1 WALL OF THORAX DESCRIBE COURSE, BRANCHES AND DISTRIBUTION OF TYPICAL INTERCOSTAL NERVE (LE). There are 12 thoracic spinal nerves. The 3 rd to 6th nerves lie in typical intercostal spaces between typical ribs. They are confined to the thoracic wall. Formation: The thoracic spinal nerve is formed by anterior and posterior roots, which arises from the anterior and posterior horns of spinal cord respectively. The anterior and posterior roots join together to form the trunk. The trunk divides into anterior and posterior rami. The anterior ramus forms the intercostal nerve. Course: The nerve passes through the respective intervertebral foramen and appears in the posterior part of the intercostal spaces. On reaching the angle of the upper rib, the trunk of the nerve passes forwards along the costal groove between intercostalis internus and intimus muscle. Intercostal nerves runs in the costal groove and ends near the sternum. 2 In the costal groove the
