Download Anterior - Dr. Par Mohammadian

PowerPoint® Lecture Slides
prepared by
Barbara Heard,
Atlantic Cape Community
Ninth Edition
College
Human Anatomy & Physiology
CHAPTER
15
The Special
Senses: Part A
© Annie Leibovitz/Contact Press Images
© 2013 Pearson Education, Inc.
Special Senses
• Special sensory receptors
– Distinct, localized receptor cells in head
•
•
•
•
•
Vision
Taste
Smell
Hearing
Equilibrium
© 2013 Pearson Education, Inc.
The Eye and Vision
• 70% of body's sensory receptors in eye
• Visual processing by ~ half cerebral cortex
• Most of eye protected by cushion of fat and bony
orbit
Accessory Structures of the Eye
• Protect the eye and aid eye function
– Eyebrows
– Eyelids (palpebrae)
– Conjunctiva
– Lacrimal apparatus
– Extrinsic eye muscles
Figure 15.1a The eye and accessory structures.
Eyebrow
Eyelid
Eyelashes
Site where
conjunctiva
merges with
cornea
Palpebral
Fissure (eyelid slit)
Lateral
commissure
Iris
Eyelid
Pupil
*Lacrimal Medial
Sclera
(covered by caruncle commissure
conjunctiva)
Surface anatomy of the right eye
© 2013 Pearson Education, Inc.
*Contains oil and sweat glands
Figure 15.1b The eye and accessory structures.
Levator palpebrae
superioris muscle (raises eyelid to open the eye)
Orbicularis
oculi muscle (contraction: eye closes)
Eyebrow
Tarsal plate (connective tissue; supports the
eyelids)
Cornea
Palpebral
fissure
Eyelashes
Orbicularis
oculi muscle
Lateral view; some structures shown in sagittal section
© 2013 Pearson Education, Inc.
Conjunctiva
• Transparent mucous membrane
– 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
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Lacrimal Apparatus
•
•
•
Lacrimal gland and ducts
that drain into nasal cavity
Lacrimal gland in orbit
above lateral end of eye
Lacrimal secretion (tears)
– Dilute saline solution
containing mucus,
antibodies, and
lysozyme
– Blinking spreads tears
toward medial
commissure
– Tears enter paired
lacrimal canaliculi via
lacrimal puncta
– Then drain into lacrimal
sac and nasolacrimal
duct
Lacrimal gland
Excretory ducts
of lacrimal glands
Lacrimal sac
Lacrimal punctum
Lacrimal canaliculus
Nasolacrimal duct
Inferior meatus of nasal cavity
Nostril
Extrinsic Eye Muscles
Superior oblique tendon
Superior oblique muscle
Superior rectus muscle
Lateral rectus muscle
•
Six muscles:
•
Four rectus muscles; names
indicate movements
– Superior, inferior, lateral,
medial rectus muscles
•
Inferior
rectus
muscle
Inferior
oblique
muscle
Lateral view of the right eye
Two oblique muscles move eye in
vertical plane and rotate eyeball
– Superior and inferior oblique
muscles
Figure 15.3b Extrinsic eye muscles.
Trochlea
Superior oblique muscle
Axis of
rotation
of eye
Superior oblique tendon
Superior rectus muscle
Inferior
rectus muscle
Medial
rectus muscle
Lateral
rectus muscle
Common
tendinous ring
Superior view of the right eye
© 2013 Pearson Education, Inc.
Figure 15.3c Extrinsic eye muscles.
Muscle
Action
Controlling cranial nerve
Lateral rectus
Moves eye laterally
VI (abducens)
Medial rectus
Superior rectus
Inferior rectus
Moves eye medially
III (oculomotor)
Elevates eye and turns it medially
III (oculomotor)
Depresses eye and turns it medially
III (oculomotor)
Elevates eye and turns it laterally
III (oculomotor)
Depresses eye and turns it laterally
IV (trochlear)
Inferior oblique
Superior oblique
Summary of muscle actions and innervating cranial nerves
© 2013 Pearson Education, Inc.
