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Anatomy 2 > Lect 4 The eye > Flashcards

Lect 4 The eye Flashcards

1
Q

the eye

A

housed in the bony orbit
optic canal at back though which the optic nerve leaves the bony orbit to enter cranial cavity
-specialized for photoreception
-light passes through several structures before encountering light sensitive retina in back of eye

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2
Q

3 layers of the eye

A

Fibrous tunic
vascular tunic
neural tunic/retina

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3
Q

Fibrous tunic

A

outer layer

includes sclera ‘white of eye’; anteriorly, the sclera is continuous with transparent cornea

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4
Q

Vascular tunic

A

middle layer
most of this layer is the choroid, which contains abundant capillaries that supply a portion of the retina
anteriorly, this layer inclueds ciliary body and the iris

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5
Q

Neural tunic/retina

A

inner layer
comprised of retinal pigment epithelium (outer) and neural retina (inner)
Photosensitive retina ends at the ora serrata, but both continue anteriorly and cover the inner layer of ciliary body and iris

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6
Q

Sclera

A

in fibrous tunic
White of the eye
thick layer of dense CT(goes in all directions), mainly Type I collagen with few elastic fibers, some elongated fibroblasts
Sensory innervation
vascularized (few)
Function: serves as protective envelope for internal eye structures; provides attachment site for extraocular eye muscles

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7
Q

Cornea

A 
fibrous tunic
Transparent
avascular - gets nutrients from aqueous humor and lacrimal fluid (includes o2 absorbed from air)
Highly innervated, very sensitive
used in refraction of light to focus
5 histologically distinct layers
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8
Q

Five corneal layers

A
  1. corneal epithelium
  2. bowmans membrane
  3. stroma
  4. descemet’s membrane
  5. corneal endothelium
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9
Q

conreal epithelium

A

stratified squamous, non keratinized epithelium (5-7 days)
Turnover rate ~7 days (corneal injury)
highly innervated

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10
Q

Bowman’s membrane

A

basement membrane

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11
Q

stroma

A

90% of corneal thickness
Abundant type 1 collagen, few elastic and fibroblasts
lamella organization of this layer is important in transparency of cornea

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12
Q

descemet’s membrane

A

basement membrane

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13
Q

corneal endothelium

A

simple squamous layer, lines posterior surface of the cornea

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14
Q

Conjunctiva

A

mucous membrane covering anterior sclera and lines inside of eyelid

  • stratified columnar epithelium which contain goblet cells
  • goblet cell secretions contribute to tear film
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15
Q

conjunctivitis

A

clinical note
aka pink eye
inflammation of the conjunctiva. caused by virus or bacteria and easily spread person to person. can become inflamed in response to allergens and irritating substances

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16
Q

Choroid

A

posterior portion of vascular tunic
-loose CT
highly vascularized - provides nutrients to retinal pigment epithelium and outer layers of the neural retina (inner layers supplied by central retinal artery
and pigmented)
Pigmented: melanocytes give the choroid its dark appearance. melanocytes function in absorbing light that has passed through the retina. This prevents visual interference from light deflection

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17
Q

ciliary body

A 
vascular tunic
wedge shaped region 
loose CT 
well vascularized w/ smooth muscle
double layer of cuboidal epithelium (1 pigmented and 1 non pigmented=surface layer)
Function: produce aqueous humor
change shape of the lens
18
Q

ciliary body

A

ciliary processes have abundant fenestrated capillaries. plasma filtrate is transported across the epithelium as aqueous humor

19
Q

aqueous humor

A

provides nutrients to lens and cornea
enters posterior chamber -> pupillary aperature -> anterior chamber -> leaves via canal of Schlemm to enter the venous system

20
Q

glaucoma

A

increase intraocular pressure caused by failure of resorption of aqueous humor
-leads to compromised retinal blood flow and progressive retinal damage
can cause blindness if untreated

21
Q

zonule fibers

A

radiate from ciliary body and insert into the lens capsule forming the suspensory ligament of the lens

22
Q

Ciliary muscle activation

A

contraction: reduces tension on zonule fibers and cause lens to buldge, (convex)
allows eye to focus on near objects = accomodation

Relaxation: increases tension on zonule fibers and causes the lens to flatten. this allows the eye to focus on distant objects

23
Q

iris

A

anterior extension of vascular tunic

posterior surface of iris is composed of heavily pigmented cells- block light from passing directly though the iris

24
Q

anterior pigmented cells of iris

A

(and within stroma of iris) impart eye color

dark eyes have high # of pigmented cells

25
smooth muscle in stroma of iris
dilator pupillae (radially oriented) and sphincter pupillae (circumferentially oriented) control pupillary aperture
26
lens
``` biconvex, transparent disc that functions to focus light on retina 3 parts lens capsule subcapsular epithelium lens fibers ```
27
lens capsule
basement membrane, completely envelops the lens
28
subcapsular epithelium
single layer of cuboidal cells located only on the anterior surface of lens. at equators, the subcapsular epithelium give rise to lens fibers
29
lens fibers
generated at the equator and continue at a very slow rate throughout lilfe. immediately deep to subcap epi. bulk of lens is composed of these 2000-3000 elongated cells. elongate as the mature, lose nuclei and organelles become filled with proteins called crystallins
30
cataract
opaque lens
31
vitreous body
transparent, refractile gel that fills the vitreous cavity located behind the lens composed of 99% water, but contains collagen and hyaluronic acid
32
hyalocytes
at periphery of vitreous body believed to synthesize collagen and hyaluronic acid Phagocytic cells are also reportedly present at low numbers
33
retina
direction of light opposes direction of info flow to optic nerve
34
retinal pigment epithelium
RPE cuboidal to columnar cells w/ basally located nuclei Apical aspect have abundant melanin granules, microvilli and sleeve like extensions that surrounds tips of photoreceptor cells Function: reduces light scatter by absorbing stray light & phagocytose membrane shed from photoreceptors desmosomes, zonulae occludens and zonulae adherents present and form blood retina barrier
35
Anatomy layer of retinal
Top 1. inner limiting membrane 2. ganglion cell axons 3. cell body of ganglions 4. inner plexiform synaptic layer 5. inner nuclear layer (bipolar cell bodies, amacrine cells) 6. outer plexiform synaptic zone 7. outer nuclear layer (cell bodies of rods and cones) 8. outer limiting membrane 9. photoreceptor layer (rods and cones) 10. retinal pigment epithelium
36
photoreceptors
absorb photons -> receptor potential, info is processed through retinal layers before reaching retinal ganglion cells rods vs cones
37
Rods
extremely sensitive to light and are used at night | monochromatic: all rods have same rhodopsin
38
cones
sensitive in daylight, require higher intensity of light compared to rods trichromatic=3 opsins for different wavelengths relative activity of different opsins can be interpreted as color
39
colorblindness
altered gene expression of one or more cone opsins red-green color blindness affects 2% males often occur together because of the proximity of these genes on the X chromosome
40
fovea
specialized feature of retina region for high acuity vision particulary rich in cones several of the retinal layer are absent at the fovea so that the light does not have to traverse these layers, instead these retinal layers are positioned at the edges of the fovea
41
Optic disk
exit point of the retinal ganglion cell axons -unmyelinated retinal ganglion cell axons collect here, pierce sclera, acquire myelin sheath and form the optic nerve No photoreceptors at the optic disk so we are blind to any image that falls on this part no awareness to this blindspot as we walk around

Anatomy 2 (8 decks)

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