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The ear is a complex sensory organ responsible for hearing and balance. It is divided into 3 parts and involves an intricate interplay among structures that transduce sound waves into neural impulses, which are interpreted by the brain. This topic provides a brief overview of the parts of the ear, their corresponding histologies, and some critical clinical conditions that can cause hearing loss.

Infections are the most common pathologies seen in patients. It can either occur as otitis externa, otitis media, tympanitis, or labyrinthitis. Otitis externa is primarily caused by disruption of protective barriers, leading to infection of the external ear. The 2 main pathogens that cause it are Pseudomonas aeruginosa and Staphylococcus aureus. In contrast, otitis media is a middle ear infection. It is most commonly observed after upper respiratory tract viral infection. Post-infection edema can obstruct the eustachian tube, leading to the accumulation of secretions in the middle ear. This favors the growth of microbial agents. It can also have a bacterial origin by Streptococcus pneumoniae, Moraxella catarrhalis, and non-typeable Haemophilus influenzae.[12] Labyrinthitis is caused by viruses such as herpes simplex virus and adenovirus. It causes inflammation of the vestibulocochlear nerve, presenting as peripheral vertigo. Cholesteatoma is a benign collection of keratinized squamous epithelium in the middle ear. It is caused by prolonged negative pressures that lead to the retraction of the tympanic membrane or a perforation in the tympanic membrane, which causes the keratinized squamous debris to accumulate.[13] Meniere's disease is another common disease caused by fluid build-up in the endolymphatic system.[14] Benign paroxysmal positional vertigo presents as a spinning sensation secondary to calcium debris (canalithiasis) within the semicircular canals, disrupting the endolymph movement in the canals.[15]