Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Boards > Ocular Physiology > Flashcards

Ocular Physiology Flashcards

1
Q

What purpose does the abundant sarcoplasmic reticulum (SR) in EOMs serve?

A

The large amount of SR allows the EOMs greater access to calcium which promotes muscle contraction. Remember that the EOMs are constantly active and must respond quickly and precisely to stimulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the approximate number of muscle fibers in an EOM motor unit?

  1. One
  2. 10
  3. 100
  4. 1000
A

Correct answer: 2 (10 muscle fibers per motor unit)

This question may seem very picky, but it is important to know that EOMs have very small motor units which allow for small, precise, accurate movements. Minor misalignments of the EOMs cause major problems for patients (such as diplopia) so proper alignment is critical!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Botulinum toxin (Botox) works by inhibiting the release of acetylcholine (Ach) at the neuromuscular junction. Clinically, what two ocular conditions can Botox be used to treat?

A

Strabismus and blepharospasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the purpose of aqueous? List 4.

A

helps maintain the shape of the anterior chamber.
helps transmit light to the retina.
helps provide nutrients and oxygen to cornea and lens
promotes movement of waste products from the anterior portion of the eye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is carbonic anhydrase important in aqueous production?

A

Carbonic anhydrase is an enzyme that aids in the production of bicarbonate. The ion gradients which active secretion depends on are, in part, created by bicarbonate. This is why CAIs (carbonic anhydrase inhibitors) are useful in reducing IOP by decreasing aqueous production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the mathematical relationship between liquid content of the vitreous and age?

  1. Exponential
  2. No relationship
  3. Linear
  4. Reciprocal
A

Linear- As age increases, the amount of liquid in the vitreous increases linearly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which of the following is not a function of the vitreous?

  1. Provides a vascular supply to the retina
  2. Stores nutrients
  3. Transmits light
  4. Cushions the retina from trauma
A
  1. Provides a vascular supply to the retina. Remember that the vitreous is avascular. It does provide support to the retina in other ways, but it does not perfuse the retina with blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Regarding axonal conduction in the ONH, which of the following is true?

  1. Inside of the axon is negative compared to the environment
  2. Concentration of sodium is higher within the axon
  3. The resting potential is positive
  4. Axonal conduction is propagated through graded potentials
A
  1. Inside of the axon is negative compared to the environment, which means the resting potential would be negative. Remember that action potentials are active in carrying the signal along the optic nerve.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The blood/retinal barrier is formed by all of the following EXCEPT:

A. Tight junctions within wall of retinal vessels
B. Tight junctions between RPE cells
C. Tight junctions between the choriocapillaris

A

C. Remember, NOTHING in the choroid (bruch’s, choriocapillaris, etc) contributes to the blood/retinal barrier.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The majority of blood within the eye is found within the:

A. Central retinal artery
B. Long and short posterior ciliary arteries
C. Conjunctiva
D. Ciliary body vasculature

A

B. Recall that the choroid has the majority of blood flow. Two blood vessels combine to provide the choroidal flow – each artery does two main things:
–LPCA: supplies anterior choroid, and contributes to major arterial circle of the iris (MACI).

–SPCA: supplies posterior choroid, and forms the Circle of Zinn (provides blood supply for the surface of the optic disc).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q 
Where is the majority of oxygen in the eye? within the...
A. Retinal arteries
B. LPCAs
C. SPCAs
D. CRA
A

A. Retinal arteries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Stimulation of sympathetic receptors cause

A. Increase in IOP
B. Decrease in IOP
C. Both
D. Neither

A

C. Both – it depends on which receptors are acted upon.

A2 — stimulation constricts blood vessels in the major arterial circle of the iris and decreases IOP. This is how apraclonidine and brimonidine (the alpha 2 agonists) decrease IOP.Recall that apraclonidine is often used to prevent IOP spikes following surgery or laser treatment.

