Ear

Review of Anatomy and Physiology of Ear

◙ EAR..

Ears are located one on both sides of the head. It is an organ associated with hearing and maintaining body balance.

The ear is anatomically divided into three parts in terms of shape

External or outer ear

Middle Ear

Inner Ear

1. External or outer ear

The external ear collects the sound waves and transfers them to the inside. The external ear consists of the following parts.

♦ Oricles or pinna

External acoustic meatus ie auditory canal

Auricles

It is a flap-like part on either side of the head made of elastic cartilage and covered with skin on the outside that collects sound waves from the external environment and transmits them to the internal cavity. Its upper most raised part is called helix and the soft part hanging down is called lobule.

External Acoustic Meatus

Also known as the auditory canal, it is an S-shaped curved tube. Its length is about 2.5 cm. It is an elongated canal inside and the glands in its wall secrete a waxy viscous fluid known as cerumen. This canal also contains some hairs which mix with the viscous fluid. Does not allow dust and foreign bodies to reach the inner wall i.e. tympanic membrane.

Tympanic Membrane

It is a thin membrane that separates the external ear and the middle ear and is oval in shape. This membrane is made up of epithelium tissue and connective tissue in which fibroblast cells are located.

2. Middle ear

It is a small air-filled cavity located in the temporal bone. The lining of the cavity is made of epithelial tissue and it is separated from the external ear by the tympanic membrane, the ear drum, and the internal ear, which is separated from the middle ear by an oval and round window. Falls.

There is an opening in its anterior wall known as the Eustachian tube. This tube connects the middle ear to the structure of the nose fairings and the tube maintains pressure inside the cvt, thereby preventing rupture of the tympanic membrane during yawning and swallowing.

♦ Auditory ossicles

The bones in the middle ear are called auditory ossicles which include the malleus, incus and stapes bones. Its number is one in each ear, that is, there are total 6 auditory ossicles in the body.

▲ Malleus

It is hammer-shaped with its handle attached to the wall of the tympanic membrane. The head of the malleus is attached to the incus bone.

▲Incus (incus)

It is the middle bone which is in an anvil shape and is attached to the malleus bone and its head is attached to the stapes bone.Fibrous tissue is present around the joint.

▲ stapes

It is a stirrup-shaped bone whose head attaches to the incus bone and its foot plate attaches to an oval window with a round window below it.

Thus the structure of the part from the tympanic membrane to the oval and round window is called the middle ear.

3. Inner Ear (Inner Ear)

It is also known as Labyrinth. It has a complex structure and is involved in hearing and maintaining balance.

It has two parts Bony Labyrinth and Memrenius Labyrinth.

♦ Bony Labyrinth

It is located in the petrous portion of the KVT temporal bone

♦ vestibule

It is an oval-shaped portion between the bony labyrinth no, which contains the utricle and saccular structures, and has oval and round windows in its lateral wall.

♦ Cochlea

This part of the bony labyrinth is connected to hearing is a tangle-like part also known as Snails cell.

♦Semi-circular canal

The structure of this canal is associated with balance. The three tubes of the semicircular canal are arranged at right angles to each other.

◙ Membranous Labyrinth

Inside the bony labyrinth is a tube of membrane called membranous labyrinth which contains a fluid called endolymph. The properties of this fluid are similar to CSF.

Vestibule which contains utricle and saccule.

Vestibule and semicircular canal…

The vestibule and semicircular canals in the internal ear work to maintain the balance of the body.

In which the semicircular canal saccule and utricle help to maintain the dynamic equilibrium of the body. The semicircular canal is a tube-like structure that lies behind and above the vestibule and the canals are arranged at an angle to each other. The semi-circular canal and the cochlea have a bony labyrinth on the outer wall and perilymph fluid inside, another tube called the mammary labyrinth contains endolymph.

The utricle is a membranous sac that is part of the vestibule and all ducts open to a dilated portion called the ampulla. The saccule is part of the vestibule and communicates with the utricle and cochlea.

The walls of the utricle, saccule and ambula contain small hair-like projections of specialized epithelial cells containing sensory nerve endings that form the vestibular portion and through which the vestibulo cochlear nerve passes.

3. Cochlea

Cochlea means Snail It is a coiled structure like a snail Inside the cochlea is a membrane known as the cochlear duct which is the part mainly connected with the act of hearing The following parts are seen in the cross section of the cochlea.

♦Scala vestibuli

♦Scala media or cochlear duct

Scala Tympany

The cochlear duct is a triangular shaped tube. The bony part of the cochlea has two parts, upper and lower, in which the upper part is called the scala vestibuli and the lower part is called the scala tympani. In the middle part lies the cochlear duct and the membrane of its roof is called the basilar membrane. The organ of Corti called the organ of hearing is located on the basilar membrane.

◙ Physiology of Hearing

Physiology of hearing is the act of hearing. Audible waves have a wavelength of 20 to 20,000 Hz. The human ear is capable of frequencies between 500 and 5,000 hz. The frequency at which the sound waves vibrate is known as the pitch, as the vibration increases, so does the pitch.

Every sound produces sound waves which strike the outer part of the auricle and from there enter through the external auditory canal, these sound waves vibrate the tympanic membrane i.e. the ear drum which is the junction between the external ear and the middle ear.

The sound waves are connected to the tympanic membrane by the malleus bone to the incus and incus to the stapes and the stapes bone is further connected to the oval window. goes and from there goes to the endolymph and the round window vibrates and the vestibule goes to the cerebrum through the cochlear nerve and the sound is recognized.

◙ Balance and Ear (Balance of Ear)

♦Vestibule & Semi circular canal

The vestibule and semicircular canal in the internal ear work to maintain the balance of the body.

In which the semicircular canal saccule and utricle help to maintain the dynamic equilibrium of the body. The semicircular canal is a tube like structure that lies behind and above the vestibule and the canals are arranged at an angle to each other. The semicircular canal and cochlea have a bony labyrinth on the outer wall and perilymph fluid inside, another tube called the membranous labyrinth that contains endolymph fluid.