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FoundSci Unit 7 > Eye I > Flashcards

Eye I Flashcards

1
Q

What are the accessory structures of the eye?

A
  1. Eyelid
  2. Conjunctiva
  3. Lacrimal Gland
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2
Q

What is the function of the eyelid?

A

Protect eyeball

Prevent evaporation of tears when closed

Distribute tear film across surface of eyeball

Maintain moisture

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3
Q

What are the characteristics of the eyelid?

A

Thin skin externally

Palpebral conjunctiva internally

Orbicularis oculi - skeletal muscle that closes the eye

Tarsal plates - skeleton of eyelid

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4
Q

What are the tarsal plates of the eyelid?

A

Provide structural support of eyelid

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5
Q

What are the glands of the eyelid?

A

Glands of Zeis - Sebaceous glands of eyelashes

Glands of Moll - modified apocrine glands of eyelashes that open into eyelash follicles

Tarsal (Meibomian) glands

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6
Q

What is the function of the Tarsal (Meiobomian) glands of the eyelid?

A

Modified sebaceous glands within the tarsal plates

Open onto free edge of the lid

Oily secretion slows the evaporation

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7
Q

What occurs when there is a blockage to the Tarsal (Meibomian) glands?

A

Chalazion which is inflammation of the tarsal gland

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8
Q

What is a bacterial infection of the sebaceous glands of eyelashes (Glands of Zeis)?

A

Stye

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9
Q

What is the function of the conjunctiva?

A

Maintain moisture, provide lubrication between eyeball and eyelid

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10
Q

What are the parts of the conjunctiva?

A

Bulbar - covers sclera

Palpebral - covers inside of eyelid

Stratified columnar epithelium with goblet cells - mucous secretion of goblet cells lubricate and protect anterior aspect of the eye

Continuous with corneal epithelium - transition to stratified squamous at corneosclera limbus and continuous with corneal epithelium

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11
Q

What is the function of the lacrimal gland?

A

Maintain moisture

Removal of foreign materials

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12
Q

What is the structure of the lacrimal gland and what does it contain?

A

Compound tubuloacinar gland that secretes lacrimal fluid (tears)

Lacrimal fluid (tears) - sterile, composed mostly of water, contains lysozyme (antibacterial agent).

Maintains hydration of eyeball, flush irritants from surface of eyeball

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13
Q

What is the structure of lacrimal canaliculi?

A

Stratified squamous

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14
Q

What is the structure of lacrimal sac?

A

Pseudostratified ciliated columnar

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15
Q

What is the structure of nasolacrimal duct?

A

Pseudostratified ciliated columnar

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16
Q

What is flow of lacrimal fluid?

A

Produced by lacrimal gland

Secreted onto eyeball by lacrimal ducts

Flow medially across the surface of the eyeball

Collected by the lacrimal canaliculi (lined with stratified squamous epithelium)

Canaliculi drain into the lacrimal sac - lacrimal sac lined by pseudostratified ciliated columnar epithelium

Lacrimal sac drains into nasolacrimal duct - lined by pseudostratified ciliated columnar epithelium

Nasolacrima duct drains into nasal cavity

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17
Q

What is pseudostratified ciliated columnar epithelium considered?

A

Respiratory epithelium

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18
Q

What is the anterior segment of the eye and what does it contain?

A

Anterior to lens and ciliary body and filled with aqueous humor. Contains anterior and posterior chamber.

Contains:
Cornea
Anterior sclera
Iris
Pupil
Ciliary body and muscle
Aqueous humor = aqueous fluid

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19
Q

What is the anterior chamber?

A

Anterior to the iris

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20
Q

What is the posterior chamber?

A

Posterior to the iris

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21
Q

What is the posterior segment of the eye and what does it contain?

A

Posterior to the lens and ciliary body and filled with vitreous humor

Contains:
Posterior sclera
Choroid
Retina
Vitreous body

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22
Q

What is vitreous humor?

A

Transparent gel made of mainly water, but also contains collagen, hyaluronic acid, and hyalocytes.

23
Q

What are hyalocytes?

A

Vitreous cells

Function as macrophages and synthesize hyaluronic acid

24
Q

What are the layers of the eye and what is it divided up into?

A

Fibrous layer - most external layer of the eye and divided into sclera and cornea

Vascular layer - divided into iris, ciliary body, and choroid

Retina - divided into retinal pigment epithelium (RPE) and neural retina

25
Q

What are the characteristics of the Lens? What is its function?

A

Biconvex, transparent and very elastic

Avascular

No innervation

Layers include lens capsule, subscapular epithelium, and lens fibers

Function is to focus light rays on the retina

26
Q

What is the structure of the lens capsule?

A

Basement membrane/basal lamina of the subscapular epithelial cells

27
Q

What is the structure of the subscapular epithelium?

A

Cuboidal layer of cells

Only present on the anterior surface of the lens

Differentiate into lens fibers near the equator of the lens

28
Q

What is the structure of the lens fibers?

A

Subscapular epithelial cells differentiate into lens fibers

Near equator of lens

Produced throughout life, rate decreases with age

Mature fibers lose nuclei and acquire crystallins (lens proteins)

Fibers stiffen and enlarge with age

29
Q

What are the function of crystallins within lens fibers?

A

Proteins that increase refractor index of lens fibers

30
Q

What is cataracts?

A

Loss of transparency of the lens

31
Q

What can occur when lens fibers stiffen and enlarge with age?

A

Leads to presbyopia

Age related farsightedness related to loss of accomodation

32
Q

What is the structure and function of the sclera?

