All are typical intercostal nerves except ?

Ans. is 'a' i.e., 2" A typical intercostal nerve is the one that is confined to the intercostal space in its distribution.Based on this, the intercostal spaces are also designated as typical or atypical.The typical intercostal space is traversed by a typical intercostal nerve.The first and second thoracic nerves are atypical because they also innervate pa of upper limb brachial plexus (T1) and intercostobrachial nerve (T2). The lower six thoracic nerves (T7-T12) are atypical because they also innervate anterior abdominal wall.Thus only 3"' to 6" are called typical intercostal nerves, and 3'd to 6' intercostal spaces are called typical intercostal spaces.