Overview of Eye Histology Tunica fibrosa (fibrous, supporting layer

Overview of Eye Histology



Tunica fibrosa (fibrous, supporting layer)
 Cornea (ant 1/6); Sclera (post 5/6)
Tunica vasculosa (uvea) (vascular layer)
 Ciliary body, Iris, Choroid
Tunica interna (retina) (retinal, neural layer)
 Neural retina; Retinal pigment epithelium
 Pars optica: ora serrata
 Pars ciliaries reinae; Pars iridica retinae
Histo: Eye Ear - 1
Cornea
Histo: Eye Ear - 2
Cornea: transparent, avascular,
refractive index = 1.376





Corneal epithelium:
noncornified, stra. Squ. Epi.;
thin basal lamina; nuclear
DNA-ferritin for UV protection
Bowman’s membrane:
collagen fibril; acellular
Substantia propria (stroma):
transparency, collagen fibrils in
orthogonal array, fibroblast
(CF), cornal proteoglycans
Descemet’s membrane: thick
basal lamina of endothelium
Endothelium: simple squ.;
metabolic exchange; limited
proliferation
Histo: Eye Ear - 3
Sclera (S); Choroid (C); Retina (R)
Histo: Eye Ear - 4
Sclera: dense fibroelastic tissue;
fibers parallel to eye surface
Episcleral tissue - loose vascular c.t. + conjunctiva
Sclera proper - dense network of collagen fibers
Suprachoroid lamina (fusca) - thin transitional layer to
choroid; elastic fibers, pigment cells
Sclera
Histo: Eye Ear - 5
1. Bruch’s membrane (lamina vitrea)- basement mem. of
pigment epi. (retina)
2. Choroid capillaries layer
3. Vascular layer (contains pigment cells and vessels)
2008/01/02
& Ear ff. & pigment
4. Suprachoroid
layer – collagen andEye
elastic
cells (melanoytes)
choroid
6
Histo: Eye Ear - 6
Ciliary body and iridocorneal angle


Ciliary body: forward continuation of choroid,
highly vascular, with abundant melanins
Ciliary (smooth) muscles of 3 functional groups:
meridional (longiudinal), radial (oblique),
circular (sphincteric)
Histo: Eye Ear - 7
Ciliary process




Branching epithelial folds with c.t.
core (C), fenestrated capillaries,
producing
 aqueous humor: refractive
index of 1.33
Double cuboid epi. (E)
 Non-pigmented: superficial
 Pigmented: deep
Suspensory ligaments (S, ciliary
zonule)
M: smooth muscles of ciliary body;
PC: posterior chamber
Histo: Eye Ear - 8
Iris



Anterior (facing cornea): fibroblast & stromal melanocyte;
endothelium (in fetus)
General stroma: loose, highly vascular c.t., chromophores; smooth
muscles (sphincter & dilator pupillae)
Posterior (facing lens): 2 layers of pigment epithelium continuous
from ciliary process (ant. pig. epi.; post. pig. epi.); myoepithelial cell,
(dilator pupillae)
Histo: Eye Ear -
9
Circulation of Aqueous humor
 Ciliary
process: production
 Posterior chamber
 Anterior chamber
 collagenous endothelium-lined
Trabecular meshwork (T; space
of Fontana): endothelium-lined
 Canal of Schlemm (CS):
endothelium-lined
 Episcleral venous system in
sclera
 Glaucoma: Increased
intraocular pressure (IOP)
I: root of iris; C: cornea
Histo: Eye Ear - 10





10: inner limiting mem.: basal lamina
of Muller cells
9: optic nerve fiber: axons of retina
ganglia neurons
8: ganglia cell layer: cell bodies of
retina ganglia neurons
7: inner plexiform layer: synaptic
connections between dendrites of
retina ganglia neurons and axons of
bipolar neurons
6: inner nuclear layer: nuclei of
interneurons (horizontal, amarcrine,
bipolar et al.) and Muller cells
Muller cell
Retinal organization: photoreceptors,
interneurons, retinal ganglia neurons,
retinal pigment epithelium
Histo: Eye Ear - 11





5: outer plexiform layer: processes
of photoreceptors and interneurons
4: outer nuclear layer: nuclei of
photoreceptors
3: outer limiting mem.: zonulae
adherentes between Muller cells
2: photoreceptor layer: rods and
cones with organelles
1: retina pigment epithelium:
junctional complexes and gap
junctions on Bruch’s mem. of
choroid; blood-retina barrier
Muller cell
Retinal organization: photoreceptors,
interneurons, retinal ganglia neurons,
retinal pigment epithelium
Histo: Eye Ear - 12
Retina: Muller cell (glia)


inner limiting mem.
outer limiting mem.
Histo: Eye Ear - 13
Photoreceptor: rod, cone




