Functional aspects of musles of the external nose in pigs (Sus scrofa f. domestica)

The origin and attachments of the muscles of the external nose were examine d in 17 pigs comprising both sexes and different age groups. The modificati on of the porcine nasal apex to the snout-disc leads to different functiona l aspects of the muscles of the external nose. Accordingly, all these muscl es are attached to the snout-disc. Only the nasolabial levator and caninus muscles are also attached to the upper lip. In addition, the snout-disc inc ludes an intrinsic muscle, the nasal muscle. With regard to morphological a nd functional aspects, the nostrils can be divided into two parts. The supe rficial part consists of muscle and connective tissue and is dilated by the cooperative contraction of all muscles of the external nose. In contrast, the second and cartilaginous part of the nostrils dilates less readily, thr ough contraction of the rostrally located deep fibres of the levator nasola bial muscle. As an adaptation for rooting, a special supportive system for muscles of the external nose has developed in pigs, including osseous (emin entia canina) and muscular (muscular slip of the m, levator labii superiori s attached to the nasal bone, species-specific development of the m. levato r nasolabialis) structures. The observed cartilaginous connection between t he ventral lateral nasal and the vomeronasal cartilages suggests another tr ansport mechanism for odours into the vomeronasal organ. Due to this connec tion, movement of the snout-disc and the cartilages of the external nose co uld imply passive movement of the vomeronasal cartilage and therefore of th e vomeronasal organ.