4. The human ear is one of the more remarkable parts of the human body , the ear is conventionally and conveniently divided into three parts: (( the outer, the middle and the inner ears. )) The structure of the ear The ear is a remarkable part of the body sensing sound and balance. It is divided into three parts: the outer, middle and inner ears.
5. The outer ear The outer ear comprises:- (1)the pinna (auricle): which is made of a convoluted plate of flexible cartilage, has small hairs that point outwards to form a line of defence against small animals creeping in. The roots of the hairs produce oils and these mix with the secretions from nearby sweat-like glands to form the basis of wax. (2)the ear canal has a bony wall lined with thin and rather fragile skin which is devoid of glands. (3) the eardrum (tympanic membrane): which forms the boundary between the outer and middle ears.
6. The middle ear (tympanum) The eardrum is a circle of thin skin about eight to nine millimetres (one-third of an inch) in diameter. Despite its name, it is not flat like the skin of a drum, but is slightly conical with the curved sides sloping inwards. The eardrum has three layers.
7. The inner ear (labyrinth) 1- It makes hearing possible by converting sound into electrical impulses that then travel along the hearing nerve (the acoustic nerve or auditory nerve) to the brain. 2-The inner ear also plays a major role in balance. The electrical signals that arise in response to head movement pass along the balance nerve (vestibular nerve), which in due course joins with the hearing nerve to form a single bundle (stato-acoustic, vestibulo-acoustic or eighth nerve, nerve VIII) which then enters the brain
8. Mechanism of hearing An inner hair cell found within the organ of Corti. When the endolymph is disturbed by sound deflecting the basilar membrane, small channels open up somewhere near the tips of the inner hair cells. This allows the positive charge into the body of the inner hair cell, stimulating the nerve cells at its base to send an impulse to the brain.
9. Eustachian tube and mastoid The middle ear is connected to the nasal cavity via the eustachian tube. This tube allows the middle ear to maintain an equal pressure with the outside and replenish the cells of the middle ear with oxygen.
10. Science is the life with my best wishes Mr / Tarek .M.H.
