Brainscape's Knowledge GenomeTM

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


See full index

A&P > Cornea > Flashcards

Cornea Flashcards

1
Q

What is the anterior horizontal diameter of the cornea?

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

What is the anterior vertical diameter of the cornea?

A

11mm

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

How does the curvature of the cornea vary?

A
  • curvature steeper in the centre
  • flatter at periphery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the radius of curvature of the cornea a the posterior surface?

A

6.5mm

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

What is the radius of curvature of the central cornea at the anterior surface?

A

7.8mm

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

What is the central corneal thickness?

A

0.53mm

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

What is the corneal periphery thickness?

A

0.71mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is the cornea optimum for light transmittance?

A
  • transparency and avascularity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What covers the anterior surface of the cornea?

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

What posteriorly borders the cornea?

A

anterior chamber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the cornea continuous with at the periphery?

A
  • conjunctiva and sclera
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the five layers of the cornea?

A
  • epithelium
  • Bowmans layer
  • stroma
  • Descemets membrane
  • endothelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the outermost layer of the cornea epithelium?

A
  • stratified corneal epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What’s the amount of cells and thickness of the stratified corneal epithlium?

A
  • five to seven cells thick
  • 50um
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where is the corneal epithelium thickest?

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

What is the corneal epithelium continuous with at the limbus?

A

conjunctival epithelium

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

What’s the thickness of the surface layer epithelium?

A
  • two cells thick
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the surface layer of corneal epithelium consist of?

A
  • nonkeratinized squamous cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the features of nonkeratinized squamous cells?

A
  • contain flattened nucleus
  • fewer organelles than deeper cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What the cell size of the superficial cells of the surface layer corneal epithelium?

A

-50um diameter
- 5um height

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

What does the plasma membrane of the surface epithelial cells secrete?

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

What is the function of glycocalyx?

A
  • adjoins the mucin layer of the tear film
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the many projections on the apical surface on the outermost cells of the corneal epithelium?

A
  • microvilli
  • microplicae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What’s the functions of the microvilli and microplicae on the corneal epithelium?

A
  • increases surface area
  • enhances tear film stability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What’s the function of the Zonula occludens?

A
  • barrier to intercellular movement of substances from the tear layer
  • prevent excess fluid uptake from the tear film
  • semipermeable membrane allows passage of fluid and molecules through the cells, but not between them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What joins the surface layer corneal epithelium cells?

A
  • zonula occludens
  • tight junctions
  • additional adhesion between cells from desmosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What happens as the corneal surface epithelium cells age?

A
  • they degenerate
  • cytoskeleton disassembles
  • cytoplasm condenses
  • cells lose attachments, sloughed off
  • constantly replaced by cells below
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does the corneal surface look like when viewed through an electron microscope?

A
  • variously sized cells
  • lighter cells are newly replaced
  • darker cells those that are degenerating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What’s the middle layer of the corneal epithelium made up of?

A
  • two to three layers of wing cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What’s the structure of the corneal epithelium wing cells?

A
  • wing like lateral processes
  • polyhedral
  • convex anterior surface
  • concave posterior surface
  • 20um in diameter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What joins wing cells together?

A
  • desmosomes
  • gap junctions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What joins wing cells to surface and basal cells?

A
  • desmosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the innermost layer of corneal epithelium?

A
  • basal cell layer
  • single layer of columnar cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What’s the diameter of the cells of the basal cell layer?

A

8 to 10um

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What do the basal cells contain?

A
  • oval shaped nuclei displaced towards the apex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Where do basal cells lie?

A
  • rounded apical surface of each cell lies adjacent to the wing cells
  • basal surface attaches to underlying basement membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What do the basal cells secrete?

A
  • basement membrane to attach the cells to the underlying tissue through hemidesmosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Where does epithelial cell proliferation take place?

A
  • basal layer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

How do new cells reach the epithelial cell surface?

A
  • basal cells move up to become wing cells
  • wing cells move up to become surface cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What are the only epithelial cells that are able to divide?

A
  • cells in contact with the basement membrane(basal cells)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is the source for renewal of the corneal basal cell layer?

