Lecture 9: Histology of the Visual, Vestibular, and Auditory Systems Flashcards
What are the 3 layers of Tunica of the eye?
- Outer tunic (sclera and cornea)
- Middle tunic (Uvea)
- Inner tunic (Retina)
In the outer tunic, what is the difference between the cornea and sclera; what is the zone of transition between the 2 called?
- The cornea is transparent
- The sclera is opaque (white)
- Zone of transition = Limbus
The stroma of the cornea is formed by; which is layed down by what?
- Collagen lamellae oriented at an angle to one another
- Fibroblasts are present between the lamellae and lay down the collagen
What are the nerves in the cornea like and how do they change as they pass through?
Myelinated nerves are found in the stroma, but after crossing Bowman’s layer the nerves become unmyelinated and extend towards the surface in the intracellular spaces of corneal epithelium
Are there blood vessels in the cornea?
Blood vessel are NOT present
What makes up the uvea of the middle tunic of eye?
Choroid (aka choroid plexus) + Ciliary body + Iris
What is the vascular layers of the middle tunic of the eye?
Choroid (AKA choroid plexus)
Identify the layers A-E
A) Corneal epithelium
B) Bowman’s layer
C) Stroma
D) Descemet’s membrane
E) Corneal epithelium
What is the relevance of the ciliary body?
Lined with ciliary epithelium, which produces aqueous humor
What are the 2 surfaces of the iris and how are they different?
1) Anterior surface: lacks an epithelial lining
2) Posterior surface: lined by a dual layer of pigmented epithelial cells
Where is the dilator pupillae muscle; contains what receptors and innervated by; contraction causes?
- Found on the iris and consits of myoepithelial cells
- Contains α-adrenergic receptors and innervated by sympathetic nerve fibers
- Contraction causes pupil dilation
Where is the sphincter pupillae; what does it consist of; contains what receptors and innervated by; contraction causes?
- In the iris and consists of smooth muscle cells
- Contains acetylcholine receptors and is innervated by parasympathetic nerve fibers
- Contraction reduces the diameter of the pupil
The ciliary body occupies the bulk of _______; its fibers extend where; contraction causes?
- Occupies the bulk of the ciliary body
- Zonular fiber from the ciliary epithelium extend toward the lens
- Contraction causes relaxation of the tension exerted by the zonular fibers on the lens during accomodation
Label A-D
A) Sclera
B) Ciliary muscle
C) Iris
D) Ciliary Process
What are the 2 layers of the inner tunic (retina)?
1) Outer pigmented layer
2) Inner retinal layer
What are the 10 layers of the retina from inner (deep) to outer (superficial)?
10) Inner limiting membrane
9) Nerve fiber layer (axons of ganglion cells)
8) Ganglion cell layer
7) Inner plexiform layer
6) Inner nuclear layer
5) Outer plexiform layer
4) Outer nuclear layer
3) Outer limiting membrane
2) Inner and outer segments of rods and cones
1) Pigmented epithelium
Which retinal layer are the nuclei of rods and cones found in?
Outer nuclear layer
Which retinal layer contains the cell bodies of the bipolar cells?
Inner nuclear layer
Amacrine cells synapse with axons of?
Bipolar cells and dendrites of ganglion cells
Horizontal cells synpase with?
Rods and cones (photoreceptor cells)
Label all of the layers from 10-1?
10) Inner limiting membrane
9) Nerve fiber layer (axons of ganglion cells)
8) Ganglion cell layer
7) Inner plexiform layer
6) Inner nuclear layer
5) Outer plexiform layer
4) Outer nuclear layer
3) Outer limiting membrane
2) Inner and outer segments of rods and cones
1) Retinal pigment epithelium
The axons of rods and cone project into which retinal layer and synspase with?
- Outer plexiform layer
- Synapse with dendrites of bipolar cells
What are 4 function of the retinal pigemented epithelial (RPE) layer?
