Download Sensory System

D- sensory system
Anatomy and Phyiology
Chapter 12
Lecture
PowerPoint
12.1: Introduction
• General senses
• Receptors that are widely distributed throughout the body
• Skin, various organs and joints
• Special senses
• Specialized receptors confined to structures in the head
• Eyes, ears, nose and mouth
2
12.2: Receptors, Sensation,
and Perception
• Sensory receptors
• Specialized cells or multicellular structures that collect information from
the environment
• Stimulate neurons to send impulses along sensory fibers to the brain
• Sensation
• A feeling that occurs when brain becomes aware of sensory impulse
• Perception
• A person’s view of the stimulus; the way the brain interprets the
information
3
Pathways From Sensation to Perception
(Example of an Apple)
4
Receptor Types
• Chemoreceptors
• Respond to changes in chemical concentrations
• Pain receptors (nociceptors)
• Respond to tissue damage
• Thermoreceptors
• Respond to changes in temperature
• Mechanoreceptors
• Respond to mechanical forces
• Photoreceptors
• Respond to light
5
Sensory Impulses
• Stimulation of receptor causes local change in its receptor potential
• A graded electrical current is generated that reflects intensity of
stimulation
• If receptor is part of a neuron, the membrane potential may generate
an action potential
• If receptor is not part of a neuron, the receptor potential must be
transferred to a neuron to trigger an action potential
• Peripheral nerves transmit impulses to CNS where they are analyzed
and interpreted in the brain
6
Sensory Adaptation
• Ability to ignore unimportant stimuli
• Involves a decreased response to a particular stimulus from the
receptors (peripheral adaptation) or along the CNS pathways leading to
the cerebral cortex (central adaptation)
• Sensory impulses become less frequent and may cease
• Stronger stimulus is required to trigger impulses
7
12.3: General Senses
• Senses associated with skin, muscles, joints and viscera
• Three (3) groups:
• Exteroceptive senses (exteroceptors)
• Senses associated with body surface such as touch,
pressure, temperature, and pain
• Visceroceptive senses (interoceptors)
• Senses associated with changes in the viscera such as
blood pressure stretching blood vessels and ingestion of a
meal
• Proprioceptive senses
• Senses associated with changes in muscles and tendons
such as at joints
8
Touch and Pressure Senses
Free nerve endings
• Common in epithelial tissues
• Simplest receptors
• Sense itching
Tactile (Meissner’s) corpuscles
• Abundant in hairless portions of skin and
lips
• Detect fine touch; distinguish between two
points on the skin
Lamellated (Pacinian) corpuscles
• Common in deeper subcutaneous tissues,
tendons and ligaments
• Detect heavy pressure and vibrations
9
Touch and Pressure Receptors
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Free nerve
endings
Section of
skin
Epithelial
cells
Epidermis
(a)
Sensory
nerve fiber
Epithelial
cells
Dermis
Tactile (Meissner’s)
corpuscle
(touch receptor)
Sensory nerve
fiber
(b)
Lamellated
(Pacinian) corpuscle
(pressure receptor)
Connective tissue
cells
Sensory nerve
fiber
(c)
b, c: © Ed Reschke
10
Temperature Senses
• Warm receptors
• Sensitive to temperatures above 25oC (77o F)
• Unresponsive to temperature above 45oC (113oF)
• Cold receptors
• Sensitive to temperatures between 10oC (50oF) and 20oC (68oF)
• Pain receptors
• Respond to temperatures below 10oC
• Respond to temperatures above 45oC
11
Sense of Pain
• Free nerve endings
• Widely distributed
• Nervous tissue of brain lacks pain receptors
• Stimulated by tissue damage, chemical, mechanical forces, or extremes in
temperature
• Adapt very little, if at all
12
Visceral Pain
• Pain receptors are the only receptors in viscera whose stimulation produces
sensations
• Pain receptors respond differently to stimulation
• Pain receptors are not well localized
• Pain receptors may feel as if coming from some other part of the body
• Known as referred pain…
13
Referred Pain
• May occur due to sensory impulses from two regions following a
common nerve pathway to brain
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Liver and
gallbladder
Lung and diaphragm
Liver and
gallbladder
Heart
Stomach
Pancreas
Small
intestine
Appendix
Ovary
(female)
Colon
Kidney
Ureter
Urinary bladder
14
Pain Nerve Pathways
• Acute pain fibers
• A-delta fibers
• Thin, myelinated
• Conduct impulses rapidly
• Associated with sharp pain
• Well localized
• Chronic pain fibers
• C fibers
• Thin, unmyelinated
• Conduct impulses more slowly
• Associated with dull, aching pain
• Difficult to pinpoint
15
Regulation of Pain Impulses
• Thalamus
• Allows person to be aware of pain
• Cerebral cortex
