musculature without expulsion of any gastric contents, "dry heaves".


  • Neurophysiological Emesis:

    • Area of Postrema (vomiting center):

      • Has the “Chemoreceptor trigger zone” CTZ lies outside the BBB

      • Anatomically, located in the brain stem at the caudal extremity of the floor of the fourth ventricle.

      • Triggered by: systemic chemicals through the following pathways:

        •  Vagal Afferents:

          •  Mechanical or chemosensory


          •  Examples of sensations that

            trigger this pathway: over
            distension, food poisoning, mucosal irritation, cytotoxic drugs, and radiation.

        •  Vestibular System:

          •  When vestibular input is in conflict with visual


          •  Plays a role in motion sickness.

          •  E.g.: Irritation or labyrinthine inflammation,


        •  Amygdala:
          Receives input from the olfactory bulb and

          olfactory cortex. 

  • Somatomotor Events of Emesis (emptying out the stomach, characterized by cycles of retching followed by the forceful expulsion of gastric contents):

    • Diaphragm descends and the intercostal muscles contract while the glottis is closed.

    • The abdominal muscles contract and the gastric contents are forced into upper

      gastric vault and lower esophagus.

    • The abdominal muscle relaxes and the esophageal refluxates.

    • Several cycles of retching.

    • Abdominal contraction with elevation of diaphragm results in forceful expulsion of

      gastric contents. 



  • Food poisoning (toxins):

  • Pain-induced:

    • Any deep visceral pain

    • E.g.: Acute appendicitis, MI, Renal stone pain

  • Obstructive:

    • Pyloric or intestinal obstruction 

  • Cerebral or Central:

    • Psychogenic: anxiety, bad odor, sight of blood, and tension.

    • Fever.

    • Pregnancy.

    • Drugs: digitalis, salicylates, morphine, alcohol…etc..

    • Increased intracranial pressure.  

    • Disturbance of electrolytes: ketosis, uremia.

    • Labyrinthine Disturbances. 



  2. Clinical Approach to Diagnosis Major Sign and Symptoms by Dr. Salah Ibrahim.

  3. Crash course Gastrointestinal System 4th edition.  

  4. Crash course Gastroenterology 4th edition. 


Written by:          ​Roaa Amer

Reviewed by:      Haifa Al-Issa
                             Haneen Al-Farhan

Format editor:   Roaa Amer

Web publisher:  Bayan Alzomaili 

                                Salman Alahmed

bottom of page