Exam 1 Remington- Corneal Physiology Flashcards Preview

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Flashcards in Exam 1 Remington- Corneal Physiology Deck (106)
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1

What are the 4 functions of the cornea?

Transmits light, absorbs short wavelength UV, refracts light, and proper corneal function requires minimal scattering and distortion

2

Cornea scatters less than __% incident light.

1

3

Cytoplasm of epi and endo cells in the cornea contain what?

Corneal crystallins, water soluble proteins

4

What do corneal crystallins do?

They make cytoplasm homogenous and decrease light scattering

5

What range does the cornea transmit?

UV 310 nm to IR 2500 nm

6

What is the reason for photokeratitis?

The cornea absorbs short wavelength UV

7

Photokeratitis

Inflammation caused by absorption of UV

8

What are causes of photokeratitis?

Welder's arc, tanning beds, and snowblindness

9

What is the refraction of light of the cornea determined by?

Curvatures of the various surfaces, interfaces between different indices of light, and length of pathway through the structures

10

Proper corneal function requires what?

Minimal scattering and distortion, no blood vessels, proper hydration

11

Relative corneal deturgescenes means the corneal is ___% water

78

12

Corneal hydration is dependent on what?

Temperature, swells when cooled and returns to normal at body temperature

13

What is the role of tears in maintaing proper hydration?

As tears evaporate the tear fluid becomes more concentrated, tear film osmolarity increases relative to the cornea, the hypertonicity of tear film draws water from cornea and the blink response is elicited because hypertonicity causes a slight sting and thus tear film is restored

14

What is the role of the epithelium in maintaining proper hydration?

ZO barrier prevents intercellular water influx from tears, ions move across both surfaces, aquaporins are water transport channels

15

What do channels of the epithelium allow?

Channels allows Na+ to pass into epi from tears and Cl- to pass into tears

16

What are major driving forces for water transport?

Cl- extrusion and Na+ influx

17

The co-transporter mechanism moves what ions in the cornea?

Na, K, and Cl ions

18

Na+/K+ ATPase pumps located in ______ ______ of the cornea actively move ions

Basolateral membrane

19

Aquarporins are present where?

Epithelial cell membranes

20

There is a ________ flow of water across the plasma membrane in the cornea.

Bidirectional

21

What is the role of the stroma in maintaining proper hydration?

GAGs are present in ground substance surrounding collagen fibers, increasing hydration leads to decreasing transparency

22

What is the role of GAGs in the stroma of the cornea?

Due to anionic characteristics they bind with water- there is an inherent tendency to imbibe water and to swell

23

Water content of the stroma should be approximately ___%

78

24

The normal water content of the sclera is ___%, if it falls below ___% or above ___% the sclera becomes lucent

68, 40, 80

25

What is the role of endothelium in the cornea in maintaining proper hydration?

These cells have high metabolic activity, apparent by large number of mitochondria and Golgi apparatus, slow leak of fluids and solutes from the aqueous, the Na+/K+ ATPase pump is located in the basolateral membrane of the endothelium

26

How does the Na+/K+ ATPase pump located in the basolateral membrane of the endothelium act?

Pumps act at a steady rate and the rate of leakage is dependent upon the pressure gradient across the endo

27

What are the ions that cotransporters move across membranes?

Na, K, Cl, HCO3

28

Where are aquaporins located in the endothelium?

In the endo cell membrane

29

What are 4 measures of endothelial function?

Coefficient of variation CV, cell density, polymegathism, and pleomorphism

30

What is the coefficient of Variation CV?

Indicates the degree of uniformity among endo cells