Ocular Physiology - Cornea: Midterm 1
(240).jpg "Ocular Physiology - Cornea: Midterm 1 - Quiz")
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Questions and Answers
- 1.
Na+fluorescein is taken up by damaged epithelial cells.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Na+fluorescein is a fluorescent dye that is commonly used to assess cellular damage. When cells are damaged, their membrane integrity is compromised, allowing the dye to enter the cells. Therefore, if Na+fluorescein is taken up by damaged epithelial cells, it indicates that the cells have been damaged. Hence, the statement "Na+fluorescein is taken up by damaged epithelial cells" is true.Rate this question:
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- 2.
Select the FALSE statements
- A.
The cornea is the major refractive element of the eye (+48D)
- B.
Corneal curvature and axial length determine power of the eye Corneal curvature and axial length determine power of the eye Corneal curvature and axial length determine power of the eye
- C.
Cataract surgery was the first type of refractive surgery
- D.
Damage to the corneal endothelium during RK is a minor problem
- E.
In the lasik procedure the epithelial layer is also removed completely similarly to PRK
Correct Answer(s)
D. Damage to the corneal endothelium during RK is a minor problem
E. In the lasik procedure the epithelial layer is also removed completely similarly to PRKExplanation
The cornea is not the major refractive element of the eye. It only contributes about 40D to the total refractive power of the eye. The corneal curvature and axial length do determine the power of the eye. Cataract surgery was not the first type of refractive surgery, it is a procedure to remove a cloudy lens. Damage to the corneal endothelium during RK (Radial Keratotomy) is a major problem, not a minor one. In the LASIK procedure, the epithelial layer is not completely removed, only a flap is created. However, in PRK (Photorefractive Keratectomy), the epithelial layer is completely removed.Rate this question:
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- 3.
The epithelium: A. Has superficial cells, wing cells and basal cells B. Three types of collagen (IV, VII, XII) C. Contains MPS, keratocyes D. Is one cell layer thick with tight juntions
- A.
A
- B.
B
- C.
C
- D.
D
Correct Answer
A. AExplanation
Option B: for the basement membrane of the epithelium
Option C: Refers to the stroma
Option D: refers to the endotheliumRate this question:
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- 4.
Desmosomes (where two cells come together) help to prevent the flow of substances b/t cells
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Desmosomes are cell junctions that provide strong adhesion between cells. They consist of proteins that link the cytoskeletons of adjacent cells together. This adhesion helps to prevent the flow of substances between cells, maintaining the integrity and stability of tissues. Therefore, the statement that desmosomes help to prevent the flow of substances between cells is true.Rate this question:
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- 5.
A tight junction is where two cell membranes fuse together. Also only carbon dioxide, O2 and small ions through
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
A tight junction is a type of intercellular junction where two adjacent cell membranes fuse together, forming a barrier that prevents the passage of molecules and ions between the cells. This barrier is important for maintaining the integrity and selective permeability of tissues. The statement that only carbon dioxide, O2, and small ions can pass through a tight junction is true because these molecules are small enough to pass through the tight junction's narrow channels, while larger molecules and ions are unable to do so.Rate this question:
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- 6.
Gap junction don't allow passage b/t cells. They keep the wing cells and basal cells from becoming electrically coupled
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Gap junctions allow for the passage of ions b/t cells, connecting wing cells and basal cellsRate this question:
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- 7.
Select True statements regarding the corneal epithelium
- A.
Basal cells undergo mitosis to produce wing cells
- B.
In wing cells we see internal degradation of the organelles of the cell
- C.
Superficial cells contain only cytoplasm and no debris
- D.
The epithelium of the cornea in general is very different in lifecycle and characteristic from the epithelium of the skin.
- E.
Like the epithelium of the skin, the epithelium of the cornea excretes keratin
Correct Answer(s)
A. Basal cells undergo mitosis to produce wing cells
B. In wing cells we see internal degradation of the organelles of the cell
C. Superficial cells contain only cytoplasm and no debrisExplanation
Keratin is hydrophobic, would not want that on the corneaRate this question:
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- 8.
You view the endothelium of the cornea with specular reflection
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Specular reflection is a type of reflection that occurs when light hits a smooth surface and bounces off at the same angle. In the context of viewing the endothelium of the cornea, specular reflection refers to the reflection of light off the smooth surface of the endothelium. This reflection allows for clear visualization of the endothelium and its characteristics. Therefore, the statement "You view the endothelium of the cornea with specular reflection" is true.Rate this question:
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- 9.
Only the corneal endothelium and epithelium have tight junctions.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
The statement is true because the corneal endothelium and epithelium are the only layers of cells in the cornea that have tight junctions. Tight junctions are specialized connections between cells that form a barrier, preventing substances from passing between the cells. This barrier function is important for maintaining the transparency and integrity of the cornea. Other layers of the cornea, such as the stroma and Bowman's layer, do not have tight junctions.Rate this question:
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- 10.
What conditions must be met in order for large particle light scatter to occur? A. An interface with refractive index different from the medium. B. The interface has to be longer than 1 wavelength C. A photon must be lost and energy given off as heat.
- A.
A
- B.
B
- C.
C
- D.
A and B
- E.
B and C
Correct Answer
D. A and BExplanation
Option C : refers to absorptionRate this question:
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- 11.
