Why do we vomit when we have appendicitis?

JordanN

Hello Physics Forum. Long time lurker, I've decided to make an account for myself to participated in such an awesome community.

Now, my question is, why do humans vomit when the appendix gets infected? Does the bacteria that invades the deteriorating gut wall really travel far up the intestines and through the pyloric sphincter? Also, how come food doesn't easily get stuck in appendix opening (since the way it's shape looks like anything could get lodged in there)?

bobze

Vomiting is a non-specific protective reflex. It is controlled by a region of medulla which is outside the blood-brain barrier, so can be the target of long range signals like hormones. When you are having GI problems, like infections, part of the immune response is the release of hormones and chemokines. Which starts non-specific immune functions, like recruiting neutrophils and monocytes.

One of those non-specific responses is to target the receptive area in the medulla which causes nausea and then vomiting.

Think about it from an evolutionary stand point. If you filled your belly up with bad food, that could potentially be causing problems, it would be beneficial to your survival to eject said food, rather than retain it and continue absorption of any toxins it may contain.


Actually, most of the symptoms you get "from being sick", are really non-specific immune responses from your immune system. Things like fever, headache, malaise, aches, hot/cold flashes, etc.

madcat8000

I think its a pain reaction. http://www.abdopain.com/symptoms-of-appendicitis.html
"They may actually vomit. It is important to note that vomiting in appendicitis usually follows the pain. If you vomit before the pain commenced, it is not likely that the appendix is to blame."

nismaratwork

Visceral pain is unique and often debilitating due to its intensity, or nauseating due to the pain. There is nothing about the appendix itself, or the infection (in an un-ruptured appendix) that would DIRECTLY cause vomiting.

Also, welcome to PF JordanN.

bobze

This is true and I think probably has a great deal to due with "referred pain", the misfortune that our brains don't have a dermatome map for general visceral afferent (GVA) nerves as it does for general somatic afferent (GSA) nerves. And also because we are unlucky enough returning synapses to be shared by GSA and GVA neurons (consequently why your left arm hurts during a heart attack!)

That part I can't agree with. The 4th cerebral ventricle or "vomit center" receives input from various locals of the body. One of these inputs is from enteric nervous system. The appendix directly gets innervation from superior mesenteric plexus. Irritant or pain stimulus to any of the enteric plexuses can induce the vomit reflex.

Another input in via chemical receptor, which the 4 CV is packed full of. People with appendicitis have infection and inflammation, resulting in increased white cell counts. Of particular interest would be the granular leukocytes and mast cells (which may or may not arise from granular leukocyte lineage, I don't think anyone knows for sure at the moment), which would all be capable of releasing long rang signals and elevated counts often are associated with nausea.

nismaratwork

I should be clear, the PAIN can directly induce nausea, I mean that there is no means by which the appendix returns its contents via the almighty "tract"... directly... if you catch my drift. The question earlier concerned the notion that infection somehow made its way back into or the near the stomach, this is the 'direct' I referred to.

bobze

Got ya And I agree with that, when I wrote that I was pretty tired so the fault was probably mine in not comprehending what you were saying

nismaratwork

Oh, having been there and done that myself, no sweat. I did say "direct" after all, and that was fairly unclear.