Histology Testbank: Special Senses 2a

Instructions: For each histology question, pick the one best answer. This histology test bank is also useful for the histology questions on the USMLE (USMLE step 1).

1.
What are the receptors for vision?
a. Rods
b. Cones
c. Bipolar cells
d. Ganglion cells
e. Both a and b

Answer: e

The retina consists of the rods, cones, bipolar cells, ganglion cells, horizontal cells, and amacrine cells. The receptors for vision are the rods and cones. The rods are located on the periphery, and are not color sensitive. The cones are the receptors for color.

2.
Where is the ciliary muscle located?
a. Ciliary body
b. Optic disc
c. Fovea centralis
d. Lamina vitrea
e. Lamina cribrosa

Answer: a

The ciliary body is a thickening in the uvea. It contains the ciliary muscle.

The site where the optic nerve leaves the eyeball is the optic disc. This region is also called the anatomical blind spot. Since there are no photoreceptors at this spot, it causes a blind spot in the visual field.

The fovea centralis is part of the retina. There are only cone cells in the fovea centralis. It is the site for maximal visual acuity.

The inner layer of the choroid is the lamina vitrea. The lamina vitrea is also referred to as Bruch's membrane.

The lamina cribrosa are small openings within the sclera where the fibers forming the optic nerve travel through.

3.
Where is the ciliary muscle located?
a. Choroid
b. Ciliary body
c. Iris
d. Ora serrata
e. Sclera

Answer: b

The vascular pigmented structure of the uvea is the choroid. The ciliary body contains the ciliary muscle. The ciliary muscle is responsible for adjusting the lens. The most anterior portion of the uvea is the iris. The anterior pigmented portion of the retina is called the ora serrata. The sclera is the "white of the eye".

4.
What are the openings within the sclera which allow nerve fibers to exit?
a. Os
b. Optic chiasm
c. Lamina cribrosa
d. Optic disc
e. Ora serrata

Answer: c

An os is an opening or mouth. The optic chiasm is the anatomical region shaped like an "X" where the two optic nerves join. The region where the optic nerve exits the eye is the optic disc. The openings within the sclera which allow nerve fibers to exit is the lamina cribrosa. The anterior pigmented portion of the retina is called the ora serrata.

5.
Which of the following is NOT part of the retina?
a. Receptor cells
b. Neurons
c. Pigmented epithelium
d. Ciliary body
e. Supporting cells

Answer: d

The retina contains receptor cells, neurons, pigmented epithelium and supporting cells. The nervous element in the retina consists of bipolar cells and ganglion cells.

6.
What structure adjusts the shape of the lens?
a. Internal oblique muscle
b. Orbicularis oculi
c. Tarsus
d. Ciliary muscle
e. Levator muscle

Answer: d

The ciliary muscle is within the ciliary body. The ciliary muscle adjusts the shape of the lens.

7.
What is the inner layer of the choroid?
a. Ciliary body
b. Optic disc
c. Fovea centralis
d. Lamina vitrea
e. Lamina cribrosa

Answer: d

The ciliary body is a thickening in the uvea. It contains the ciliary muscle.

The site where the optic nerve leaves the eyeball is the optic disc. This region is also called the anatomical blind spot. Since there are no photoreceptors at this spot, it causes a blind spot in the visual field.

The fovea centralis is part of the retina. There are only cone cells in the fovea centralis. It is the site for maximal visual acuity.

The inner layer of the choroid is the lamina vitrea. The lamina vitrea is also referred to as Bruch's membrane.

The lamina cribrosa are small openings within the sclera where the fibers forming the optic nerve travel through.

8.
Where does aqueous humor from anterior chamber collect into?
a. Canaliculi
b. Canal of Hering
c. Canal of Muller
d. Canal of Descemet
e. Canal of Schlemm

Answer: e

Aqueous humor collected from the anterior chamber via the canal of Schlemm.

9.
Which layer of the cornea is acellular?
a. Epithelium
b. Endothelium
c. Descemet's membrane
d. Substantia propria
e. None of the above

Answer: c

There are five layers to the cornea: epithelium, Bowman's membrane, substantia propria, Descemet's membrane, and endothelium.

The surface of the cornea is covered by a non keratinized stratified squamous epithelium. Bowman's membrane and Descemet's membrane are acellular. The majority of the cornea is from the substantia propria. The endothelium is a simple epithelium.

10.
Which structure is avascular?
a. Retina
b. Cornea
c. Choroid
d. Sclera
e. Uvea

Answer: b

The cornea is avascular.