CONTRIBUTION OF THE INTERCOSTAL NERVES TO THE DIAPHRAGMATIC INNERVATION IN MIXED-BREED SHEEP (OVIS ARIES LINNAEUS, 1758): AN ANATOMICAL STUDY IN FETUSES

The costal grooves house vascular and nervous structures known as intercostal nerves, which are responsible for innervating the intercostal muscles and, occasionally, supplying syntopic structures such as the diaphragm. This study aimed to verify the existence of collateral diaphragmatic innervation via the intercostal nerves in fetal sheep (Ovis aries Linnaeus,1758),of both sexes and at different stages of development. Thirty specimens, previously fixed in 10% aqueous formaldehyde solution for over 72 hours, were analyzed. After thoracotomy through the costochondral joints, the intercostal nerves were dissected along their entire course, preserving their branches, especially those directed to the diaphragm. The findings revealed that, on the right antimere, the 6th intercostal nerve contributed in 11.11% of cases, the 7th to 12th pairs in 100% of cases, and the 13th in 66.66%. On the left antimere, the 5th intercostal nerve was present in 11.11% of cases, the 7th to 12th pairs in 100%, and the 13th in 66.66%. The results demonstrate the recurrent participation of the intercostal nerve particularly the 7th to 12th pairs in the collateral innervation of the diaphragm, with significant anatomical variation. These findings provide relevant information for understanding the respiratory physiology of sheep and for planning thoracic surgical procedures in this species.