Download Chapter 16 Lecture Outline A. gustation

Anatomy Lecture Notes
Chapter 16
Chapter 16 Lecture Outline
A. gustation - gustatory receptor cells are located in organs called taste buds
1. taste buds located in mucosa of mouth and pharynx
most are on the sides of fungiform and circumvallate papillae
2. taste buds made of epithelial cells
taste pores are openings in the surface of the epithelium
gustatory cells - receptor cells
supporting cells - separate gustatory cells from each other
basal cells - immature cells that replace the other cells
3. gustatory cells
have microvilli on apical surface, just inside taste pore
membrane covering microvilli contains receptors for sweet, salty, sour, bitter
and umami (glutamate)
gustatory cells synapse with sensory neurons at base of taste bud
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4. gustatory cells activated when molecules dissolved in saliva bind to membrane
receptors on microvilli
gustatory cell releases neurotransmitter, which initiates action potential in
sensory neuron
5. afferent pathways:
VII - facial anterior 2/3 of tongue
IX - glossopharyngeal posterior 1/3 of tongue
X - vagus epiglottis and pharynx
sensory neurons terminate in solitary nucleus in medulla oblongata
thalamus
gustatory cortex
B. olfaction - receptors located in olfactory epithelium
1. olfactory epithelium covers superior nasal conchae and superior nasal septum
2. olfactory epithelium contains
olfactory cells bipolar neuron receptors
supporting cells columnar e.
basal cells form new olfactory cells
3. olfactory cells
have apical dendrites that project to surface of mucosa
olfactory cilia project from surface of olfactory epithelium
the membrane of each olfactory cell covering the cilia contains one (out of
about a possible 1000) type of olfactory receptor
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the axons of the olfactory cells (cranial nerve I) project through the cribriform
plate of the ethmoid bone into the olfactory bulb
there they synapse with mitral cells in clusters called glomeruli
each glomerulus gathers all olfactory cells for the same olfactory receptor
convergence amplifies the signal
4. each odorant molecule combines with a unique set of olfactory cell membrane
receptors (signature)
5. afferent pathway for olfaction:
olfactory cells - axons form cranial nerve I; project to olfactory bulb
mitral cells - axons form olfactory tract; project to:
limbic system
olfactory cortex
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C. vision
1. eyelids / palpebrae = skin-covered folds
tarsal plates - c.t. attachment for orbicularis oculi
levator palpebrae superioris m. - roof of orbit to tarsal plate of upper eyelid
tarsal (Meibomian) glands - open onto margin of eyelid; secrete oil
ciliary glands - associated with eyelashes; sebaceous and sweat glands
palpebral fissure - space between eyelids
canthus (canthi) - medial and lateral corners of palpebral fissure
lacrimal caruncle - tissue in medial canthus
2. conjunctiva = mucous membrane lining eyelids and covering exposed sclera
palpebral conjunctiva - lines eyelids
ocular (bulbar) conjunctiva - covers sclera
conjunctival sac - space between eyelids and eyeball
3. lacrimal apparatus
a. lacrimal gland - in orbit superiorlateral to eyeblal
secretes tears (water, mucus, antibodies, lysozyme)
excretory ducts open under superior lateral eyelid
b. lacrimal puncta - 2 openings in lacrimal caruncle
puncta open into lacrimal canals (canaliculi)
canals open into lacrimal sac, drains by nasolacrimal duct into nasal cavity
under inferior choncha
4. eyeball - spherical sac made of 3 layers and filled with fluid
a. fibrous tunic (outermost) made of dense c.t.
sclera posterior 5/6; white; opaque anterior 1/6;
cornea clear, more curved, avascular
corneal epithelium - covers surface of cornea
corneal endothelium - lines inside of cornea; removes excess water
from cornea
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scleral venous sinus - vein at junction of cornea and sclera
b. vascular tunic
i. choroid - posterior to ciliary body, vascular, pigmented membrane
absorbs light
ii. ciliary body - posterior to iris, anterior to choroid
ciliary muscle – circular fibers, controls lens shape
ciliary processes - anchor suspensory ligaments (ciliary zonula)
iii. iris - anterior to ciliary body; between cornea and lens
opening in center = pupil
iris contains muscle fibers that control pupil diameter
sphincter inner circular fibers
constrict pupil
dilator
outer radial fibers
dilate pupil
color caused by brown melanin in pigmented epithelial cells
blue or gray - melanin is in posterior epithelial layer of iris only
green, hazel and brown - melanin is in the anterior muscular layer
and the posterior epithelial layer
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c. sensory tunic = retina
i. pigmented layer next to choroid.
