Special Senses
• Vision
• Taste
• Smell
• Hearing
• Equilibrium
___% of body's sensory receptors in eye
70%
Accessory Structures of the Eye
– Eyebrows
– Eyelids (palpebrae)
– Conjunctiva
– Lacrimal apparatus
– Extrinsic eye muscles
Eyebrows
• Overlie supraorbital margins
the eyes are protected by the mobile _______ or _______
eyelids or palpebrae
Eyelids separated at
palpebral fissure
Eyelids meet at
medial and lateral commissures
At medial commissure there is a fleshy elevation called the
Lacrimal caruncle
The Lacrimal Caruncle contains
sebaceous (oil) and sweat glands
During sleep the caruncle can produce a whitish oily secretion called
sandmans eye sand
In most Asian peoples a vertical fold of skin called ________ commonly appears on both sides of the nose and sometimes covers the medial commissure.
epicanthic fold
They eyelids are thin skin cover folds supported internally by connective tissue sheets called
tarsal plates
The tarsal plates also anchor the ________ and the ___________ muscles that run within the eyelid
obicularis oculi
levator palpebrae superioris
An infected tarsal gland results in an unsightly cyst called a _________. Inflammation of any of the smaller glands is called a ________
-chalazion
-sty
Which eyelid is more mobile and why
The upper
because of the levator palpebrae superioris
Which glands are associated with the eyelids
–Tarsal (Meibomian) glands
Modified sebaceous glands
Oily secretion lubricates lid and eye
–Ciliary glands between hair follicles
Modified sweat glands
Conjunctiva
Transparent mucous membrane that produces a lubricating mucous secretion
Palpebral conjunctiva
lines eyelids
Bulbar conjunctiva
covers white of eyes
Conjunctival sac
between palpebral and bulbar conjunctiva
– Where contact lens rests
Inflammation of the conjunctiva called
conjunctivitis
a conjuctival infection caused by bacteria or viruses is highly contagious
Pinkeye
The Lacrimal Apparatus consists of
the lacrimal gland and the ducts that drain into the nasal cavity
the lacrimal gland lies
in the orbit above the lateral end of the eye
What are Lacrimal secretion and what does it contain.
Dilute saline solution containing mucus, antibodies, and lysozyme
Blinking spreads tears toward the __________
medial commissure
Once tears reach the medial commissure, they then enter the paired_________ _________ via two tiny opening called _________ ________
Lacrimal canaliculi
lacrimal puncta
From the lacrimal canaliculi, the tears drain into the_______ ______ and then into the _____________ _____
lacrimal sac
nasolacrimal duct
finally tears empties into the nasal cavity at the
inferior nasal meatus
How many extrinsic eye muscles
how many rectus
how many oblique
6
4
2
Name the rectus muscles and the oblique muscles
Rectus:
Superior, inferior, lateral, medial
Oblique:
Superior and inferior
Lateral rectus
action:
Controlling CN:
Action: Moves eye Laterally
Controlling CN: VI (abducens)
Medial rectus
action:
Controlling CN:
action: Moves eye medially
Controlling CN: III (oculomotor)
Superior rectus
action:
Controlling CN:
action: Elevates eye and turns it medially
Controlling CN: III (Oculomotor)
Inferior Rectus
action:
Controlling CN:
action: Depresses eye and turn medially
Controlling CN: III (Oculomotor)
Superior Oblique
action:
Controlling CN:
action: Depresses eye and turns it laterally
Controlling CN: IV (Trochlear)
Inferior Oblique
action:
Controlling CN:
action: Elevates eye and turns it laterally
Controlling CN: III (oculomotor)
What are the three layers of the eyeball
– Fibrous
– Vascular
– Inner
The eyeball's internal cavity filled with fluids called________.
humors
What separates internal cavity into anterior and posterior segments (cavities)?
Lens
What is the outermost coat of the eyeball
The fibrous layer
What are the two different regions of the fibrous layer
-Sclera
-Cornea
Which is called the "white of the eye"
A. sclera
B. cornea
A. Sclera
Answer correctly :
Sclera forms the______
A. Opaque anterior region
B. Opaque posterior region
B. Opaque posterior region
What are some functions of the Sclera
anchors extrinsic eye muscles
shapes eyeball
protect
What helps to maintain clarity of cornea
Sodium pumps of corneal endothelium on inner face
How much of the fibrous layer does the cornea take up?
1/6
Name a function of the cornea
Bends light as it enters eye
Name of the layer that forms the middle coat of the eyeball
Vascular layer
T or F
The Vascular Layer is Pigmented
True
What are the Three regions of the Vascular layer
choroid,
ciliary body,
and iris
Choroid region
• Posterior portion of uvea
• Supplies blood to all layers of eyeball
• Brown pigment absorbs light to prevent light scattering and visual confusion
Anteriorly the choroid becomes the ____________
ciliary body
Ciliary body is a
thickened ring of tissue that encircles the lens
ciliary muscles
interlacing smooth muscle bundles that chiefly make up the ciliary body and control the lens shape.
ciliary processes
secrete the fluid that fills the cavity of the anterior segment of the eyeball
The ciliary zonule
extends from the ciliary process to the lens. helps hold the lens in its upright position
Iris
Visible colored part of the eye
most anterior portion of the vascular layer
Pupil
central opening that regulates amount of light entering eye
what muscle contracts for Close vision and bright light
sphincter pupillae
What muscle contracts for Distant vision and dim light
dilator pupillae
The innermost layer of the eyeball is the
Retina
The Retina originates as an
outpocketing of the brain
What are the two layers the Retina consists of
-Outer Pigmented Layer
-Inner neural Layer
Only the ____________ of the retina plays a direct role in vision
Inner neural layer
The outer pigmented layer act as phagocytes participating in___________ Cell renewal.
And store vitamin _____
photoreceptor
A
The neural layer is composed of three main types of neurons
photoreceptors
bipolar cells
ganglion cells
T or F
The Neural Layer is transparent
T
Optic Disc
where the optic nerve exits the eye
The optic disc is also called the blind spot because it lacks _____
photoreceptors
Rods
Dim light and peripheral vision
no sharp no color vision
cones
bright light
high resolution color vision
Macula lutea
• Mostly cones
• Fovea centralis
– Tiny pit in center of macula with all cones; best vision
What are the two sources of blood supply to the retina
– Choroid supplies outer third (photoreceptors)
– Central artery and vein of retina supply inner two-thirds
• Enter/exit eye in center of optic nerve
• Vessels visible in living person
Internal Chamber Posterior segment contains ________ humor
vitreous
Internal Chamber Anterior segment contains ________ humor
aqueous
Glaucoma
blocked aqueous humor
cataract
clouding of lens
Visible light spectrum range
400-700nm
light can be small particles or packets of energy called
photons or quanta
How does light move sequentially into the eye
1. cornea
2. aqueous humor
3. lens
4. vitreous humor
5. neural layer of retina
6. photoreceptors
During its passage into the eye, what three times is light bent
1. entering the cornea
2. entering the lens
3. leaving the lens
The Majority of refractory power is in the ________
cornea
Light passing through convex lens (as in eye) is bent so that rays converge at
focal point
Image formed at focal point is ________ and reversed _________
upside-down
right to left
transduction
The neural layer of the retina is directly involved in changing light energy to nerve impulses that the brain can interpret
Are our eyes best adapted for distant or close vision
distant
The Far point of vision
that distance beyond which no change in lens shape is needed for focusing
For the normal or emmetropic eye, the far point is
6m (20 feet)
Close vision requires eye to make active adjustments using three processes:
• Accommodation of lenses
• Constriction of pupils
• Convergence of eyeballs
Accommodation of lenses
– Changing lens shape to increase refraction
Presbyopia
loss of accommodation over age 50
Constriction of pupils
pupillary reflex constricts pupils to prevent most divergent light rays from entering eye
Convergence of eyeballs
