The ear is a sensitive organ of the human body. It is mainly concerned with detecting, transmitting and transducing sound. Maintaining a sense of balance is another important function performed by the human ear.
Structure of ear
Structure of Ear
The human ear consists of three parts:
External ear
Middle ear
Internal ear
Human Ear Parts
The human ear parts are explained below:
External Ear
The external ear is further divided into the following parts:
Auricle (Pinna)
The auricle comprises a thin plate of elastic cartilage covered by a layer of skin. It consists of funnel-like curves that collect sound waves and transmits them to the middle ear. The lobule consists of adipose and fibrous tissues supplied with blood capillaries.
External Auditory Meatus
It is a slightly curved canal supported by bone in its interior part and cartilage in the exterior part. The meatus or the canal is lined with stratified epithelium and wax glands.
Tympanic Membrane
This membrane separates the middle ear and the external ear. This part receives and amplifies the sound waves. Its central part is known as the umbo.
Middle Ear
The middle ear comprises the following parts:
Tympanic Cavity
It is a narrow air-filled cavity separated from the external ear by tympanic membrane and from inner ear by the bony wall. The tympanic cavity has an auditory tube known as the eustachian tube in its anterior wall.
Eustachian Tube
The eustachian tube is a 4cm long tube that equalizes air pressure on either side of the tympanic membrane. It connects the tympanic cavity with the nasopharynx.
Ear Ossicles
These are responsible for transmitting sound waves from the eardrum to the middle ear. There are three ear ossicles in the human ear:
Malleus: A hammer-shaped part that is attached to the tympanic membrane through the handle and incus through the head. It is the largest ear ossicle.
Incus: An anvil-shaped ear ossicle connected with the stapes.
Stapes: It is the smallest ossicle and also the smallest bone in the human body.
Inner Ear
It comprises two parts:
Bony labyrinth
Membranous labyrinth
Bony Labyrinth
The bony labyrinth comprises a vestibule, three semi-circular canals, and spirally coiled cochlea. It is filled with perilymph.
Membranous labyrinth
The bony labyrinth surrounds the membranous labyrinth. It comprises sensory receptors responsible for balance and hearing. The membranous labyrinth is filled with endolymph and comprises three semi-circular ducts, cochlear duct, saccule and utricle. The sensory receptors include cristae, an organ of corti, and ampullaris maculae
Function of Ear
Following are the important function of the ear:
Hearing
The mechanism of hearing involves the following steps:
The sound waves pass through the auditory canal and reach the eardrum.
The vibrations produced pass through the tympanic membrane to the tympanic cavity.
The ear ossicles in the tympanic cavity receive the vibrations and the stapes pushes the oval window in and out.
This action is passed on to the organ of corti, the receptor of hearing, that contains tiny hair cells that translate the vibrations into an electrical impulse that are transmitted to the brain by sensory nerves.
