Chapter 1 : Introduction to Ear, Nose and Throat
Topics covered in this snack-sized chapter:
ENT is a medical abbreviation for ears, nose and throat. A doctor who specializes in treating these disorders is called an "ENT," or less commonly an Otorhinolargyngology.
The word “Otorhinolargyngology” is made up of several Latin root words: ology means the study of the ear (oto), the nose (rhino), and the throat (laryn, as in the word larynx). This long word is frequently shortened to Otolaryngology.
An Ear, Nose and Throat specialist is usually called an Otolaryngologist, but is also referred to as an “ENT Specialist,” with the letters E, N, T standing for Ear, Nose and Throat
Ears are sensory organs responsible for hearing and maintaining body equilibrium or balance.
Ear contains three parts-the outer, middle and the inner ear.
All the three parts are involved in hearing and only the inner ear is responsible for maintaining body equilibrium.
There are three components to the ear: The outer ear, middle ear and inner ear.
All three are involved in hearing but only the inner ear is responsible for balance.
The outer ear is composed of the pinna, or ear lobe, and the external auditory canal.
Both structures funnel sound waves towards the ear drum or tympanic membrane allowing it to vibrate.
The pinna is also responsible for protecting the ear drum from damage.
Modified sweat glands in the ear canal form ear wax.
The middle ear begins with the eardrum at the end of the ear canal.
The middle ear is an air filled space located in the temporal bone of the skull.
Air pressure is equalized in this space via the Eustachian tube which drains into the nasopharynx or the back of the throat and nose.
There are three small bones, or ossicles, that are located adjacent to the tympanic membrane.
The malleus, incus, and stapes are attached like a chain to the tympanic membrane and convert sound waves that vibrate the membrane into mechanical vibrations of the three bones.
The stapes fills the oval window which is the connection to the inner ear.
The inner ear has two functions:
It is a warren of tubes filled with fluid encased within the temporal bone of the skull.
The bony tubes also contain a set of cell membrane lined tubes.
The bony tubes are called the bony labyrinth filled with perilymph fluid, which the membranous labyrinth tubes are filled with endolymph.
This is where the cells responsible for hearing are located (the hairy cells of Corti).
The bony labyrinth itself has three sections:
- The cochlea is responsible for hearing.
- The semicircular canals have function associated with balance.
- The vestibule which connects the two and contains two more balance and equilibrium related structures, the saccule and utricle.
The final structures of the inner ear are the round window and the eighth cranial nerve which is composed of the vestibular nerve (balance) and the cochlear (hearing) nerve.
The respiratory tract begins with the nose which includes the external nose, internal nasal cavities and paranasal sinuses.
As well as being vital for transport of gases to the lower respiratory tract, the nasal cavity is also the site for one of the special senses - Olfaction.
The nose consists of the external nares with nasal cartilages, the nasal cavity (including the nasal meatus and conchae), and the paranasal sinuses.
The nasal cavity is essentially a tube with a wall established by several bones of the skull. The borders of the nasal cavity are as follows:
- Caudal: The cribrifrom plate of the ethmoid bone.
- Ventral: Continuous with the nasopharynx.
- Dorsal: The maxilla and the palatine processes of the incisive bone.
Rostrally, the median septum is a continuation of the ethmoid bone. The median septum is made up of hyaline cartilage, and divides the nasal cavity into left and right halves.
The nasal cavity is occupied to a large extent by nasal conchae.
These are turbinate bones which project into the nasal cavity with the purpose of supporting the olfactory mucus membranes and increasing the respiratory surface area, creating turbulence within the passing air.
This helps to filter and warm or cool the air that passes through.
In addition to olfaction, the function of the nasal cavity is to modify the incoming air before it is transported further down the respiratory tract.
Air is warmed as it passes over the highly vascularised mucosal surfaces of the conchae, humidified by the evaporation from nasal secretion and cleaned as it contacts the secretion from mucus glands within the nasal cavity.
The mucus secreted from the glands traps particles and cilia transport them down to the pharynx for swallowing, this process is known as the mucociliary escalator.
The nasal cavity offers further protection via the sneezing reflex.
The throat is a ring-like muscular tube that acts as the passageway for air, food, and liquid. The throat also helps in forming speech. The throat consists of:
- Larynx - houses the vocal cords and is crucial to speech and breathing. The larynx also serves as a passageway to both the trachea (windpipe to the lung) and the esophagus (canal to the stomach).
- Epiglottis - located above the larynx and works with the larynx and vocal cords to push the food into the esophagus, therefore keeping food from entering the windpipe.
- Tonsils and adenoids - made up of lymph tissue and are located at the back and the sides of the mouth. They protect against infection, but generally have little purpose beyond childhood.