The intercostal nerves are a group of twelve pairs of nerves that arise from the thoracic spinal cord. They run between the ribs and are responsible for providing sensation to the skin and muscles in the chest and upper abdomen. These nerves play a crucial role in the movement of the ribcage during breathing. Each intercostal nerve also supplies motor function to the intercostal muscles, which help expand and contract the chest cavity. Additionally, they contribute to the sensory innervation of the pleura and peritoneum, allowing for the perception of pain and other sensations in these areas.