Human Ear: Introduction to Ear, Structure of Ear and Outer Ear (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Ear

  • One of the five sensory organs of our body.
  • It is the organ for hearing and the outer ear consists of the pinna and the ear canal.
  • On the either side of the head, the ears of vertebrates are placed symmetrically.
  • Being a sensitive organ of the human body, it is concerned with detecting, transmitting and transducing sound.
  • In mammals, the hair cells present in the inner ear help in sensing the position of the body.
    • In accordance with gravity and maintain the equilibrium.

Structure of Ear

Outer Ear

Structure of Ear: Outer Ear
  • The outermost part is Pinna with very fine hairs and glands.
  • Wax is secreted by the glands.
  • The dust along with the foreign organism is protected from entering.
  • External auditory canal or meatus is connected to pinna.
    • Extends till tympanic membrane or eardrum.
    • Also have wax glands.
  • Tympanic membrane or eardrum
    • Made up of connective tissue.
    • The outer portion is covered by the skin the mucous membrane covers the inside portion.
  • The sound is received in the form of vibration from Pinna.
  • Through the external auditory canal, the sound waves reach and vibrate the eardrum.

The Middle Ear

The Middle Ear
  • It lies between the outer ear and the inner ear and consists of an air-filled cavity called the tympanic cavity.
  • It includes the three ossicles and their attaching ligaments; the auditory tube; and the round and oval windows.
  • The ossicles are three small bones.
    • Function is to receive, amplify, and transmit the sound from the eardrum to the inner ear.
    • The malleus (hammer) , incus (anvil) , and the stapes (stirrup) .
    • Helps amplify sound waves by 15 – 20 times.
  • Via the pharyngeal opening of the Eustachian tube, the middle ear also connects to the upper throat at the nasopharynx.
  • Vibrations are transmitted through the oval window, causing movement of fluid within the cochlea as the stapes vibrates.
  • The fluid within the inner ear to move is allowed by the round window.

The Inner Ear

The Internal Ear
  • The inner ear is called the labyrinth.
  • It consists of a group of interconnected canals and sacs.
  • A central area known as the vestibule contains two small fluid-filled recesses, the utricle and saccule.
  • The three semicircular canals angled at right angles to each other which are responsible for dynamic balance.
  • A spiral shell-shaped organ responsible for the sense of hearing is called cochlea.

Physiology of Ear

Hearing and equilibrium maintenance are the two functions performed.

The Organ of Corti (Cochlea)

Performs the hearing function.

Maculae (Saccule and Utricle)

This is responsible for static equilibrium.

Cristae (Semicircular Canals)

This is responsible for dynamic equilibrium.

Developed by: