1 Introduction BOPANNA B. BALLACHANDA The Human Ear Canal The human ear canal is a skin-lined cul-de-sac that extends from the concha of the auricle to the tympanic membrane. The ear canal and the outer ear are special parts of the hearing mechanism seen only in certain mammals. Its primary function is to serve as a conduit for the passage of sound waves to the tympanic membrane. It also functions to protect the middle and inner ear from external trauma by impeding the entry of foreign objects a -- 2 Developmental Anatomy of the Outer Ear BOPANNA B. BALLACHANDA INTRODUCTION The developmental aspects of the human ear canal reflect changes that span from the embryonic period of fetal development to those that occur in older ears later in life. Remarkable and continual changes in size, shape, and dimension of the ear take place during the prenatal stage compared to those that occur in childhood and adulthood. Consequently, the emphasis of this chapter is predominantly on the mechanism of embr -- 3 Anatomy of the Ear Canal RICHARD T. MIYAMOTO AND R. CHRISTOPHER MIYAMOTO A schematic view of the ear canal is shown in Figure 3-1. The skeletal structure of the ear canal consists of elastic cartilage laterally and bone medially. The narrowest portion of the ear canal or the isthmus is located just medial to the junction of the fibrocartilaginous and bony canals. The cartilage of the ear canal is continuous with that of the auricle. The cartilage of the tragus is in continuity with that of the.

4 Ear Canal Examination BOPANNA B. BALLACHANDA PURPOSE Ear canal examination is an important aspect of audiology practice. Be it for diagnosis or for rehabilitation, visually inspecting the pinna, ear canal, and tympanic membrane aids in the identification of conditions that might subvert audiological test results or complicate audiological rehabilitation. The purpose of ear canal examination can be divided into the following five major areas. Identifying Pathological Conditions of the Pinna and -- 5 Ear Canal Pathology RICHARD T. MIYAMOTO AND R. CHRISTOPHER MIYAMOTO Pathological conditions of the ear canal may be of congenital, infectious, traumatic, or neoplastic origin. Congenital Abnormalities Congenital abnormalities of the external auditory canal occur in mild to severe forms and may range from mild stenosis to complete atresia. The continuum of deformities that can occur with congenital atresia of the ear are the result of arrested development of the bony or cartilaginous portion of -- 6Ear Canal Acoustics BOPANNA B. BALLACHANDA Introduction The role of the outer ear (pinna and the ear canal) is to couple airborne sound waves to the middle ear. Understanding the functions of the outer ear requires an appreciation of basic acoustics and the process of transformation from the free-field or the earphone to the tympanic membrane. In the past several years there has been a considerable interest in specifying the dimensions of the outer ear to explain accurately the acoustic charact.

7Deep Canal Hearing Aids BRIAN TAYLOR The external auditory canal is an important factor in any hearing aid fitting, as the canal directs amplified sound toward the tympanic membrane. In the case of many deep canal fittings, however, the external auditory canal also serves as the location for the hearing instrument itself. Regardless of the specific type of hearing aid fitting, the external ear canal plays three significant roles in the fitting of hearing aids. One, it serves to direct amplified -- 8 Cerumen: Genetics, Anthropology, Physiology, and Pathophysiology BOPANNA B. BALLACHANDA Anthropologists, biochemists, dermatologists, otolaryngologists, and audiologists have all conducted numerous studies on cerumen and the secretory system. The result of one such study has been to define the material we call cerumen as a composition of secretions from modified apocrine glands, sebaceous glands, dust particles, desquamated epithelial cells, dislodged hair follicles, and foreign bodies trapped -- 9 Cerumen Management BOPANNA B. BALLACHANDA Introduction Much of the discussion in this chapter relates to the topic of managing patients with cerumen impaction. The previous chapter on cerumen (Chapter 8) described the various types of cerumen, prevalence of cerumen impaction and consequences of cerumen impaction on audiological services. Cerumen impaction is perhaps the condition most frequently observed by audiologists during a patient's ear canal examination. Approximately 2 to 6% of the gen.