Download The rod and cones are the outer segment of photoreceptor cells .The

Sense Organ
Jun Zhou (周俊), M.D. & Ph.D.
School of Medicine, Zhejiang University
20121218
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LEARNING METHODS
•Listen attentively and think actively during the lecture.
•Preview and review the textbook and atlas as much as you
can.
•NEVER passing by a word without knowing its definition.
•To understand the structure and function of each organ, not
just memorize them.
•Email: [email protected]
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Special sense receptors

Responsible for the five special senses: taste,
smell, seeing, hearing, feeling

Tranduce stimuli from the environment into
electrical impulses
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
Specialized diffuse receptors
Two important sensory organ

The eye

The ear

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Specialized diffuse receptors
Free nerve terminals
-- feel cold, hot, pain and slight touch
 Encapsulated nerve ending

--have CT capsule



Pacinian corpuscle
Meissner corpuscle
Proprioceptive receptors
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Free nerve ending
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Meissner corpuscle
Ellipsoid,
encapsulated
receptor
Located
in the dermal
papillae of thick skin
Fine
touch perception
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Pacinian corpuscle
Large
ellipsoid encapsulated
receptor
Located
in the dermis.
hypodermis, mesenteries
Multilayer
capsule surrounds
inner unmyelinated nerve
terminal
Perceive
pressure, vibration
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Muscular
spindles
Proprioceptive receptors
3-12
small encapsulated
intrafusal muscle fibers
Sense
differences in muscle
length and tension
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Two special sensory organs

Eyes: visual organ

Ears: the organ of hearing and equilibrium.
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THE EYE
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Fibrous layer
Walls
eyeball
eye
Vascular layer
Retina
Content：Aqueous humor、Lens、
Vitreous body
Accesory structure:Eyelid、Muscles of the eye、
Lacrimal gland
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Eyeball Walls
Cornea 1/6
Fibrous layers Sclera 5/6
Eye ball Vascular layers
Choroid 2/3
Ciliary body
Iris
Retina
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Cornea
Colorless, transparent
5 layers:
epithelium
Bowman’s membrane
Stroma
Descemet’s membrane
endothelium
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Cornea
a.epithelium:





Non-keratinized stratified squamous epi.
5-6 layers
Numerous mitotic figures
No vessels.
Free nerve ending
b.Bowman’s membrane( anterior
basement membrane)


An acellular homogeneous membrane
(collagen fibrils)
Stability & strength, no regeneration
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C. Stroma or substantia propria
 Several lamellae of fine collagen
f.network
 Flattened fibroblasts
 G.S.rich in chrodroitin sulfate
D. Descemet’s membrane
(posterior limiting lamina)


Acellular homogeneous membrane
Can be repaired by endothelial cells
E.Endothelium
 Like mesothelium in its morphology
 Regulate the water content of the
stroma  maintain transparency
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The reasons of cornea transparent




No blood vessels & pigments
Basal of epi. is plane
Uniform spacing of collagen fibrils and lamellae
in stroma
G.S. with transparent nature & maintains proper
water
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Retina
Two regions:
The nonphotosensitive region
(nonvisual part)
Located anterior to the ora serrata,
no photoreceptors.
The
photosensitive region
(optic part)
Lines the inner surface of the eye
posterior to the ora serrata (except
the optic papilla)
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Retina
4 layers of cells:
 Pigment cells
 Optic cells
 Bipolar cells
 Ganglion cells
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Pigment epithelium
Structure：
1) Simple cuboidal epi. Attached to choroid and
easy separated from retina (detachment of
retina)
2) Junctional complex ,
3) Melanin granules
4) Processes (contain pigment granules)
Function：
1) absorb light,protect rod and cone from
strong light
2) Blood-retina barrier
3) Phagocytize the membranous discs from
retinal photoreceptor cells
4) Store vitamin A to assist in forming
rhodopsin
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Optical cells



bipolar neurons
The rods and cones
Glial cells（Müller cell）
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Rod cell





Thin,elongated cells，
about 120 million rods
A body and two opposite processes
Outer segment and inner segment
separated discs ,shed disc
phagocytized by pigment cells
rhodopsin (visual purple)
Function:
 sensitive to low intensity light
 Night vision (lack of vitamin A leads
night blindness)
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cone cell




About 7 million cells
Located in posterior part of
retina,especially in fovea
Outer and inner segments
(conical)
Continuous discs & not renewed
Function
 1）sensitive to high intensity light
 2）color distinguishing（red、
blue、green iodopsin）
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Bipolar cells
An axon & a dendrite
Synapse with photoreceptor
cells and ganglion cells
Müller cells
Extend entire thickness of retina
Neuroglia
Horizontal cells
Amacrine cells
Interconnected cells—provideing greater
visual acuity
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Ganglion cells


