References
Down the ear
Abstract
A basic knowledge of the normal architecture of the external and middle ear of the cat and dog is important in the investigation and diagnosis of ear disease in these species. The appearance of the canal is very different in cases where infection is present with yeast where the canal may be hyperplastic and contain a thick ceruminous discharge compared to that with infections such as Pseudomonas spp. where the canal is ulcerated, swollen and contains a malodorous green-yellow mucoid discharge. The appearance of the canal together with cytology can help in the selection of ear cleaners and drops.
Basic knowledge of the feline and canine ear canal is important. The external ear canal is similar in both species but there are subtle differences which can make investigation and management of disease different (Njaa et al, 2012).
The external ear canal is composed of the ear pinna and the external auditory meatus. There is a wide range in size and conformation of the canine ear pinna, ranging from the short prick ears of the terrier to the long pendulous ears of the spaniels.
The vertical canal is formed from the auricular cartilage which is rolled into a tube. The funnel-shaped vertical canal extends from the entrance down to the tympanic membrane. As it turns medially, it telescopes over the annular cartilage. The horizontal canal is composed of the annular cartilage and the proximal part of the auricular cartilage. The external ear canal in the dog is relatively longer than that in the cat and contains more hair. Some of the newer ‘designer’ breeds such as the cockapoo and labradoodle contain large amounts of hair in their ears which represents a challenge in treatment when they develop ear disease.
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