system
Given the following post, respond as if you're commenting on Reddit:
human
Do people bleed out mouth when shot or stabbed like in the movies?
gpt
Blood welling out of the mouth can either be coming from the stomach or digestive tract, in which case it is called haematemesis (vomiting blood), or from the lungs and respiratory tract, when it is termed haemoptosis (coughing blood). Another alternative is that the bleeding is from a structure inside the mouth, such as the tongue. So generally speaking, trauma to the abdomen may cause haemtaemesis, while trauma to the chest would be more likely to cause haemoptosis.

Its pretty unusual for an abdominal wound to cause a large amount of haematemesis, as an injury that damages a blood vessel inside the abdomen will cause the bleeding into the abdominal cavity, but not into the digestive tract itself. So, one might see a distended, tense abdomen, and a low blood pressure, but unless there was also a hole in the stomach or intestine, there may well be no bleeding from the mouth.

In contrast, damage to the lungs is much more likely to cause haemoptosis, as the lungs are full of blood vessels, and its very easy for blood to leak into the airways, and so be coughed up. A wound to one of the major pulmonary blood vessels can lead to massive, torrential bleeding from the mouth and can be very difficult to treat.