Middle superior alveolar nerve arise from infra orbital branch of maxillary nerve in the infra orbital groove and canal.Course of superior alveolar nerve:It is given off from the maxillary nerve just before its exit from the infra orbital foramen. It descends in a canal in the anterior wall of the maxillary sinus, and divides into branches which supply the incisor and canine teeth. It communicates with the middle superior alveolar branch, and gives off a nasal branch and supplies the mucous membrane of the anterior pa of the inferior meatus and the floor of the nasal cavity. Ref: Essentials of Anatomy By I. B. Singh, 2nd Edition, Page 391