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y SCO Ocular Anatomy > Ocular exam 2 > Flashcards

Ocular exam 2 Flashcards

1
Q

What of the iris can be seen anteriorly?

A

The collarette

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2
Q

what is the collarette?

A

It’s the thickest part of the iris. It is a zigzag circular ridge of collagenous remains of vessels and some active vessels. it divides into pupillary and ciliary zones

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3
Q

What is the ciliary zone of the collarette? What structures are here?

A

small peripheral crypts, middle furrowed subzone, Fuch’s crypts, and radial streaks

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4
Q

what are small peripheral crypts?

A

in the ciliary zone of the collarette, they are pits where there is no surface layer of the iris

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5
Q

what is the middle furrowed subzone?

A

in the ciliary zone of the collarette, it has concentric wrinkles that are individual-specific

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6
Q

what are Fuch’s crypts?

A

They are pits where there is no surface layer of the iris, it can be on the ciliary zone or pupillary zone of the collarette

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7
Q

What are radial streaks?

A

in the ciliary zone of the collarette, these are white columns that run throughout the ciliary zone

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8
Q

What’s the pupillary zone of the collarette? What parts are there?

A

Radial streaks (finer than ciliary zone) and Fuch’s crypts

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9
Q

How does a blue eye appear blue?

A

the body or stroma of the iris absorbs long wavelengths and the pigmented epithelium of the iris reflects the short wavelength light back.

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10
Q

How does a brown eye appear brown?

A

the body or stroma of the iris absorbs few wavelengths and the pigmented epithelium of the iris reflects both long and short wavelength light back.

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11
Q

What makes up the posterior surface of the iris?

A

It has Schwalbe’s structural furrows, circular contraction furrows, Schwalbe’s radial contraction furrows

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12
Q

What is the pigment frill?

A

the epithelium that curves around to appear at the anterior surface

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13
Q

the furrows at the pigment frill are the continuation of what?

A

The continuation of the posterior radial contraction furrows of Schwalbe

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14
Q

What are the layers of the iris?

A

The anterior border layer, Iris stroma, and pigmented iris epithelium

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15
Q

what is the anterior border layer of the iris?

A

it is composed of widely spaced fibroblasts with collagen fibrils, making it porous to aqueous. more posterior are layers of melanocytes.

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16
Q

What are iris processes?

A

They come of the anterior border layer of the iris and travel to the trabecular meshwork. Extension made up of fibroblasts and melanocytes and collagen

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17
Q

What is the Iris stroma? What does it contain?

A

the second layer of the iris. It is loose connective tissue of collagen. it has aqueous, fibroblasts, melanocytes, lymphocytes, macrophages, mast cells, clump cells, ground substance, vessels, nerves and iris sphincter smooth muscle cells. note that lymphocytes and macrophages are from the blood

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18
Q

Why is it hard to tell the difference between an iris artery and vein?

A

Vessel walls are thick from fibroblasts, melanocytes, and collagen.

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19
Q

What has a blood-aqueous barrier? What is it made of?

A

The iris capillaries have a blood-aqueous barrier of zonula occludens.

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20
Q

What are clump cells? what is the most common type of clump cell?

A

They are found in the iris stroma where they clump around the iris sphincter. Macrophages are the most common clump cell type.

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21
Q

What is the iris sphincter? where is it found? What kind of muscle?

A

It is in the stroma of the iris. it is anchored into the pupillary dilator muscle by the spurs of the dilator. Para-ANS smooth muscle

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22
Q

What is the Pigmented iris epithelium? what is it an extension of?

A

It is the third layer of the iris, made up of the anterior and posterior iris epithelium. It’s an extension of the retinal tunic

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23
Q

What is the anterior epithelium (iris)?

A

The first layer of the pigmented iris epithelium (which is the 3rd layer of the iris). pigmented ciliary epithelium of ciliary body turns into pigmented anterior epithelium. It sends muscular processes (spurs) to anchor into the stroma of the iris root. It is myoepithelial except near the pupil.

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24
Q

What is the posterior epithelium (iris)?

A

The second layer of the pigmented iris epithelium (which is the 3rd layer of the iris). before the iris root, the nonpigmented ciliary epithelium of ciliary body becomes the posterior epithelium

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25
Q

what does the pigmented ciliary epithelium of the ciliary body turn into?

A

The anterior epithelium of the iris

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26
Q

what does the nonpigmented ciliary epithelium of the ciliary body turn into?

A

The posterior epithelium of the iris

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27
Q

How is the pigmented iris epithelium arranged?

