SPECIAL SENSE ORGANS

Organs/tissues that enable the animalto interact

with the environment.

i. The eye- organ of vision.

ii. The ear - organ of hearing and balance

iii. Olfactory epithelium - detection of smell.

iv. Vomeronasal organ -detection of pheromones

v. The gustory organ - taste buds, detect taste

vi. Diffuse receptors in the skin- detect temperature,

pressure, pain, touch

THE EYE

The eye is the organ of vision and is normally paired

in animals. The components of the eye may be

divided into the main structures and accessory

structures.

:

The main structures:

• the eyeball

• the optic nerve.

The accessory structures:

i the orbit, orbital fascia and muscles.

ii eyelids

iii conjuctiva.

iv lachrimal apparatus

THE ORBIT

The eyeball is contained in an osseous cavity known as

the orbit, which is formed by the following bones:

i frontal

ii lachrimal

iii zygomaticus

iv temporal

v palatine

vi maxilla

vii sphenoid.

The eye orbit contains muscles, nerves and vessels

of the eye. It is closed in the horse, buffalo, sheep,

deer, , cattle but open in rabbits and dogs. The

position of eyes depends on the environmental

needs of an animal. In carnivores, the eyes assume

a frontal position while in herbivores they are more

lateral.

THE EYE BALL (BULBOUS OCULI)

consists of 3 concentric tunics (coats, layers):

i) The fibrous tunic Sclera + Cornea.

ii) The vascular tunic choroi d+ ciliary body + iris.

iii) The nervous tunic Retina

THE EYE BALL

Optic Disk

The optic disk is the spot on the retina where the optic

nerve leaves the eye. There are no sensory cells here,

creating a blind spot. Each eye covers for the blind spot

of the other eye and the brain fills in the missing

information

THE EYE

http://en.wikipedia.org/wiki/File:Gray896.png

ANTERIOR CHAMBER

The space between the cornea and iris filled with Aqueous Humor.

Aqueous Humor

A water like fluid, produced by the ciliary body, it fills the front of

the eye between the lens and cornea and provides the cornea and

lens with oxygen and nutrients. It drains back into the blood

stream through the canals of schlemm.

Brain

• Vitreous Cavity

• The space between the lens and retina

filled with the gel like Vitreous Humor.

• Vitreous Humor

• The vitreous humor is a jelly like liquid that

fills most of the eye (from the lens back).

Macula - (yellow spot)

This part of the retina is the most sensitive. Its diameter

is only 7 mm or about 1/4 inch. It is responsible for our

central, or reading vision. Without the macula, you would

be blind - Legally Blind that is. People with eye diseases

like Macular Degeneration have vision from poor vision

Fovea - (small pit)

The fovea is an indentation in the center of the macula.

Its diameter is only 1.5 mm or about 1/16 inch. This

small part of our retina is responsible for our highest

visual acuity. It is the center of our central vision.

Cranial nerve Muscle

Oculomotor nerve

(N. III)

Superior rectus muscle Inferior

rectus muscle

Medial rectus muscle

Inferior oblique muscle

Levator palpebrae superior

muscle

Trochlear nerve

(N. IV) Superior oblique muscle

Abducens nerve

(N. VI)

Lateral rectus muscle

Retractor bulbi muscle

1 – upper lacrimal canaliculus

2 – lacrimal caruncle

3 – nasolacrimal duct

4 - gland of the third eyelid

5 – punctum lacrimale

6 – third eyelid

7 – conjuctival fornix

8 - pupil

The iris is composed of stroma (S) and a posterior epithelial

lining (PEL). The sphincter muscle (SM) of the iris is evident

within the stroma. The pigmented posterior epithelial lining

normally extends around the lip of the pupil anteriorly for a

short distance.

The conjunctiva can be divided into three parts. The palpebral

conjunctiva (arrow) lines the posterior surface of the eyelid. The

bulbar conjunctiva (double arrows) extends from the limbus over the

anterior sclera. The bulbar and palpebral conjunctiva converge upon

the conjunctiva of the superior and inferior fornices (triple arrows).

1 – levator palpebrae superioris

2 – 0rbital septum

2‘ – tarsus

3 – obicularis oculi

4 – punta lacrimalia

5 - Cilium, sebaceous glands

6 – tarsal glands

1-dorsal rectus

2-lateral rectus

3- Ventral rectus

4 – medial rectus

5- ventral oblique

6- dorsal oblique

7 - retractor bulbi

6‘ trochleanerve

8 – optic nerve

Third eyelid carcinoma

THE EAR

1) External ear – auris externa

2) Middle ear – auris media

3) Internal ear – auris interna

The ear consists of three parts

THE EAR

Consists of two parts:

i. The pinna or auricle

ii.The external acoustic meatus

THE EXTERNAL EAR

The outer ear includes:

•auricle (cartilage covered by skin placed on

opposite sides of the head)

•auditory canal (also called the ear canal)

•eardrum outer layer (also called the tympanic

membrane)

•

The outer part of the ear collects sound. Sound

travels through the auricle and the auditory canal,

a short tube that ends at the eardrum.

The Middle Ear

The middle ear includes:

Eardrum cavity (also called the tympanic cavity)

• Has ear ossicles (3 tiny bones)

•malleus (or hammer) – long handle attached to

the eardrum

•incus (or anvil) – the bridge bone between the

malleus and the stapes

•stapes (or stirrup) – the footplate; the smallest

bone in the body

The Inner Ear

The inner ear includes:

•oval window – connects the middle ear with the inner ear

•semicircular ducts – filled with fluid; attached to cochlea

and nerves; send information on balance and head position

to the brain

•cochlea – spiral-shaped organ of hearing; transforms

sound into signals that get sent to the brain

•auditory tube – drains fluid from the middle ear into the

throat behind the nose

The Middle Ear

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Center // Anatomy of the Ear // The

Middle Ear

The middle ear includes:

eardrum

cavity (also called the tympanic cavity)

ossicles (3 tiny bones that are attached)

malleus (or hammer) – long handle

attached to the eardrum

incus (or anvil) – the bridge bone

between the malleus and the stapes

stapes (or stirrup) – the footplate; the

smallest bone in the body

http://www.innerbody.com/image/nerv13.html

Malleus

Head lies in epitympanic recess.

Articulates with incus

Handle attached to TM.

Chorda tympani nerve crosses medial surface of neck.

Base fits into fenestra vestibuli (oval window).

Head articulates with incus

Stapes

Incus

Lies in epitympanic recess.

Head articulates with head of malleus.

Long process articulates with stapes.

Short process connected by ligament to posterior wall

http://upload.wikimedia.org/wikipedia/commons/5/58/Cochlea-crosssection-de.png