Structure of the Eyeball
• Wall of eyeball contains three layers
– Fibrous
– Vascular
– Inner
• Internal cavity filled with fluids called humors
• Lens separates internal cavity into
anterior & posterior segments (cavities)
© 2013 Pearson Education, Inc.
Figure 15.4a Internal structure of the eye (sagittal section).
Ciliary body
Sclera
Ciliary zonule
(suspensory
ligament)
Choroid
Cornea
Iris
Pupil
Anterior
pole
Anterior
segment
(contains
aqueous humor)
Lens
Retina
Macula lutea
Fovea centralis
Optic nerve
Scleral venous sinus
Central artery and
vein of the retina
Posterior segment
(contains vitreous humor)
Optic disc
(blind spot)
Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball.
© 2013 Pearson Education, Inc.
Figure 15.4b Internal structure of the eye (sagittal section).
Ciliary body
Vitreous humor
in posterior
segment
Iris
Margin
of pupil
Anterior
segment
Lens
Cornea
Retina
Choroid
Sclera
Fovea centralis
Optic disc
Optic nerve
Photograph of the human eye.
http://www.youtube.com/watch?v=
TXFt1Ikl__I&feature=endscreen
© 2013 Pearson Education, Inc.
Fibrous Layer
• Outermost layer; dense avascular connective tissue
• Two regions: sclera and cornea
1. Sclera
• Opaque posterior region
• Protects, shapes eyeball
2. Cornea
• Transparent anterior
• Bends light as it enters eye
Vascular Layer (Uvea)
• Middle pigmented layer
• Three regions: choroid, ciliary body, and iris
1. Choroid region (posterior portion of uvea)
• Supplies blood to all layers of eyeball
Brown pigment absorbs light to prevent light scattering and visual
confusion
2. Ciliary body
• Ring of tissue surrounding lens
• Smooth muscle bundles (ciliary muscles) control lens shape
• Ciliary zonule (suspensory ligament) holds lens in position
3. Iris (Colored part of eye)
• Pupil—central opening that regulates amount of light entering eye
– Close vision and bright light—sphincter pupillae (circular
muscles) contract; pupils constrict
– Distant vision and dim light—dilator pupillae (radial muscles)
contract; pupils dilate – sympathetic fibers
– Changes in emotional state—pupils dilate when subject matter
is appealing or requires problem-solving skills
Figure 15.5 Pupil constriction and dilation, anterior view.
Sympathetic +
Parasympathetic +
Sphincter pupillae
muscle contracts:
Pupil size decreases.
© 2013 Pearson Education, Inc.
Iris (two muscles)
• Sphincter pupillae
• Dilator pupillae
Dilator pupillae
muscle contracts:
Pupil size increases.
Inner Layer: Retina
• Delicate two-layered membrane
– Outer Pigmented layer
• Single-cell-thick lining
• Absorbs light and prevents its scattering
• Phagocytize photoreceptor cell fragments
• Stores vitamin A
– Inner Neural layer
• Transparent
• Composed of three main types of neurons
– Photoreceptors, bipolar cells, ganglion cells
• Signals spread from photoreceptors to bipolar cells to ganglion cells
• Ganglion cell axons exit eye as optic nerve
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The Retina
• Optic disc (blind spot)
– Site where optic nerve leaves eye
– Lacks photoreceptors
• Quarter-billion photoreceptors of two types
– Rods
– Cones
http://www.youtube.com/watch?v=1YHghqvGtg&feature=related
© 2013 Pearson Education, Inc.
Figure 15.6a Microscopic anatomy of the retina.
Neural layer of retina
Pigmented
layer of
retina
Choroid
Pathway of
light
Sclera
Optic disc
Central artery
and vein of retina
Optic
nerve
Posterior aspect of the eyeball
© 2013 Pearson Education, Inc.
Figure 15.6b Microscopic anatomy of the retina.