The dendrite synapse with
bipolar cells
The axons concentrate
together form optic nerve
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Specilized regions of the retina
 Ora serrata ：neural layer ends anteriorly at ciliary body,pigment cells
extend to cover posterior iris
 Macula lutea:directly on eye’s posterior pole. “yellow spot”,mostly cones
 Fovea centralis: central pit of macula,only cones, vision acuity straight on
 Optic disc:blind spot,no rods or cones,optic nerve exits,medial and inferior
to fovea centralis.
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10 layers
1 = pigmented epithelium
2 = layer of photoreceptors
3 = external limiting membrane
4 = outer nuclear layer
5 = outer plexiform layer, where
photoreceptors synapse
6 = inner nuclear layer of bipolar
neurons
7 = inner plexiform layer, where
bipolar neurons synapse with
ganglion cells
8 = ganglion cell layer
9 = optic nerve layer
10 = internal limiting membrane
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Visual pathways
light cornea champer lens vitreous body
retina
pigment epithelium
rods and cones
bipolar cells
ganglion cells
optic nerve fibers
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Ear
External, middle, inner ear
•External and middle ear:
gathers and funnels sound waves
•Inner ear:
sensory of hearing and balance
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Mastoid process
External ear ：
(auricle)
• auricle
• external acoustic meatus
• tympanic membrane
(eardrum)
Middle ear：
• tympanic cavity
• auditory tube
• mastoid process
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Internal ear
Bony labyrinth
Membranous labyrinth
Bony labyrinth：
Menbranous labyrinth：
•Semicircular canals
•Cochlear labyrinth
•Vestibule
•Vestibular labyrinth
•Cochlea
three semicircular ducts
Utricle and saccule
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Six sensory regions of the membranous labyrinth:
Three crista ampullaris
Two maculae(maculae of utricle, maculae of saccule)
The spiral organ of Corti
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Crita ampullaris
three，located in the membranous
ampullae of the semicircular ducts
Composition：
Supporting cells：support，forming cupula
Sensory hair cells：with stereocilia and
kinocilium are embedded in the cupula
Function：
sensors of angular acceleration of the head
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Maculae of utricle
and saccule：
•Located in the vestibule
•Sense the position of the
head and its linear
movement
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Note：
• The position of cochlear duct within the bony
cochlea
• The scala vestibuli and the scala tympani,
containing perilymph
• The scala media containing endolymph
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Schematic diagram of the cochlea:
Scala vestibuli
Scala tympani
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Corti’s organ：sensor of sound vibration
On the lower wall of the scala media
Tectorial membrane
Inner (close to spiral lamina)and outer (farther from the spiral
lamina) hair cells
Supporting cells: inner and outer phalangeal cells
pillar cells
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Sounds Pathawy
• Sound comes
• Hits tympanic membrane to vibrate
• three auditory ossicles vibrate
• vibration at tympanic (oval) window
• Vibration in the perilymph of the scala
vestibular to the scala media
• Vibrates of basilar membrane and
tectorial membrane,and hair cells
attached to also vibrates
• Vibrate the stereocilia of the hair cells
and initiate neuronal transduction
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Clinical Correlation
 Vertigo: dysfunction of vestibular system
Causes: viral infections, certain drugs, tumors, excessive stimulation
(seasickness, carsickness, or airsickness)
 Hearing loss
1)Conductive hearing loss: sound waves are mechanically
impeded from reaching the auditory sensory receptors within the
internal ear.such as excessive accumulation of cerumen.
2)Sensorineural hearing impairment: injury to the auditory hair
cells or the cochlea nerve. May be congenital or acquired. Causes
include infections, trauma (exposure to excessive noise),
administration of certain antibiotics, aging.
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cornea
Ciliary body
iris
lens
sclera
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OBJECTIVES
• Know the general layers of the eye.
• Describe the structure of Cornea and its reason of
transparent.
• Describe the structure of Retina and the function of pigment
cell, rod cell and cone cell.
• Know the definition of Ora serrata, Macula lutea, Fovea
centralis and Optic disc.
• Know the general structure of ear.
• Describe six sensory regions of the membranous labyrinth
and their function.
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Sclera
Choroid
Retina
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Scala vestibuli
Scala
media
Scala tympani
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Choice: Select the single most appropriate answer.
1.The posterior wall of eyeball from outside inward contains
A.fibrous layer,vascular layer and retina
( A)
B.retina,choriod and sclera
C.choriod,sclera and retina
D.cornea,iris and retina
E.Retina, vascular layer and fibrous layer
2. The Müller cells of retina belong to
A.sensory neurons
B.neuroglial cells
C.interneurons
D.photoreceptors
E.motor neurons
3.The cells used color perception and fine visual acuity are
A. ganglion cells
B. Müller cells
C. bipolar cells
D.rods
E. cones
(B)
(E)
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4.The optic nerve fibers are constituted by axons of
A.ganglion cells
B.Müller cells
(A)
C.Bipolar cells
D.rods
E.Cones
5.The receptor of hearing is located on
A.Vestibular membrane
B.Crista ampullaris
C.Maculae saccule
D.Maculae utricle
E.Organ of Corti
(E)
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