The harp seal, Pagophilus groenlandicus , (Erxleben 1777). XIV. The gross and microscopic structure of the middle ear

• 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 1973
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Harp Seal; Pagophilus groenlandicus
• Online Access: http://dx.doi.org/10.1139/z73-085; http://www.nrcresearchpress.com/doi/pdf/10.1139/z73-085

The large, heavy ossicles of Pagophilus groenlandicus are firmly attached to the epitympanic wall by a single fold of epitympanic mucosa. The epithelium of the middle ear mucosa is pseudostratified columnar epithelium. Large cavernous sinuses are present below the dense collagenous fibers of the submucosa. The cavernous sinuses are prominent around the promontory and the medial wall of the tympanic orifice of the auditory tube, and also in the tympanic sulcus of the tympanic membrane. The distension of the cavernous tissue may aid in hearing.The wall of the auditory tube consists of thick collagenous and elastic fibers. The medial wall is a thick fibrous block of connective tissue. Hyaline cartilage forms the central core of the thick fibrous medial wall of the auditory tube. The robust wall of the tube makes it unlikely that the tube wall is collapsed by the increase pressure in the nasopharynx during diving. Pressure equilibration during diving may be achieved by the opening of the nasopharyngeal orifice by muscular contraction. The closing of the tube may be achieved by the elasticity in the tube wall.