Sensory organs

By: Dr. Pamela Joseifna T. Fabie

• A. The Eye and its Appendages

• B. Ear and Ear Ossicles

 Elevated by a muscle called Levator Superioris Muscle
 Nerve supply: facial n. – orbicularis muscle
occulomotor n. – levator palpebrae
muscle
 Blood Supply:
• arterial supply – superior and inferior palpebral
branches of ophthalmic artery
• Venous drainage – ophthalmic vein

Superior Plica
Conjunctiva semilunaris

Lateral canthus
Lacrimal
caruncle in
lacrimal
lake

Inferior lacrimal
papilla

1. Lacrimal Gland
 located at the superolateral angle of the orbit
 Oval in shape
 Divided into 2 parts: Superior (orbital portion) and
Inferior (Palpebral portion)
 Pour tears by means of 8-12 tiny ducts

Function of Tears:
A. Wash away iritating materials, e.g.
dust
B. Lyzozyme prevents microbial
infection
C. Prevents drying of conjunctiva and
cornea

2. Lacrimal Ducts
 Situated one on each eyelid starting
from lacrimal punctum to lacrimal sac

3. Lacrimal Sac
 Situated in the lacrimal fossa

4. Nasolacrimal Ducts
 Downward continuation
of the sac
 About ¾ inch in length
 Drains into the inferior
nasal concha

 Likened to a quadrilateral pyramid
 Each orbit contains the globe of one eye
and its appendages

 Approximately 1 inch in diameter
 Situated in the anterior parts of the orbit
nearer the roof than the floor

3 COATS OF THE EYEBALL

FIRST COAT
 Sclera – white of the eye; tough
fibrous external capsule which encloses
the posterior 5/6 of the eyeball
 Cornea – anterior transparent and
clear portion

SECOND COAT

 Choroid – nourishing coat of the eyeball composed
manily of blood vessel
 Ciliary Body - dangerous area of the eye since the
wound here can involve the iris, chorois, retina or the
cornea
o Ciliary muscle – bundles of smooth muscle; aka the
“muscle of accomodation”
o Ciliary Processes – about 70 in number; forms the
Aqueous Humor.
 Iris – aka Uveal Tract; corresponds to the diapragm of
the camera and has a central opening called “pupil”
which regulate the amount of light that reach the retina

THIRD COAT

 Retina– expanded termination of the Optic nerve; considered part of
the brain.
 Optic Disk – considered as the physiologic blind spot
 Macula Lute (yellow spot) – forms a yellowish, circular area
that lacks blood vessels
 Fovea Centralis – tiny depression at the center; the point of
highest visual acuity
 Refractive Media – are he Cornea, Aqueous Humor, the Lens and
the Vitreous Humor (in order from outside to inside)
 Aqueous Humor - clear fluid that occupies the space between the
cornea in fromnt and lens behind. It is the Lymph of the eye.
 Lens- biconvex, transparent and colorless body found between
aqueous humor in front and vitreous humor behind. It has the
“Power of Accomodation” due to its elastic nature of change.
 Vitreous Humor – soft, gelatinous substance that fills whole of the
eyeball behind the lens; supports retina behind

1. Lateral rectus m. – pulls the eye laterally
2. Medial Rectus m. – pulls the eye medially
RECTI 3. Superior Rectus m. – pulls the eye superiorly and
medially
4. Inferior Rectus m. – pulls the eye inferiorly and
laterally
5. Superior Oblique m. – pulls the eye inferiorly and
OBLIQUE laterally
6. Inferior Oblilque m. – pulls the eye superiorly and
laterally
7. Levator Palpebrae superioris m. – raises the
upper eyelid

- acute and painful
pyogenic infection of
the sebacious or
Meibomian glands of
the eylid margin

- Inflammation of the
conjunctiva may be
caused by irritants such
as smoke, dust, wind
cold, dry air, micronial
infection or allergic
reations

-increased intraocular
pressure due to
defective drainage of
aqueous fluid through
the scleral venous sinus
(canal of Schlemm)

Opacity of the lens which
may be degenerative or
congenital, bilateral or
unilateral. Opacity
interferes with
transmission of light rays
so that vision is impaired.

Inability of eyes to move
so that the same image
falls on the corresponding
parts of the retina in both
eyes cause by extraocular
muscle weakness or
defective nerve supply

a. AURICLE b. EXTERNAL
(Pinna) AUDITORY MEATUS

Its purpose is to collect and convey sound
waves to the tympanic membrane (ear drum).

- a cartilagenous framework
covered by skin
- Aka “Pinna”

- Nerve Supply:
• Greater auricular n., auriculo-
temporal n., lesser occippital n.

- Blood Supply:
 Supplied by posterior auricular
artery and superficial temporal
artery
 Venous drainage by
superficial temporal vein and
external jugular vein

- A canal that extends from concha to tympanic membrane
- About 1 inch long
- 1st part – cartilagenous; 2nd part - osseuos

Blood supply:
 Skin of cartilagenous part is
by hair follicles, sebaceous
and ceruminous glands

Nerve Supply:
 Auriculo-temporal nerve

o Separates the external and the middle ear
o It trnasmits the vibrations of soundd waves along the
auditory ossicles to the inner ear
o It bulges into the middle ear, making the outer wall
concave

 It is the space in the petrous portion of the temporal,
lined by mucuos membrane
 Contains the OSSICLES (Malleus, Incus, Stapes),
which transmit sound vibrations from the eardrum to
the internal ear

MIDDEL EAR

Anterior wall – presenst the Auditory(Eustachain) tube
Medial wall – present 3 structures:
 Foramen Ovale (fenestra vestibule)
 Promontory
 Foramen rotundum

2 muscles:

a. Tensor tympani
muscle
b. Stapedius
muscle – draws
stapes
backward

 It is situated in the petrous portion of the temporal bone
 Concerned with sound perception, orientation and
balancing
 Made up of TWO LABYRINTHS

BONY
LABYRINTH

MEMBRANOUS
LABYRINTH

- About 3mm thick, hard as ivory.
- Consists of:
o Cochlea – small shell that
makes ½ turns around a
central pillar called the
“modiolus”
o Vestibule – central part,
attached to stapes
o 3 Bony Semicircular Canals –
horseshoe-shaped, contain the
membranous semicircular
ducts. They have no auditory
functions but they provide
information about the position
of the head in space,
contributing to the maintenance
of equilibrium and balance

- This lies within the bony
labyrinth consisting of sac that
contains fluid known as
“endolymph”
- Separated between the bony
walls by a fluid known as
“perilymph”

- It consists of:
 Cochlear Duct – contains the
spiral organ of Corti, essential
part of the organ of hearing
 Utricle and Saccule –
situated inside bony vestibule
 Semicircular Ducts – smaller
in size but have the same
shape as the bony canals

Infection by
staphylococcus
aureus is the usual
cause of the
localized
inflammation (boils)
in the external aud.
canal

Inflammation of the
middle ear and may be
due to spread of
microbes from the upper
respiratory tract through
the eustachain tube or
from the outer ear
through the rupture of
tympanic membrane.

There is excessive
endolymph causing Repetitive motion cause
generalized dilation and excessive stimulation of the
increased pressure within semicircular canals & vestibular
the membranous labyrinth. apparatus and result in nausea
With episodes of vertigo, and vomiting in some people
nausea, vomiting, tinnitus.

The deafness of old age
due to the degeneration of the
sensory cells of the organ of
Corti.

Sensory organs

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Sensory organs