Referred Pain – Autonomic Nerves of Abdominopelvic Organs

by James Pickering, PhD

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    00:00 So that's a brief overview of the autonomic nervous system for the specific areas, the specific organs.

    00:10 I just want to concentrate on the referred pain now and before I do that, I just want to review this diagram which we looked at in the very first lecture of the surface anatomy.

    00:19 And here we have the spinal cord. The spinal cord giving rise to two pairs of spinal nerves. One here and one here. These spinal nerves are going to be running around the body wall and they are going to be receiving cutaneous innervation from the surface of the skin.

    00:42 So this banding is what we see on this diagram this dermatomal distribution. So if something was to irritate the skin here, that cutaneous nerve say here, will pick it up and it will take it back to spinal cord at say, T9.

    00:59 That may happen at T8 or T7 or T6, or T5, L1, T12, whatever.

    01:06 So the visceral afferent fibers, these are not cutaneous afferent fibers. These are visceral afferent fibers These visceral afferent fibers taking sensation from the visceral travel retrograde from the organ to the central nervous system, just like sensation from the skin.

    01:31 Except that is coming from the skin, it's coming from the organ.

    01:37 The point of this is to promote visceral or somatic reflexes so we can release more juice depending on the condition and we are unaware of these happening.

    01:49 This is just a feedback mechanism to control our internal environment.

    01:54 During various pathological states, however, noxious stimuli, the accumulation of the noxious stimuli from an internal organ can become so elevated that it actually reaches our consciousness.

    02:08 However, this is usually poorly localized.

    02:12 It's poorly localized because we are not used to having it and also because the body is served by laterally, that it passes from both sides into the central nervous system, so the body is not clear where it's coming from.

    02:29 So when you have a tummy ache, you tend to have a dull ache right in the center.

    02:36 It hasn't localized to a specific region.

    02:39 However, with time this pain can radiate to the dermatome level that receives the visceral afferents.

    02:53 So the dermatome level say here at T9, we know that the 9th thoracic spinal cord segment gives rise to sympathetic fibers, the greater splanchnic nerve that go to serve the stomach.

    03:12 Noxious stimuli from the stomach are going to travel in this retrograde direction back to T9.

    03:21 Now, we are not really used to feeling that.

    03:27 What we are used to feeling is pain coming from the surface of the skin. So our brain believes that this pain is actually originating from the surface of the skin and that's why we called it referred pain.

    03:45 The pain is actually coming from the stomach or whatever organ.

    03:49 But it's been referred to the surface of the skin. That's why we need to be confident in knowing the spinal cord segment that gives rise to those autonomic nerves.

    04:03 So let's have a look at the appendicitis.

    04:07 Appendicitis pain is initially felt in the kind of periumbilical region. Around about in this region here.

    04:16 The appendix is part of the midgut and the midgut is served from the greater, lesser and least splanchnic nerves. And these come into the spinal cord following their afferent fibers at around about the T10 level of lesser splanchnic nerve here.

    04:39 If the inflammation of the appendix irritates the parietal peritoneum.

    04:44 Now remember that the parietal peritoneum that could be irritated by the appendix is down in your lower inguinal region. Your appendix is in this right inguinal region here.

    04:55 Then the parietal peritoneum here is going to become irritated.

    04:59 So if the inflammation of the appendix (appendicitis) irritates the parietal peritoneum as this is supplied by the somatic nervous system, the parietal peritoneum, as this is supplied by the somatic nervous system down in here this pain can now be precisely localized. So it's starting off here and then its radiating down here. It localizes to the lower right quadrant, where the appendix is located.

    About the Lecture

    The lecture Referred Pain – Autonomic Nerves of Abdominopelvic Organs by James Pickering, PhD is from the course Pelvis.

    Included Quiz Questions

    1. T10
    2. T12
    3. T11
    4. T9
    5. T8
    1. Heart
    2. Liver
    3. Spleen
    4. Pancreas
    5. Kidneys
    1. Right lower quadrant
    2. Right upper quadrant
    3. Umbilicus
    4. Left upper quadrant
    5. Left lower quadrant

    Author of lecture Referred Pain – Autonomic Nerves of Abdominopelvic Organs

     James Pickering, PhD

    James Pickering, PhD

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