Thoracic Wall: Innervation – Thorax Muscles and Thoracic Wall

by Craig Canby, PhD

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    00:00 Innervation of the thoracic wall, there are several nerves that will help provide for innervation to the wall. These would include the intercostal nerves, the subcostal nerves, long thoracic nerves and the medial and lateral pectoral nerves. This slide is showing the same illustration, but it shifts our attention to the intercostal nerves. There are 11 pairs of intercostal nerves traveling within the intercostal spaces. The nerves accompany the intercostal arteries and nerves within those spaces. And here, we have a couple of examples of intercostal nerves. These are anterior rami of spinal nerves.

    00:46 And as you proceed along the lateral margin of an intercostal space, you will see that we have this lateral branch that’s issuing from the intercostal nerve and this lateral branch can help supply the lateral portion of the skin associated with the thoracic wall.

    01:04 And then the intercostal nerve will continue within its intercostal space and assume an anterior course and then end on along the lateral border of your sternum and provide for some other cutaneous branches that will pop through the intercostal space. And certainly, as they travel within the intercostal spaces, these nerves are also going to provide for muscular innervation of the intrinsic muscles that we mentioned earlier.

    01:35 Now, we can put everything together with respect to the nerves, to the arteries and to the veins that travel within the intercostal spaces. So, here, we’re looking at our intercostal neurovasculature. And there is a relationship that exists between these three structures as they travel in the intercostal space. If we take a look right here, here is a rib.

    02:07 Here is the inferior margin of the rib. This groove area that we see here is that costal groove. And then we see our intercostal structures traveling within or inferior to that groove and there is this consistent relationship of having the intercostal vein being the more superior of the three. Intercostal artery being the middle one of the three. And you can see your intercostal nerve being the inferior most structure of the three.

    02:42 And the mnemonic to remember this relationship is VAN for the intercostal vein is most superior, artery is the middle and then your intercostal nerve would be the most inferior of these three structures. Understanding this relationship is extremely important in performing a procedure referred to as a thoracentesis. In a thoracentesis, a needle would have to be advanced through the intercostal space into the pleural cavity to remove excessive fluid. When you advance the needle into the intercostal space, you want to make sure that you avoid the intercostal structures that are located more superiorly, so you’ll advance your needle over the superior margin of the rib below, for example.

    03:38 Another nerve that innervates the thoracic wall is your long thoracic nerve. That is seen in through here. The long thoracic nerve has a superficial course which is a bit unusual for nerves. Most nerves that innervate muscles will assume a deep course and be protected by the more superficial muscle mass. But, this one is superficial. It lies just underneath the skin and the fascia. So, a laceration along the lateral side of the thoracic wall that does go through the skin and the subcutaneous fascia could injure this particular nerve.

    04:21 And as we mentioned earlier, when we were talking about the fact it innervates the serratus anterior, injury to this nerve could result in paralysis of the serratus anterior muscle.

    04:32 And a common sign here, in that case, would be the fact the the scapula would wing out, particularly if you had the patient push against resistance.

    04:40 The pectoral nerves, the medial and lateral pectoral nerves, are going to innervate your pectoral muscles. The medial pectoral nerve will issue from the medial cord of the brachial plexus whereas the lateral pectoral nerve issues from the lateral cord of the brachial plexus. The medial pectoral nerve is running deep to the pectoralis minor, so we kind of just see it and its branching pattern. It will pierce the pectoralis minor and innervate the minor and then once it gets pierced through the minor, it will then pierce into the major to assist in innervating that muscle as well. The lateral pectoral nerve, which we see coming in through here, sends branches into the pectoralis major. So, the major is also innervated by the lateral pectoral nerve. That now brings us to the important take-home messages from this presentation. First, the ribs, sternum and thoracic vertebrae constitute the osteology of the thoracic wall. The 12 pairs of ribs define 11 intercostal spaces that house intercostal vessels and nerves. And remember your VAN relationship.

    06:05 Ribs are classified on the basis of points of articulation as well as being true or false.

    06:11 The sternal angle is a landmark for the identification of the second rib.

    06:17 Thoracic vertebrae possess facets for articulation with the head and, in most cases, the tubercle of the rib. Movements of the thoracic wall are designed to alter thoracic volume as required for ventilation or respiratory movements.

    06:34 Muscles of the thoracic wall can be categorized as extrinsic and intrinsic on the basis of their attachments. Innervation and vasculature of the thoracic wall is segmental and non-segmental. The acronym VAN, as mentioned a moment ago, again, describes the relationship of neurovascular structures in the intercostal spaces.

    07:00 Thank you for joining me on this journey of “The Thoracic Wall”.

    About the Lecture

    The lecture Thoracic Wall: Innervation – Thorax Muscles and Thoracic Wall by Craig Canby, PhD is from the course Abdominal Wall.

    Included Quiz Questions

    1. Long thoracic
    2. Intercostal
    3. Lateral pectoral
    4. Medial pectoral
    5. Thoracodorsal
    1. 11
    2. 12
    3. 13
    4. 10
    5. 14
    1. Intercostal vein
    2. Intercostal artery
    3. Intercostal nerve
    4. Lymphatics
    1. Long thoracic
    2. Medial pectoral
    3. Lateral pectoral
    4. Intercostal
    5. Short thoracic

    Author of lecture Thoracic Wall: Innervation – Thorax Muscles and Thoracic Wall

     Craig Canby, PhD

    Craig Canby, PhD

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