1) Serves as blood-neural retinal barrier (from choroid)
2) Absorbs stray light
3) Phagocytoses membranous discs shed from rods and cones
4) Isomerizes all-trans RA to 11-cis RA, transporting it back to photoreceptors
What is the fovea centralis; contains highest concentration of?
- Highest concentration of cones
- Where we see the best
- Surrounded by the macula lutea
Label A and B
Label A and B
The axons of ganglion cells turn into the optic nerve at the _______, which lacks ______ and corresponds to the ________ of the retina
The axons of ganglion cells turn into the optic nerve at the optic disc, which lacks photoreceptors and corresponds to the blind spot of the retina
What are the 3 chambers of the eye and where is each found?
1) Anterior chamber: space between cornea and iris
2) Posterior chamber: space between posterior surface of iris and the anterior surface of the lens
3) Vitreous (body) chamber: space between the posterior surface of lens the neural retina. Filled with vitreous humor to maintain shape of eye bulb
Describe the pathway followed by the aqueous humor after being produced by the epithelial lining of the ciliary processes.
- Flows from the posterior chamber through the pupil into the anterior chamber
- Aqueous humor is wicked up by an area called the trabecular meshwork and drained into the canal of Schlemm
- Aqueous veins are collector channels draining the canal of Schlemm into the episcleral veins
How does aqueous humor production contribute to Glaucoma?
- Obstruction of aqueous humor leads to an increase in intraocular pressure.
- Either by blockage of the canal of Schlemm (most common) or inflammation preventing aqueous humor from reaching the trabecular network
Histologically what leads to cataracts?
Opacity of the lens causes by change in solubility of lens proteins
What is the function of the Tarsal glands of the eye?
Special sebaceous glands; secretion a lipid-containing product retards evaporation of tears.
Infection and disruption of the walls of the tarsal glands causes?
Chalazion, a swelling of the eyelid
Identify the gland types labeled by A and B
A) Tarsal glands
B) Moll’s glands
Axons of the bipolar cells synapse with dendrites of the ganglion cells in which layer?
Inner Plexiform Layer
What is found within the bony labyrinth of ear?
- Semicircular canals
- Vestibule - central space containing saccule and utricle
- Cochlea
What 3 spaces are found within the Membranous Labyrinth?
1) Endolymphatic space: within membranous labyrinth
2) Perilympathic space: between bony and membranous labyrinths
3) Corticolymphatic space: lie within organ of Corti
What is the Scala media and what is found inside it?
- Cochlear duct (middle part)
- Contains endolymph
What is the Stria Vascularis; what does it produce?
- Found in the lateral wall of the Scala Media of the Cochlea
- Source of endolymph
The Scala Tympani contains what and is continous with?
- Perilymph
- Continous with Scala Tympani
Label A-G
Where are the stereocilia of hair cells embedded within the Organ of Corti?
Tectorial Membrane
What vibrates within the organ of Corti causing deflection of stereocilia?
Basilar membrane vibraes with sound causing deflection of stereocilia attached to tectorial membane - initiates neural transduction carried by cochlear nerve
Where is perilymph found within the Cochela?
- Scala Vestibuli
- Scala Tympani
Label A-C
What is the function of the Semicircular Canals and Ampulla, sensors for?
Rotational velocity
What is the function of the Saccule and Utricle found within the Vestible, sensors for?
- Sensors for gravity and linear acceleration
Label A-C
ID this structure
Sclera
ID this structure
Choroid
Identify the white, black, and yellow arrow layers.
White: Outer Nuclear Layer
Black: Optic nerve layer/nerve fiber layer
Yellow: Retinal pigment epithelium
What is this structure?
Helicotrema
- ID the white arrow
- ID the purple arrow
- ID the red arrow
- Corneal stroma
- Corneal endothelium
- Corneal epithela
ID the black and white arrows
Black: Optic nerve (CN II)
White: Optic disc
- What is the red arrow?
- What is the black arrow?
- What is the yellow arrow?
- Tectorial membrane
- Outer hair cell(s)
- Inner hair cell