• Judges intensity of pain
• Locates source of pain
• Produces emotional and motor responses to pain
• Pain inhibiting substances:
• Enkephalins
• Serotonin
• Endorphins
16
Proprioception
• Mechanoreceptors
• Send information to spinal cord and CNS about body position and length,
and tension of muscles
• Main kinds of proprioceptors:
• Pacinian corpuscles – in joints
• Muscle spindles – in skeletal muscles*
• Golgi tendon organs – in tendons*
*considered to be stretch receptors
17
Stretch Receptors
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Sensory
nerve fiber
Sensory
nerve endings
Golgi tendon organ
Sensory
nerve fiber
Tendon
Intrafusal
fiber
Skeletal muscle
fiber
Muscle spindle
Skeletal muscle fiber
Connective
tissue sheath
(a)
(b)
18
18
Visceral Senses
• Receptors in internal organs
• Convey information that includes the sense of fullness after eating a
meal as well as the discomfort of intestinal gas and the pain that
signals a heart attack
19
Summary of Receptors of the
General Senses
20
12.4: Special Senses
• Sensory receptors are within large, complex sensory organs in the head
• Smell in olfactory organs
• Taste in taste buds
• Hearing and equilibrium in ears
• Sight in eyes
21
Sense of Smell
• Olfactory receptors
• Chemoreceptors
• Respond to chemicals dissolved in liquids
• Olfactory organs
• Contain olfactory receptors and supporting epithelial cells
• Cover parts of nasal cavity, superior nasal conchae, and a portion of the
nasal septum
22
Olfactory Receptors
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Nerve fibers within
the olfactory bulb
Olfactory
tract
Olfactory
bulb
Cribriform
plate
Olfactory area of
nasal cavity
Superior nasal
concha
Nasal cavity
Cilia
(a)
Olfactory
receptor cells
Columnar
epithelial cells
Cribriform
plate
(b)
23
Olfactory Nerve Pathways
• Once olfactory receptors are stimulated, nerve impulses travel
through
• Olfactory nerves
olfactory bulbs
olfactory tracts
limbic system (for emotions) and olfactory cortex (for interpretation)
24
Olfactory Stimulation
• Olfactory organs located high in the nasal cavity above the usual pathway
of inhaled air
• Olfactory receptors undergo sensory adaptation rapidly
• Sense of smell drops by 50% within a second after stimulation
25
Sense of Taste
• Taste buds
• Organs of taste
• Located on papillae of tongue, roof of mouth, linings of cheeks and walls of
pharynx
• Taste receptors
• Chemoreceptors
• Taste cells – modified epithelial cells that function as receptors
• Taste hairs –microvilli that protrude from taste cells; sensitive parts of taste
cells
26
Taste Receptors
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Papillae
Taste buds
Epithelium
of tongue
Taste cell
(a)
Taste hair
Supporting
cell
Taste
pore
(b)
Connective
tissue
Sensory
nerve fibers
27
Taste Sensations
• Four primary taste sensations
• Sweet – stimulated by carbohydrates
• Sour – stimulated by acids
• Salty – stimulated by salts
• Bitter – stimulated by many organic compounds
28
Taste Nerve Pathways
• Sensory impulses from taste receptors travel along:
• Cranial nerves to…
• Medulla oblongata to…
• Thalamus to…
• Gustatory cortex (for interpretation)
29
Sense of Hearing
• Ear
• Organ of hearing
• Three (3) sections:
• External ear
• Middle ear
• Inner ear
30
External Ear
• Auricle
• Collects sounds waves
• External auditory meatus
• Lined with ceruminous glands
• Carries sound to tympanic
membrane
• Terminates with tympanic
membrane
• Tympanic membrane
• Vibrates in response to sound
waves
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Auricle
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
31
Middle Ear
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• Tympanic cavity
Auricle
• Air-filled space in
temporal bone
• Auditory ossicles
• Vibrate in response to tympanic
membrane
• Malleus, incus and stapes
• Hammer, anvil and stirrup
• Oval window
• Opening in wall of tympanic
cavity
• Stapes vibrates against it to
move fluids in inner ear
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
32
Auditory Tube
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• Also known as the Eustachian Auricle
tube
• Connects middle ear to throat
• Helps maintain equal pressure on
both sides of tympanic membrane
• Usually closed by valve-like flaps
in throat
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
33
Inner Ear
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• Complex system of labyrinths
• Osseous labyrinth
• Bony canal in temporal bone
• Filled with perilymph
• Membranous labyrinth
• Tube within osseous labyrinth
• Filled with endolymph
Bony labyrinth
Perilymph
Membranous
labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Saccule
Vestibular nerve
