Origin and branching of the phrenic nerve (Sus scrofa domesticus Linnaeus, 1758) of the Pen Ar Lan Line

Abstract

Swine farming has increasingly developing worldwide due to advances in genetic improvement, thus, researchers are investigating possible anatomical variations in new lineages. The objective of this study was to assess the origin and branching of the phrenic nerve in 27 swine (Sus scrofa domesticus – Linnaeus, 1758) fetuses of the Pen Ar Lan line—19 males and 8 females. They were dissected after fixing in a 10% formaldehyde solution. The phrenic nerve originated from 51 (94.4%) antimeres of the fifth cervical spinal nerve (C5), 54 (100%) antimeres of the sixth cervical spinal nerve (C6), and six (11.11%) antimeres of the seventh cervical spinal nerve (C7). Considering this distribution, the phrenic nerve emitted fibers to the pericardium and branched into the diaphragm muscle in all specimens evaluated. Six different branching were found, most frequently in the dorsal, lateral, and ventral branches in 22 (40.74%) antimeres, followed by branching to dorsal branches and ventrolateral trunk in 18 antimeres (33.33%). In addition, two of the branching found are not cited in scientific literature, denoting their variability. The dorsal branches were distributed to the pillar muscles in the lumbar part, the ventral branches to the sternal part, and the lateral branches to the dorsal part.