Rod for low light intensity;
cone for color, high light
intensity
Outer segment:
photoreceptor proper
Connecting stalk: cilium
(9 microtubule doublets),
calyceal process
Inner segment: with
organelles, microtubules
 outer (ellipsoid):
mitochondria
 inner (myoid): Golgi,
rER, free ribosomes
calyceal process
M: outer limiting mem.; P: pigment epi.
B: Bruch’s mem.
Histo: Eye Ear - 14
Discs in rods and cones


regularly spaced horizontal discs from transverse infoldings of plasma
membranes in outer segment near cilium
shed and phagocytosed by retina pigment epithelium (phagosome)
rod
cone
cone
rod
Histo: Eye Ear - 15
Retina pigment epithelium: basally-located nucleus;
mitochondria, melanin granule; microvilli
Histo: Eye Ear - 16
Optic papilla (optic disc; blind spot)
Optic disc (optic papilla)
 Optic
nerve: axons of
retina ganglia neurons
 accompanying central
retinal artery and vein
 no photoreceptors in
optic disc (blind spot)
 Traversing sclera (lamina
cribrosa, cribriform plate)
 Sclera: equivalent to
dura
 Uvea tract: equivalent
to pia-arachnoid
Histo: Eye Ear - 17
Fovea centralis (FC)




retina of conical depression;
4 mm lateral to optic disc;
surrounded by 1 mm-wide
macula lutea
only closely packed cones
(100,000 cones); 1-to-1 ratio
of cones to bipolar neurons
maximal photosensitivity: on
the visual axis with least
refractory distortion; reduced
inner layers of retina;
absence of retina vessels
Macular degeneration: loss
of visual acuity
Histo: Eye Ear - 18
Lens



Lens capsule: basal lamina, produced by anterior lens cells (type IV
collagen, proteoglycans); connected to suspensory lig.
Subcapsular epithelium: a cuboid layer, only on anterior surface of
lens; with gap junctions
Lens fibers: derived from subcapsular epithelium
 lose nuclei & organelles; filled with crystalins
 Refractive index of 1.38~1.5
Histo: Eye Ear - 19
Vitreous body


Homogenous gel:
 99% water (vitreous humor)
bound to hyaliuronic acid
 some hyalocytes (round or
fusiform) for collagen,
glycosaminolycans
(hyaluronan)
 Colorless, refractive index of
1.334
Hyaloid (Cloquet’s) canal:
remnant of hyaloid artery (at
center of vitreous body from
optic disc to post. lens capsule)
Histo: Eye Ear - 20
 tarsal
plate: dense c.t.;
superior tarsal muscle of
Muller
 tarsal sebaceous
(Meibomian) gland: 25
(upper), 20 (lower); oily
layer on tear film
 accessory lacrimal gland
of Wolfring
 apocrine glands of
eyelashes (glands of Moll)
 all gland secretion:
synchronized with lacrimal
glands via vasoactive
intestinal peptide (VIP)
Eyelid: hairy skin + orbicularis
oculi + palpebral conjunctiva
Histo: Eye Ear - 21
Eyelid, Tarsal plate, Meibomian gland: Histology
Histo: Eye Ear - 22
Conjunctiva
 Stratified columnar epi., goblet cells
 Loose vascularized c.t.
 (melanocyte at basal layer)
Histo: Eye Ear - 23
Lacrimal glands
 compound
tubulo-acinar
serous gland
 similar to parotid gland
 tear film: proteins (tear
albumins, lactoferrin),
enzymes (lysozyme), lipids,
metabolites, electrolytes,
drugs during therapy
Histo: Eye Ear - 24
Review: Eye


Muller cell

Histological and Gross
correlations: tunica
 fibrosa: cornea, sclera
 vasculosa: choroid, ciliary,
iris
 neural retina, retina
pigment epithelium (RPE)
Retina
 Cells: photoreceptors,
neurons (ganglia,
interneurons), retina
pigment epithelium, Muller
cell
 Organization: 10 layers
 Optic disc, Fovea
Glands: lacrimal, tarsal
Histo: Eye Ear - 25
Ear



Ext. ear: ext. acoustic meatus
Mid. ear: auditary ossicles, Eustachian
(auditory) tube
Inn. ear: cochlear, vestibular apparatus
Histo: Eye Ear - 26






TM: tympanic mem.
LSC: lateral
semicircular canal
AC: mastoid air
cells
V: vestibule
C: cochlea
arrowhead: oval
window
Histo: Eye Ear - 27
External acoustic meatus (Skin)


Cartilage (ext. 3/1) and inside temporal bone (inner 2/3)
Hair follicles (F), Sebaceous gland, Ceruminous (apocrine) gland
Histo: Eye Ear - 28
Tympanic membrane



Outer: stratified squamous epi. (SSE)
Connective tissue (CT)
Inner: simple cuboid epi. (SCE)
Histo: Eye Ear - 29
Eustachian (auditory) tube: bony and cartilaginous parts



Simple columnar epi. near tympanic cavity
Pseudostratified columnar epi. with goblet cells near pharynx
Submucosa: mixed galnds
Histo: Eye Ear - 30
Inner ear: Labyrinth


Bony labyrinth
 Vestibule, Cochlea
Membranous labyrinth: with
endolymph inside (perilymph
outside)
 Vestibular labyrinth (Utricle,
Saccule, Semicircular duct)
 Cochlear duct
Histo: Eye Ear - 31
Sensory organs of
Vestibular mem. labyrinth


