Histology of the Eye and Ear Flashcards
Special sebaceous glands whose secretion retards evaporation of tears
Tarsal (meibomian) glands
Blockage of Tarsal (Meibomian) glands leads to _______, or inflammation of the gland
Chalazion
Infections of these glands causes a “stye”
Sebaceous (Zeis) gland of eyelashes
Gland that produces tears; located beneath the conjunctiva
Lacrimal gland
The lacrimal gland is made up of ____ ____ glands; approximately 12 ducts empty beneath the upper lid; drains into ______ duct
Tubuloacinar serous
Nasolacrimal
2 types of conjunctiva lining the space between the inner eyelid and ending just lateral to the cornea
Palpebral conjunctiva
Bulbar conjunctiva
The palpebral and bulbar conjunctiva are made up of thin mucous membrane with _____________ epithelium + _____ cells
Stratified columnar; goblet
Development of the eye begins with evagination of _______ from the forebrain, forming the _____ _____
Neuroectoderm; optic vesicles
Invagination of the optic vesicle forms the ____ _____, connected to the forebrain by an ____ ____
Optic cup; optic stalk
Optic vesicles induce overlying ______, forming a lens vesicle located within the cup
Ectoderm
The inner layer of the optic cup forms the ____ _____
The outer layer of the optic cup forms the ____ ____ ____
Neural retina
Retinal pigmented epithelium
The inner layer of the optic cup forms the neural retina while the outer layer forms the retinal pigmented epithelium. What 3 things does the outer mesenchyme form?
Choroid
Sclera
Cornea
What is formed by the rim of the optic cup
Iris
Ciliary body
Ectoderm overlying the lens vesicle forms the lid and ______ ____ ____
Outer corneal epithelium
During eye development, blood vessels enter via a groove called the ___ ___
Optic fissure
What is the site where detached retina occurs?
Inner/outer optic cup layers
3 basic layers of the eye from outer to inner
Corneosclera
Vascular coat (uvea)
Retina
The corneoscleral layer of the eye is the outer fibrous coat, and is penetrated by the _____ n.
It consists of the sclera and retina
Optic
Composition of the sclera
Dense CT
What part of the corneoscleral layer of the eye do extrinsic mm attach to?
Sclera
The anterior surface of the cornea is transparent and continuous with the _____
Sclera
3 components of the vascular coat (Uvea) layer of the eye
Choroid
Stroma of ciliary body
Stroma of iris
Describe function of choroid contained in vascular coat (uvea) layer of the eye
Heavily pigmented; absorbs scattered light
Rich blood vessels lined with fenestrated capillaries for providing nutrients to retina
Well-attached to retina
Which part of the vascular coat (uvea) of the eye contains the ciliary mm responsible for accommodation?
Stroma of ciliary body
Function of stroma of iris (part of vascular coat/uvea layer of eye)
Contractile diaphragm where pupil is central aperture
The inner coat of the eye is the retina, which rests on the _____
Choroid
3 components of the retina layer of the eye
Epithelium of ciliary body and iris
Neural retina
Retinal pigmented epithelium (RPE)
Function of neural retina
Contains photoreceptors and support cells
4 primary functions of retinal pigmented epithelium (RPE) in retina layer of eye
Absorbs light
Prevents reflections
Major component of blood-retinal barrier
Phagocytosis
3 chambers of the eye
Anterior chamber
Posterior chamber
Vitreous (body) chamber
The anterior chamber of the eye is the space between the ____ and ____
Cornea; iris
The posterior chamber of the eye is the space between the posterior surface of the ______ and the anterior surface of the ______
Iris; lens
The vitreous chamber of the eye is the space between the posterior surface of the _____ and the ____ ____
Lens; neural retina
The vitreous chamber of the eye is filled with ____ ____ to help maintain its shape; it is made up of 99% water with proteins and hyaluronan
Vitreous humor
_____ = thick fibrous opaque layer pierced by blood vessels and posteriorly by optic n.
Sclera
Chief refractive element of eye that is continuous with sclera, made up of 5 layers
Cornea
5 layers of cornea from superficial to deep
Corneal epithelium Bowman’s membrane Corneal stroma Descemet’s membrane Corneal endothelium
Corneal epithelium type
Nonkeratinized stratified squamous
Stem cells for the corneal epithelium are located in the ____ region
Limbus
Anterior basement membrane for corneal epithelium
Bowman’s membrane
Describe orientation of cells in corneal stroma, as well as its vascularization
Unique orientation of cells and stroma
Avascular
Very thick posterior basement membrane for corneal endothelium
Descemet’s membrane
Corneal endothelium type
Simple squamous epithlium facing the anterior chamber
T/F: the corneoscleral coat is not innervated
False; it is well innervated with afferent nerves extending to the surface
The vascular coat of the eye consists of what 3 components?
