Innervation – Thoracic Diaphragm

by Craig Canby, PhD

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    00:01 On the following slide, we will take a look at the innervation of the diaphragm. And here I’ll call back that rhyme: C345 keeps the diaphragm alive.

    00:15 So, now, let’s take a look at the slide demonstrating the innervation of the diaphragm.

    00:22 There are several nerves that innervate the diaphragm. But, your key take-home point here is that the phrenic nerve is the only nerve that provides for motor innervation. So, we have a right phrenic nerve going to the right hemidiaphragm, we have a left phrenic nerve going to your left hemidiaphragm. Here’s your right phrenic nerve, here’s your left phrenic nerve and if you follow the nerves distally, you see these muscular branches innervating the diaphragm. These spinal nerve levels that contribute to the formation of the phrenic nerve are spinal nerves C3, C4 and C5. So, again, it’s the phrenic nerve that has sole function of motor innervation of the diaphragm.

    01:17 The phrenic nerve also conveys sensory innervation. And this is a key point because when you look at the dermatomes that are innervated by C3, 4, 5, again, those same spinal nerves that provide for innervation of the phrenic nerve, that’s going to be on the shoulder region and even up into your neck, here on the left side and then also on the right side. If there’s any irritation of the diaphragm, maybe there’s a liver abscess that’s irritating the inferior surface of the diaphragm, maybe there’s accumulation of blood in the peritoneal cavity; blood is very irritating and if it’s at the level of the diaphragm, it will irritate the diaphragm. That will cause pain to be referred to those dermatomal patterns of C3, the shoulder into the neck area.

    02:12 In addition, we have intercostal nerves running within intercostal spaces 5, 6, 7, 8, 9, 10 and 11 as well as the nerve that travels just below the twelfth rib called the subcostal nerve. We can kind of see those dermatomal patterns along here in this particular figure.

    02:38 But, again, these nerves are running within the intercostal spaces or, in the case of T12, below the twelfth rib, there's a cutaneous branches that supply the skin from those intercostal nerves and the subcostal nerves, but there are also branches from these intercostal nerves and subcostal nerves that will provide for sensory innervation of the diaphragm.

    03:05 That now brings us to our summary, the key take-home points from this lecture.

    03:13 The diaphragm is a musculotendinous structure separating the thoracic cavity from the abdominal cavity.

    03:21 The right hemidiaphragm has a more superior surface projection than left due to the presence of the liver on the right.

    03:29 The sternal, costal and lumbar parts constitute the muscular diaphragm.

    03:37 Arterial supply and venous drainage is provided by vessels with phrenic as a part of their name.

    03:46 Motor innervation is via the phrenic nerves - C345 keeps the diaphragm alive, whereas sensory is mediated by the phrenic intercostals T5 through T11 as well as your subcostal nerves T12.

    04:02 Potential herniation sites include the oesophageal hiatus and the sternocostal and lumbocostal triangles.

    04:14 Pain from the diaphragm is referred to the C3, 4, 5 dermatomes. Again, the neck, shoulder and lateral arm.

    04:25 Thank you for joining me on this lecture on “The Diaphragm”.

    About the Lecture

    The lecture Innervation – Thoracic Diaphragm by Craig Canby, PhD is from the course Abdominal Wall.

    Included Quiz Questions

    1. Phrenic nerve
    2. Intercostal nerve
    3. Subcostal nerve
    4. Thoracic nerves
    5. Musculocutaneous nerves
    1. C3–C5
    2. C2–C3
    3. C4–C6
    4. C5–C7
    5. C1–C2
    1. Neck and shoulders
    2. Forearms
    3. Shoulder and abdomen
    4. Shoulder and back
    5. Both arms

    Author of lecture Innervation – Thoracic Diaphragm

     Craig Canby, PhD

    Craig Canby, PhD

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