Organ of Senses.ppt

8/11/2019 Organ of Senses.ppt

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Senses

Histology Department

Medical Faculty

University of Sumatera Utara

2008


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References:

Noback CR. The Human Nervous System. Tokyo. McGraw Hill.1967

Gartner LP. Hiat JL. Color Textbook of Histology. 2nded.Philadelphia. W.B. Saunders. 2001

Mulvaney BD. Chemography of lysosome-like structures in

olfactory epithelium. Jcb 1971;51:568-75 Marfurt CF, Kingsley RE, Echtenkamp SE. Sensory and

sympathetic of the mammalian cornea: A retrograde tracingstudy. Invest. Opt. Vis. Sci.1989:30(3);461-72

Los LI, van der Worp RJ, van Luyn MJA, Hooymans JMM.Presence of collagen IV in the cilliary zonules of the human eye:

An immunohistochemical studies by LM and TEM. jhc2004:52(6);789-95


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General Terms

Peripheral nerve terminals are of two

types:

Terminal of axons w/ transmit impulses from

CNS to effectors (efferent)

Terminal of dendrites w/ perceive stimuli and

transmit to CNS (afferent), called receptor

(sensory endings) recognizes a stimulus, then

change the stimulus into impulses.


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Senses can be: General afferent

Pain, touch, visceral senses, and thermal appreciation

Result in unconscious reflexes

Special afferent Associated with highly specialized senses

Smell, sight, hearing, taste

Located in the head

Are conveyed by cranial nerves

Somatic refers to the body wall and limbs;visceral refers to the vital organ systems(circulatory, digestive, respiratory, and excretory systems)


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Receptor Classification

Depending on the source of the stimulus Exteroceptor

General somatic afferent

Special somatic afferent: vision and hearing

Special visceral afferent: smell and taste

Proprioceptor (kinesthetic, deep sensibilities) General somatic afferent: intrafusal fibers

Special somatic afferent: equilibrium (ear)

Interoceptor (visceral senses) General visceral afferent: visceral organ

Depending dendrite response to a particular stimulus Mechanoreceptor

Thermoreceptor

Nociceptor


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Mechanoreceptor

Stimulated by anything moving or physical perturbation.

Classification tactile receptors- touch, pressure, vibration

i. encapsulated receptors

a) Meissners corpuscles- fine touch

b) Pacinian corpuscles- deep pressure

c) Ruffini corpuscles- tension, crude touch

ii. unencapsulated receptors

a) free nerve endings- pain

b) Merkels discs- fine touch

c) root hair plexes- hair movement baroreceptorsare sensitive to internal pressures such as blood

pressure, lung stretch, digestive tract tension

proprioceptorsare kinesthetic monitors of tendon muscle stretch.


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Thermoreceptor and Nociceptor

thermoreceptors- detect heat or absencethereof, phasic, same pathways as pain

nociceptorstimulation results in pain.Heat,mechanical stress and chemicals can all

cause pain by stimulating different classes ofreceptors.a. fast pain- deep cuts, etc. - referred immediately to

primary sensory cortex, usually trigger reflexes

b. slow pain- later, persistent, indistinct source,thalamic

c. referred pain- visceral, "incorrect" sourceperceived


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Special Sense

1. Taste

2. Olfaction (smell)

3. Vision4. Equilibrium and Hearing ear


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Olfaction


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Olfaction

on the susperior aspect of the nasal septum

Mucosa: epithelium and lamina propria Olfactory epithelium comprises 3 types of cells:

Olfactory cells

Sustentacular cells Basal cells

Lamina propria houses Serous fluid-secreting Bowmans gland

A rich vascular plexus

Loose to dense collagens Lymphoid elements

Collection of axons of olfactory cells

is firmly attached to the underlying periosteum


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Olfactory cells

Bipolar neurons

Dendrite Apical aspect of olfactory cell

Distal terminus is modified to form olfactory vesicle

6-8 long nonmotile cilia extend from olfactory vesicle to free surface

Unusual axoneme pattern (9+2 config) doublets to nine singlets + 2central singlets