Mucula in Utricle and Saccule
 Hair cells: Single kinocilium;
bundle of stereocilia
type I (goblet)
type II (columnar)
 Supportive cells
 Otolith membrane (otoliths):
otoconia
Crista amuplualris in ampular
parts of semicircular ducts
 Hair cells (type I goblet & type
II columnar), Supportive cells
 Cupula: without otoliths
Histo: Eye Ear - 32
Macula: overview
Histo: Eye Ear - 33
Macula: Histology
 Hair
cells: type I (goblet);
type II (columnar)
 Kinocilium; Stereocilia
 Supportive cells
 Otoliths
Histo: Eye Ear - 34
Crista ampularis in
Semicircular duct




Hair cells
 Type I; Type II
Cupula: gelatinous proteinpolysaccharide complex
No otoliths
exposed to endolymph
Histo: Eye Ear - 35
Crista ampularis
(CA): Histology
 Cu:
cupula
 EP: epithelium
 HC: hair cell
 SC:
supportive cell
 CT:
connective
tissue
Histo: Eye Ear - 36
Vestibular sensory
hair cells
 Hair
cells as
mechanoelectric
transducer
 Kinocilium with basal
body
 Steroecila (hair bundle)
 Actin filaments
 Cross-linked by fimbrin
and espin (actinbundling proteins)
 anchored to terminal
web (cuticular plate)
Histo: Eye Ear - 37
Plaque
Kinocilium and Stereocilia
 Mechanoelectric
transducer
channel protein at tip of plasma
membrane of stereocilia
(electron-dense plaque)
 tip link: tip of stereocilium with
adjacent shaft of longer
stereocilium (transduction K+
channels are located)
 Kinocilium: cilium (microtubules)
 Stereocilia: microfilaments
(actins)
Histo: Eye Ear - 38
Tip link in Stereocilia


Tip link: mechanoelectric
transduction (MET) channel
proteins at the tip of
stereocilium associated with
adjacent shaft of longer
stereocilium (transduction
K+ channels are located)
Activated by deflection
toward kinocolium, influx of
K+ (endolymph: rich in K+);
activation of Ca++ channels
to release neurotransmitters
Histo: Eye Ear - 39
Mechanoelectric transduction:
Displacement of stereocilia and
Activation of vestibular sensory neurons
Histo: Eye Ear - 40
Cochlea and cochlear
duct (labyrinth)


Cochlea (bony labyrinth): 2 and ¾
turns
 Modiolus (central axis)
 Helicotrema
Cochlear duct (mem. labyrinth)
 Scala vestibule (SV): perilymph
 Vestibular membrane
(Reissner’s membrane)
 Scala media (SM, cochlear
duct): endolymph
 Basilar membrane
 Scala typamni (ST): perilymph
 Spiral ganglia (SG)
 Frequency-position: Low in
apex; High in basal turn
Histo: Eye Ear - 41
Vestibular (Resissner’s) membrane: EM
 Mesothelium:
facing peilymph of
scala vestibular
 Epithelium facing endolymph of
scala media
Histo: Eye Ear - 42
Endolymph
Organ of Corti on
Basilar membrane (BM)
Osseous spiral lamina (O)
Spiral limbus (SL)
Spiral ganglia (G), nerve (N)
Stria vascularis (SVasc)
Spiral igaments (SLig) on
endosteum
Histo: Eye Ear - 43
Organ of Corti: Sensory organ of cochlear duct (labyrinth)



Hair cells: Inner (close to spiral lamina): single row; Outer (farther
from spiral lamina): 3 ranks in basal coil; 5 ranks in apex
Tectorial mem.: from spiral limbus to organ of Corti by stereocilia
of hair cells; radially oriented bundles of collagens embedded in
glycoprotein matrix
Phalangeal (supporing) cells: inner and outer; Pillar cells et al.
Histo: Eye Ear - 44
Hair cells of organ of Corti



Stereocilia in hair cells of
organ of Corti;
1 inner row; 3 outer rows
Apical cuticular plate (ACP)
of phalangeal cells
Histo: Eye Ear - 45
Organ of Corti: hair cells


Hair bundle (stereocilia)
No cilium (kinocilium), basal body retains
Inner hair cell
Outer hair cell
Histo: Eye Ear - 46
Sound perception:
mechanoelectric transduction

sound wave → stapes → oval
window → scala vestibuli →
 scala media → basilar mem.
(organ of Corti, stereocilia of
hair cells) and tectorial mem.
 scala tympani → round window
Histo: Eye Ear - 47
Membranous labyrinth
Histo: Eye Ear - 48
Review: Membranous
labyrinths
Vestibule
Cochlea
Utricle
Saccule
Semicircular duct
Cochlear duct
Macula
Macula
Crista ampularis
Organ of Corti
Otolith mem
(otoconia)
Otolith mem
(otoconia)
Cupula
Tectorial membrane
Angular movements
Sound perception
Linear movements
Vestibular ganglia (of Scarpa), near int. acoustic meatus
Spiral ganglia, modiolus
Histo: Eye Ear - 49