Choroid
Ciliary body
Iris
The choroid of the vascular coat consists of an inner vascular layer (choriocapillary) and ______ membrane which is a thick amorphous ECM layer
Bruch’s
The _____ ____ is comprised of 17-34 thickened ridges of anterior vascular coat located between the iris and choroid
Ciliary body
Smooth muscle originating at corneoscleral junction; drives accommodation of the lens
Ciliary muscle
Function of ciliary processes in vascular coat of eye
Secretion of aqueous humor and formation and anchoring of zonular fibers forming suspensory ligament of the lens
_____ forms the contractile diaphragm in front of the lens
Iris
The iris arises from the anterior border of the ____ _____; the pupil is the central aperture.
It contains ______ (radial band) and ______ ______ (circular band) mm., as well as posterior pigmented epithelium
Ciliary body
Dilator; sphincter pupillae
Aqueous humor is secreted into the ____ chamber by ciliary processes.
Fluid passes through the pupil to enter the ______ chamber. Excess fluid is taken up by ____ _____, aka the trabecular network and canal of Schlemm
Posterior
Anterior; limbus apparatus
Named angle between the sclera/iris and ciliary muscle seen on histological slide
Iridocorneal angle
Functions of aqueous humor
Provides nutrients and oxygen to avascular structures and maintains ocular shape
Risks of excess aqueous humor production
Increased intraocular pressure, may lead to glaucoma
The lens is a transparent, bi-concave structure suspended by _____ fibers
Zonular
3 components of lens
Capsule
Subcapsular lens epithelium
Lens fibers
Composition of lens capsule
Flexible, elastic ECM
Cells on the periphery of the subcapsular lens epithelium proliferate and migrate to make mature lens fibers cells.
What happens to the rate of this proliferation/migration with age?
Decreases
Describe composition of lens fibers cells
Filled with crystallins (all organelles are lost)
Central lens nucleus laid down during embryonic/fetal development
Lens accomodation is provided by tension from ciliary body, transmitted via ______ fibers, thus changing lens shape
Zonular
Condition characterized by loss of lens elasticity with age
Presbyopia
Condition characterized by loss of transparency of lens or capsule
Cataracts
The retinal pigmented layer is a layer of ______________ epithelial cells resting on _____ membrane of the choroid
Simple cuboidal; Bruch’s
3 primary functions of retinal pigmented layer
Serves as blood-neural retinal barrier (from choroid) — absorbs stray light
Phagocytoses membranous discs shed from rods and cones
Isomerizes all-trans RA to 11-cis RA, transporting it back to photoreceptors
What layer of the retina contains photosensory cells but does not contain lymphatics?
Neural retina
Blind spot in retina where optic nn from ganglion layer exit the eye
Optic disc
10 layers of retina
- RPE (not part of neural retina)
- Rod/cone ends of photoreceptors
- Outer limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglion layer
- Layer of optic n. fibers
- Inner limiting membrane
Which retinal layer serves as the apical boundary of Muller cells (row of zona adherens attaching apical ends of Muller cells)?
Outer limiting membrane
Which retinal layer contains cell bodies (nuclei) of photoreceptor cells?
Outer nuclear layer
Which retinal layer contains processes of rods/cones, as well as the horizontal, amacrine, and bipolar cells connecting them?
Outer plexiform layer
Which retinal layer contains cell bodies of horizontal, amacrine, and bipolar cells, as well as the nuclei of muller cells?
Inner nuclear layer
Which retinal layer contains processes of interconnecting ganglion, amacrine, bipolar, and horizontal cells?
Inner plexiform layer
Which retinal layer contains cell bodies (nuclei) of ganglion cells?
Ganglion layer
Which retinal layer contains processes of ganglion cells?
Layer of optic nerve fibers
Which retinal layer forms the inner limiting membrane of Muller cells?
Inner limiting membrane
Which are more numerous - rod cells or cone cells?
Rod cells
120 million rod/7 million cone photoreceptor cells
Which are more sensitive - rod cells or cone cells?