A

apex to apex.

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28
Q

What composes the iris dilator muscle? What kind of innervation is it?

A

myoepithelial cells from the anterior epithelium, from the iris root to the midpoint of the sphincter. It is Symp-ANS.

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29
Q

what is the classic viewpoint of blood supply to the iris?

A

the two long posterior ciliary arteries anastomose with the anterior ciliary arteries in the loose connective tissue of the ciliary body near the root of the iris, forming the major circle of the iris.

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30
Q

what is the major circle of the iris?

A

the blood supply made when the anterior and posterior ciliary arteries anastomose near the root of the iris. (classic viewpoint)

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31
Q

what is the modern viewpoint of the blood supply of the iris?

A

the two long posterior ciliary arteries for the circle major circle of the iris. The secen anterior ciliary arteries anastomose to form the intramuscular circle.

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32
Q

what is the minor arterial circle of the iris?

A

radial arteries come together at the collarette.

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33
Q

what are the veins of the iris?

A

radial veins drain to ciliary body veins, then choroidal veins, and then out the eye through the vortex veins.

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34
Q

What does Cocain 10% do?

A

Normal response is dilation, Horner’s response is reduced pupil dilation because there is litttle NE for reuptake in affected eye.

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35
Q

What does Apraclonidine 0.5% do?

A

it directly excites the sympathetic receptors of the iris dilator muscle to cause dilation. Normal response is dilation. Horner’s pupil will have marked dilation because affected pupil is very sensitive to NE.

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36
Q

What does hydroxy-amphetamine 1% do?

A

It helps narrow down which type of Horners syndrome. The normal response is dilation. If the affected pupil dialates less than good pupil, then it’s 3rd order Horner’s syndrome. If they dialate equally, then it’s 2nd or 1st order Horner’s.

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37
Q

What is Iopidine?

A

it’s the same thing as Apraclonidine

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38
Q

What is horner’s syndrome?

A

The affected eye has issues with the sympathetic innervation in Hypothalamus, Anterior gray horn, or in the cervical ganglion. This causes the pupil to have miosis because it struggles with dilating. The pupilary fissure is also narrowed

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39
Q

What is the clinical importance of the pupil? 5

A

It can indicate brainstem TBI (RAPD), level of wakefulness (as in narcolepsy), sphincter damage, photophobia. certain eye surgeries need the pupil big.

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40
Q

What is the parasympathetic loop for iris control?

A

Optic nerve > Optic tract > Pretecum nucleus >Edinger-westphal nucleus > CN III > Ciliary ganglion > Optic nerve > iris. This is the only instance where Para-ANS constricts

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41
Q

Miosis happens through what ANS feature to what muscle?

A

Para-ANS to sphincter muscle

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42
Q

Mydriasis happens through what ANS feature to what muscle?

A

Symp-ANS to dilator muscle

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43
Q

Is pupillary dilator lateral or medial to the pupilarry sphincter?

A

The dilator is lateral to the sphincter. The sphincter is near the edge

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44
Q

How can type 1 diabetes affect the pupil?

A

It causes a loss of parasympathetic fibers, causing mydriasis.

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45
Q

Is the ciliary body inner or outer the sclera?

A

it is inner

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46
Q

What is posterior the ciliary body?

A

The choroid

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47
Q

What makes the aqueous of the eye?

A

The ciliary body

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48
Q

What is the ora serrata?

A

it is the junction between the retina and the ciliary body

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49
Q

what is the pars plana?

A

It’s the posterior, flat, 4mm part of the ciliary body that ends when you get to ciliary process. It borders the pars plicata and the ora serrata.

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50
Q

what is the pars plicata?

A

It’s the anterior, 2mm part of the ciliary body after the pars plana. its ends at the scleral spur.

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51
Q

What is a denate process?

A

it’s the ciliary body in between oral bays.

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52
Q

What are oral bays?

A

its the small gaps in between the dentate processes of the ora serrata

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53
Q

Going from posterior to anterior, what is before, during, and after the ciliary body?

A

Before is the retina,ora serrata,pars plana, pars plicata (major ciliary processes: tail, head), after is zonule

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54
Q

What does the head of the major ciliary process do?

A

being free of zonules, they secrete aqueous

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55
Q

how does the length of the head and tail of the major ciliary process compare with the length of the pars plicata?

A

they are the same length.

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56
Q

where are the minor ciliary processes located?

A

in the valleys in between major ciliary processes

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57
Q

what are the borders of the inner side of the ciliary body?

