THEME: AURICULAR
ORGANS
Student: Izzatullayev Javohirbek
 The ear is a complex part of an even more
complex sensory system. It is situated
bilaterally on the human skull, at the same
level as the nose. The main functions of the
ear are, of course, hearing, as well as
constantly maintaining balance. The ear is
anatomically divided into three portions:
 External ear
 Middle ear
 Internal ear
 The auricle, also known as pinna, is a wrinkly
musculocutaneous tissue that is attached to
the skull and it functions to capture sound.
The auricle is mostly made up of cartilage
that is covered with skin. There are two
aspects of the auricle: and medial (inner)
and lateral (outer). The medial aspect of the
ear lobe is attached to the skull and has no
major practical significance.
 The lateral aspect is concave and presents
numerous grooves and ridges. The outer
rim of the auricle is called the helix, which
then inferiorly ends as soft tissue known as
the lobule of auricle (or ear lobe). The helix
has three parts: crus, spine, and tail. The
crus is the anterosuperior convex arch the
helix, the spine the thick superior part of
the helix, while the tail is continuous with
the lobule. Parallel to the helix is another
convex curvature referred to as
the antihelix, which has two parts: the
triangular fossa bound by the crus of the
helix and the antihelix; and the crura of the
antihelix which is the widening of the
antihelix directed posteriorly toward the
helix.
 This is definitely the most complex part of the
ear, so it’s not a coincidence that it is called
the labyrinth. It is placed in the petrous part
of the temporal bone and is made up of
bony cavities in which specific membranous
parts fit. For this reason, the internal ear is
analyzed as the bony labyrinth and
the membranous labyrinth which fits within
the bony labyrinth.
 The vestibule is a central bony cavity. It
contains two sacs: the utricle and saccule of
the vestibular labyrinth (part of the
membranous labyrinth). The vestibule
communicates with the tympanic
membrane through the oval window on its
lateral wall. Anteriorly it communicates with
the cochlea, and postero-superiorly with the
semicircular canals.
 The vestibule communicates with the
posterior cranial fossa through the vestibular
aqueduct. It is a membranous structure that
leaves the vestibule, courses medially,
passes through the temporal bone and
opens on the posterior surface of the petrous
part of the temporal bone
 COCHLEA
 Cochlea is Greek for snail, and that’s exactly how this structure looks–a spiral and
hollow bone chamber in which sound waves propagate from the base (near the
oval window) to the apex.
 After the base of the cochlea is a tube, called spiral canal of the cochlea, that
twists around a central bony column (called the modiolus) two and a half times.
Inside the spiral canal of the cochlea is the osseous spiral lamina that is attached to
the outer wall of modiolus and extends into the cochlear canal. In this way it follows
the wrapping of the spiral canal around the modiolus.
 Since the spiral lamina is attached only to the modiolus, it incompletely divides the
inner space of the spiral canal into the two canals:
 The superior scala vestibuli
 The inferior scala tympani
 The membranous labyrinth is a system of
membranous cavities filled with endolymph
which are suspended in the perilymph of the
bony labyrinth.

The membranous structures found within the
bony labyrinth are:
 Vestibular labyrinth – Comprises of two sacs,
the utricle and saccule, and
three membranous semicircular ducts. They
all comprise the vestibular apparatus that is
the sensory organ of balance. The utricle and
saccule are within the vestibule of the bony
labyrinth while the semicircular ducts are in
the bony semicircular canal.
 Cochlear labyrinth – The bony cochlea
contains the cochlear duct, that is the organ
of hearing
 The saccule is smaller than the utricle and it is placed in
the antero-inferior part of the vestibule. Through
the ductus reuniens, the cochlea is connected to the
saccule, and in this way empties into the saccule.
 On the inner surface of the saccule is the sensory tissue
called macula of the saccule that responds to linear
acceleration. The information registered here transmits
further through the saccular nerve that begins in this
macula. The saccule extends a communicating duct
with the utricle, called the utriculosaccular duct. From
this duct the endolymphatic duct extends–it enters the
vestibular aqueduct, passes through the temporal
bone and ends as the endolymphatic sac at the
posterior surface of the petrous part of the temporal
bone.