Major points of reflection include:
- A.
Keratocytes
- B.
Mitochondrial reflection
- C.
Epithelium - and Bowman's interface
Correct Answer(s)
A. Keratocytes
B. Mitochondrial reflection
C. Epithelium - and Bowman's interfaceExplanation
Also air-tear interface, endothelium - aqueousRate this question:
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- 12.
It is theoretically possible to have small particle light scatter at every collagen fibril.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
In collagen fibrils, small particles of light can scatter. This means that when light passes through collagen fibrils, it can be deflected or redirected in different directions due to the scattering effect caused by the particles. Therefore, it is theoretically possible for small particle light to scatter at every collagen fibril.Rate this question:
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- 13.
Select TRUE statements A. Maurice - perfect lattice hypothesis gives destructive interference B. Perfect lattices are found on electron micrographs C. Benedek and Farrell stated that the average number of fibrils in an area must not fluctuate too greatly from the overall average for destructive interference to predominate D. In the sclera the collagen fibrils range in size and concentration.
- A.
A
- B.
B
- C.
C
- D.
D
Correct Answer(s)
A. A
C. C
D. DExplanation
The perfect lattice hypothesis suggests that destructive interference occurs in Maurice, which supports statement A. Statement C is supported by Benedek and Farrell's statement that destructive interference predominates when the average number of fibrils in an area does not fluctuate greatly from the overall average. Statement D is supported by the fact that in the sclera, collagen fibrils vary in size and concentration. Statement B is not supported as there is no mention of perfect lattices being found on electron micrographs.Rate this question:
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- 14.
Select false statements:
- A.
Stromal swelling pressure is the mechanical load/unit area required to maintain the tissue at a fixed water content
- B.
Stroma swells parallel to its surface
- C.
Collagen fibrils pull H20 into the cell
- D.
GAGS are the origin of swelling pressure
- E.
Swelling pressure is reduced over time in contact with aqueous solutions, GAGS lost to the solution
- F.
Substances that precipitates GAGS decrease swell pressure
- G.
IOP acts as external pressure
Correct Answer(s)
B. Stroma swells parallel to its surface
C. Collagen fibrils pull H20 into the cellExplanation
The stroma does not swell parallel to its surface; instead, it swells perpendicular to its surface. Collagen fibrils do not pull water into the cell; they provide structural support to the tissue. Therefore, these statements are false.Rate this question:
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- 15.
Water added to the stroma only adds to its thickness, not diameter
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Adding water to the stroma of a plant only increases its thickness and not its diameter. This means that the overall size of the stroma remains the same, but it becomes thicker.Rate this question:
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- 16.
The ___________ Hypothesis explains the maintenance of stromal hydration and for that matter transparency.
Correct Answer
Pump-leakExplanation
The Pump-leak Hypothesis suggests that the maintenance of stromal hydration and transparency is achieved through a balance between active fluid transport (pumping) and passive fluid movement (leakage) in the stroma. This hypothesis proposes that the endothelial cells of the cornea actively pump fluid out of the stroma, while the epithelial cells create a barrier to prevent excessive leakage. This balance is crucial for maintaining the proper hydration levels and transparency of the cornea.Rate this question:
- 17.
Both epi and endo pump water, but greater than 905 of the water pumping is provided by the endothelium. Blockingthe endothelium essentially eliminates fluid transport.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
The explanation for the given correct answer is that both the epi and endo pump water, but the majority of the water pumping, specifically greater than 90%, is provided by the endothelium. Therefore, if the endothelium is blocked, it essentially eliminates fluid transport. This supports the statement that the answer is true.Rate this question:
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- 18.
Which of the following do you need to know in order to calculate the flow across the tissue for a given pressure? A. Flow conductivity B. Thickness of a tissue C. Area of a tissue
- A.
A
- B.
B
- C.
C
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
To calculate the flow across the tissue for a given pressure, you need to know the flow conductivity, which determines how easily fluid can flow through the tissue. Additionally, you need to know the thickness of the tissue, as this affects the resistance to flow. Finally, the area of the tissue is also required, as it determines the overall flow capacity. Therefore, all of the options A, B, and C are necessary to calculate the flow across the tissue for a given pressure.Rate this question:
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- 19.
Darcy's law of bulk flow tells us how much water flows through the cornea
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Darcy's law of bulk flow is a principle in fluid dynamics that relates the flow rate of a fluid through a porous medium to the pressure difference across the medium. In the context of the question, it implies that Darcy's law can be used to determine the amount of water that flows through the cornea, which is the clear front surface of the eye. Therefore, the statement is true.Rate this question:
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- 20.
Fluid transport in the cornea requires Na+, Cl- and HCO3-
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Fluid transport in the cornea requires Na+, Cl- and HCO3- because these ions play important roles in maintaining the osmotic balance and pH regulation in the cornea. Na+ helps in the active transport of fluid across the corneal endothelium, while Cl- and HCO3- ions are involved in maintaining the electrochemical balance and pH of the corneal stroma. Without these ions, the fluid transport mechanism in the cornea would be disrupted, leading to imbalances in fluid volume and pH, which can affect corneal transparency and function.Rate this question:
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Current Version
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Mar 22, 2023Quiz Edited by
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Sep 26, 2011Quiz Created by
Mchllmijares
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