A
  • stem cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Where are the stem cells that renew the basal layer located?

A
  • a 0.5 to 1mm band around the cornea periphery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

How do new basal cells reach the centre cornea?

A
  • slow migration of basal cells from the periphery stem cells
44
Q

What is the turnover time for the entire corneal epithelium?

A

7 days

45
Q

How does the epithelial healing differ to damage to the basement membrane?

A
  • repair to corneal epithelium heals quickly
  • basement membrane takes much longer to heal
46
Q

How is the corneal epithelial barrier function maintained despite constantly being sloughed?

A
  • the cell below moves into the position to be replaced
47
Q

What is the second layer of the cornea?

A

Bowmans layer

48
Q

What’s the thickness of the Bowmans layer?

A
  • 8 to 14um thick
49
Q

What’s the structure of the Bowmans layer?

A
  • dense, fibrous sheet of interwoven collagen fibrils randomly arranged in a mucoprotein ground substance
50
Q

What’s the diameter of the bowman’s layer fibrils?

A
  • 20 to 25um
51
Q

How are the Bowmans layer fibrils arranged?

A
  • run in various directions
  • not arranged into bundles
52
Q

What happens to corneal nerves when they pass through the Bowmans membrane?

A
  • lose their Schwann cell covering and pass into the epithelium as naked nerves
53
Q

What kind of layer is the Bowmans layer?

A
  • a transition layer to the stroma
54
Q

How does the Bowmans layer differ to the stroma?

A
  • its acelluar
  • contains collagen fibrils of a smaller diameter
55
Q

How do the anterior and posterior surfaces of the Bowmans layer differ?

A
  • anterior surface pattern irregular and reflects the contour of the bases of the basal cells epithelium
  • posteriorly the fibrils adopts a more orderly arrangement and merge into bundles that intermingle with those of the stroma
  • posterior surface not clearly defined
56
Q

What happens if the Bowmans layer is injured?

A
  • layer usually replaced by epithelial cells or stromal scar tissue
57
Q

What’s the thickness of the corneal stroma?

A

500um

58
Q

How much of the corneal thickness does the stroma take up?

A
  • 90%
59
Q

What is the corneal stroma composed of?

A
  • collagen fibrils
  • keratocytes
  • extracellular ground substances
60
Q

What is the stroma collagen Fibrils diameter?

A
  • 25 to 35 nm
61
Q

What do the stroma collagen fibrils form?

A
  • run parallel to one another forming lamellae
62
Q

How many lamellae lie within the corneal stroma?

A
  • 200 to 300
63
Q

How are the lamellae and collagen fibrils arranged?

A
  • Fibrils and lamellae parallel to corneal surface
  • adjacent lamellae lie at angles to one another
  • all fibrils within lamellae run in same direction
  • each lamellae extends across entire cornea
  • interweaving occurs between lamellae
64
Q

How are the lamellae arranged in the anterior one third of the stroma?

A
  • lamellae are thin
  • branch and interweave more than deeper layers
65
Q

How are the lamellae arranged in the posterior two thirds of the stroma?

A
  • arrangement more regular
  • lamellae larger
66
Q

Why does the anterior cornea have a high incidence of lamellae cross linking?

A
  • makes it more rigid to help maintain cornea curvature
67
Q

What happens to the fibrils in the innermost layer of the corneal stroma?

A
  • the fibrils interlace to form a thin collagenous sheet that contributes to the binding between the stroma and Descemet’s membrane
68
Q

What are the Keratocytes?

A
  • flattened cells that lie between and within the lamellae
69
Q

How are the Keratocytes distributed?

A
  • a corkscrew pattern from the anterior to posterior
  • density higher in anterior stroma
70
Q

How do the keratocytes maintain the stroma?

A
  • synthesize collagen and extracellular matrix components
71
Q

What fills the areas between stroma fibrils, lamellae and cells?

A
  • ground substance
72
Q

What contributes to stromal transparency?

A
  • regular arrangement of stromal components
  • small diameter of fibrils
73
Q

What’s the index of refraction of the stromal fibrils and extracellular matrix?

A
  • fibrils is 1.411
  • extracellular matrix is 1.365
74
Q

How does the distance between areas of different refractive indices affect transparency?