B1 and B2 — stimulation increases aqueous humor production. B-blockers block these receptors, decreasing IOP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sympathetic stimulation of uveal vessels leads to:

A. Vasodilation
B. Vasoconstriction
C. Neither

A

B. Sympathetic stimulation throughout the body causes vasoconstriction.Remember that the retina differs from the choroid because it does not respond to sympathetic stiumulation because of its own ability to autoregulate its blood supply.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Perfusion pressure refers to:

A. The pressure inside a capillary bed that favors filtration
B. The pressure difference between the inside and outside of a capillary wall
C. The pressure difference between arteries and veins of a particular tissue
D. The pressure inside arteries generated from the heart

A

C. Don’t make this difficult. It is a term that indicates how much blood flow a certain tissue is receiving (arteries to capillaries to veins within the SAME tissue.) The equation for ocular perfusion pressure involves the relationship between the systolic BP, diastolic BP and IOP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which of the following is true regarding the corneal stroma, when the patient is not sleeping:

A. It obtains its oxygen via the tears and nutrients via the aqueous.
B. It obtains its oxygen and nutrients via the aqueous humor.
C. It obtains its oxygen and nutrients via the tears.

A

A. Open eye – the tear film is fully responsible for the oxygen supply..
Nutrient portion of the question is easy – aqueous humor always is the main provider, regardless of the corneal layer.

Remember…. a small amount of CORNEAL EDEMA, upon awakening in the morning, is NORMAL.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which of the following does NOT occur with lens aging?

A. Increase in Glutathione activity
B. Increase in Ca
C. Decrease in ATP
D. Decrease in soluble (crystalline) lens proteins

A

A. Recall that Glutathione is Good for the lens. Calcium is Crappy – leads to cataracts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which of the following does NOT improve lens transparency?

A. Avascular nature of the lens
B. No nerve supply in the lens
C. Presence of membrane bound organelles to decrease light scattering
D. High concentration of crowded crystalline proteins

A

C. Membrane bound organelles would INCREASE light scattering by disrupting the precise alignment of lens fibers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which of the following is true regarding crystalline proteins:

A. Beta is insoluble — has unknown function
B. Alpha is insoluble — acts as a molecular chaperone
C. All crystallins are soluble proteins that decrease in concentration with age.

A

C. Crystallins are SOLUBLE LENS PROTEINS. Your most likely boards question is to know that alpha crystallin acts as a molecular chaperone, reducing cataract formation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The refractive index gradient of the lens…

A. Allows more precise focusing of light, despite increased spherical aberration.
B. Allows the periphery to be steeper, reducing spherical aberration
C. Allows for lower refractive index in the center of the lens
D. Allows for higher refractive power in the center of the lens, while reducing spherical aberration in the periphery.

A

D. Recall that the embryonic nucleus has the highest concentration of crystallins – this is why the index of refraction (1.41) is the highest in the lens center.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Pancoast tumor affects….

A. Preganglionic sympathetic fibers
B. Postganglionic sympathetic fibers

A

A. Recall that Pancoast tumor arises at the apex of the lung.

Sympathetic fibers become postganglionic after synapsing in the superior cervical ganglion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Postganglionic sympathetic fibers to the eye begin:

A. After Ciliospinal Center of Budge
B. At Posterior Hypothalamus
C. After Superior Cervical Ganglion
D. Optic Nerve

A

C. Remember that the sympathetic pathway begins at the hypothalamus and descends to its first synapse at the Ciliospinal Center of Budge. The fibers which exit this center are still considered pre-ganglionic. The next synapse occurs at the superior cervical ganglion and it is after this point in the pathway that the fibers are considered post-ganglionic. In summary, the sympathetic pathway to the eye has three major divisions: 2 pre-ganglionic and one post-ganglionic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Pupillary constriction in response to the location of a near stimulus begins in the:

A. Retina
B. Midbrain
C. Frontal Eye Fields (FEF)
D. Optic Nerve

A

C. Pupil constriction occurs in two situations:

1) Light- mediated by pretectal to EW to Ciliary ganglion
2) Near object- mediated by FEF to EW to Ciliary ganglion

The main point here is that pupil constriction to a near object bypasses the pretectal nucleus.

Recall that Argyll Robertson Pupil (ARP) results from disruption in the tectotegmental tract – which is the tract that connects the pretectal to the EW nucleus. Think of it like a lesion of the pretectal nucleus. This is a perfect example of what is described above…. patients with ARP do not constrict well with light, but they do constrict to a near object.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The blood aqueous barrier consists of tight junctions in all of the following except:

A. Iris vessels
B. Endothelium of Schlemm`s canal
C. Walls of junxtacanalicular tissue
D. Nonpigmented ciliary body epithelium

A

C. Recall that uveitis is caused by a breakdown in the blood aqueous barrier.

  • The blood/aqueous barrier has tight junctions in 3 places.
  • The blood/retinal barrier has tight junctions in 2 places.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Which of the following is true regarding the composition of the aqueous humor?