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae
(a)
Oval Vestibule
window
Round Maculae
window
Cochlea
34
Inner Ear
• Three (3) parts of labyrinths:
• Cochlea
• Functions in hearing
• Semicircular canals
• Functions in equilibrium
• Vestibule
• Functions in equilibrium
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Bony labyrinth
Perilymph
Membranous
labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Saccule
Vestibular nerve
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae
(a)
Oval Vestibule
window
Round Maculae
window
Cochlea
35
Cochlea
• Scala vestibuli
• Upper compartment
• Leads from oval window
to apex of spiral
• Part of bony labyrinth
• Scala tympani
• Lower compartment
• Extends from apex of the
cochlea to round window
• Part of bony labyrinth
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Stapes vibrating in
oval window
Helicotrema
Scala vestibuli
filled with perilymph
Vestibular
membrane
Basilar
membrane
Scala tympani
filled with
perilymph
Round window
Cochlear duct
filled with endolymph
Membranous
labyrinth
36
Cochlea
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• Cochlear duct
• Portion of membranous
labyrinth in cochlea
• Vestibular membrane
• Separates cochlear duct
from scala vestibuli
• Basilar membrane
• Separates cochlear duct
from scala tympani
Scala vestibuli
(contains perilymph)
Vestibular membrane
Branch of
cochlear
nerve
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Basilar membrane
Scala tympani
(contains perilymph)
(a)
37
Animation:
Effect of Sound Waves
on Cochlear Structures
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38
Organ of Corti
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• Group of hearing receptor cells
(hair cells)
• On upper surface of basilar
membrane
• Different frequencies of vibration
move different parts of basilar
membrane
• Particular sound frequencies
cause hairs of receptor cells to
bend
• Nerve impulse generated
Scala vestibuli
(contains perilymph)
Vestibular membrane
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Branch of
cochlear
nerve
Basilar membrane
Scala tympani
(contains perilymph)
(a)
Tectorial
membrane
Hair cells
39
(b)
Branch of
cochlear nerve
Nerve
fibers
Supporting
cells
Basilar
membrane
Organ of Corti
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Cochlear duct
Tectorial membrane
Scala tympani
Hair cells
Basilar
membrane
(a)
(b)
a: © John D. Cunningham/Visuals Unlimited; b: © Fred Hossler/Visuals Unlimited
40
Auditory Nerve Pathways
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Auditory cortex
(temporal lobe)
Thalamus
Medial geniculate
body of thalamus
Midbrain
Pons
Cochlear
nuclei
Superior
olivary
nucleus
Medulla
oblongata
Vestibulocochlear
nerve
41
Summary of the Generation of
Sensory Impulses from the Ear
42
Sense of Equilibrium
• Static equilibrium
• Vestibule
• Senses position of head
when body is not moving
• Dynamic Equilibrium
• Semicircular canals
• Senses rotation and movement of
head and body
43
Vestibule
• Utricle
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• Communicates with saccule
and membranous portion of
Ampullae of
semicircular
semicircular canals
canals
• Saccule
• Communicates with cochlear
duct
• Macula
• Hair cells of utricle and saccule
Vestibulocochlear
nerve
Cochlea
Utricle
Cochlear
duct
Maculae Saccule
Vestibule
44
Macula
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• Responds to changes in
head position
• Bending of hairs results in
generation of nerve impulse
Hairs of
hair cells bend
Gelatinous
material sags
Otoliths
Macula
of utricle
Hair cells
Sensory nerve fiber
Gravitational
force
Supporting cells
45
(a) Head upright
(b) Head bent forward
Semicircular Canals
• Three (3) canals at right angles
• Ampulla
• Swelling of membranous
labyrinth that communicates
Ampullae of
semicircular
with the vestibule
canals
• Crista ampullaris
• Sensory organ of ampulla
• Hair cells and supporting
cells
• Rapid turns of head or body
stimulate hair cells
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Vestibulocochlear
nerve
Cochlea
Utricle
Cochlear
duct
Maculae Saccule
Vestibule
46
Crista Ampullaris
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Endolymph
Semicircular canal
Cupula
Crista
ampullaris
(a) Head in still position
Ampulla
Crista ampullaris
Hairs
Hair cell
Supporting cells
Sensory nerve fibers
(b) Head rotating
(c)
47
Sense of Sight
• Visual accessory organs
• Eyelids
• Lacrimal apparatus
• Extrinsic eye muscles
48
Eyelid
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• Palpebra
• Composed of four (4) layers:
• Skin
• Muscle
• Connective tissue
• Conjunctiva
• Orbicularis oculi – closes
eyelid
• Levator palpebrae superioris –
opens eyelid
