Briefly describe the structure of the Ear
The ear consists of photoreceptors and statoreceptors. So, it helps in hearing mechanism and balancing of the body. 1. External ear: It helps in collection of sound waves. It consists of the pinna, external auditory meatus, and a tympanic membrane. (a) Pinna collects and directs the vibrations into the ear to produce sound. (b) External auditory meatus is a tubular passage supported by cartilage in the external ear. (c) The tympanic membrane separates the middle ear from external ear. It helps in the conduction of vibrations to the middle ear. 2. Middle ear: The middle ear contains a flexible chain of three middle bones called ear ossicles. The three ear ossicles are malleus, incus, and stapes that are attached to each other. It helps to amplify the sound. 3. Internal ear: It is also known as the labyrinth. Labyrinth is divided into the bony labyrinth and a membranous labyrinth. Bony labyrinth is filled with perilymph while membranous labyrinth is filled with endolymph. Membranous labyrinth is divided into two parts - (a) Vestibular apparatus: Vestibular apparatus is a central sac-like part that is divided into utriculus and sacculus. A special group of sensory cells called macula are present in sacculus and utriculus. Vestibular apparatus also contains three semi-circular canals. The lower end of each semi-circular canal contains a projecting ridge called crista ampularis. Each ampulla has a group of sensory cells called crista. Crista and macula are responsible for maintaining the balance of body and posture. (b) Cochlea : The cochlea is a long and coiled outgrowth of sacculus. It is the main hearing organ. Cochlea consists of three membranes. The organ of Corti, a hearing organ, is located on the basilar membrane that has hair cells. It conducts the auditory impulse to brain by the auditory nerves.