A. Has higher protein concentration than plasma.
B. Has higher amino acid, Cl-, and lactate concentrations than plasma.
C. Has lower ascorbate concentration

A

B. Ascorbate, is the same as Vitamin C, which we know is high in the aqueous humor, and even higher in the lens (to protect against cataracts

25
Q

Which of the following is true regarding aqueous production?

A. Almost entirely relies on active secretion — a process which leaves the aqueous hypertonic to the plasma — favoring movement of ions into the posterior chamber and thus aqueous formation.
B. Almost entirely relies on active secretion — a process which leaves the aqueous hypotonic to the plasma — favoring movement of ions into the posterior chamber and thus aqueous formation.
C. Almost entirely relies on diffusion.
D. Almost entirely relies on ultrafiltration.

A

A.

26
Q

Which of the following explains why wearing a neck-tie can increase IOP?

A. Increase in arterial flow to ciliary body
B. Decrease in uveoscleral drainage
C. Increase in veinous pressure

A

C. The theory is that a necktie constricts the veins that drain Schlemm’s canal, decreasing outflow via the trabecular meshwork.

This is a perfect example of what I keep stressing…. an increase in episcleral venous pressure INCREASES IOP.

27
Q

Which of the following is true regarding routes of aqueous outflow:

A. Uveoscleral route is considered pressure dependent
B. Episcleral venous pressure increases uveoscleral outflow
C. Trabecular meshwork outflow depends on IOP and the pressure within the conjunctival veins.
D. Trabecular meshwork outflow is constant — regardless of IOP.

A

C. Recall that the episcleral vein is one of the conjunctival veins that drains Schlemm’s canal. Recall that if episcleral veinous pressure increases, IOP increases.

28
Q

Which of the following cause a decrease in IOP?

A. Uveitis
B. Blood acidosis
C. Plasma hyperosmolality
D. All of the above

A

D

29
Q

Which of the following explains how isosorbide decreases IOP?

A. Lowers aqueous osmolarity
B. Increases plasma osmolarity
C. Increases aqueous osmolarity
D. Decreases plasma osmolarity

A

B. Remember the picture I drew 1,000 times in lecture with the cornea/iris/etc. We talked about how fluid leaves MACI and sits in the reservoir area, hoping to get the opportunity to become aqueous – Na and Bicarb leave the reservoir area constantly to become aqueous humor.

Because Na and Bicarb are constantly being pumped across, a gradient is established in which the AQUEOUS HUMOR IS HYPERTONIC (has more ions) to the plasma (reservoir area).

Isosorbide and glycerine are high molecular weight compounds. They sit in the reservoir area and can not get across the tight junctions of the NPCE to reach the aqueous humor. Thus, they reverse the normal gradient – now the PLASMA IS HYPERTONIC to the aqueous, which sucks water out of the eye, reducing IOP.

30
Q

Which of the following is NOT true regarding methods of IOP measurement:
A. In Noncontact Tonometry, the puff of air is
always constant, and the IOP measurement is ultimately based on a time interval.
B. In Goldmann Applanation Tonometry the prism
is always constant, and the IOP measurement
is ultimately based on the amount of force
necessary to flatten the cornea.
C. Noncontact Tonometry is more uncomfortable to the patient but provides more consistent and
reliable measurements.

A

C, is not true

31
Q

Goldmann Applanation Tonometry IOP measurements can lead to:

A. Overestimation of IOP in thinner corneas
B. Underestimation of IOP in thicker corneas
C. Overestimation of IOP in thicker corneas

A

C. The thicker the cornea is, the more resistant it is to flattening by the tonometer probe; this phenomenon leads to an artificially high IOP measurement.

32
Q

Which of the following is NOT true regarding aging changes within the cornea:

A. Descemet`s thickens with age
B. Endothelium cell count decreases with age
C. Becomes more WTR

A

C. You’re born ATR and you die ATR.

A and B are true – remember D3 for Descemet’s, it triples throughout your lifetime. Endothelium cell count decreases – in severe cases, like Fuch’s Endothelial Dystrophy, the loss of endothelial cells makes it difficult to keep water out of the corneal stroma.