Ganglion
cells
Axons
of
ganglion
cells
Bipolar
cells
Photoreceptors
• Rod
• Cone
Amacrine cell
Horizontal cell
Pathway of signal output
Pathway of light
Pigmented
layer of retina
Cells of the neural layer of the retina
© 2013 Pearson Education, Inc.
Figure 15.6c Microscopic anatomy of the retina.
Nuclei of
ganglion
cells
Outer segments
of rods and cones
Nuclei of Nuclei of
bipolar rods and
cells
cones
Photomicrograph of retina
Axons of
ganglion cells
© 2013 Pearson Education, Inc.
Choroid
Pigmented
layer of retina
Photoreceptors
• Rods
– Dim light, peripheral vision receptors
– No color vision or sharp images
– Numbers greatest at periphery
• Cones
– Vision receptors for bright light
– High-resolution color vision
• Fovea centralis
– Tiny pit in center of macula with all cones; best vision
Internal Chambers and Fluids
• The lens and ciliary zonule separate eye
into two segments
– Anterior and posterior segments
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Internal Chambers and Fluids
• Posterior segment contains vitreous humor that
– Transmits light
– Supports posterior surface of lens
– Holds neural layer of retina firmly against pigmented
layer
– Contributes to intraocular pressure
– Forms in embryo; lasts lifetime
• Anterior segment composed of two chambers
– Anterior chamber—between cornea and iris
– Posterior chamber—between iris and lens
© 2013 Pearson Education, Inc.
Internal Chambers and Fluids
• Anterior segment contains aqueous humor
– Plasma like fluid continuously formed by capillaries of
ciliary processes
– Supplies nutrients and oxygen mainly to lens and
cornea but also to retina, and removes wastes
• Glaucoma: blocked drainage of aqueous humor
increases pressure and causes compression of
retina and optic nerve  blindness
Figure 15.4a Internal structure of the eye (sagittal section).
Ciliary body
Sclera
Ciliary zonule
(suspensory
ligament)
Choroid
Cornea
Iris
Pupil
Anterior
pole
Anterior
segment
(contains
aqueous humor)
Lens
Scleral venous sinus
Posterior segment
(contains vitreous humor)
Retina
Macula lutea
Fovea centralis
Posterior pole
Optic nerve
Central artery and
vein of the retina
Optic disc
(blind spot)
Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball.
© 2013 Pearson Education, Inc.
Figure 15.8 Circulation of aqueous humor.
Cornea
Lens
Posterior
segment
(contains
vitreous
humor)
Iris
Lens epithelium
Lens
Cornea
2
Corneal epithelium
Corneal endothelium
Aqueous humor
1 Aqueous humor
forms by filtration
from the capillaries
in the ciliary
processes.
2 Aqueous humor
flows from the
posterior chamber
through the pupil into
the anterior chamber.
Some also flows
through the vitreous
humor (not shown).
3 Aqueous humor is
reabsorbed into the
venous blood by the
scleral venous sinus.
© 2013 Pearson Education, Inc.
Anterior
segment
(contains
aqueous
humor)
Anterior chamber
Ciliary zonule
(suspensory
ligament)
Posterior chamber
Scleral venous
sinus
Corneoscleral
junction
3
1
Ciliary
processes
Ciliary
muscle
Bulbar
conjunctiva
Sclera
Ciliary
body
Lens
• Biconvex, transparent, flexible, and avascular
• Changes shape to precisely focus light on retina
• Two regions
– Lens becomes more dense, convex, less elastic with
age
• cataracts (clouding of lens) consequence of aging, diabetes
mellitus, heavy smoking, frequent exposure to intense
sunlight
© 2013 Pearson Education, Inc.
Figure 15.9 Photograph of a cataract.
© 2013 Pearson Education, Inc.