A

the lens zonules, posterior chamber, and the vitreous

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58
Q

what are the borders of the outer side of the ciliary body?

A

the sclera except in the anterior pars plicata where the ciliary muscle strongly connects to the scleral spur

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59
Q

what are the different layers of the ciliary body? outer to inner

A

supraciliary layer, ciliary muscle layer, Stroma, Bruch’s membrane, and ciliary epithelium

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60
Q

what is the supraciliary layer? what is it’s anterior boundary? what is it composed of?

A

it is the loose connective tissue junction between the sclera and the ciliary body. it’s the most outer part of the ciliary body. It’s continuous with the suprachoroid. It is sealed off at the scleral spur. It’s composed of collagenous fibers, melanocytes, and fibroblasts.

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61
Q

What is the ciliary muscle layer? what happens to drainage during accommodation? How does it compare to other smooth muscle?

A

2nd outer layer.it’s the largest intrinic eye muscle, inner to the supraciliary layer. It inserts into the scleral spur with it’s tendon. The trabecular meshwork opens up when accomodating to increase drainage. It has more actin, myosi, and mitochonrdiathan other smooth muscle

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62
Q

What are the different divisions of the ciliary muscle fibers?

A

Longitudinal (meridional): attach at scleral spur anteriorly and end posteriorly at muscle stars in suprailiary layer of pars plana (and suprachoroid of anterior choroid). They are more outer.Radial: start at spur and end at pars plicata.and circular fibers: run perpandicular around the lens. ALL smooth muscle and all turn on to cause accommodation.

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63
Q

Where do muscle stars attach?

A

they connect with choroidal blood vessels and Bruch’s membrane (in the pars plana)

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64
Q

What are the two drain pathways and when do they function the most? what does accommodation do to drainage rate?

A

uveoscleral pathway (during relaxation through ciliary muscles) and trabecular meshwork (during contraction) 90% drainage through here. Accommodation increases draiange becaue it opens up trabecular meshwork

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65
Q

what is the Stroma of the ciliary body?

A

3rd outer layer. This has more vessels in the pars plicata and is thicker. The blood vessels are fenestrated (“holed” but not really) because it’s they are to produce aqueous (plasma but not RBC enters the stroma)

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66
Q

What is Bruch’s membrane? what are the 3 layers in the pars plana? what layer remains in the pars plicata?

A

4th outer layer of the ciliary body. It’s very thin, extracellular membrane made by fibrobrasts in stroma.it’s part of the choroid (outer the retina). The 3 layers in the pars plana are: elastic layer, basal lamina, and collagen layer. in the pars plicata is only the basal lamina

67
Q

what is ciliary epithelium? What are the 2 layers? how does aqueous flow?

A

most inner layer. 2 layers. 1st layer is Pigmented epithelium (also in retina and anterior epithelium of iris). more inner: nonpigmented epithelial cells become neurosensory retina after the ora serrata (and posterior epithelium of the iris). They are arranged apex to apex as simple cuboidal cells. Aqueous flows from blood past bruch’s membrane through pigmented epithelium to non-pigmented epithelium

68
Q

what is the internal limiting membrane? What happens to it as you age?

A

the basal lamina of the non-pigmented epithelium of the ciliary body. zonular fibers and fibrils come off of this basal lamina and mark the border between posterior chamber and vitreous. The basal lamina thickens with age

69
Q

What forms the blood aqueous barrier in the ciliary body?

A

apices

70
Q

what is the blood supply of the ciliary body in the classic view? the modern view?

A

blood from long posterior and anterior ciliary arteries. Classic: From the major arterial circle of the iris.Modern: Major arterial circle and the intramuscular circle. the capillaries are large.

71
Q

describe the parasympathetic supply of the ciliary body

A

preganglionic 2nd order: myelinated Edinger-Westphal nucleus. Postganglionic to ciliary muscle fibers from ciliary ganglion.

72
Q

describe the sympathetic supply of the ciliary body

A

preganglionic 2nd order: myelinated thoracic spinal cord. Postganglionic from superior cervical ganglion innervating the arteries of the ciliary body.

73
Q

what happens to ciliary body during para and symp ANS activity?

A

parasympathetic: ciliary body causes accommodation. sympathetic: ciliary body is turned off. and there is vasodilation.

74
Q

what somatic innervation does the ciliary body have?

A

since it can feel pain, there are sensory axons that travel with ophthalmic division of CN V (trigeminal). There are soma in the ciliary body and it’s unknown what they do.

