Figure 3-49.The ear.
Figure 3-50.The hearing process.
to the eardrum. The lining of the auditory canal
contains glands that secrete a waxy substance
The ear is the primary organ of hearing. It is
called cerumen. The cerumen aids in protecting
divided into three parts: the external, middle, and
the eardrum against foreign bodies and
inner ear (figs. 3-49 and 3-50).
The eardrum, or tympanic membrane, is an
oval sheet of fibrous epithelial tissue, 10 mm by
The external, or outer, ear is composed of two
9 mm in size, which stretches across the inner end
parts, the auricle and the external auditory canal.
of the external auditory canal and separates the
The auricle, or pinna, is a cartilaginous structure
outer and middle ear. The sound waves cause the
located on each side of the head. The auricle col-
eardrum to vibrate. This vibration transfers the
lects sound waves from the environment, which
sounds from the external environment to the
are then conducted by the external auditory canal