Chapter 1 Anatomy of the Canine and Feline Ear
The basic anatomical components of the dog and cat ear are as follows:
Structure of the External Ear
The external ear is composed of three elastic cartilages: annular, scutiform, and auricular (Figure 1-1). The annular and auricular cartilages form the external ear canal, and the auricular cartilage expands to form the pinna. The scutiform cartilage lies medial to the auricular cartilage within the auricular muscles that attach to the head (Figure 1-2).

Figure 1-1 Cartilages of the right external ear.
(From Evans HE, ed: Miller’s Anatomy of the dog, ed 3, Philadelphia, 1993, WB Saunders.)

Figure 1-2 Location of the scutiform cartilage in relation to some of the external ear muscles in the dog.
Pinna, or Auricle
The leaf-shaped pinna of the external ear is broad with medial (rostral) and lateral (caudal) margins. The caudal margin of the pinna exhibits a cutaneous pouch called the marginal pouch (Figure 1-3). This pouch has no obvious function. The skin on the concave surface of the pinna is very tightly connected to the underlying auricular cartilage, accentuating all the auricular prominences (see Figure 1-3). The skin covering the auricular cartilage may show breed-specific pigmentation. The shape and size of the external ear vary greatly among different breeds of dogs, mainly owing to the auricular cartilage that forms the skeleton of the pinna. It is the largest cartilage of the external ear. The broad auricular cartilage has numerous holes (see Figure 1-1), which are traversed by branches arising from the caudal auricular artery.
The auricular cartilage is broad dorsally and funnels to a narrow tubelike structure, the tubus auris, which fits around the annular cartilage ring. The parotid salivary gland occupies the base of the external ear, partially surrounding the tubus auris (Figures 1-4 and 1-5). The tubus auris encloses the vertical part of the external canal and, together with the tragal, antitragal, and antihelicene borders, forms the external acoustic meatus (see Figure 1-3).

Figure 1-5 Structure of the ear canal.
(Redrawn from Bojrab MJ: Current techniques in small animal surgery I, Philadelphia, 1975, Lea & Febiger.)