Visual Pathways
Visual Pathways
• Ganglion cells of the retina make up optic nerves
• Left and right optic nerves (II) into brain via optic
foraminae
• Optic chiasma (nasal side fibers cross to contralateral
brain)
• Optic tracts (carry fibers back to the thalamsus)
• Ganlion cell axons terminate in lateral geniculate n. of
thalamus
• Optic radiations carry fibers back to occipital cortex
The Chemical Senses: Smell And Taste
• Smell (olfaction) and taste (gustation)
• Chemoreceptors respond to chemicals in
aqueous solution
Taste – to substances dissolved in saliva
Smell – to substances dissolved in fluids of the nasal
membranes
Sense of Smell
Taste Buds
• Most of the 10,000 or so taste buds are found on the
tongue
• Taste buds are found in papillae of the tongue mucosa
• Papillae come in three types: filiform, fungiform, and
circumvallate
• Fungiform and circumvallate papillae contain taste
buds
Taste Buds
Basic Taste Sensations
• There are five basic taste sensations
1. Sweet—sugars, saccharin, alcohol, some
amino acids, some lead salts
2. Sour—hydrogen ions in solution
3. Salty—metal ions (inorganic salts)
4. Bitter—alkaloids such as quinine and
nicotine; aspirin
5. Umami—amino acids glutamate and
aspartate
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Gustatory Pathway
The Ear: Hearing and Balance
•
Three major areas of ear
1. External (outer) ear – hearing only
2. Middle ear (tympanic cavity) – hearing only
3. Internal (inner) ear – hearing and
equilibrium
•
Receptors for hearing and balance respond to
separate stimuli
•
Are activated independently
© 2013 Pearson Education, Inc.
External Ear
• 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
© 2013 Pearson Education, Inc.
Figure 15.24a Structure of the ear.
Middle Internal ear
External ear
(labyrinth)
ear
Auricle
(pinna)
Helix
Lobule
External
acoustic Tympanic Pharyngotympanic
meatus membrane (auditory) tube
The three regions of the ear
© 2013 Pearson Education, Inc.
Middle Ear (Tympanic Cavity)
• A small, air-filled, mucosa-lined cavity in temporal bone
– Connected laterally by eardrum
– Connected medially by bony wall containing oval (vestibular)
and round (cochlear) windows
• 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
Figure 15.24b Structure of the ear.
Oval window
(deep to stapes)
Entrance to mastoid
antrum in the
epitympanic recess
Malleus
(hammer)
Incus
Auditory
(anvil)
ossicles
Stapes
(stirrup)
Tympanic membrane
Semicircular
canals
Vestibule
Vestibular
nerve
Cochlear
nerve
Cochlea
Round window
Middle and internal ear
© 2013 Pearson Education, Inc.
Pharyngotympanic
(auditory) tube
Otitis Media
• Middle ear inflammation
– Especially in children
• Shorter, more horizontal pharyngotympanic tubes
• Most frequent cause of hearing loss in children
– Most treated with antibiotics
– Myringotomy to relieve pressure if severe
Myringotomy (myringa: eardrum):A surgical procedure; a tiny incision is created in the
eardrum to relieve pressure caused by excessive build-up of fluid or to drain pus from the
middle ear.
© 2013 Pearson Education, Inc.
Ear Ossicles
• Three small bones in tympanic cavity: the
malleus, incus, and stapes
– Suspended by ligaments and joined by
synovial joints
– Transmit vibratory motion of eardrum to oval
window
– Tensor tympani and stapedius muscles
contract reflexively in response to loud
sounds to prevent damage to hearing
receptors
© 2013 Pearson Education, Inc.
Figure 15.25 The three auditory ossicles and associated skeletal muscles.
View
Superior
Malleus
Incus Epitympanic recess
Lateral
Anterior
© 2013 Pearson Education, Inc.
Pharyngotym- Tensor
tympani
panic tube
muscle
Tympanic Stapes Stapedius
membrane
muscle
(medial view)
Internal Ear
• Bony labyrinth
– Tortuous channels in temporal bone
– Three regions: 1) vestibule, 2) semicircular
canals, and 3) cochlea
– Filled with perilymph – similar to CSF
• Membranous labyrinth
– Series of membranous sacs and ducts
– Filled with potassium-rich endolymph
© 2013 Pearson Education, Inc.