33
Q

Your patient has a corneal abrasion. What is the first response of their epithelium after the injury?

A. Migration
B. Adhesion
C. Inhibition of basal cell mitosis
D. Synthesis of new hemidesmosomes

A

C. Second response is migration.

34
Q

Your patient has corneal edema following contact lens overwear. The corneal epithelium can respond by moving which of the following ions into the tears?

A. Na2+
B. Cl-
C. Ca2+
D. K+

A

B. Endothelium – primary source of reducing corneal thickness via Na/K pump.

Epithelium – also helps reduce corneal thickness via the K+ channel – which pumps K+ to the aqueous humor and Cl- to the tears (with water following).

35
Q

Which of the following is FALSE regarding corneal transparency?

A. Collagen fibrils must be precisely spaced to avoid light scattering
B. GAGS provide the appropriate spacing of collagen fibrils
C. The corneal epithelium is the primary contributor to corneal deturgescence

A

C. Remember the following facts about corneal transparency:
The precise size and spacing of collagen fibrils are critical for transparency.
GAGS bind to the collagen fibrils are regularly spaced intervals and maintain the interfibrillar spacing.
Corneal deturgescence refers to the dehydration of the corneal stroma (approximately 78% water); this is primarily the responsibility of the endothelium, but the corneal epithelium also plays a role as well.

36
Q

Which of the following are true regarding retinal cells and receptive fields:

A. Horizontal cells are center-surround and along with bipolar cells generate graded potentials.

B. Amacrine, bipolar, and ganglion cells are center-surround and all three generate action potentials.

C. Amacrine and Ganglion cells generate action potentials, while Horizontal, Bipolar and Photoreceptor cells generate graded potentials.

A

C

37
Q

Which of the following are true regarding retinal neurotransmitters:

A. Glutamate is excitatory, used by photoreceptors and horizontal cells.
B. GABA is excitatory, used by photoreceptors, bipolar cells, ganglion cells.
C. Glycine and GABA are inhibitory, used by horizontal cells, and most amacrine cells.

A

C. Recall that the three main players in the retina, PHOTORECEPTORS, BIPOLARS, AND GANGLION CELLS, utilize EXCITATORY neurotransmitters.

The two main modifiers, amacrine and horizontal cells, utilize INHIBOTORY neurotransmitters – GABA and GLYCINE.

38
Q

Phototransduction in the outer segment leads to the following:

A. Hyperpolarization, generation of graded potential, and a decrease in glutamate release from photoreceptors.
B. Depolarization, generation of action potential, and an increase in glutamate release from photoreceptors.
C. Hyperpolarization, generation of action potential, and an increase in glutamate release from photoreceptors.
D. Hyperpolarization, generation of graded potential, and an increase in glutamate release from photoreceptors.

A

A. The eye is unusual in that stimulation leads to hyperpolarization. Recall that AMACRINE and GANGLION cells are the only retinal cells to perform ACTION POTENTIALS.

Quick Reminder….

  • Action potentials — all or nothing response.
  • Graded potentials — the response depends on the number of photons absorbed.
39
Q

Which of the following differs between rod spherules and cone pedicles?

A. Vitamin A derivative: 11-cis in rods, all-trans in cones
B. Opsin component
C. In cones, iodopsins are embedded within the disc membranes. In rods, rhodopsin is not stored in discs, but rather invaginations of the outer segment plasma membrane.

A

B. Rhodopsin in rods, Iodopsins in cones.

40
Q

Which of the following is NOT true regarding the vitreous?

A. Cushions and protects the globe from external trauma
B. Disruption in the hyaluronic acid/ collagen complex leads to floaters
C. Collagen concentration is highest in the center, leading to more floaters centrally with aging.
D. Acts as a reservoir for metabolic activities in the retina and ciliary body.