75
Q

what is the development of the ciliary body?

A

All ectoderm. the neural tube of the optic cup makesthe both NPE and PE of ciliary body. Neural crest mesenchyme forms the ciliary muscle and other stuff. mesoderm: endothelial blood vessels. Bruch’s membrane is ectoderm (both neural crest and neural tube)

76
Q

what developmental tissue creates the NPE and PE of ciliary body?

A

Ectoderm, specifically neural tube

77
Q

what developmental tissue creates the ciliary muscle?

A

Ectoderm, specifically neural crest

78
Q

what developmental tissue creates Bruch’s membrane?

A

Ectoderm, both neural crest and neural tube

79
Q

what are zonules?

A

they cover the pars plana and pars plicata and ciliary processes but don’t cover the heads of the ciliary processes.

80
Q

what is the chemical nature of zonules? what’s in between the fibrils?

A

it’s similar to fibrillin microfibrils of elastic fibers but zonules don’t have elastin. mucopolysaccaride ground substance is in between the fibrillin zonular fibrils.

81
Q

what are the functions of aqueous humor? 4

A

circulation of good stuff, maintenance if IOP, control of inflammatory mediators, maintenance of a reducing environment.

82
Q

what is the turnover of aqueous humor? how does osmolarity compare to plasma? what does it resemble?

A

it turns over every 100 min, aqueous has a greater osmolarity than plasma, and it resembles CSF.

83
Q

what is Schlemm’s canal?

A

it collects aqueous humor from the anterior chamber and delivers it into the bloodstream. It’s covered by the trabecular meshwork.

84
Q

How is aqueous humor produced with pumps? What does ouabain block?

A

Na/K atpase, Na/K/2Cl, Cl-/Bicarb, Na/H+, Cl transport, AA and ascorbic acid transport. ouabain blocks Na/K atpase

85
Q

what do alpha-2 receptors do?

A

they inhibit aqueous production

86
Q

what do beta-2 receptors do?

A

they stimulate aqueous production

87
Q

what does neuropeptide Y do for aqueous production?

A

it reduces aqueous production.

88
Q

what does ACh do for aqueous production?

A

it inhibits

89
Q

increasing cAMP does what to aqueous production?

A

it increases production of aqueous (think beta)

90
Q

what molecules are higher and lower in aqueous compared to plasma?

A

higher: ascorbate, lactate, amino acids. LOWER: protein, Glucose

91
Q

what are the routes of aqueous humor drainage?

A

major route is through trabecular meshwork into Schlemm’s canal. secondary is uveoscleral drainage

92
Q

what happens to IP when endothelial cells of the trabecular meshwork contact? what signals mediate this?

A

IOP increases. cholinergic, alpha epi, endothelin receptors

93
Q

what happens to IP when endothelial cells of the trabecular meshwork relax? what signals mediate this?

A

IOP decreases. beta epi, nitric oxide, Ca blockers, cGMP

94
Q

how does tonicity influence endothelial cells of the trabecular meshwork?

A

hypotonic causes endothelial cells to swell, reducing drainage, increasing IOP

95
Q

what happens to the trabecular meshwork as you age?

A

you lose cells

96
Q

What happens to blood flow when IOP increases?

A

blood flow decreases

97
Q

what is open angle glaucoma?

A

the anterior angle is open, but you have high IOP

98
Q

what is closed angle glaucoma?

A

something is blocking the angle of the eye. Surgery, shunt, snorkel, or laser can take care of this.

99
Q

what is low tension glaucoma?

A

there is lower blood flow and IOP is normal

100
Q

what can cause a low IOP?

A

a previous surgery

101
Q

what is the pathology of glaucoma?

A

optic nerve head cupping, peripheral field loss, decreased blood flow

102
Q

what can cause glaucoma?

A

genes, East asian, african (3x), and women (3x)are more likely to develop glaucoma

103
Q

What causes neovascularization of the optic nerve disc?

A

RPE expresses VEGF (vessel endothelial growth factor) because of reduced blood flow from glaucoma. These new blood vessels are leaky–albumin shouldn’t be in the eye.

104
Q

What medications can treat glaucoma?

A

Prostaglandin analogs, beta blockers, adrenergic, carbonic anhydrase, miotics, and marijuana

105
Q

How do prostaglandin analogsaffect glaucoma?

A

increase outflow because of vasodilations

106
Q

How does beta blockersaffect glaucoma?

A

beta one decrease production of aqueous

107
Q

How do Adrenergics affect glaucoma?

