Human_Ear_PPT research about human ear [1].pptx

The outer ear, also known as the external ear, comprises the pinna (or auricle) and the ear canal (external auditory meatus). The pinna is the visible part of the ear, made up of cartilage covered by skin. It acts like a funnel, collecting sound waves from the environment and directing them into the ear canal. The shape of the pinna helps to enhance certain frequencies of sound, aiding in the localization of sound sources.The ear canal is a narrow, tube-like structure that extends from the pinna to the eardrum (tympanic membrane). It is lined with skin that contains hair follicles and glands that produce earwax (cerumen). Earwax serves as a protective barrier, trapping dust and debris and preventing them from reaching the eardrum. The ear canal also has a slight curvature, which helps to amplify sounds and protect the eardrum from direct injury.The middle ear is an air-filled cavity located between the eardrum and the inner ear. It contains three tiny bones called ossicles: the malleus (hammer), incus (anvil), and stapes (stirrup). These bones form a chain that transmits sound vibrations from the eardrum to the inner ear. The ossicles are the smallest bones in the human body, yet they play a crucial role in hearing.

The malleus is attached to the eardrum, and when sound waves cause the eardrum to vibrate, these vibrations are transferred to the malleus. The malleus then transmits the vibrations to the incus, which in turn passes them to the stapes. The stapes is connected to the oval window, a membrane-covered opening that leads to the inner ear.

The Eustachian tube, another important structure in the middle ear, connects the middle ear cavity to the nasopharynx (the upper part of the throat). It helps to equalize the air pressure on both sides of the eardrum, ensuring that the eardrum can vibrate freely. The Eustachian tube opens briefly during activities such as swallowing or yawning, allowing air to enter or exit the middle ear.he inner ear, or labyrinth, is a complex structure embedded deep within the temporal bone of the skull. It consists of two main parts: the cochlea and the vestibular system.

The cochlea is a spiral-shaped, fluid-filled structure responsible for converting sound vibrations into electrical signals that the brain can interpret. It contains the organ of Corti, which houses sensory hair cells that detect sound waves. The cochlea is divided into three chambers: the scala vestibuli, scala media, and scala tympani. The scala vestibuli and scala tympani are filled with perilymph, while the scala media contains endolymph.

The vestibular system is responsible for maintaining balance and spatial orientation. It comprises three semicircular canals and two otolith organs (the utricle and saccule). The semicircular canals are oriented at right angles to each other and detect rotational movements of the head. The utricle and saccule, on the other hand, detect linear accelerations and the position of the head relative to gravity.Hea

1. FAKIR MOHAN UNIVERSITY, BALASORE. DEPARTMENT OF ENVIRONMENTAL SCIENCE PAPER :- ENS-414 SUBJECT :- STRUCTURE OF HUMAN EAR & HEARING MECHANISM SUBMITTED TO:- MISS SHIBANI HANSDAH SUBMITTED BY:- ANURADHA JENA

2. INTRODUCTION 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.

3. STRUCTURE OF HUMAN EAR The human ear consists of three parts:-  

4. External Ear The external ear is further divided into the following parts- I 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 transmit them to the middle ear. The lobule consists of adipose and fibrous tissues supplied with blood capillaries.   II 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.   III Tympanic membrane :-   This membrane separates the middle ear and the external ear. This part receives and amplifies the sound waves. It’s central part is known as umbo . Its

5. Middle Ear The middle ear comprises the following parts –     I. T ympanic Cavity:- It is a narrow air-filled cavity separated from the external ear by the tympanic membrane and from the inner ear by the bony wall. The tympanic cavity has an auditory tube known as the eustachian tube in its anterior wall.   II. Eustachian Tube:- The Eustachian tube is a 4-centimeter-long tube that equalizes air pressure on either side of the tympanic membrane. It connects the tympanic cavity with the nasopharynx.   III. Ear Ossicles:- These transmit sound waves from the ear drum to the middle ear. There are three ear ossicles in the human ear:- 1. Malleus: A hammer-shaped part is attached to the tympanic membrane through the handle and incus through the head. It is the largest ear ossicle.     2. Incus: An anvil-shaped ear ossicle connected with the stapes. 3. Stapes:- It is the smallest ossicle and bone in the human body.

6. Inner Ear It comprises two parts -   I. Bony labyrinth:- The bony labyrinth comprises a vestibule, three semi-circular cannels, and spirally coiled cochlea. It is filled with perilymph.   II. 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 ampullary maculae.

7. STEPS OF HEARING Sound Waves received by external auditory meatus The eardrum vibrates Malleus, incus and stapes amplify the vibrations Vibrations reaches inner ear through oval window Movement of fluid by pressure waves Hair cells of the organ of corti get stimulated by vibration in the basilar membrane The auditory nerve transmits impulses to the brain

8. MECHANISM OF HEARING The pinna receives the sound waves and it reaches the tympanic membrane through the meatus. The eardrum vibrates the these vibrations get transmitted to the three ossicles present in the middle ear. Malleus, incus, and stapes amplify the sound waves. These vibrations then reach the perilymph ( Scala vestibuli) through the oval window. Then the pressure waves get transferred to the endolymph of scala media and reach the basilar membrane and then to the perilymph of scala tympani. This movement of fluid is facilitated by the round window present at the end of the scala tympani. The basilar membrane movement causes the rubbing of stereocilia against the tectorial membrane. Stereocilia are bent resulting in the opening of ion channels in the plasma membrane of hair cells. Glutamate, a neurotransmitter, is released due to Ca ++ ion movement inside the cell. These neurotransmitters bind to the receptors of afferent neurons, which synapse with hair cells causing depolarization of neurons. A nerve impulse is generated and transmitted to the auditory cortex of the brain through the auditory nerve ( Cranial nerve viii). The brain analyses the impulses and we hear the sound. The brain not only recognizes the sound but also judges the direction, loudness, and pitch of the sound .

9. BALANCE The eustachian tube and vestibular complex are the important parts of the ear responsible for balance.   . The eustachian tube equalizes the air pressure in the middle ear and maintains the balance. . The vestibular complex contains receptors that maintain body balance.

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