Water is an inorganic substance composed of hydrogen and oxygen, which is nontoxic and drinkable. It is a colorless and odorless transparent liquid at normal temperature and pressure, which is called the source of human life and an important substance to maintain life.
Introduction to the Structure and Function of Ear
The human ear can be divided into three parts: outer ear, middle ear and inner ear. The outer ear and the middle ear are devices that receive and transmit sound, and the inner ear is the place where sound is initially felt and analyzed. Therefore, the outer ear and the middle ear are collectively called the sound transmission system, and the inner ear and its nerve conduction pathway are called the acoustic nervous system.
The external ear consists of two parts: auricle and external auditory canal. Its main function is to collect and partially amplify sound and participate in the identification of sound direction. The structure of the middle ear is more complicated than that of the external ear, and it consists of four parts: tympanum, eustachian tube, tympanic sinus and mastoid. The tympanum, also known as the middle ear cavity, is about 2 ml in volume. There is a tube leading to the nasopharynx in the middle ear cavity, which is called eustachian tube.
The middle ear communicates with the outside world, which plays a role in regulating tympanic pressure, but it is easy to cause bacterial infection. There are ossicles, muscles, ligaments and nerve tissue in the tympanum.