A

does both increase outflow and decrease production

108
Q

How do Carbonic anhydraseaffect glaucoma?

A

decreases production of humor

109
Q

How do miotics affect glaucoma?

A

affects trabecular meshwork

110
Q

How does marijuana affect glaucoma?

A

affects trabecular meshwork through vasodilation

111
Q

what is the alternative to LASIK?

A

visian implantable collamer lens. It goes behind the lens

112
Q

where do new cells of the lens come from?

A

the epithelium along the periphery

113
Q

what percent of light gets transmitted from the lens?

A

95%, similar to cornea

114
Q

what happens to the lens sutures as you age?

A

they increase from 3 to more (like 8)

115
Q

what portion of refraction takes place throught the lens?

A

about a third

116
Q

what happens to the power of the lens as you age? what about weight and width?

A

there is a hyperopic shift from 50 to 65, myopic shift after age 65. weight and width and resistanceincrease as you age

117
Q

what does glutathione do in the lens?

A

it does amino acid transport to avoid protein aggregation as a protective mechanism.

118
Q

what is the process of accommodation?

A

the ciliary muscle contracts and the lens moves inward and slightly forward. The zonules relax

119
Q

why is retinal detachment a risk for myopes?

A

myopia causes the eye to grow,but the retina does not and stretches. there is also decreased choroidal blood flow.

120
Q

What are some theories of accommodation? What causes myopia?

A

near work causes the eye to grow, possibly dopamine is released from the retina. if you relax your ciliary muscle it might prevent myopia. genetics influence myopia, too.

121
Q

what happens to accommodation when you stimulate the edinger-westphal?

A

accommodation is stonger with more stimulaiton.

122
Q

what are some theories about presbyopia?

A

lens gets stuff (most accepted), zonules get hard.

123
Q

what are the different types of zonules?

A

anterior, posterior, equatorial, tension, and circular

124
Q

what are anterior zonules?

A

they come from the basal lamina of the nonpigmented ciliary epithelium of the pars plana, just anterior to the ora serrata. They insert in the lens capsule anterior of the equator. (this is the internal limiting membrane)

125
Q

what are posterior zonules?

A

they come from the basal lamina of the nonpigmented ciliary epithelium of the pars plana, just anterior to the ora serrata. They insert in the lens capsule posterior of the equator. (this is the internal limiting membrane). some of the most posterior posterior zonules run along the anterior hyaloid of the vitreous, which both attach to the lens at Wieger’s ligament.

126
Q

what is the Wieger’s ligament?

A

its the attachment between the anterior hyaloid of the vitreous and the lens capsule

127
Q

what is the anterior hyaloid?

A

it’s the most anterior part of the vitreous, it attaches to the lens through Wieger’s ligament (along with some posterior zonules)

128
Q

what are equatorial zonules?

A

they originate from NPE basal lamina of the valleys between the pars plicata ciliary process AND from anterior zonules as branches. They insert into the equator of the lens capsule

129
Q

what are tension zonules?

A

they originate from the NPE basal lamina of both the valleys of the ciliary processes and the anterior pars plana. They run across the ciliary body anchoring down anterior, posterior, and equatorial zonules. (don’t attach to lens)

130
Q

what are circular zonules?

A

they help attach vitreous. there is lenticular zonule (retrolental ligament), coronary ligament, and median ligament.

131
Q

what are lenticular zonules?

A

this is the inner ring attached to the lens and anterior hyaloid of the vitreous. it’s at the midlength of the pars plicata. They are continuous with the fibrils of the posterior zonules that are attached to the Wieger’s site.

132
Q

what are coronary ligaments?

A

this is the middle of three rings that attach the midlength of the pars plicata to the anterior hyaloid of the vitreous. they have fibrils that curve to run into the anterior and posterior zonular fibers.

133
Q

what are median ligaments?

A

this is the outside of three rings attach the midlength of the pars planato the anterior hyaloid of the vitreous. they have fibrils that curve to run into the anterior and posterior zonular fibers.

134
Q

infants or young adults have finer, less aggregated zonules?

A

infants

135
Q

infants or young adults have obvious, clearly aggregated zonules?

A

young adults

136
Q

what happens to the zonules as you age?

A

as the lens grows in thickness during life, the equatorial zonules migrate anterior and/or posteriorly

137
Q

what is the canal of Pedet?

A

it doesn’t exist! there is no space between the posterior zonules and vitreous. Canal of Hanover does exist, though.

138
Q

what kind of tissue is the lens?

A

100% epithelium

139
Q

what is posterior to the lens?