• Tarsal glands – secrete oil onto
eyelashes
• Conjunctiva – mucous
membrane; lines eyelid and
covers portion of eyeball
Tendon of levator
palpebrae superioris
Superior
rectus
Orbicularis
oculi
Eyelid
Tarsal glands
Eyelash
Cornea
Conjunctiva
Inferior
rectus
49
Lacrimal Apparatus
• Lacrimal gland
• Lateral to eye
• Secretes tears
• Canaliculi
• Collect tears
• Lacrimal sac
• Collects from canaliculi
• Nasolacrimal duct
• Collects from lacrimal sac
• Empties tears into nasal
cavity
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Lacrimal gland
Superior and
inferior canaliculi
Lacrimal sac
Nasolacrimal
duct
50
Extrinsic Eye Muscles
• Superior rectus
• Rotates eye up and medially
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Medial Superior
rectus rectus
Superior
oblique
• Inferior rectus
• Rotates eye down and
medially
• Medial rectus
• Rotates eye medially
Lateral
rectus
(cut)
Inferior rectus
Inferior oblique
51
Extrinsic Eye Muscles
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• Lateral rectus
• Rotates eye laterally
Medial Superior
rectus rectus
Superior
oblique
• Superior oblique
• Rotates eye down and
laterally
• Inferior oblique
• Rotates eye up and laterally
Lateral
rectus
(cut)
Inferior rectus
Inferior oblique
52
Structure of the Eye
• Wall has three (3) layers:
• Outer fibrous tunic
• Middle vascular tunic
• Inner nervous tunic
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Lateral rectus
Retina
Ciliary body
Choroid coat
Sclera
Suspensory
ligaments
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
53
Outer Tunic
• Cornea
• Anterior portion
• Transparent
• Light transmission
• Light refraction
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Lateral rectus
Retina
Ciliary body
Choroid coat
Sclera
Suspensory
ligaments
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
• Sclera
• Posterior portion
• Opaque
• Protection
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
54
Middle Tunic
• Iris
• Anterior portion
• Pigmented
• Controls light intensity
• Ciliary body
• Anterior portion
• Pigmented
• Holds lens
• Moves lens for focusing
• Choroid coat
• Provides blood supply
• Pigments absorb extra light
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Lateral rectus
Retina
Ciliary body
Choroid coat
Sclera
Suspensory
ligaments
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
55
Anterior Portion of Eye
• Filled with aqueous humor
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Cornea
Anterior chamber
Iris
Posterior
chamber
Ciliary process
Suspensory
ligaments
Ciliary muscles
Ciliary
body
Conjunctiva
Vitreous
humor
Lens
Sclera
56
Lens
• Transparent
• Biconvex
• Lies behind iris
• Largely composed
of lens fibers
• Elastic
• Held in place by
suspensory ligaments
of ciliary body
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Cornea
Anterior chamber
Iris
Posterior
chamber
Ciliary process
Suspensory
ligaments
Ciliary muscles
Ciliary
body
Conjunctiva
Vitreous
humor
Lens
Sclera
57
Ciliary Body
• Forms internal ring around the front of the eye
• Ciliary processes – radiating folds
• Ciliary muscles – contract and relax to move lens
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Ciliary processes
of ciliary body
Suspensory
ligaments
Lens
Retina
Choroid coat
Sclera
58
Accommodation
• Changing of lens shape to view objects
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Ciliary muscle
fibers contracted
Suspensory
ligaments relaxed
Lens thick
(a)
Ciliary muscle
fibers relaxed
Suspensory
ligaments taut
Lens thin
59
(b)
Iris
• Composed of
connective tissue and
smooth muscle
• Pupil is hole in iris
• Dim light stimulates
radial muscles and pupil
dilates
• Bright light stimulates
circular muscles and
pupil constricts
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Sympathetic
motor nerve
fiber
In dim light
Radially arranged
Smooth muscle fibers
of the iris
Parasympathetic
ganglion
Circularly arranged
smooth muscle fibers
of the iris
Pupil
In normal light
Parasympathetic
motor nerve fiber
In bright light
60
Aqueous Humor
• Fluid in anterior cavity of eye
• Secreted by epithelium on inner surface of the ciliary body
• Provides nutrients
• Maintains shape of anterior portion of eye
• Leaves cavity through Canal of Schlemm
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Cornea
Aqueous humor
Anterior
chamber
Iris
Scleral venous sinus
(canal of Schlemm)
Lens
Sclera
Ciliary process
Ciliary
body
Ciliary muscles
Vitreous humor
Posterior
chamber
61
Inner Tunic
• Retina
• Contains visual receptors
• Continuous with optic nerve
• Ends just behind margin of the ciliary body
• Composed of several layers
• Macula lutea – yellowish spot in retina
• Fovea centralis – center of macula lutea; produces sharpest vision
