Origin and Distribution of the Phrenic Nerve in the Diaphragm of Collared Peccary (Tayassu tajacu)

This study on the origin and distribution of the phrenic nerve to the diaphragm was conducted using 16 collared peccaries (Tayassu tajacu). The phrenic nerves originated from the fourth to the seventh cervical spinal nerves, and in a few specimens, from the fourth to the sixth cervical nerves. A contribution from the cranial pectoral nerve to the phrenic nerve was observed. The phrenic nerve terminated in the costosternal and lumbar branches, and less frequently as the lumbocostal trunk and sternal branch. The lumbar branch innervates the crura of the diaphragm, while the costal branch serves the entire costal region. The sternal branch is distributed to the ventrolateral costal area and the sternal portion of the diaphragm on both the left and right sides. These branches send ramifications to the central tendon and the dorsal and ventral surfaces of the caudal vena cava, and also form homo- and heterolateral connections between the branches.