Medial rotation of eyeballs toward object being viewed
Myopia
nearsightedness
– Focal point in front of retina, e.g., eyeball too long
– Corrected with a concave lens
Hyperopia
(farsightedness)
– Focal point behind retina, e.g., eyeball too short
– Corrected with a convex lens
Astigmatism
– Unequal curvatures in different parts of cornea or lens
– Corrected with cylindrically ground lenses or laser procedures
Light Adaptation
• Rod system turns off
• Retinal sensitivity decreases
• Cones and neurons rapidly adapt
Dark Adaptation
– Cones stop functioning in low-intensity light
– Rod pigments bleached; system turned off
– Rhodopsin accumulates in dark
– Transducin returns to outer segments
– Retinal sensitivity increases within 20–30 minutes
– Pupils dilate
The axons of the retinal ganglion cells exit the eye in the
optic nerves
Medial fibers of optic nerve cross at the _________
optic chiasma
Most fibers of optic tracts continue to __________
lateral geniculate body of thalamus
Fibers from thalamic neurons form optic radiation and project to ________________________________
primary visual cortex in occipital lobes
Other optic tract fibers send branches to midbrain, ending in ________________________________________
superior colliculi (initiating visual reflexes)
The receptors for smell and taste are
chemoreceptors
The organ of smell is called the
olfactory epithelium
The olfactory epithelium is located in the
roof of the nasal cavity
the olfactory epithelium covers the
superior nasal conchae
Some of what we smell is really
pain
the nasal cavities contain _______ and _______ receptors that respond to irritants.
pain and temperature
Taste buds are _________ organs
receptor
Most 10,0000 taste buds are on
tongue papillae
Taste buds are also found on tops of
fungiform papillae
Taste buds are found on side walls of _____ and _______
foliate and circumvallate (vallate) papillae
There are even a few taste buds on
-Soft palate
-cheeks
pharynx
epiglottis
Each flask shaped taste bud consists of 50–100 flask-shaped epithelial cells of 2 types
gustatory epithelial cells
basal epithelial cells
Which is the taste cell
gustatory epithelial cells
basal epithelial cells
gustatory epithelial cells
What are the three major areas of the ear
1. External (outer) ear – hearing only
2. Middle ear (tympanic cavity) – hearing only
3. Internal (inner) ear – hearing and equilibrium
External Ear
• Auricle (pinna
• External acoustic meatus (auditory canal
• Tympanic membrane (eardrum
Auricle (pinna)Composed of
– Helix (rim); Lobule (earlobe)
– Funnels sound waves into auditory canal
External acoustic meatus (auditory canal)
– Short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous glands
– Transmits sound waves to eardrum
Tympanic membrane (eardrum
– Boundary between external and middle ears
– Connective tissue membrane that vibrates in response to sound
– Transfers sound energy to bones of middle ear
Middle Ear
• Epitympanic recess
• Mastoid antrum
• Pharyngotympanic (auditory) tube
Epitympanic recess
superior portion of middle ear
Mastoid antrum
Canal for communication with mastoid air cells
Pharyngotympanic (auditory) tube
connects middle ear to nasopharynx
– Equalizes pressure in middle ear cavity with external air pressure
Two Major Divisions of Internal Ear
• Bony labyrinth
• Membranous labyrinth
Bony labyrinth has three regions
vestibule, semicircular canals, and cochlea
Semicircular canal function
-Equilibrium
-rational angular acceleration
Vestibule function
-Equilibrium
-head position relative to gravity
-linear acceleration
cochlea function
hearing
What are the two fluids that conduct the sound vibrations involved in hearing and that respond to the mechanical forces occuring during changes in body position and acceleration
perilymph
endolymph
Sound Pressure waves move through perilymph of
scala vestibuli
Equilibrium information goes to reflex centers in _________
brain stem
Impulses travel to vestibular nuclei in __________ or ________, both of which receive other input
vestibular nuclei
cerebellum
What are the three modes of input for balance and orientation:
- Vestibular receptors
– Visual receptors
– Somatic receptors
Meniere’s Syndrome
is a disorder of the inner ear that can affect hearing and balance to a varying degree. It is characterized by episodes of vertigo, low-pitched tinnitus, and hearing loss. The hearing loss is fluctuating rather than permanent,