Nucleus Spherical

closer to basal lamina than to olfactory vesicle

Organeles: surrounding nucleus

Axons Unmyelinated, has a sheath of Schwan cell

Basal region, penetrates the basal lamina and joins similar axons toform bundles of nerve fiber. The nerve fibers pass through thecribrom plate to synapse w/ secondary neurons in the olfactory bulb


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Olfactory cell Sustentacular cell


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EM of Olfactory cell


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Sustentacular Cells

5060 m tall columnar cells

Apical aspect: striated border microvilli; terminal web

Secretory granules housing yellow pigment

Nuclei: Oval; in apical third of the cell, somewhat superficial to

olfactory cell nuclei

Lateral: junctional complexes Olfactory vesicles of olfactory cells

Contiguous sustentacular cells

Function: provide physical support, nourishment, andelectrical insulation for the olfactory cells


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Basal Cells

Short, basophilic, pyramid shaped cells

whose apical aspects donot reach the

epithelial surface

Nuclei: centrally located, occupy basal

third of the epithelium

Proliferative capacity and can replace

both sustentacular and olfactory cell

stem cells


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Lamina Propria

Is composed of :

richly vascularized, loose to dense, irregular

collagenous connective tissue

lymphoid elements

collection of axons of the olfactory cells

Bowman glands

Is firmly attached to the underlyingperiosteum


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Eye Anatomy - Internal and External

External (Accesory) Eyelids (palpebrae)

Conjunctiva (mucousmembrane) Glands and ducts

Internal

Orb! 3 Tunics

Fibrous: Cornea andSclera

Vascular: Choroid,Ciliary body, and Iris

Sensory: Retina(pigmented and neurallayers)


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Eye

Photosensory organs of the body

Light passes through the cornea, lens, and severalrefractory structures of the orb; light is then focused bythe lens on the retina, which contains the

photosensitive rods and cones. Through a series ofseveral layers of nerve cells and supporting cells, thevisual information is transmitted by the optic nerve tothe brain for processing.

The bulb of the eye is composed: A fibrous tunic, forming the tough outer coat

A vascular tunic, the pigmented and vascular midle coat

A neural tunic (retina), the innermost coat
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Special Senses: VisionGeneral Anatomy

Fibrous Tunic

Vascular Tunic

Sensory Tunic
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Tunica Fibrosa

Tunica fibrosa is composed of the sclera

and cornea

The white, opaque sclera covers the

posterior five sixth of the orb

Colorless, transparent cornea covers the

anterior one sixth of the orb.


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Sclera

A tough fibrous connective tissue + 1 mm thick posteriorly, thinning at the equator, thickening near its

junctions with the cornea

Consists of interlacing type I collagenbundles alternating withnetworks of elasticfibers

Nearly devoid of blood vessels

Cells: Fibroblast and melanocytes Tendons of the extraocular insert into the surface layer of the

sclera, which is enveloped by the capsule of Tenon

capsule of Tenon A fascial sheath that covers the optic nerve and the orb as far

anteriorly as the ciliary region

Separates the orb from the periorbital fat

Episclera: a thin layer of loose connective tissue that is connectedto capsula Tenon


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Cornea

Transparent, avascular, and highly innervatedanterior portion of the fibrous tunic that bulgesout anteriorly of the orb

Thicker than sclera Five layers:

Corneal epithelium

Bowmans membrane

Stroma Descemets membrane

Corneal endothelium


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Corneal epithelium

Stratified squamous nonkeratinized ep 57 layers of cells

Larger superficial cells have microvilli and exhibit zonulaeoccludentes

Interdigitation; junctions: desmosome

Have usual array of organelles and intermediate filaments

Mitotic figures: mostly near the periphery of the cornea Turn over rate: 7 days

Cells can migrate to injured regions

Functions: Covers the anterior surface of the cornea

Transferring water and ions from the stroma into conjunctival sac Innervated by numeous free nerve endings

Sensory nerve fibers from trigeminal ganglion

Sympathetic nerve fibers from superior cervical ganglio


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Bowmans membrane

Lies immediately deep to the corneal

epithelium

Fibrillar lamina, composed of type I collagen

fibers arranged in random fashion Synthesized by corneal epithelium and stroma

Sensory nerve fibers pass bowmans

membrane to enter and terminate in theepithelium


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Stroma

The thickest layer of the cornea (90%) Transparent

Composed of collagen (mostly type I) that are arranged in 200250 lamella in

parallel to one another

Thin elastic fibers, interspersed with collagen fibers

Ground substances: (mostly) chondroitin sulfate and keratansulfate

Cells: Fibroblasts

Lymphocytes and neutrophil (inflammation condition)

Limbus Trabecular meshwork

Canal of schlemm


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Descemets membrane

Thick basement membrane interposed

between the stroma and endothelium

Thin and homogenous in younger

becomes thicker and has cross-striations

and hexagonal fiber patterns in older

adults


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Corneal endothelium

Posterior surface of the cornea

Simple squamous epithelium

Exhibit numerous pinocytotic vesicles

Their membrane have sodium pumps

Functions:

Responsible for protein synthesis necessary for

secreting and maintaining Descemets membrane Keeping relatively dehydrated maintaining the

corneal refractive quality


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Tunica Vasculosa

Middle tunic of the eye

Is composed of:

Choroid

Ciliary body

iris


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Choroid

Well vascularized, pigmented layer of the posterior wall Is composed of loose connective tissue

The black color is due to the myriad of melanocytes

Small blood vessels in the inner surface of choroid,choriocapillary layer, are responsible providing nutrients to theretina

The choroid is separated from retina by Bruchs membrane 14 m thick membrane composed of elastic fibers in the central

region and sandwhiched on both sides by collagen fibers.

The outer aspect of each collagen fiber layer is covered by basallamina that belongs to capillaries on one side and the pigmentepithelium of the retina on the other side


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Ciliary Body

Wedge-shaped extension o/t choroid: rings the inner wall o/t eye a/t level o/t lens

Occupies the space between the ora serrata o/tretina and the iris

Surface Sclera: sclerocorneal junction

Vitreous body

Medial surface projects toward lens: ciliary process

Is composed of loose connective tissuecontaining elastic fibers, blood vessels, andmelanocytes


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Ciliary body

Inner surface is lined by pars ciliaris o/t retina that is composed of2 cell layers: Outer cell layer, w/ faces the lumen o/t orb, is a nonpigmented

columnar epithelium

Inner cell layer is a pigmented simple columnar epithelium

Ciliary process Anterior one third o/t ciliary body Radiate out f/ central core of connective tissue containing fenestrated

capillaries

Are covered by the same epithelias as ciliary body Nonpigmented layer has many interdigitations and infolding forming

aqueous humor that provides nutrients and oxygen for lens n cornea

Fiber of Zonula fibers radiate f/ ciliary process to insert into lenscapsule suspensory ligaments o/t lens and macromolecul barrier


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of Aqueous Humor** Flow of Aqueous Humor


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Ciliary Body

Bulk o/t ciliary body is composed of 3 bundles

of smooth muscle (ciliary muscle)

1 bundles stretches the choroid altering the

canal schlemm for drainage o/t aqueous humor

2 bundles

Attached a/t scleral spur

Contraction is mediaterd CN III stretch the choroid body

Reducing tensions o/t zonulae lens become thicker

and more convex accomodation


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Iris

The anteriormost extension o/t choroid, lies between posterior and anterior chamber; covering

the lens excep pupil Anterior surface

consists of 2 concentric rings:

Pupillary zone

Ciliary zone; wider

Is irregular

Is covered by incomplete layer of pigmented cells and fibroblast

Stroma:

Poorly vascularized

Loose connective tissue: fibroblast and melanocytes

Posterior surface:

Smooth; covered by two layers of retinal epithelium

Heavily pigmented block the light from passing through the iris except pupil

Muscle

Dilator pupillae; myoepithelial in nature, extension of epithelial cells, innervated by

sympathetic nerve, dilates the pupil Sphincter pupillae muscle; smooth muscle, alter diameter of pupil, innervated by CN III

(parasympathetic nerve), constricts the pupil

Melanocytes

block the light from passing through the iris except pupil

Imparts the eye color

High dark

Low blue


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Lens

Flexible, biconvex, transparent disc consist of lens capsule, subcapsularepithelium, and lens fiber

Lens capsule Basal lamina

Type IV collagen + glycoprotein

Covers the epithelial and envelops the entire lens

Subcapsular epithelium

Only on the anterior surface Single layer of cuboidal cells but becoming columnar in the vicinity o/t equator;

communicate each other via gap juntions, interdigitation

Apices of the cells interdigitate with lens fibers

Lens fiber 2000 long cells

Compose the bulk o/t lens

The cells of subcapsular epithelium give rise to highly differentiated andhexagonal cells (lens fiber) which lose nuclei and organelles and continueelongating; a process called maturation

Hexagonal cells are filled with crystallin, lensprotein, increase the refractoryindex


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Vitreous Body

Transparent, refractive gel that fills thevitreous cavity behind the lens

Is composed of water (99%), electrolytes,collagen fibers, hyaluronic acid

Cells: macrophages and hyalocytes at theperiphery o/t vitreous body

Hyaloid canal

Narrow channel that was occupied by the hyaloidartery in the fetus

From the posterior lens to optic disk


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Neural Tunic (Retina)

Innermost tunic; neural portion; contain

photoreceptor cells (rods and cones)

Is composed of 10 distinct layer

Optic disk

On the posterior wall o/t orb

Is the exit site o/t optic nerve

Contains no photoreceptor cells blind

spot


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N l T i (R ti )


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Neural Tunic (Retina)

Macula lutea (Yellow spot)

2.5 mm lateral to optic disk

Fovea centralis:

An oval depression in the center of yellow spot

Greatest of visual acuity

Contains only cones which are packed tightly as

the other layers o/t retina are pushed aside


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Pi t E ith li (RPE)


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Pigment Epithelium (RPE)

Cuboidal to columnar cells; basal nuclei Basal

are attached to Bruchs membrane

Mitochondria; invaginations transport

Lateral Blood-retina barrier

Apical Microvilli and sleeve-like structures that surround and isolate the photoreceptor Abundance Melanin granules

Residual bodies

Functions Blood-retina barrier

Absorb light

Preventing reflection from the tunics

Phagocytose spent membranous Esterifying vit A derivatives


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R d d C


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Rods and Cones

Rods

Activated in dim light only

Elongated cells oriented parallel to one

another but perpendicular to the retinaAre composed of outer an segment, an

inner segment, a nuclear region, a synaptic

region


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Outer segment o/t rod

Dendritic end; longer in rods th/ in cones

Flattened membranous lamellae oriented

perpendicular to its long axis

Each lamella represents an invaginations o/t

plasmalemma

Detachment of plasmalemma form a disk

Disk is composed of 2 membranes containing rhodopsin

Disk migrate to apical end and shed into the sheaths o/t

pigment cells and theyll be phagocytosed


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Inner segment o/t rod

separated f/ outer segment by connecting

stalk

Abundant mitochondria and cytoplasmicgranules necessary for production

energy for visual process

Protein produced in the inner segment

migrate to outer segment


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Figure A. Drawing of a conephotoreceptor, a bipolar cell, and aganglion cell showing their relativepositions in the retina, which generate the"layers" of the retina shown in Figures Band C. From the top down, structures are:OS, cone outer segment; E, ellipsoid; N,nucleus of cone photoreceptor; A, axon ofcone; S1, synapse between cone and

bipolar cell; DB, dendrite of bipolar cell;NB, nucleus of bipolar cell; AB, axon ofbipolar cell; S2, synapse between bipolarand ganglion cell; NG, nucleus of ganglioncell; AG, axon of ganglion cell. 1,000 X

Figures B and C. Matched pair of l ightand electron m icrogr aphs of the ret inaof the macaque. A, axon of c one; Ch,choro id; E, el l ipsoid; INL, inner nuc learlayer; IPL, inner plexifo rm lay er; LGC,layer of gangl ion cel ls; LRC, layer ofrods and c ones; N, nucleus of c one;NFL, nerve fiber layer; ONL, outernuclear layer; OPL, outer plexi formlayer; PE, pigm ent epithel ium; arrow ,ligh t path thro ugh retina. 1,000 X


