Middle ear
The middle ear is located within the temporal bone extending from the tympanic membrane to the lateral wall of the inner ear. The main function of the middle ear is to transmit vibrations from the tympanic membrane to the inner ear via the auditory ossicles.
Structure;
The middle ear can be divided into two parts:
- Tympanic cavity – contains the auditory ossicles, which consists of the three small bones known as the malleus, incus and stapes. They transmit sound vibrations through the middle ear.
- Epitympanic recess –which lies next to the mastoid air cells( which releases air into the tympanic cavity when the pressure is low) above the tympanic cavity. The malleus and incus extend upwards slightly entering the epitympanic recess.
Auditory ossicles;
Consists of 3 bones which are linking the tympanic membrane to the oval window of the internal ear.
- The malleus - largest and most lateral of the ear bones. The handle of the malleus attaches to the tympanic membrane. The head of the malleus articulates with the body of the incus
- The incus – consists of a body and two limbs. The long limb joins the stapes.
- The stapes is the smallest bone in the human body. It joins the incus to the oval window of the inner ear. It contains a head, two limbs, and a base. The head articulates with the incus, and the base joins the oval window.
Auditory tube;
The auditory tube (eustachian tube) is a cartilaginous and bony tube that connects the middle ear to the nasopharynx. It aims to equalise the middle ear pressure and the pressure of the external auditory meatus.
however the pathway can increase the risk of upper respiratory infections that can spread into the middle ear.
The tube is shorter ,straighter and more horizontal in children, therefore middle ear infections tend to be more common in children than adults.
Reference
The Middle Ear - Parts - Bones - Muscles - TeachMeAnatomy
