Defecation Reflex- Definitioin, Intrinsic & Extrinsic Reflexes

One of the most important terms from the medical sciences is Defecation Reflex. Today, not only the definition but also, I am going to give you a quite detailed account on the topic. We will discuss its definition, structure, working, and also, what is a normal bowel movement. These are very important medical terms and being a medical student, it very important for you to understand them correctly. Ok, so let’s move on with our task and start from a basic definition of our primary topic which Defecation Reflex.

Defecate Reflex Definition:

This could be described as, an involuntary response that arrives from the lower bowels to different stimuli which further causes the bowel movement. The autonomic system is the key here. And that’s because all of these systems are under the autonomic system. This plays a major role in the defecation movement. We should not forget about the somatic system, on which autonomic system have some effects. The somatic system is the key principle for the control of voluntary actions of the defecation reflex. Defecation then gets divided into further types. Those can be named as intrinsic myenteric defecation reflex and parasympathetic defecation reflex. These two types are explained in great detail below.

intrinsic and extrinsic defecation reflex

Intrinsic Myenteric Defecation Reflex:

This is the first type of Defecation reflex.

In this part of the Defecation reflex, the increment of the rectum happens when feces enter into the rectum. Signals are then being sent to the descending and sigmoid colon. That is possible when myenteric plexus to increase the peristalsis. If you don’t know what myenteric plexus is then kept in mind that it is a sort of enteric nervous system. This is the internal neural network of the gut.  Then comes the next thing in this process which is the extension of the peristaltic waves to the rectum in the form of the anus. When this happens, fecal matter is then inclined to move to close to the anus. The internal anal sphincter is then caused by the wave when it reaches anus.

At this point, there are chances that defecation reflex might occur only in the case of the relaxation of the external sphincter. Defecation that depends only on the intrinsic reflex can never be strong if the parasympathetic reflex is absent.

Parasympathetic Defecation Reflex:

This is the second main sort of Defecation reflex. In both these types, when you will study, you will not find any major difference. In fact, it is quite the same as the first one. But in this one, it involves the action of parasympathetic nerve fibers. These fibers come from the pelvic nerves. These are also responsible for the sending of peristaltic waves in the sigmoid colon and descending. Not only this, relaxation of the internal and external sphincter is also caused by this. Another main difference that you should keep in mind is that this process works for the hastening of the above process which is intrinsic defecation reflex.

So, this was all on this topic. I hope you learned very well. Leave us your feedback in the comments section. Also, leave us your questions there. You can ask for special lectures from us. I will try my best to bring out the best knowledge out of each topic. Your feedback is important so keep leaving it. Stay tuned to Medics Center for more!

Hi, This is Hamza Khan from Peshawar, Pakistan. I am a 2nd prof MBBS Student at Bannu Medical College and a hobby Blogger. The Purpose of this site is to share my knowledge and Guide new Medical Students.

Leave a reply:

Your email address will not be published.