made of a single layer of melanocytes
extends forward to cover the back of the ciliary body and the iris
absorbs excess light; helps photoreceptors maintain photopigments
ii. nervous layer inside
consists of 3 cell layers:
photoreceptor cells (rods and cones) - tips embedded in pigmented
layer, sensitive to light
bipolar cells - superficial to photoreceptors, connect photoreceptors to
ganglion cells
ganglion cells - surface of nervous layer; axons form cranial nerve II
(optic nerve)
anterior margin of nervous layer = ora serrata
macula lutea - spot in exact center of back of eyeball
fovea centralis - indentation in the macula lutea; contains only cones; maximal
visual acuity
optic disc = where II leaves eyeball; medial to macula lutea; lack of
photoreceptors causes blind spot
central artery and vein - enter/leave with optic nerve
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d. lens = biconvex transparent elastic disc
changes shape to focus images on retina
outside is an elastic capsule
inside the capsule on the front of the lens is a layer of lens epithelium
behind the lens epithelium are lens fibers, which are made by the peripheral
cells of the lens epithelium
the lens is avascular
its density increases with age and its elasticity decreases with age, preventing
focusing on near objects (presbyopia)
cataracts are clouding of the lens and are correlated with smoking, exposure to
UV radiation, and diarrhead. cavities and fluids
e. cavities and fluids
i. posterior segment
posterior to lens
filled with vitreous body (humor)
made mostly of collagen and water
holds retina in place
helps maintain intraocular pressure
ii. anterior segment
anterior to lens
subdivided into:
o anterior chamber - anterior to iris
o posterior chamber - posterior to iris
contains aqueous humor
o formed at ciliary processes in posterior chamber
o circulates through pupil to anterior chamber
o drains into scleral venous sinus
o maintains intraocular pressure
glaucoma - caused by increased intraocular pressure
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5. photoreceptors (rods and cones) = specialized neurons
outer segment = receptor region of cell
embedded in pigmented layer
plasma membrane contains visual pigment molecules that are sensitive
to light
plasma membrane folded inwards
increases surface area
folds form membrane-covered discs
rods
1 type
sensitive to entire visual spectrum
shades of gray
work in dim light only
low acuity (convergence of rods onto
bipolar cells)
concentrated around periphery of
retina
cones
3 types: red, blue, green
each sensitive to part of the visual
spectrum
color
work in bright light only
high acuity (no convergence)
concentrated in center of retina
6. afferent pathway
rods and cones
bipolar cells
ganglion cells
optic nerve
optic chiasma
optic tract
superior colliculus of midbrain
thalamus
primary visual cortex
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D. hearing and equilibrium
1. outer ear
a. auricle/pinna - funnels sound into ear canal
b. external auditory canal goes through external acoustic meatus
2.5 cm long, angled anteriorly
skin contains ceruminous glands, hair follicles, hair, sebaceous glands
c. tympanic membrane
made of 2 layers of collagen and elastin fibers
external surface covered by skin
internal surface covered by simple squamous or cuboidal e.
2. middle ear - inside petrous temporal bone
a. ossicles amplify sound vibrations (they form a "bridge" between the tympanic
membrane and the inner ear)
malleus attached to tympanic membrane
incus
stapes fits into oval window of inner ear
b. muscles adjust sensitivity of middle ear:
tensor tympani
(O) pharyngotympanic tube (I) tympanic membrane
increases tension of tympanic membrane, decreases vibration
stapedius
(O) posterior wall of middle ear cavity (I) stapes
limits movement of stapes
c. openings into inner ear:
oval window - where sound waves enter cochlea
round window - where sound waves leave cochlea
d. pharyngotympanic (auditory or Eustachian) tube
connects middle ear to nasopharynx
equalizes air pressure across eardrum
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3. inner ear
a. bony labyrinth = cavity inside temporal bone
filled with perilymph
3 subdivisions:
semicircular canals (posterior)
vestibule
cochlea (anterior)
b. membranous labyrinth = set of interconnected membrane tubes that are
suspended in the perilymph
filled with endolymph
3 subdivisions:
semicircular ducts
utricle and saccule
cochlear duct
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4. cochlea - hearing
a. overall structure
modiolus - pillar of bone in center of cochlea
spiral lamina - shelf of bone coiling around modiolus
scala vestibuli - filled with perilymph, oval window located at basal end
vesibular membrane divides scala vestibuli from cochlar duct/scala
media
scala media/cochlear duct - contains organ of Corti, filled with endolymph
basilar membrane - divides cochlar duct/scala media from scala vestibuli
scala tympani - filled with perilymph, round window located at basal end
scala vestibuli and scala tympani are continuous at the helicotrema
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b. organ of Corti
sits on basilar membrane
columnar supporting cells
cochlear "hair" cells
o on apical end they have microvilli (hairs) , also called stereocilia
o on basal end they synapse with sensory neurons that form the
cochlear branch of VIII
tectorial membrane - jelly-like flap that sits on hair cells
c. afferent pathway
cochlear hair cells
afferent neurons (1st order)
dendrites synapse with hair cells
cell body located in spiral ganglion
central processes form cochlear branch of VIII
terminate in cochlear nuclei in medulla oblongata
second order neurons go from cochlear nucleus to superior olivary nucleus
third order neurons go from medulla oblongata to inferior colliculus of
midbrain
fourth order neurons go from midbrain to thalamus
fifth order neurons go from thalamus to primary auditory cortex in temporal
lobe
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5. vestibule - between semicircular canals and cochlea
a. general structure
membranous labyrinth consists of
utricle - continuous with semicircular ducts
saccule - continuous with cochlear duct
b. each utricle and saccule contains a macula, a receptor organ for static body
position and linear acceleration
supporting cells
hair cells
o apical microvilli
o basal synapse with afferent neurons of the vestibular branch of VIII
otolithic membrane - jelly-like disc covering hair cells
otoliths - crystals of calcium carbonate embedded in surface of membrane;
"gravity amplifiers"
6. semicircular canals - 3 in each ear in 3 different planes
a. general structure
bony labyrinth located posterior and lateral to vestibule
o anterior
o posterior
o lateral
ampulla - enlargement at one end of each canal
membranous labyrinth consists of 3 semicircular ducts located inside the
canals (same names as bony labyrinth)
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b. at one end of each semicircular duct is a membranous ampulla containing
one crista ampullaris, a receptor organ for angular acceleration
supporting cells
hair cells
o apical microvilli
o basal synapse with afferent neurons of the vestibular branch of VIII
cupula - jelly-like flap covering apical microvilli of hair cells and extending
out into membranous ampulla
*the maculae and cristae are sometimes collectively called the vestibular
apparatus
c. afferent pathway for equilibrium
hair cells of maculae and cristae
first order neurons form vestibular branch of VIII and go from hair cells to
vestibular ganglia in the medulla oblongata
other subsequent neurons project to the brainstem and cerebellum
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