A
  • If the change in the index of refraction occurs across a distance that is less than one half the wavelength of visible light (400 to 700 nm), destructive interference occurs, and light scattering is reduced significantly
75
Q

How much of the light that enters the cornea is scattered?

A

1%

76
Q

What’s the Descemet’s membrane considered to be?

A
  • basement membrane of the endothelium
77
Q

How does the Descemets membrane change with age?

A
  • thickens throughout life
  • doubled by age 40
  • children 5um thick to 15um over lifetime
78
Q

What are the two lamellae the Descemets membrane consists of?

A
  • anterior lamellae
  • posterior lamellae
79
Q

What’s the difference between the anterior and posterior Descemets membrane lamellae?

A
  • anterior lamina, 3um thick, banded apperance, latticewrok of collagen fibrils
  • posterior lamina, non banded, homogenous, the portion secreted by the endothelium throughout life
80
Q

How does the Descemets membrane have elastic properties?

A
  • no elastic fibers present
  • collagen fibrils arranged in such a way
81
Q

What happens if Descemets membranes torn?

A
  • curls into the anterior chamber
82
Q

is the Descemets membrane resistant?

A

yes

83
Q

can Descemets membrane be regenerated?

A

yes

84
Q

What is the Schwalbes line?

A
  • thickened area of collagenous connective tissue at the membranes termination in the limbus
  • circular
85
Q

What’s the innermost layer of the cornea?

A
  • endothelium
86
Q

What is the endothelium composed of?

A
  • single layer of flattened cells
87
Q

What’s the thickness of the endothlium?

A
  • 5um
88
Q

What does the basal part of each endothelium cell rest on?

A

Descemets membrane

89
Q

What does the apical part of the endothlium rest on?

A
  • the anterior chamber
90
Q

What shape are the endothelial cells?

A
  • polyhedral
  • 70 to 80% of cells hexagonal
91
Q

Why are the endothelial cells hexagonal?

A
  • hexagon the most efficacious shape to provide coverage without gaps
92
Q

What is the regular arrangement of the endothelial cells called?

A
  • endothelial mosaic
93
Q

What joins the lateral walls of the endothelial cells?

A
  • interdigitations
94
Q

What do the endothelial gap junctions provide?

A
  • intercellular communication
95
Q

What are the two primary functions of the cornea?

A
  • refract light
  • transmit light
96
Q

What is the total refractive power of the eye?

A

60 to 65 diopters

97
Q

What is the refractive power of the cornea?

A

43 to 48 diopters

98
Q

How is scattering of incident light minimized in the cornea?

A
  • smooth optical surface formed by corneal epithelium and tear film
  • regular arrangement of surface epithelial cells
  • tear film fills in slight irregularities between cells
  • absence of blood vessels
  • maintenance of correct spatial arrangement of components
  • endothelial and epithelial cell cytoplasm contain large amounts of water soluble proteins so its homogenous
99
Q

What are the cell cytoplasm water soluble proteins called?

A
  • corneal crystallin’s
100
Q

How is the precise arrangement of the collagen fibrils in the cornea stroma maintained?

A
  • negatively charged molecules located around each collagen fibril maintain their precise bonds with water molecules
101
Q

What are the two primary functions of the cornea?

A
  • refract light
  • transmit light
102
Q

factors that affect amount of corneal refraction?

A
  • curvature of anterior surface
  • change in refractive surface from air to cornea
  • corneal thickness
  • curvature of posterior cornea surface
  • change in refractive index from cornea to aqueous humor
103
Q

total refractive power of eye focused at infinity?

A
  • 60 to 65 diopters
104
Q

refractive power of cornea?

A
  • 43 to 48 diopters
105
Q

What is the corneal deturgescence required precise control of stromal extracellular water content dependent on?

A
  • barrier function of the epithelium and endothelium
  • anionic characteristics of molecules within the stromal matrix
  • water and ion transport through the epithelial and endothelial cell membranes.
106
Q

How is fluid continuously entering the cornea?

A
  • enters through leaky barrier formed by the junctions joining the endothelial cells

A&P (7 decks)

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