A

C. Collagen concetration is highest at the vitreous base. Lowest in the center.

41
Q

Which of the following is correct regarding waves of the ERG:

A. A-wave is for Mueller cells
B. B-wave is for Photoreceptors
C. C-wave is for RPE cells
D. D-wave is for Photoreceptors

A

C. Remember the waves of the ERG by….

A photoreceptor
B bipolor and mueller
C RPE

42
Q

Which is true regarding the Arden ratio in an EOG:

A. Indication of sensory retina health / 1.25 reading would indicate healthy
B. Indication of RPE health/ 1.90 reading would indicate healthy.
C. Indication of sensory retina health / > 1.50 is healthy
D. Indication of RPE health /

A

B. Arden ratio should be greater than 1.8. 1.65-1.80 is considered subnormal, and

43
Q

Which of the following is NOT true regarding simple and complex cells?

A. Simple and Complex cells first appear in V1 along the visual pathway.
B. Each simple cell is programmed to specialize in objects with a particular orientation in space.
C. Each complex cell is programmed to specialize in objects with a particular orientation that move in a specific direction.
D. Simple cells are likely a product of combined input from retinal cells.

A

D

44
Q

Which of the following is the first place in the visual pathway to combine monocular input for binocular processing?

A. LGN
B. V2
C. V1
D. Optic Chiasm

A

C

45
Q

Which of the answer(s) below can cause a retinal arterial occlusion?

A. Hollenhorst plaque
B. Calcifications from heart valves
C. Giant Cell Arteritis
D. Sickle Cell Anemia

A

A,B,C,D (All Answers)

Recall that ARTERY OCCLUSIONS will cause a WHITE retina. However, weeks after the occlusion, the retina will look normal.

EMBOLI cause ARTERIAL OCCLUSIONS. HOLLENHORST PLAQUES are small, cholesterol plaques. CALCIFIC EMBOLI are large, dangerous plaques from heart valves.

THROMBI cause VEIN OCCLUSIONS. Recall that in a vein occlusion (CRVO, BRVO) arteries compress a vein, which causes the thrombus formation.

46
Q

Even though NEOVASCULARIZATION can lead to devastating visual outcomes – not all cases of neo in a diabetic are treated, only those who meet high-risk characteristics (HRC’s). Which of the following is a HRC?

A. NVD > 1/4 DD, but no preretinal hemorrhage
B. IRMA with Retinal hemorrhages in all 4 quadrants
C. Macular thickening within 1DD of the macula
D. Venous beading in 2 quadrants

A 
A. 
Be sure to review the notes for DIABETIC RETINOPATHY. There are 3 different series of rules you need to know.
1. 4-2-1 RULE
2. High Risk Characteristics
3. Definition CSME

Recall the following….
-DURATION of DM is biggest risk factor for development of DIABETIC RETINOPATHY… NOT A1C, blood sugar, etc..

-MACULAR EDEMA is the MOST COMMON reason for legal blindness in a diabetic.

47
Q

Macular edema is the leading cause of blindness in a diabetic, but NOT all cases of macular edema are treated – only CLINICALLY SIGNIFICANT MACULAR EDEMA (CSME). Which of the following criteria falls under CSME?

A. Retinal thickening within 600 um of foveal center
B. Exudate within 600 um of foveal center
C. Thickening of 1.5DD within 2DD
D. Retinal thickening of 1/10DD within 200 um of foveal center.

A

D. ANY RETINAL THICKENING within 500 um of FOVEAL CENTER is CSME.

–1/3DD is approximately 500 um.

48
Q

What are the layers of the tear film and what structures contribute to each layer?

A

LIPID = Meibomian, Zeis, Moll glands

AQUEOUS = Main lacrimal gland, Glands of Krause, Glands of Wolfring

MUCOUS = Goblet cells

49
Q

Which of the following is not a characteristic of extraocular muscles?

A. Quick reaction speed
B. Fatigue-resistant
C. Rapid contraction times
D. Small number of mitochondria

A

Correct answer: D (small number of mitochondria).

The EOMs have a large number of mitochondria because the EOMs are very active and require lots of energy.

50
Q

Ocular blood flow can be altered, through autoregulation, in which of the following areas? Pick 2

  1. Optic Nerve
  2. Ciliary Body
  3. Choroid
  4. Retinal vessels
  5. Iris vessels
A

Correct Answers = 1, 4

Remember, autoregulation only occurs in two prime spots in the eye (retina, optic nerve). Do NOT choose choroid as an answer if asked on the examination.