Rod cells
3 classes of cone cells
Blue
Green
Red
Area of highest concentration of cones; avascular; and surrounded by macula lutea
Fovea centralis
In terms of visual pigments, rods have ______, and cones have ______
Rhodopsin; iodopsin
General structure of rods and cones
Outer segment: photosensitive part comprised of series of plasma membrane discs; discs connected to inner segment via modified cilium; discs shed during normal functioning; phagocytosed by RPE cells
Connecting stalk: contains basal body of cilium
Inner segment: major organelles
Autosomal dominant genetic disorder caused by a mutation in the Rb gene on chromosome 13q14.1
Retinoblastoma
What type of gene is Rb
Tumor suppressor gene (G1–>S transition in cell cycle)
Clinical features of retinoblastoma
Malignant tumor of retina that develops in children younger than 5
Leukocoria (white pupil) — abnormal white light reflection off retina
Strabismus — misalignment of eyes
Auditory portion of inner ear
Cochlea
What are the 3 components of the vestibular portion of the inner ear?
Semicircular canals, utricle, saccule
The _____ _____ is what interconnects the cavities and canals within inner ear bones, including semicircular canals, vestibule (saccule+utricle), and cochlea
Bony labyrinth
The _____ _____ lies within the bony labyrinth and consists of small sacs and tubules forming continuous spaces enclosed by an epithelium
Membranous labyrinth
3 spaces associated with membranous labyrinth of inner ear
Endolymphatic space: within membranous labyrinth
Perilymphatic space: between bony and membranous labyrinths
Corticolymphatic space: lies within organ of Corti
Spiral space within bone containing cochlear duct
Cochlear canal
The ____ ____ divides cochlear canal into 3 parallel soft tissue-lined compartments.
What are the 3 compartments?
Cochlear duct
3 compartments:
Scala media
Scala vestibule
Scala tympani
The scala media (cochlear duct) is the middle compartment which contains _______
It consists of the ____ ____, which is the lateral wall of scala media and the source of the above substance
Endolymph; stria vascularis
Turnover of endolymph in the scala media involves resorption into what structures via the endolymphatic duct and sac?
Dural venous sinuses
The scala vestibule contains ______ moved by the stapes at the ____ window; it is continuous with the scala tympani
The scala tympani is connected to the ____ window
Perilymph; oval
Round
What specialized structure is found on the floor of scala media resting on the basilar membrane?
Organ of corti
Inner spiraling bony shelf serving as support for tectorial membrane and spiral ganglia
Outer spiral lamina (OSL)
Composition of organ of corti
Hair cells (sensory)
Inner and outer phalangeal cells (support for hair cells)
Pillar cells (support between basilar membrane and tympanic lip)
In the organ of corti, there are 3 rows of outer hair cells and a single row of inner hair cells.
_____ of hair cells is embedded in overlying _____ membrane extending from the spiral lamina
Basilar membrane vibrates with sound, causing deflection of these structures; this is what initiates neural transduction carried by the ____ n.
Stereocilia; tectorial
Cochlear
Path of sound waves
Sound waves enter ear and cause TM to vibrate
TM vibration moves auditory ossicles; sound waves amplified
Stapes at oval window generates pressure waves in perilymph within scala vestibuli
Pressure waves cause vestibular membrane movement —> pressure wave formation in endolymph in cochlear duct and displacement of hair cells in organ of corti, initiating nerve signal in cochlear branch of CN VIII
Remaining pressure waves are transferred to scala tympani and exit inner ear via round window
The 3 semicircular canals are oriented in 3 axes. They are filled with ______ and are connected to utricle. Ends of canals have ______ with gelatinous-like cap called a cupulla (innervated hair cells with stereocilia are attached here).
The _____ is displaced by fluid motion within canal which serves as sensor of rotational velocity
Endolymph; ampullaris
Cupulla
The vestibule contains the ____ and _____.
Of these structures, each contain a ________ which is comprised of clusters of hair cells with stereocilia with overlying gelatinous material called the ______ membrane. This membrane is covered with calcium carbonate/protein crystals called _______.
This serves as sensor for gravity and ______ acceleration
Utricle; saccule
Macula; otolithic; otoconia
Linear
3 parts of audio-vestibular system
Outer ear
Middle ear
Inner ear
3 sensory systems in audio-vestibular system
Audition
Rotational velocity
Gravity/linear acceleration
3 nerves in internal acoustic meatus
Vestibular n.
Acoustic n.
Facial n.
How many maculae are present in the audio-vestibular system?
Only TWO maculae, responsible for detecting linear acceleration in THREE dimensions