6.2.2. Somatic Nerves: Intercostal Nerves, Part 1
The intercostal nerves are technically T1 – T11. T12 is not ‘intercostal’ because it lies below the twelfth rib only. The intercostal nerves have a variety of functions – they do more than just provide motor innervation to the intercostal muscles…
All intercostal nerves give off cutaneous branches to provide sensory innervation to the skin, branches to provide motor innervation to the intercostal muscles and branches to the costal pleura.
Additional Actions of the Intercostal Nerves
T1 also gives off a branch to the brachial plexus. This is a bundle of nerves at the root of the neck that provides almost all of the nerve supply to the upper limb.
T2 - T6 do not provide additional innervation.
T7 - T11 also supply the muscles of the anterior abdominal wall (e.g. the obliques, rectus abdominis). T7 – T9 nerves run all the way around to the anterior aspect of the thorax. They then dive deep to the costal cartilages of the ribs and travel inferiorly, to the abdominal wall. T10 – T11 nerves enter the anterior abdominal wall directly because they are floating ribs and have no costal cartilage.
T12, also called the subcostal nerve, runs along the inferior border of the twelfth rib and then directly enters the anterior abdominal wall to supply the muscles there.