Histology Exam 2

Cornea

window like region that is transparent, principle refractile element of the eye, contains 3 cellular layer and 2 lamellae, avascular

Sclera

whites of the eyes

Choroid

highly vascularized layer that is the principle nutrient source to the retina, contains melanin pigment that reduces reflected light

Ciliary Body

ring like thickening that extends inward from the corneoscleral junction, contains intralocular smooth muscle that changes shape of lens thereby refocusing the image

Iris

contractile diaphragm that regulates amount of light coming into the eye, contains smooth muscle that control its size response to differing light levels

Pupil

opening in the iris

Retina

Neural retina and retinal pigment epithelium, where photo reception occurs, continuous with CNS

Corneosceleral coat

cornea is transparent and sclera is opaque

Uvea

vascularized layer inside the eye, includes the choroid and stroma of ciliary body and iris

Anterior Chamber of eye

occupies space between cornea and anterior surface of the iris

Posterior Chamber of eye

occupies space between posterior surface of iris and anterior surface of the lens

Vitreuos body/humor

viscous fluid that help maintain shape of the eye and occupies space between posterior surface of the lens and the neural retina, water collagen type II and hyaluronic acid

Refractile elements of the eye

cornea, anterior chamber, lens, and vitreous humor

Aqueous humor

watery fluid that has a minor role in image formation but a major role in the nourishment to the cornea and lens, produced by ciliary bodies

Hyaloid Artery

nourishes developing lens and eventally disappears

Macula (lutea)

oval shaped highly pigmented yellow spot near the center of the retina near the human eye, has 2 or more layers of ganglion cells, contains fovea

Fovea

a small pit that contains the largest concentration of con cells and is responsible for central vision in the macula

Ciliary arteries

supplies the outer retina, photoreceptor cells, as well as the uvea, choroid, sclera, and ciliary processes

Central retiinal artery

enters eye with optic nerve, branches between retina and vitreous humor, and supplies inner surface of retina, includes ganglion cells and inner nuclear layer

Bruch’s membrane

basal lamina of the otic cup, hyaline membrane, lies between choriocapillary layer and retinal pigment epithelium

Lamina Fusca

loose, pigmented connective tissue on the inner surface of the sclera that connects it to the underlying choroid layer, collage and elastic fibres plus pigment cells

Corneal epithelium

stratified squamous epithelium, non keratinized, highly inervated, microplicae and microvilli help retain moisture, preforms metabolic exchange with anterior chamber

Corneal fibroblasts

lie between collagen layers

Aponeurosis

flat sheet of highly oriented collagen fibres

Substanstia Propia

corneal stroma, type 1 collagen fibrils at 90 degrees to each other

Water regulation in stroma

fluid enters through the endothelium, exists through the canal of Schlem

Descemet’s membrane

thick basal lamina that regenerates, extends beneath sclera and maintains curvature of the eye, contains type VIII collagen

Episclera

external layer adjacent to periorbital fat, loose connective tissue below sclera

Sclera proper/ Tenon’s capsule

whites of eyes, dense irregular network of collagen fibres and elastic tissue, anterior surface covered by conjunctival epithelium, pierced byy vasculature and nerves

The limbus

junction between cornea and sclera, trabecular network and canal of Schlemm, apparatus for outlfow of aqueous humor to blood vessels in the sclera

Ciliary processes

form zonule fibres which suspend the lens

Ciliary muscle

smooth muscle for accomodation, located at base of ciliary processes, derived from mesoderm

Ora serrata

scalloped boundary that divides the photosensitive region of the retina from the non-photosensitive region, system of ridges and grooves that extend all the way to the ciliary processes

Ciliary epithelium

double layer of columnar epithelium, inside out orientation, layers attached by apical desmosomes and separated by ciliary channels, secretes aqueous humor

Zonule fibres

extend from basal lamina of non-pigmented layer to insert into the lens

Anterior stromal sheet

loose and vascularized layer of connective tissue with melanocytes

Posterior membrane

discontinuous smooth muscle

sphincter pupillae

parasympathetic innervation

pigmented epithelium

double layer of pigmented cells, derived from the optic cup

crystalline lens

suspended from the ciliary body by zonule fibres, with lens capsule, subcapsular epithelium, and lens fibres, high refractive index and elastic

Lens capsule

basal lamina

subcapular epithelium

only on anterior surface, stem cells along equator

lens fibres

structures derived from epithelium, mature fibres lack nucleus

Layers of Retina

internal limiting membrane, optic nerve fibres, ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, external limiting membrane, layers of rods and cones, pigment epithelium

Retinal pigment epithelium

surface of posterior side of vesicle formed by optic cup, single layer of cuboidal cells, absorbs light, acts as blood retinal barrier, phagocytosis and disposal of discarded discs, resynthesizes visual pigments

