Ear:
EAR (Stato-Acoustic Organ) - Organ for
hearing and balancing
Ear is anatomically divided into three parts -
External ear, middle ear and inner ear.
External ear - transfer of sound to the middle
ear
Middle ear – transfer of sound to inner ear and
amplifying the vibrations of sound
Internal ear – 1. Cochlea for hearing
- Vestibular apparatus for balancing
(equilibrium)
(a) External ear –
i. Pinna (ear lobe)
Projecting elastic cartilage covered with skin.
Its outer edge is called helix.
The lobule is lower soft pliable part made
up of fibrous and adipose tissue with blood
capillaries.
Purpose: Sound collector, Cosmetics
ii. External Auditory Meatus (ear canal)
m Extends from the pinna to the ear drum
m Protects the eardrum
m Contains numerous ceruminous glands
(modified sweat glands) which secrete ear wax
(cerumen).
m Hairs are present at the opening of ear canal.
m Wax and hairs prevent entry of foreign
particles into the ear.
m Wax repels water, traps dust, sand particles,
micro-organisms, and other debris.
Wax odour discourages insects.
yellow or brown; others’ earwax is dry,
crumbly and greyish. Variation at a single
gene determines which kind of earwax you
have. The allele for wet earwax is dominant
over the allele for dry earwax.
iii. Tympanic membrane (Ear drum)
m Ear canal ends in tympanic membrane
m Ear drum is a membrane that separates the
external acoustic meatus from the middle ear.
m It is a thin, oval semi-transparent membrane
approximately 1 cm in diameter.
m It is covered with thin skin externally and
with mucous membrane of the middle ear
internally.
m When viewed through an otoscope, the ear
drum appears concave toward the external
acoustic meatus with a shallow, cone-like
central depression.