​The ear is divided into three parts—the outer ear, middle ear, and inner ear—which work together to enable hearing. This section focuses on the structure and function of the outer ear.

The outer ear consists of three main components: the pinna (auricle), the external auditory canal, and the tympanic membrane (eardrum).

​1. The Pinna (Auricle)​​

The pinna is the visible, flexible cartilage structure on the side of the head. It acts as a sound collector and a physical barrier. Its key anatomical features and functions include:

• ​Helix:​​ The prominent outer rim of the pinna. Its curved shape helps collect and focus sound waves into the ear canal, while also providing physical protection against direct entry of wind, debris, and insects.

• ​Antihelix:​​ A ridge located inward from and parallel to the helix.

• ​Triangular Fossa:​​ A small, triangular depression situated between the two crura (branches) of the antihelix.

• ​Concha:​​ The bowl-shaped cavity leading to the opening of the ear canal. It is divided by the crus of the helix into a superior portion, the cymba conchae, and a larger inferior portion, the cavum conchae, which leads directly into the external auditory canal. The concha acts as a resonant chamber, amplifying sound frequencies in the 2000 to 5000 Hz range, which is critical for human speech perception. Subtle shape differences between the left and right conchae also aid in sound localization.

• ​Tragus:​​ A small, firm cartilaginous projection located anterior to the concha. It partially shields the external auditory meatus, helping to protect the canal from direct frontal wind and water, and works with the antitragus to attenuate noise coming from behind.

• ​Antitragus:​​ A small cartilaginous projection opposite the tragus, separated from it by the intertragic notch.

• ​Lobule (Earlobe):​​ The soft, inferior part of the pinna.

In summary, the pinna is a sophisticated structure designed to efficiently collect, focus, and partially amplify sound waves while providing physical protection.

​2. The External Auditory Canal​

The external auditory canal extends from the concha (at the external auditory meatus) to the tympanic membrane. It is approximately 2.5–3.5 cm long and has a characteristic "S"-shaped curvature: it first moves slightly upward and forward, then turns inward and backward. This curvature serves as a natural barrier against the direct intrusion of foreign objects.

The lateral third of the canal is cartilaginous, continuous with the cartilage of the pinna. The skin in this section contains ceruminous glands (which produce earwax), sebaceous glands, and fine hairs (tragi).

• ​Cerumen (earwax),​​ with its weak acidic properties, traps dust and inhibits bacterial growth.

• ​Sebum​ lubricates the skin and hairs.

• ​Hairs​ help block debris and small insects.

The medial two-thirds of the canal is the bony portion, formed by the temporal bone, providing a rigid passage for sound waves.

The length and shape of the external auditory canal create a resonant frequency around 2000–5000 Hz, amplifying sounds in this range by approximately 10–15 decibels. The skin of the canal has a self-cleaning mechanism, where epithelial cells migrate outward from the tympanic membrane, carrying cerumen and debris with them.

​3. The Tympanic Membrane (Eardrum)​​

The tympanic membrane is a thin, semi-transparent membrane located at the medial end of the external auditory canal, separating the outer ear from the middle ear. It is approximately 0.1 mm thick and is oriented at a 45-degree angle, with its concave surface facing the ear canal, which helps maximize sound energy collection. Despite its thinness, it has three distinct layers:

• Outer cutaneous layer (continuous with the skin of the external auditory canal).

• Middle fibrous layer (composed of radial and circular fibers that provide strength and elasticity).

• Inner mucosal layer (continuous with the lining of the middle ear cavity).

​Summary​

The outer ear serves as the initial stage of hearing. The pinna collects and funnels sound waves into the external auditory canal. The canal's structure provides protection, resonance, and self-cleaning, while guiding sound to the tympanic membrane. The tympanic membrane then transforms sound wave energy into mechanical vibrations, which are transmitted to the ossicles of the middle ear. These components work in concert to allow us to hear the sounds of the world clearly.