Exercise 23 – Visual System Anatomy
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Navajo Technical University *
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Anatomy
Date
Dec 6, 2023
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Exercise 23 – Visual System Anatomy
Name
Sedrick Nari
Instructions and Review Sheet
Once you have completed the below activities, please answer the questions on the following pages and
submit this completed document to me in Canvas. You must have a copy of the lab manual to complete
this exercise.
Please read the entire exercise in your lab manual. Pay particular attention to the figures
– the practical portion of the exam will use images and figures taken from the lab manual and
handouts like this one.
Activity 1
- SARS CoV-2 can be transmitted through contact with the moist tissues of the eye, so please
do not touch anyone who you are not absolutely certain is not a risk for transmission. If you have
someone you can perform this activity on, you can do so, or you can simply look in the mirror. If you pull
the medial corner of your lower eyelid down you should be able to make out the lacrimal puncta.
Activity 2
- For this activity you can refer to the images provided in the lab manual, in place of the 3D
model. There will likely be questions from any of the images in the lab, but particularly those in figure
23.3.
Activity 3
- Please carefully examine the illustrations in Fig. 23.4 and understand the arrangement and
names of cells making up the retina. I will probably ask a question using the histological section shown in
23.4b, so understand what it shows and how it relates to 23.4a.
Cow Eye Dissection
- In class we would have dissected a cow eye as part of learning the anatomy of the
eye. Unfortunately, that can’t happen in the online situation we are in now. But please go watch this
video demonstration of a cow eye dissection. You may have seen a demonstration of this before, or may
have done one, but do please watch this video and pay attention to the terms that are used:
https://www.youtube.com/watch? v=6mNs_TcUyHc&has_verified=1
Activity 4
- Examine the diagram to understand the pathways that axons take from the eye to the
primary visual cortex. Understand what passes through the optic chiasm, paying attention to what
portion of the visual field is represented in the axons within the chiasm. Answer the questions provided
there to test your understanding. (You need only turn in the Review Sheet, however
.)
Anatomy of the Eye
1. Name five accessory eye structures that contribute to the formation of lacrimal fluid (teras) and/or
help lubricate the eyeball, and then describe the major secretory product of each.
Accessory Structures
Products
Conjunctiva
Mucus
Caruncle
Whitish oily secretion
Lacrimal glands
Saline solution, lysozyme
Ciliary glands
Sweat
Tarsal glands
Oily secretion
2. The eyeball is wrapped in adipose tissue within the bony orbit. What is the function of the adipose
tissue?
To protect and cushion the eyeball.
3. Why does one often experience a runny nose after crying?
4. Identify the extrinsic eye muscle predominantly responsible for each action described below.
Action
Primary Muscle
Turns the eye laterally
Lateral rectus
Turns the eye medially
Medial rectus
Turns the eye up and laterally
Inferior rectus
Turns the eye down and medially
Inferior rectus
Turns the eye up and medially
Superior rectus
Turns the eye down and laterally
Superior oblique
5. What is a sty?
Infection of the oil gland at the base of an eyelash.
6. Correctly identify each lettered structure in the diagram by writing the letter next to its name in the
below list.
K
sclera
P
optic nerve
F
cornea
N
central artery/vein of retina
R
ganglion cell
A
ciliary process
Q
dura matter of optic nerve
H
scleral venous sinus
I
retina
E
pupil
G
anterior segment
B
ciliary zonule
M
optic disc
D
lens
J
choroid
L
fovea centralis
S
bipolar cells
T
photoreceptors
7. The iris is composed primarily of two smooth muscle layers. Which muscle layer dilates the pupil?
The dilator pupillae
8. You would expect the pupil to be dilated in which of the following circumstances? Highlight the correct
response.
a. in bright light
b. in dim light
9. The intrinsic eye muscles are controlled by (highlight the correct response):
autonomic nervous system
somatic nervous system
10. Match the key responses with the descriptive statements that follow. (Some choices will be used
more than once.)
Key:
a. aqueous humor
e. cornea
j. retina
b. choroid
f. fovea centralis
k. sclera
c. ciliary body
g. iris
l. scleral venous sinus
d. ciliary processes of
h. lens
m. vitreous humor
ciliary body
i. optic disc
A
1. fluid filling the anterior segment of the eye
K
2. the “white” of the eye
I
3. part of the retina that lacks photoreceptors
C
4. modification of the choroid that contains the ciliary muscle
L
5. drains aqueous humor from the eye
J
6. layer containing the rods and cones
M
7. substance occupying the posterior segment of the eyeball
B
8. forms the bulk of the heavily pigmented vascular layer
C
,
G
9. composed of smooth muscle structures (2)
F
10. area of critical focusing and detailed color vision
D
11. form the aqueous humor
A
,
E
,
H
,
M
12. length-bending media of the eye (4)
E
13. anterior continuation of the sclera – your “window on the world”
K
14. composed of tough, white, opaque, fibrous connective tissue
Microscopic Anatomy of the Retina
11. The two major layers of the retina are the pigmented and neural layers. In the neural layer, the
neuron populations are arranged as follows from the pigmented layer to the vitreous humor. (Highlight
the proper responses.)
bipolar cells, ganglion cells, photoreceptors
photoreceptors, ganglion cells, bipolar cells
ganglion cells, bipolar cells, photoreceptors
photoreceptors, bipolar cells, ganglion cells
12. The axons of the
ganglion
cells form the optic nerve, which exits from the eyeball.
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13. Complete the following statements by writing either
rods
or
cones
on each blank.
The dim light receptors are the
rods
. Only
cones
are found in the fovea centralis, whereas mostly
rods
are found in the periphery of the retina.
Cones
are the photoreceptors that operate best in bright light
and allow for color vision.
Dissection of the Cow Eye
14. What modification of the choroid that is not present in humans is found in the cow eye?
Tapetum lucidum
What is its function?
To reflect light stimulation
15. What does the retina look like?
Yellowish-shite tan membrane
At what point is it attached to the posterior aspect of the eyeball?
At the optic disc
Visual Pathways to the Brain
16. The visual pathway to the occipital lobe of the brain consists most simply of a chain of five cells.
Beginning with the photoreceptor cell of the retina, name them, and note their location in the pathway.
1.
photoreceptor cell: retina
2.
bipolar cell: retina
3.
ganglion cell: retina
4.
neuron: lateral geniculate nucleus of the thalamus
5.
cortical neuron: primary visual cortex of the cerebral hemisphere
17. Visual field tests are done to reveal destruction along the visual pathway from the retina to the optic
region of the brain. Note where the lesion is likely to be in the following cases.
Normal vision in the left eye visual field; absence of vision in the right eye visual field:
right optic nerve
Normal vision in both eye for right half of the visual field; absence of vision in both eyes for left half of
the visual field:
right optic tract
18. How is the right optic
tract
anatomically different from the right optic
nerve
?
Rejection is less likely and healing is slower.