A

Posterior 5/6 of the eyeball

White of the eye

Tough fibrous connective tissue (collagen and elastic fibers)

Extraocular muscles insert on the sclera

Pierced by the optic nerve, blood vessels, and other nerves

Function is to maintain the shape of the eyeball

33
Q

What is the structure and function of the cornea?

A

Anterior 1/6 of the eyeball

Continuous with the sclera

Transparent and avascular

Highly innervated

Main site of light refraction in the eye

Six layers

34
Q

What is the corneoscleral limbus?

A

Junction of cornea and sclera

Transition from highly vascularized sclera to avascular cornea

Transitions from stratified columnar epithelium to stratified squamous corneal epithelium

Trabecular meshwork (Spaces of Fontana)

Scleral venous sinus (Canal of Schlemm)

35
Q

What is the structure and function of the trabecular meshwork or Spaces of Fontana of the corneoscleral limbus?

A

Channels combine to form the scleral venous sinus

Drains aqueous humor from anterior chamber

36
Q

What is the structure and function of the scleral venous sinus or Canal of Schlemm of the corneoscleral limbus?

A

Drains aqueous humor into aqueous veins in sclera

Apparatus for outflow of aqueous humor

37
Q

What is the flow of aqueous humor?

A

Aqueous humor produced by ciliary epithelium

Secreted into posterior chamber

Flows into anterior chamber into the pupil

Drains through trabecular meshwork

Drains into scleral venous sinus to network of scleral veins

38
Q

What are the six layers of the cornea from external to internal?

A

Epithelium

Bowman’s membrane

Stroma

Pre-Descemet Layer

Descemet’s membrane

Endothelium

39
Q

What is the structure and function of the epithelium of the cornea?

A

Continuous with bulbar conjunctiva

Non-keratinized stratified squamous

Cells replaced every 7 days

Richly innervated

Cells have microvilli to help retain tears and prevent drying

40
Q

What is the structure and function of Bowman’s Membrane of the Cornea?

A

Acellular and does not regenerate

Ends at corneoscleral limbus

Contributes to strength and stability of cornea

Acts as barrier to infection

41
Q

What is the structure and function of the stroma of the cornea?

A

Most of corneal thickeness - substantia propria

Parallel collagen fibrils organized into lamellae

Precise orientation of lamellae maintain transparency of cornea

Corneal fibroblasts interspersed between lamellae to help with repair process

42
Q

What is the structure and function of Pre-Descemet Layer of the cornea?

A

Protects cornea from damage

Thin, tough collagenous membrane

Rupture leads to aqueous fluid leaking into cornea

43
Q

What is the structure and function of Descemet’s membrane?

A

Basal lamina of corneal endothelium

Secreted and maintained by corneal endothelial cells

Thickens with age

Helps maintain corneal curvature

44
Q

What is the structure and function of the endothelium of the cornea?

A

Faces anterior chamber of the eye

Simple squamous epithelium

Removes excess fluid from corneal stroma to maintain transparency

45
Q

What is the structure and function of the iris?

A

Muscular diaphragm anterior to the lens

Controls size of the pupil and amount of light that contacts retina

Melanocytes in stroma and pigment epithelium of iris bock passage of light in the eyes

Stroma

Pupil

46
Q

What is the structure and function of the pupil?

A

Central aperture of the iris

Sphincter pupillae - constricts pupil, innervated by parasympathetics

Dilator pupillae - Dilates pupil, sympathetic innervation

47
Q

What is the structure and function of the stroma of the iris?

A

Vascularized loose CT

Contains melanocytes - determine eye color

Sphincter pupillae

48
Q

What is the structure and function of pigment epithelium?

A

2 rows of cuboidal cells

Function is to block light rays

Posterior row adjacent to posterior chamber

Anterior row is myoepithelium

Basal surface is dilator pupillae muscle

49
Q

What is the structure and function of the ciliary body?

A

Ciliary Muscle + Ciliary Processes

Ciliary muscle - sphincter muscle, parasympathetic innervation, responsible for accomodation

Ciliary processes - zonular fibers (suspensory ligaments), lined with ciliary epithelium that secretes zonular fibers and aqueous humor

50
Q

What is accomodation?

A

Contraction of ciliary muscle relaxes suspensory ligament allowing lens to round for near vision

Relaxation of ciliary muscles puts tension on suspensory ligament flattening lens for far vision

51
Q

What is the structure and function of the ciliary epithelium?

A

Double layer of cuboidal cells

Only outer layer pigmented and continuous with the retinal pigment epithelium and nonphotosensitive retina

Inner layer is non pigemented and produces aqueous humor and secretes zonular fibers

52
Q

What is the structure and function of the choroid?

A

Between retina and sclera

Heavily pigmented and vascularized - absorbs light that has passed through retina and prevents reflection

Provides blood to outer layers of retina

2 layers:

Choriocapillary layer - inner vascular layer with fenestrated blood vessels, and provides nutrients to outer layers via the opthalamic artery

Bruch’s membrane - thin hyaline membrane, innermost, attached to first layer of retina

53
Q

What is glaucoma?

A

Increase in intraocular pressure due to an increase in volume of aqueous humor - either due to overproduction or impeded drainage

Sustained increase in pressure can prevent flow to eye

2 types:
Open angle glaucoma - drainage of aqueous humor slowed by blockage of trabecular meshwork , iridocorneal angle is open

Closed angle - closing of iridocorneal angle limits or obstructs drainage of aqueous humor

FoundSci Unit 7 (14 decks)

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