51
Q

Autoregulation of the retina serves to maintain a constant supply of blood to the retina by increasing or decreasing vessel diameter. What systemic disease most commonly causes this type of change?

A

Hypertension

In the early stages of hypertensive retinopathy, arteriolar attenuation is expected. In response to the high pressure (from HTN) entering the retina, the retinal arterioles undergo vasoconstriction.

52
Q

Why is flare present in the anterior chamber in patients with anterior uveitis?

A

Correct Answer = Breakdown of the blood aqueous barrier

Normally, protein molecules are too large to pass through the tight junctions found within the blood aqueous barrier (iris vessels, NPCE, Schlemm’s canal). A breakdown of these junctions allow substances to gain access to the anterior chamber which would normally NOT cross the barrier.

53
Q

Why does arteriolar narrowing occur in the early stages of ocular hypertension?

A

To counteract the effects of hypertension, the retinal vessels AUTOREGULATE and undergo vasoconstriction. Remember, autoregulation occurs in the RETINAL VESSELS and at the OPTIC NERVE.

54
Q

Why do diabetics commonly develop cataracts at a younger age as compared to non-diabetics? What type of refractive error shift is expected with high levels of blood glucose? Why does this occur?

A

Correct Answer = The aqueous and vitreous receive nutrients from the bloodstream and nourish the lens. When high amounts of glucose enter the lens, it is converted to sorbitol and an osmotic gradient is created that attracts water, ultimately leading to swelling, damage, and cataract formation.

Correct Answer = Lens swelling increases the refractive power of the eye, contributing to a myopic shift. As the blood sugar is normalized, the swelling will regress, and the refractive error will be shifted back toward the normal position (in hyperopic direction).

Increase in blood sugar = myopic shift

Cataracts in DM = sorbitol accumulation

55
Q

Why is the vitreous more viscous than water?

A

Correct Answer = the vitreous contains Hyaluronic acid. Recall that hyaluronic acid is a glycosaminoglycan (GAG) that increases with age. Recall that GAG’s are sugars that attract water.

56
Q

Which 3 of the following structures make up the blood-aqueous barrier? (Pick 3)

  1. Pigmented ciliary epithelium
  2. Conjunctival vessels
  3. Endothelium of Schlemm’s canal
  4. Posterior pigmented iris epithelium
  5. Iris vessels
  6. Nonpigmented ciliary epithelium
A

Correct Answers = 3,5,6

All three of these have tight junctions to prevent the blood and its contents from entering the aqueous.

57
Q

You decide to give a classmate a corneal abrasion for fun and have the capability of watching the corneal epithelium heal under a microscope. What would you see as the first response of the epithelium?

  1. Cells surrounding the defect migrate onto the wounded area creating an epithelial sheet
  2. Basal cell mitosis occurs at a rapid rate
  3. Basal cell mitosis stops
  4. Wing cell mitosis occurs at a rapid rate
A

Correct Answer = 3. Basal cell mitosis stops. The first response of the epithelium after injury is to STOP BASAL CELL MITOSIS.

Next, the cells surrounding the defect lose their attachment to the BM as they enlarge and create an EPITHELIAL SHEET in order to MIGRATE ONTO THE WOUNDED AREA. Hemidesmosomes are then created to allow for proper adhesion between the migrated cells and the BM. Once the wound is closed, BASAL CELL MITOSIS OCCURS AT A RAPID RATE to restore corneal integrity. Wing cells do not undergo mitosis, only basal cells do.

58
Q 
Which of the following values BEST describes the average imbibition pressure (IP) of the corneal stroma?
A. -25 mmHg
B. -55 mmHg
C. +25 mmHg
D. +55 mmHg
E. +40 mmHg
F. -40 mmHg
A

F. Explanation - The imbibition pressure of the corneal stroma is due to the anionic (negatively charged) repulsive forces of the glycosaminoglycans (GAGs), which causes the tissue to expand and suck fluid into the cornea. In vitro, the imbibition pressure (IP) and the stromal swelling pressure (SP) are equivalent. However, in vivo, the IP is lower than the SP because the hydrostatic pressure induced by the intraocular pressure must be accounted for. Therefore, the average imbibition pressure of the corneal stroma is approximately -40 mmHg.

Boards (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions