Sound is essentially a series of pressure waves in our airborne environment. Hearing places us within our external environment, allowing us to experience a multi-dimensional world, to listen and to communicate. Together this knowledge allows clinical questions to be approached from a developmental biology perspective. Here we review our current understanding of ear canal development how this biological lumen is made what determines its location and how its structure is maintained throughout life. Recent studies have built on decades-old knowledge of ear canal development and suggest a novel multi-stage, complex and integrated system of development, helping to explain the mechanisms underlying congenital canal atresia and stenosis.
Defects in development, or later blockages in the canal, lead to congenital or acquired conductive hearing loss. Unique anatomical adaptations, such as its migrating epithelium and cerumen glands, equip the ear canal for its function as both a conduit and a cul-de-sac. Within our complex hearing pathway, the ear canal is responsible for funneling sound waves toward the tympanic membrane (ear drum) and into the middle ear, and as such is a physical link between the tympanic membrane and the outside world. This review focuses on the often-neglected outer ear, specifically the external auditory meatus (EAM), or ear canal. The mammalian ear is made up of three parts (the outer, middle, and inner ear), which work together to transmit sound waves into neuronal signals perceived by our auditory cortex as sound. 2Department of Paediatric Otolaryngology, Cochlear Implants, Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom.1Centre for Craniofacial and Regenerative Biology, King’s College London, Guy’s Hospital, London, United Kingdom.These are important factors to consider when fitting earplugs.ĭue to its relative exposure to the outside world, the ear canal is susceptible to diseases and other disorders.Mona Mozaffari 1*, Robert Nash 2 and Abigail S. On the cross-section, it is of oval shape. It has a sigmoid form and runs from behind and above downward and forward. The canal is approximately 2.5 centimetres (1 in) long and 0.7 centimetres (0.28 in) in diameter. Size and shape of the canal vary among individuals. The layer of epithelium encompassing the bony portion of the ear canal is much thinner and therefore, more sensitive in comparison to the cartilaginous portion. The bony part is much shorter in children and is only a ring ( annulus tympanicus) in the newborn.
The bony part forms the inner two thirds. The cartilaginous portion of the ear canal contains small hairs and specialized sweat glands, called apocrine glands, which produce cerumen ( ear wax). The cartilage is the continuation of the cartilage framework of pinna. The elastic cartilage part forms the outer third of the canal its anterior and lower wall are cartilaginous, whereas its superior and back wall are fibrous. The human ear canal is divided into two parts. The adult human ear canal extends from the pinna to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter. The ear canal ( external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear.
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