A

the patellar fossa of the vitreous

140
Q

what is the equatorial and axial diameter of the lens?

A

Equatorial: 9mm, Axial: 4.5mm but can change w/ accommodation

141
Q

what are the layers of the lens, outer to inner?

A

Lens capsule, lens epithelium, lens cortex, lens nucleus

142
Q

what is the lens capsule?

A

1st outerof 4 layers of the lens. subdivided: zonular lamella and capsule proper (inner lamella). it helps contain the growing mass of lens fibers. it helps control accommodation. It also separates the rest of the lens from the immune system (even though the eye is immune privileged)

143
Q

what is the zonular lamella?

A

it’s the outer part of the lens capsule. it’s composed of zonular fibrils where zonules attach.

144
Q

what is the lenscapsule proper or inner lamella?

A

its the inner portion of the lens capsule (which is the main outer layer of the lens). it has about 40 layers of type IV collagen and GAGs. It’s the THICKEST basal lamina in the human body.

145
Q

what attaches epithelial cells to the capsule proper or inner lamella?

A

epithelial cells are connected to the lens capsule by hemidesmosomes.

146
Q

what is the variation ofthickness of the lens capsule?

A

this outer layer of the lens is thin posteriorly and thicker anteriorly (periequatorally and equatorially) because of contact with the lens epithelium.

147
Q

what is the lens epithelium?

A

2nd outerof 4 layers of the lens. its simple cuboidal to columnar. hemidesmosomes attach is base to the lens capsule. It can be divided into the Central epithelial zone, the intermediate epithelial zone, germinal epithelial zone, and transitional epithelial zone.

148
Q

what is the central epithelial zone?

A

this is the outermost subdivision of the second layer of the lens (the epithelium). may be the oldest living cells in the body, they transport materials to and from the aqueous.

149
Q

what is the intermediate epithelial zone?

A

this is the second (of 4) subdivision of the second layer of the lens (the epithelium). the cells are smaller and slightly mitotic

150
Q

what is the germinal epithelial zone?

A

this is the 3rd (of 4) subdivision of the second layer of the lens (the epithelium).pre-equatorial and mitotic.

151
Q

what is the transitional epithelial zone?

A

this is the innermost subdivision of the second layer of the lens (the epithelium). from the germinal zone, they elongate and migrate internally to become new and young secondary lens fibers of the cortex.

152
Q

what are the oldest cells in the body?

A

the cells in the central epithelial zone of the lens.

153
Q

what are the secondary lens fibers of the cortex

A

in the transitional epithelial zone, epithelial cells from the germinal zone elongate and migrate internally to become new and young secondary lens fibers of the cortex

154
Q

what is the lens cortex?

A

3rdouterof 4 layers of the lens. organized into shells. it surrounds the lens nucleus.

155
Q

what is the lens nucleus?

A

4th outerof 4 layers of the lens. can be subdivided into the 4 layers (starting most outer): adult, infantile, fetal (these 3 have secondary lens fibers), and embryonal nucleus (has primary lens fibers).

156
Q

what are the most clinically important layers of the lens to distinguish

A

nucleus and cortex

157
Q

what are primary lens fibers and where are they found?

A

they are found only in the embryonal nucleus. They were created posterior to anterior from posterior epithelium of the lens placode.

158
Q

what are secondary lens fibers and where are they found?

A

they are found in the other 3 nuclei of the lens and the cortex. they produce crystalline proteins. New layers are created anterior to posterior.

159
Q

how are primary and secondary lens fibers organized?

A

Transitional epithelium formed primary formed posterior to anterior, secondary forms anterior to posterior. They are six-sided when cross sectioned.

160
Q

what creates a lens suture? what nucleus doesn’t have sutures?

A

its where secondary lens fibers meet after traveling around the entire lens starting in the fetal nucleus. only the embryonal nucleus lacks sutures.

161
Q

what is the most metabolically active zone of the lens?

A

the germinal zone of the lens epithelium.

162
Q

what forces guide the shape and orientation of the secondary lens fibers?

A

capsule tension, mitotic pressure, and fiber compression by other fibers.

163
Q

what is the development of the lens?

A

the lens is surface ectoderm. The lens placode is a thickened area of surface ectoderm. it becomes a lens pit when, then pinches off to become the lens vesicle. the posterior epithelium of the lens placode forms the primary lens fibers, then the secondary lens fibers are made from anterior lens placode cells. There are blood vessels to support this growth that later go away.

y SCO Ocular Anatomy (1 decks)

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