Photoreceptors

rods (monochromatic image, discs separated from plasma membrane) and cones (colored image, discs are continuous with plasma membrane)

Mullers cells

support cells in neural retina, forms external limiting membrane, connected by zonula adherens

Outer segment of Rods & Cones

contains visual pigment

Inner segment of Rods & Cones

contains typical components of cell

Connecting stalk of Rods & Cones

connects inner and outer segment, contains a single cilium

Outer nuclear layer

contains nuclei of rod and cone cells, inner segments

Inner nuclear layer

contains nuclei of Mullers cells and 3 types of conducting cells

ganglion cell layer

nuclei of multipolar neurons, thickest around the fovea and absent in the fovea

outer plexiform layer

process of rods and cones, synaptic complexes between photoreceptors and horizontal and bipolar cells

inner plexiform layer

processes of ganglion (dendrites) and amacrine cells (axons)

Fovea centralis

thin region on optical axis

External ear

conducts sound waves to the tympanic membrane, has auricle and external auditory meatus

Auricle

shape defined by elastic cartilage, thin skin covers this skeleton

External auditory meatus (EAM)/ canal

hair follicles, sebaceous gland, and ceruminous glands

Ceruminous glands

modified apocrine sweat gland produces cerumen (earwax)

Middle Ear

converts air vibrations to fluid vibrations, contains auditory ossicles, eustacean tube, muscles and openings

auditory ossicles

malleus (hammer), incus (anvil), and stapes (stirrup)

Malleus

attached to tympanic memebrane

Incus

connects malleus to stapes

stapes

attached to oval window

eustacean tube

equilibrates air pressure, endoderm derived

Tensor tympani & Stapedius

small msucles in middle ear that attenuate sound

Vestibular (oval) & Cochlear (round) Windows

small openings in medial wall of middle ear essential to sound perception

Tympanic Membrane

skin, core of radial and circular collagen fibres (tunica propia), and inner mucous membrane (simple cuboidal)

Inner ear

contains bony labyrinth and membraneous labyrinth

Endolymphatic spaces

contained within membraneous labyrinth, similar to intracellular fluid, contains sensory receptors

Perilymphatic space

between bony and membraneous space, similar to cerebrospinal fluid

Cortilymphatic space

intracellular space within the organ of Corti, similar to extracellular fluid

Vestibular labyrinth

membraneous semicircular ducts/canals that detect angular acceleration

Utricle & Saccule

detect linar acceleration in membraneous labyrinth

Cochlear labyrinth

membraneous cochlea, cochlear duct

Cristae ampullaris

angular acceleration of the head motion detector

Macula utriculi & macula saccule

linear acceleration of head, saccule (vertical), utriculi (horizontal)

Mechanotransducers

sensory hair cells, have stereocilia and kinocillia bathed in endolymph fluid

Type 1 sensory hair cells

afferent nerve fibres only

Type 2 sensory hair cells

both afferent and efferent nerve fibres

Nonmotile (primary) Cilia

present in low numbers

Depolarizing membrane in ear

stereocilia move toward kinocilium, opens channel

Hyperpolarizing membrane in ear

stereocilia move away from kinocilium, closes channel

Accomodation in ear

tension restored to basal level by myosin, motor pulls to restore or release tension

Semicircular canals

sensors of angular motion

cristae ampularis

thickened to epithelial ridge, type 1 and 2 collagen and supporting cells

Otolythic membrane

calcium carbonate crystals senses gravity

Cochlea

spiral structure that contains 3 ducts and the organ of Corti, designed to detect pitch and intensity of sound

Scala media

cochlear duct, endolymphatic space, contains organ of Corti

scala vestibuli

perilymphatic space on oval window side, connected to ear drum

scala tympani

perilymphatic space on round window side, dissipates sound energy

Vestibular membrane

simple squamous epithelia separated by basal lamina and seperates scala media from scala vestibuli

Phalangeal cells

support hair cells and produce reticular lamina, surround inner hair cells, but only cover basal surface of outer hair cells

pilar cells

define inner spiral tunnel of Organ of Corti, triangular shaped feature between inner and outer hair cells

ossesous spiral lamina

supports limbus spiralis, which support tectorial membrane

Spiral ligament

supports stria vascularis

Cuticular plate

produced by phalangeal cells, surface that isolates scala media with its endolymph from the rest of the inner ear and fluids

Auditory reception

sound waves vibrate tympanic membrane, ossicles transmit vibrations to oval membrane, pressure wave is transmitted to perilymphatic space, pressure wave is conducted almost instantly to all parts of basilar membrane

Basilar membrane

varies in width, increasing frequency the locus of maximum amplitude moves from apical to basal end