Figure 15.26 Membranous labyrinth of the internal ear.
Temporal
bone
Semicircular ducts
in semicircular
canals
Anterior
Posterior
Lateral
Facial nerve
Vestibular nerve
Cristae ampullares
in the membranous
ampullae
Superior vestibular
ganglion
Inferior vestibular
ganglion
Cochlear nerve
Maculae
Spiral organ
Utricle in
vestibule
Cochlear duct
in cochlea
Saccule in
vestibule
© 2013 Pearson Education, Inc.
Stapes in
oval window
Round window
Vestibule
• Central egg-shaped cavity of bony labyrinth
• Contains two membranous sacs
1. Saccule is continuous with cochlear duct
2. Utricle is continuous with semicircular canals
• These sacs
– House equilibrium receptor regions (maculae)
– Respond to gravity and changes in position of
head
© 2013 Pearson Education, Inc.
Semicircular Canals
• Three canals (anterior, lateral, and posterior)
• Membranous semicircular ducts line each
canal and communicate with utricle
• Ampulla of each canal houses equilibrium
receptor region called the crista ampullaris
– Receptors respond to angular (rotational)
movements of the head
© 2013 Pearson Education, Inc.
Figure 15.26 Membranous labyrinth of the internal ear.
Temporal
bone
Semicircular ducts
in semicircular
canals
Anterior
Posterior
Lateral
Facial nerve
Vestibular nerve
Cristae ampullares
in the membranous
ampullae
Superior vestibular
ganglion
Inferior vestibular
ganglion
Cochlear nerve
Maculae
Spiral organ
Utricle in
vestibule
Cochlear duct
in cochlea
Saccule in
vestibule
© 2013 Pearson Education, Inc.
Stapes in
oval window
Round window
The Cochlea
• A spiral, conical, bony chamber
– Size of split pea
– Extends from vestibule
– Contains cochlear duct, which houses spiral
organ (organ of Corti) and ends at cochlear
apex
© 2013 Pearson Education, Inc.
The Cochlea
• Cavity of cochlea divided into three chambers
– Scala vestibuli—joins oval window, contains
perilymph
– Scala media (cochlear duct)—contains
endolymph
– Scala tympani—terminates at round window;
contains perilymph
• Scalae tympani and vestibuli are continuous
with each other at helicotrema (apex)
© 2013 Pearson Education, Inc.
Figure 15.27b Anatomy of the cochlea.
Vestibular membrane
Tectorial membrane
Cochlear duct
(scala media;
contains
endolymph)
Stria
vascularis
Spiral organ
Basilar
membrane
© 2013 Pearson Education, Inc.
Osseous spiral lamina
Scala
vestibuli
(contains
perilymph)
Scala
tympani
(contains
perilymph)
Spiral
ganglion
Figure 15.27a Anatomy of the cochlea.
•
The "roof" of cochlear duct: Vestibular membrane
•
External wall is stria vascularis – secretes endolymph
•
"Floor" of cochlear duct composed of
– Bony spiral lamina
– Basilar membrane, which supports spiral organ
•
The cochlear branch of nerve VIII runs from spiral organ to brain
Helicotrema
at apex
Modiolus: Coils around bony pillar
Cochlear nerve,
division of the
vestibulocochlear
nerve (VIII)
Spiral ganglion
Osseous spiral lamina
Vestibular membrane
Cochlear duct
(scala media)
Figure 15.27c Anatomy of the cochlea.
Tectorial membrane
Inner hair cell
Hairs (stereocilia)
Afferent nerve
fibers
Outer hair cells
Supporting cells
Fibers of
cochlear
nerve
Basilar
membrane
© 2013 Pearson Education, Inc.
Figure 15.27d Anatomy of the cochlea.
Inner
hair
cell
Outer
hair
cell
© 2013 Pearson Education, Inc.
Simplified Auditory Pathways