Lecture 9: Histology of the Visual, Vestibular, and Auditory Systems

Question 1

What are the 3 layers of Tunica of the eye?

Answer 1

• Outer tunic (sclera and cornea)
• Middle tunic (Uvea)
• Inner tunic (Retina)

Question 2

In the outer tunic, what is the difference between the cornea and sclera; what is the zone of transition between the 2 called?

Answer 2

• The cornea is transparent
• The sclera is opaque (white)
• Zone of transition = Limbus

Question 3

The stroma of the cornea is formed by; which is layed down by what?

Answer 3

• Collagen lamellae oriented at an angle to one another
• Fibroblasts are present between the lamellae and lay down the collagen

Question 4

What are the nerves in the cornea like and how do they change as they pass through?

Answer 4

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

Question 5

Are there blood vessels in the cornea?

Answer 5

Blood vessel are NOT present

Question 6

What makes up the uvea of the middle tunic of eye?

Answer 6

Choroid (aka choroid plexus) + Ciliary body + Iris

Question 7

What is the vascular layers of the middle tunic of the eye?

Answer 7

Choroid (AKA choroid plexus)

Question 8

Identify the layers A-E

Answer 8

A) Corneal epithelium

B) Bowman’s layer

C) Stroma

D) Descemet’s membrane

E) Corneal epithelium

Question 9

What is the relevance of the ciliary body?

Answer 9

Lined with ciliary epithelium, which produces aqueous humor

Question 10

What are the 2 surfaces of the iris and how are they different?

Answer 10

1) Anterior surface: lacks an epithelial lining
2) Posterior surface: lined by a dual layer of pigmented epithelial cells

Question 11

Where is the dilator pupillae muscle; contains what receptors and innervated by; contraction causes?

Answer 11

• Found on the iris and consits of myoepithelial cells
• Contains α-adrenergic receptors and innervated by sympathetic nerve fibers
• Contraction causes pupil dilation

Question 12

Where is the sphincter pupillae; what does it consist of; contains what receptors and innervated by; contraction causes?

Answer 12

• 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

Question 13

The ciliary body occupies the bulk of _______; its fibers extend where; contraction causes?

Answer 13

• 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

Question 14

Label A-D

Answer 14

A) Sclera

B) Ciliary muscle

C) Iris

D) Ciliary Process

Question 15

What are the 2 layers of the inner tunic (retina)?

Answer 15

1) Outer pigmented layer
2) Inner retinal layer

Question 16

What are the 10 layers of the retina from inner (deep) to outer (superficial)?

Answer 16

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

Question 17

Which retinal layer are the nuclei of rods and cones found in?

Answer 17

Outer nuclear layer

Question 18

Which retinal layer contains the cell bodies of the bipolar cells?

Answer 18

Inner nuclear layer

Question 19

Amacrine cells synapse with axons of?

Answer 19

Bipolar cells and dendrites of ganglion cells

Question 20

Horizontal cells synpase with?

Answer 20

Rods and cones (photoreceptor cells)

Question 21

Label all of the layers from 10-1?

Answer 21

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

Question 22

The axons of rods and cone project into which retinal layer and synspase with?

Answer 22

• Outer plexiform layer
• Synapse with dendrites of bipolar cells

Question 23

What are 4 function of the retinal pigemented epithelial (RPE) layer?

Answer 23

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

Question 24

What is the fovea centralis; contains highest concentration of?

Answer 24

• Highest concentration of cones

- Where we see the best

• Surrounded by the macula lutea

Question 25

Label A and B

Answer 25

Question 26

Label A and B

Answer 26

Question 27

The axons of ganglion cells turn into the optic nerve at the \_\_\_\_\_\_\_, which lacks ______ and corresponds to the ________ of the retina

Answer 27

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

Question 28

What are the 3 chambers of the eye and where is each found?

Answer 28

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

Question 29

Describe the pathway followed by the aqueous humor after being produced by the epithelial lining of the ciliary processes.

Answer 29

- 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**

Question 30

How does aqueous humor production contribute to Glaucoma?

Answer 30

- 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**

Question 31

Histologically what leads to cataracts?

Answer 31

Opacity of the lens causes by change in solubility of lens proteins

Question 32

What is the function of the Tarsal glands of the eye?

Answer 32

Special sebaceous glands; secretion a **lipid-containing** product retards evaporation of tears.

Question 33

Infection and disruption of the walls of the tarsal glands causes?

Answer 33

**Chalazion,** a swelling of the eyelid

Question 34

Identify the gland types labeled by A and B

Answer 34

A) Tarsal glands B) Moll's glands

Question 35

Axons of the bipolar cells synapse with dendrites of the ganglion cells in which layer?

Answer 35

Inner Plexiform Layer

Question 36

What is found within the bony labyrinth of ear?

Answer 36

- Semicircular canals - Vestibule - central space containing **saccule** and **utricle** - Cochlea

Question 37

What 3 spaces are found within the Membranous Labyrinth?

Answer 37

1) Endolymphatic space: within membranous labyrinth 2) Perilympathic space: between bony and membranous labyrinths 3) Corticolymphatic space: lie within organ of Corti

Question 38

What is the Scala media and what is found inside it?

Answer 38

- Cochlear duct (middle part) - Contains **endolymph**

Question 39

What is the Stria Vascularis; what does it produce?

Answer 39

- Found in the lateral wall of the Scala Media of the Cochlea - Source of **endolymph**

Question 40

The Scala Tympani contains what and is continous with?

Answer 40

- Perilymph - Continous with Scala Tympani

Question 41

Label A-G

Answer 41

Question 42

Where are the stereocilia of hair cells embedded within the Organ of Corti?

Answer 42

Tectorial Membrane

Question 43

What vibrates within the organ of Corti causing deflection of stereocilia?

Answer 43

**Basilar membrane** vibraes with sound causing deflection of stereocilia attached to **tectorial membane** - initiates **neural transduction** carried by **cochlear nerve**

Question 44

Where is perilymph found within the Cochela?

Answer 44

- Scala Vestibuli - Scala Tympani

Question 45

Label A-C

Answer 45

Question 46

What is the function of the Semicircular Canals and Ampulla, sensors for?

Answer 46

Rotational velocity

Question 47

What is the function of the Saccule and Utricle found within the Vestible, sensors for?

Answer 47

- Sensors for gravity and linear acceleration

Question 48

Label A-C

Answer 48

Question 49

ID this structure

Answer 49

Sclera

Question 50

ID this structure

Answer 50

Choroid

Question 51

Identify the white, black, and yellow arrow layers.

Answer 51

**White:** Outer Nuclear Layer **Black:** Optic nerve layer/nerve fiber layer **Yellow:** Retinal pigment epithelium

Question 52

What is this structure?

Answer 52

Helicotrema

Question 53

1. ID the white arrow 2. ID the purple arrow 3. ID the red arrow

Answer 53

1. Corneal stroma 2. Corneal endothelium 3. Corneal epithela

Question 54

ID the black and white arrows

Answer 54

**Black:** Optic nerve (CN II) **White:** Optic disc

Question 55

1. What is the red arrow? 2. What is the black arrow? 3. What is the yellow arrow?

Answer 55

1. Tectorial membrane 2. Outer hair cell(s) 3. Inner hair cell