Download Special Senses

Special Senses
Medical Terminology
Sense of Smell
• Very important in many species
• Warns the animal of
approaching dangers
• Helps to find food
• Connected to sex reflexes
• Primary peripheral organ is nose
• “Naso” and “rhino”
• Organ of smell is olfactory
epithelium. Vomeronasal organ
helps in detecting sexual
pheromones
• “olfact”
Structures of smell
• Nostrils or nares
• Turbinates
• Philtrum- groove in middle of nose separating nostrils
Taste
Organs of taste are taste buds- located on tongue and
mucous membrane of the soft palate.
Vision
• Orbit, optic, ocular, ophthalmo refer to eye
• Eyeball is cushioned in fat and connective tissue
CONJUNCTIVA
• mucous membrane that covers the inner surface of the
eyelid (palpebral conjunctiva) and the front portion of the
eyeball (bulbar conjunctiva). Commonly becomes
inflamed.
EYELIDS
•
(palpebrae) protect the eye’s surface. Upper and lower
join at the CANTHUS.
• Many animals also have a THIRD EYELID that
originates at the medial canthus and spreads laterally
across the eye passively when the lids close.
• Contains a lacrimal gland and a small piece of cartilage.
SCLERA
• opaque posterior fibrous portion of the eye that is
continuous with the cornea. Also known as the white of
the eye. Joins with the cornea at the LIMBUS.
• MUSCLES: 6-7 attach to each eye at the sclera to allow
movement in any direction
CORNEA
• anterior, transparent portion of the eye where light
enters.
• Circular in shape with a bulge at the cranial aspect.
• No blood vessels within it which makes it prone to
infection after injury.
• It is richly supplied with pain receptors.
CHOROID
•
located between the sclera and the retina. Known as
the vascular layer.
• Contains the TAPETUM LUCIDUM in all animals except
pigs and humans which is a reflective layer that allows
an animal to see in dimly lit conditions. Commonly seen
when a light is directed into the animal’s eye in the dark.
CILIARY BODY
• wedge-shaped ring that connects to the lens and adjusts
its shape, allowing the animal to focus. Also produces
AQUEOUS HUMOR
• IRIS: doughnut-shaped ring that regulates the amount of
light that gets through to the lens. Opening in the center
is called the PUPIL .
•
• LENS: directly behind the iris, focuses the light on the
retina. Shape is controlled via the ciliary body.
COMPARTMENTS OF THE EYE
• AQUEOUS compartment is in front of the lens and is
made of clear, watery fluid called aqueous humor
produced continuously by the ciliary body.
• -This compartment is further divided into the anterior
and posterior chambers. These help to maintain the
shape of the eyeball and the intraocular pressure.
Empties into the Canal of Schlemn, which is returned
to the bloodstream.
• VITREOUS compartment is caudal to the lens and is
made of soft gelatin called vitreous humor.
RETINA
•
innermost layer that forms the visual image and
converts it to nerve impulses that are sent to the brain
via the optic nerve.
• Nerve fibers on the inside of the retina come together at
the OPTIC DISC where they leave the eye to form the
OPTIC NERVE that carries visual info to the brain.
• The retina is composed of cells called RODS and
CONES that are receptors of light stimuli.
• CONES are the least numerous, adapted for bright light,
color, and detail.
• RODS are sensitive for low light vision, but are color
blind.
• Domestic animals can see colors, but most have very
few cones. This allows them to see with the quality of
an old colored photograph that has been over
exposed (colors are pale and faded). Their vision is
also not as sharp as humans.
•
• There are no rods or cones at the optic disc so no visual
images are formed, making it the blind spot of the eye.
LACRIMAL APPARATUS
•
Includes the lacrimal gland, the gland within the 3rd
eyelid, and the nasolacrimal duct.
• The lacrimal gland produces tears to moisten, clean,
and deliver antibacterial substances to the surface of
the eye.
• The major lacrimal gland is located in the
dorsolateral portion of each orbit.
• Blinking spreads the tears across the eye toward the
medial canthus to the tiny lacrimal punctum.
• They then drain down the NASOLACRIMAL DUCT,
which is why you get the “sniffles” when your eyes
water. Blockage of this duct forces the tears to drain
on the face.