The harp seal, Pagophilus groenlandicus (Erxleben, 1777). XIII. The gross and microscopic structure of the auditory meatus

• Published in: Canadian Journal of Zoology
• Main Authors: Ramprashad, F., Corey, S., Ronald, K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1971
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Harp Seal; Pagophilus groenlandicus
• Online Access: http://dx.doi.org/10.1139/z71-034; http://www.nrcresearchpress.com/doi/pdf/10.1139/z71-034

The gross and microscopic structure of the auditory meatus of the harp seal (Pagophilus groenlandicus) is described from dissections and serial sections. The meatus bends ventrally from the oval external orifice, posteroventrally, ventrally, and finally medially into the cranium. The ventrally directed wall of the meatus is membranous, the posteroventral and ventrally directed wall is incompletely wrapped by cartilage, and the medially directed wall is bony. The areas between sections of the cartilaginous wall ate completed by connective tissue. The meatus is closed internally by the intrinsic helicis and antitragicus auricular muscles. The external orifice is closed by the superficial auricular muscles. The auditory meatus is lined with stratified squamous epithelium, sebaceous glands, and ceruminous glands. Longitudinal blood sinuses and elastic fibers in the hypodermis may function as a pressure regulating device during diving. Blood sinuses are most prominent in the bony region of the meatus and extend into the tympanic sulcus of the pars tensa. Blood sinuses engorged with blood and a closed meatus may enhance transmission of sound to the tympanic membrane when the seal is under water.