Bates Chapter 15: Ear and Nose

External Ear Structures

Composed of the auricle and the ear canal.

Helix

The prominent curved outer ridge of the auricle.

Antihelix

Curved prominence parallel and anterior to the helix.

Lobule

Fleshy inferior projection forming the earlobe.

Tragus

Nodular protrusion pointing backward over the ear canal entrance.

Outer ⅓ of Ear Canal

Encased in cartilage, covered with hair-bearing skin, produces cerumen.

Inner ⅔ of Ear Canal

Surrounded by bone, lined by thin hairless skin, sensitive to pressure.

External Ear Function

Captures sound waves and transmits them to middle and inner ear.

Mastoid Process

Lowest palpable portion of the temporal bone behind the lobule.

Middle Ear Ossicles

Malleus (hammer), Incus (anvil), and Stapes (stirrup).

Malleus Landmarks

Handle and short process.

Ossicles Function

Transforms sound vibrations into mechanical waves for the inner ear.

Umbo

Where the eardrum meets the tip of the malleus.

Cone of Light

Light reflection fanning downward and anteriorly on eardrum.

Pars Flaccida

Small portion of the eardrum lying above the short process.

Pars Tensa

The main, stretched portion of the eardrum below the short process.

Anterior and Posterior Malleolar Folds

Folds extending obliquely upward, separating pars flaccida from pars tensa.

Eustachian Tube Function

Ventilates middle ear, regulates pressure, and drains mucous to esophagus.

Inner Ear Components

Cochlea, semicircular canals, otolith organs, and CN VIII.

Cochlea Function

Responsible for hearing.

Labyrinth Function

Semicircular canals and otolith organs in vestibule maintaining balance.

Vestibulocochlear Nerve

Cranial Nerve VIII (CN VIII).

Inner Ear Physiology: Step 1

Stapes connects to the inner ear via the oval window.

Inner Ear Physiology: Step 2

Stapes movement creates vibrations in perilymph inner ear fluid.

Inner Ear Physiology: Step 3

Perilymph vibrations move hair cells and endolymph in cochlear ducts.

Inner Ear Physiology: Step 4

Cochlear hair cells convert fluid movement into electrical nerve impulses.

Inner Ear Physiology: Step 5

Auditory nerve transmits electrical impulses to brain for interpretation.

Air Conduction (AC)

Sound waves traveling through air via external/middle ear to cochlea.

Bone Conduction (BC)

Vibrations setting skull bone in motion, directly stimulating cochlea.

Normal Hearing Conduction Ratio

Air conduction is more sensitive than bone conduction (AC > BC).

Sensorineural Phase of Hearing

Phase involving the cochlea and cochlear branch of CN VIII.

Semicircular Canals vs. Otolith Organs

Canals sense rotational movement; otolith organs sense linear movement.

Nose Structural Composition

Upper 1/3 supported by bone, lower 2/3 supported by cartilage.

Nasal Cavity Airflow Path

Anterior naris → vestibule → narrow nasal passage → nasopharynx.

Nasal Vestibule Lining

Lined with hair-bearing skin instead of mucous membrane.

Turbinates Function

Increase cavity surface area for cleansing, humidifying, and warming air.

Inferior Meatus Drainage

Drains the nasolacrimal duct.

Middle Meatus Drainage

Drains most of the paranasal sinuses.

Paranasal Sinuses

Four paired air-filled cavities: Maxillary, Ethmoid, Frontal, and Sphenoid.

Clinically Accessible Sinuses

Frontal and Maxillary sinuses.

Olfaction Pathway Step 1:

Odorant molecules enter the nasal cavity and bind to olfactory receptors located on the cilia of olfactory sensory neurons within the olfactory epithelium.

Olfaction Pathway: Step 2

Binding triggers molecular cascade converting chemical signal into electrical signal.

Olfaction Pathway: Step 3

Axons of olfactory neurons converge to form Cranial Nerve I.

Olfaction Pathway: Step 4

CN I passes through cribriform plate to reach olfactory bulb.

Olfaction Pathway: Step 5

Signal travels via olfactory tract to brain regions for odor identification.

Sudden-Onset Sensorineural Hearing Loss

Requires immediate referral to an otolaryngologist.

Tinnitus

Perceived sound (ringing, roaring) with no external stimulus.

Clarifying Dizziness in History

Ask patients how they feel without using the word 'dizzy'.

Rhinorrhea

Drainage from the nose, often accompanied by congestion.

Techniques of Ear Examination: Steps

1. Inspect/palpate auricle/tragus/mastoid 2. Otoscopy 3. Auditory acuity 4. Fork tests to test for conductive vs. sensorineural hearing loss

Weber Test

Tuning fork test used to evaluate sound lateralization.

Rinne Test

Tuning fork test comparing air conduction to bone conduction.

Nose and Paranasal Sinus Examination Steps

Inspect external/internal surfaces, test obstruction, inspect septum/turbinates, palpate sinuses.