• Optic disc – blind spot; contains no visual receptors
• Vitreous humor – thick gel that holds retina flat against choroid coat
62
Posterior Cavity
• Contains vitreous humor – thick gel that holds retina flat against choroid
coat
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Lateral rectus
Retina
Ciliary body
Choroid coat
Sclera
Suspensory
ligaments
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
chamber
Anterior
cavity
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
63
Major Groups of Retinal Neurons
• Receptor cells, bipolar cells, and ganglion cells - provide pathway for
impulses triggered by photoreceptors to reach the optic nerve
• Horizontal cells and amacrine cells – modify impulses
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Sclera
Pigmented
choroid
coat
Retinal pigment
epithelium
Rod
Cone
Receptor cells
Horizontal cell
Retina
Bipolar neuron
Amacrine cell
Layer of
connecting
neurons
Ganglion cell
Nerve fibers
Vitreous humor
Impulses
to optic
nerve
64
Light waves
Layers of the Eye
65
Light Refraction
• Refraction
• Bending of light
• Occurs when light waves pass at an oblique angle into mediums of
different densities
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Perpendicular line
Air
Light wave
Glass
Refracted
light wave
66
Types of Lenses
• Convex lenses cause
light waves to converge
• Concave lenses cause
light waves to diverge
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Light
wave
Air
Convex
surface
Concave
surface
Glass
Converging
light waves
(a)
Diverging
light waves
(b)
67
Focusing On Retina
• As light enters eye, it is refracted by:
• Convex surface of cornea
• Convex surface of lens
• Image focused on retina is upside down and reversed from left to right
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Light waves
Image
Retina
Object
Cornea
68
Visual Receptors
• Rods
• Cones
• Long, thin projections
• Short, blunt projections
• Contain light sensitive pigment called
• Contain light sensitive pigments
rhodopsin
called erythrolabe, chlorolabe, and
• Hundred times more sensitive to light
cyanolabe
than cones
• Provide vision in bright light
• Provide vision in dim light
• Produce sharp images
• Produce colorless vision
• Produce color vision
• Produce outlines of objects
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Rods and Cones
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Retinal pigment
epithelium
Cones
Rods
Single sensory
nerve fiber
(a)
Many sensory
nerve fibers
(b)
Rod
Cone
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(c)
c: © Frank S. Werblin, PhD.
12.6 Clinical Application
Refraction Disorders
• Concave lens corrects
nearsightedness
• Convex lens corrects farsightedness
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Lens
Point
of focus
Uncorrected
point of focus
Cornea
Light waves
Light waves
(a) Eye too long (myopia)
Point
of focus
Concave lens
(a)
Corrected
point of focus
Light waves
Retina
Uncorrected
point of focus
(b) Normal eye
Point
of focus
Light waves
Convex lens
(c) Eye too short (hyperopia)
(b)
71
Corrected
point of focus
Visual Pigments
• Rhodopsin
• Pigments on cones
• Light-sensitive pigment in rods
• Each set contains different light• Decomposes in presence of light
sensitive pigment
• Triggers a complex series of
• Each set is sensitive to different
reactions that initiate nerve
wavelengths
impulses
• Color perceived depends on
• Impulses travel along optic nerve
which sets of cones are stimulated
• Erythrolabe – responds to red
• Chlorolabe – responds to green
• Cyanolabe – responds to blue
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Rod Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Discs of
membrane
within cell
Mitochondria
Nucleus
Synaptic
ending
Rod cell
73
Stereoscopic Vision
• Provides perception of distance and depth
• Results from formation of two slightly different retinal images
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Light
waves
Left eye
Right eye
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Visual Nerve Pathway
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Eye
Optic
nerve
Fibers from
nasal (medial) half
of each retina
crossing over
Optic
chiasma
Optic tract
Lateral
geniculate
body of
thalamus
Optic
radiations
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Visual cortex of
occipital lobe
12.5: Lifespan Changes
• Age related hearing loss due to:
• Damage of hair cells in organ of Corti
• Degeneration of nerve pathways to the brain
• Tinnitus
• Age-related visual problems include:
• Dry eyes
• Floaters (crystals in vitreous humor)
• Loss of elasticity of lens
• Glaucoma
• Cataracts
• Macular degeneration
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