The external portion of a dog's ear is called a pinna. A dog's pinna may be upright like a Chihuahua's or German shepherd's, it may droop over like a golden retriever's, or it may fall somewhere in between. The curious-looking slit on the lower, outer edge of a dog's pinna is called a cutaneous marginal pouch. Cats too have this external ear feature.
Does It Serve a Purpose?
According to Lynette Cole, associate professor of dermatology at Ohio State University's College of Veterinary Medicine, the cutaneous marginal pouch, which is sometimes called Henry's pocket, doesn't have a known function. The pinna, however, is known to collect sound waves and transmit them to the eardrum through the ear canal.
Caring for Dogs' Ears
Veterinarian Randy Kidd of the Whole Dog Journal notes that washing your dog's ears will help prevent diseases by maintaining the normal flora of the ear. Some breeds' ear styles require more frequent washing than others. Contact your veterinarian to see which ear wash she recommends and how often you should apply it.
Because the cutaneous marginal pouch is a skin fold, it is prone to bacterial and fungal skin infections developing in its warm, moist environment. Call your veterinarian if you notice redness and inflammation on your dog's ears; these are signs of infection.