The thorax is primarily supplied by the intercostal nerves.
Intercostal Nerves: The Primary Thoracic Innervation
The intercostal nerves are the main nerves supplying the thorax. These nerves are the anterior rami of the thoracic spinal nerves T1-T11. They run along the intercostal spaces between the ribs, providing sensory and motor innervation to the thoracic wall. The T12 nerve is called the subcostal nerve because it runs below the 12th rib.
Functions of Intercostal Nerves:
- Sensory Innervation: The intercostal nerves give rise to anterior and lateral cutaneous branches. These branches provide sensation to the skin of the thorax and the abdominal wall.
- Motor Innervation: Muscular branches from the intercostal nerves innervate the muscles of the thoracic wall. This includes the intercostal muscles themselves, which are essential for breathing.
- Sympathetic Connection: The intercostal nerves communicate with the sympathetic trunk via rami communicantes. These communicating branches connect the intercostal nerves to the sympathetic trunk on the same side, facilitating sympathetic innervation of structures in the thorax and abdomen.
Other Nerves Involved (Less Directly)
While the intercostal nerves are the primary suppliers, other nerves also play a role:
- Phrenic Nerve: While not directly supplying the thoracic wall, the phrenic nerve (primarily from C3, C4, and C5) is crucial for innervating the diaphragm, the primary muscle of respiration located at the inferior border of the thorax.
- Vagus Nerve (CN X): Passes through the thorax and provides parasympathetic innervation to organs within the thoracic cavity (e.g., heart, lungs).
- Sympathetic Trunk: Located along the vertebral column within the thorax, the sympathetic trunk provides sympathetic innervation to thoracic organs and communicates with the intercostal nerves via rami communicantes.
Summary Table
| Nerve | Primary Function | Area of Supply |
|---|---|---|
| Intercostal Nerves | Sensory & Motor to Thoracic Wall, Sympathetic Connection | Skin and muscles of the thoracic wall, abdominal wall, and connection to the sympathetic trunk. |
| Phrenic Nerve | Motor & Sensory to Diaphragm | Diaphragm |
| Vagus Nerve | Parasympathetic Innervation | Thoracic organs (heart, lungs, etc.) |
| Sympathetic Trunk | Sympathetic Innervation | Thoracic organs and connection to intercostal nerves |