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Figure A. Electron micrograph oflongitudinal section throughphotoreceptors of the monkey retina. A,axon of cone; C, cone photoreceptor; E,ellipsoid; IS, inner segment of cone; N,nucleus of cone; OPL, outer plexiformlayer; OS, outer segment of cone; R, rodphotoreceptor; RN, nucleus of rod; ROS,rod outer segment; arrow, direction of lightpassing through retina. 2,700 X

Figure B. Electron micro graph ofchoro id, pigment epithel ium, and dis ta lport ion of pho toreceptors of themon key ret ina. Ca, capi l lary in cho roid;M, melanocyte in c horoid; PE, pigmentepithelium ; ROS, rod o uter segm ent,,arrow, direct ion of l ight passingthrough ret ina; arrowh ead, residualbody in pigm ent epithel ium con tain ing

remains of phagocytos ed tip of rodouter segm ent. 5,700 X

How does light travel through the


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g g

eye?


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Pathway of light

Pathway ofexcitation

Action potentialgenerated at

ganglion cell layer.

Cones


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Cones

Are activated in bright light

Elongated cells

3 types of cones; different variety of iodopsin

sensitivity to red, green, and blue The structure is similar to that of rods with a

few exceptions: outer segments, the disk,

protein location in outer segment, sensitivity to

light and color, and pigment recycling.


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External (outer) limiting membrane A region of zonulae adherens between Muller cells and

photoreceptors

Outer nuclear layer Occupied by nuclei o/t rods and cones

Outer plexiform layer Axodendritic synapses btw photoreceptor cells and dendrites

of bipolar and horizontal cells

Two types of synapses: Flat

Invaginated: triad a dendrite of a bipolar cells and a dendritefrom each of two horizontal cells

Ribbon-like lamellae (synaptic ribbon)

neurotransmitter


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Inner Nuclear layer Occupied by nuclei of bipolar, horizontal, amacrine, and

Muller cells

Inner plexiform layer The processes of amacrine, bipolar, and ganglion cells

Axodendritic synapses Axons of bipolar cells and dendrites of ganglion cells and

amacrine cells

Two types of synapses: flat and invaginated Dyad: axon of bipolar cell and two dendrites of either amacrine cells

or ganglion cells or one dendrite from each two different cells

Synapted ribbon

Ganglion cell layer Cell bodies of ganglion cells


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Optic nerve fiber layer

Unmyelinated axons of ganglion cells

Inner limiting membrane

Basal lamina o/t Muller cells

Accesory Structure o/t eye


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Conjuctiva

A transparent mucous membrane palpebral conjunctiva: lines the inner surface o/t

eyelids

Bulbar conjunctiva: covers the sclera

is composed of a stratified columnar ep that contains goblet cells

Basal lamina

Lamina propria composed of loose connective tissue

Secretions o/t goblet cells is a part of tear film

continues as stratified squamous corneal ep atcorneoscleral junction and is devoid of gobletcells

Eyelid conjunctiva


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Eyelid conjunctiva

Eyelids


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Eyelids

Fold of skins Are supported by a framework of tarsal plate

The margin contain eyelashes arranged in rows of 3 or4 w/out arrector pilli muscle

External surface: str squamous ep of skin Sweat glands, fine hairs, and sebaceous glands of skin

Glands of Moll (modified sweat glands) form a spiral beforeopening into the eyelash follicles

Modified sebaceous glands Meibomian glands located in the tarsus of each lid and open on

the free edge of the lids

Glands of Zeis are associated w/ eyelashes and secretetheirproduct into eyelash follicles

Internal surface: palpebral conjunctiva

Eyelid


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Eyelid

Lacrimal apparatus


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Lacrimal apparatus

Lacrimal gland secretes tears

Serous, tubuloalveolar gland

Myoepithelial cells surround acini

Lacrimal canaliculi Lacrimal canaliculi join into a common conduit to lacrimal sac

Stratified squamous ep. Lacrimal sac

Is a dilated superior portion of nasolacrimal duct

Pseudostratified ciliated columnar ep

Nasolacrimal duct

Inferior continuation o/t lacrimal sac Pseudostratified ciliated columnar ep

Carries the lacrimal fluid into inferior meatus located in the floor ofnasal cavity

Organ of Senses.ppt

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