Human Ear – Class 11 | Chapter – 21 | Biology Short Notes Series PDF

Human ear, being one of the most sensitive organs in the human body, performs the function of detection, transmission and transduction of sound waves. Whenever we hear a sound, we are able to absorb and interpret it accordingly. All this is possible because of the presence of multiple organs within the ears, such as, ear canal, ear drum, etc. Apart from hearing, the human ear performs one of the most significant functions of balancing.

Working of Human Ear

Ears serve to be the most significant part in the human body. The working of the human ears could be understood in terms of analysing the surrounding vibrations and sending the assumed signals to the brain. We all know that the brain in human beings is the ultimate unit of processing, thus, on receiving the auditory signals from ears, it perceives the sound and reverts back the output to the ears for complete understanding of the received sound. Moreover, the entire procedure of recognizing the sound, analysing the vibrations and perceiving the meanings is attributed to the ears.

Structure of Human Ear

In simple words, the human ear is collectively formed by constituting the outer ear, middle ear and the inner ear. All these parts of a human ear have their own specific significance, as mentioned below:

Anatomy of Human Ear

Outer Ear: The outer ear comprises Auricle, External Auditory Meatus and Tympanic Membrane. The structure and functions of outer ear are as follows:

  • Auricle (Pinna): Another name for the outer ear is pinna which mainly constitutes the rigid cartilage that is covered by the skin, adipose and the fibrous tissues are also included in the existing lobule filled with the blood capillaries. It is mainly known for collecting the sound waves in the funnel-like structure which further transmits the signals to the middle ear.
  • External Auditory Meatus: The folded cartilage helps the ear canals and the ear drums in analysing the sound by receiving them with maybe greater or lower intensity, accordingly. Following the meatus lies the stratified epithelium which is commonly known as the wax gland.
  • Tympanic Membrane: It consists of umbo which lies in its centre. Following it, the pinna leads to the opening of the ear canal which is nothing but a small cylindrical tube which creates the passage for the sound vibrations to reach the eardrum.

Middle Ear: Middle ear comprises Tympanic Cavity, Eustachian Tube and Ear Ossicles. It’s structure and functions are as follows.

  • Tympanic Cavity: Tympanic cavity is separated from the outer ear through the tympanic membrane. It is in this part of the ear where the vibrations are created through the sound waves after they strike the eardrum. Moreover, the anterior wall of the cavity consists of the eustachian tube which works as the auditory tube.
  • Eustachian Tube: Eustachian Tube is connected to the tympanic membrane and contributes in equalising the air pressure to ease the transmission of the waves.
  • Ear Ossicles: Ear Ossicles help in transmitting the sound waves to the middle ear from the ear drum. Malleus (hammer), incus (anvil) and the stapes (stirrups) are the three important types of ossicles which are present in the human ear. Incus are mainly anvil shaped connected to the stapes and stapes is the tiniest of all, whereas, malleus has a hammer – like structure attached to the tympanic membrane of the outer ear, however, it is also known as the largest of all the ossicles. These ossicles can also be termed as the tiniest bones which are present in the middle ear and contribute in the passage of the sound waves from the middle ear into the inner ear, that is, into the cochlea.

Inner Ear: Inner ear comprises Bony Labyrinth and Membranous Labyrinth. It’s structure and functions are as follows.

  • Bony Labyrinth: It mainly consists of the cochlea, vestibule and three semi – circular canals and performs the most significant function in the entire procedure which ultimately enables the human beings to recognize the sound.
  • Membranous Labyrinth: It is surrounded by the bony labyrinth. The presence of a sac-like structure filled with the fluid helps in converting the sound waves into the meanings. It is this part of the ear which transforms the sound waves into the nerve impulse. The nerve impulse is transmitted to the brain and the brain, in turn, analyses this electrical signal and maintains the sense of hearing in human beings.

Functions of Human Ear

The two main important functions of human ear are:

  • Hearing: Hearing is one of the functions of the human ear. It involves the function of performing an entire chemical procedure where the sound waves reach the eardrum from the auditory canal and further the vibrations are generated in the outer ear. These vibrations pass through the tympanic cavity in the three ossicles where stapes push the oval window in and out. Later, the vibrations are transformed into the electrical impulses which are understood by the brain to complete the process of hearing.
  • Balance: Another major function of the human ear is Balance. This significant function is mainly performed with the help of the eustachian tube and the vestibular complex. Here the eustachian tube contributes by equalising the air pressure across the tympanic cavity and the receptors present in the vestibular complex helps maintain the body balance.

Range of Hearing

Most of the sounds are heard and perceived by the human ears but this hearing comes with some limitations. Human ears cannot hear or perceive all the sounds. The frequency of the sound ranging between the 20 Hz. to 20,000 Hz is acceptable to human ears, ie., this frequency range is heard, recognised and perceived by the ears. The sound frequency more than or less than the given range remains either completely or partly unidentified by the human ears.

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By Team Learning Mantras