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Whitney - Histology Test 2 > Lecture 22 Histology of the Eye II > Flashcards

Lecture 22 Histology of the Eye II Flashcards

1
Q

Layers of the Retina

A 
Pigmented epithelium 
Inner and outer segments of rods and cones
External limiting membrane 
Outer nuclear layer
Outer plexiform layer
Inner nuclear layer
Inner plexiform layer
Ganglion cell layer
Optic nerve layer
Internal limiting membrane
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2
Q

Pigmented epithelium

A

Adjacent to choroid

Derived from outer (thinner) layer of the optic cup

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3
Q

Inner and outer segments of rods and cones

A

Outer segment consists of rhodopsin-containing lamellae
Inner segment consists of areas of rods and cones possessing mitochondria, RER, Golgi, and glycogen (metabolically active)

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4
Q

External limiting membrane

A

Area at junction of inner and outer segments of rods and cones and outer nuclear layer
Includes adherens junctions between rods and cones and Mueller cells.

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5
Q

Outer nuclear layer

A

Cell bodies of rods and cones (1st order neurons)

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6
Q

Outer plexiform layer

A

Area of synapses between axons of rods and cones and dendrites of bipolar neurons and horizontal cells.

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7
Q

Inner nuclear layer

A

Cell bodies of bipolar cells (2nd order neurons), horizontal cells, amacrine cells, and mueller cells

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8
Q

Inner plexiform layer

A

Area of synapses between axons of bipolar cells and dendrites of ganglion cells

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9
Q

Ganglion cell layer

A

Cell bodies of ganglion cells (3rd order neurons)

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10
Q

Optic nerve layer

A

Axons of ganglion cells

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11
Q

Internal limiting membrane

A

Terminations of mueller cell processes and their basement membrane

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12
Q

Cells of the Retina

A 
Pigmented epithelial cells
Bipolar cells
Horizontal cells
Amacrine cells
Mueller cells
Ganglion cells
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13
Q

Pigmented epithelial cells

A

Adjacent to choroid
Synthesize melanin
Apical processes surround & protect outer segments of rods & cones
Phagocytose & degrade lamellae from rods & cones
Connected via tight junctions to form blood-retina barrier
Esterify vit. A used in formation of photosensitive pigments

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14
Q

Bipolar cells

A

Conducting neurons that synapse with rods and cones

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15
Q

Horizontal cells

A

Interneurons that interconnect rods and cones with each other and with bipolar cells

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16
Q

Amacrine cells

A

Interneurons that connect ganglion cells and bipolar cells

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17
Q

Mueller cells

A

Neuroglial cells that extend throughout retina.
Form external limiting membrane via zonula adherens between mueller cells and rods and cones .
Internal limiting membrane is formed by the basement membrane of these cells

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18
Q

Ganglion cells

A

Conducting neurons whose axons form the fibers of the optic nerve

19
Q

Macula lutea

A

Yellow region surrounding fovea

Highest visual acuity

20
Q

Fovea centralis

A

Depression of visual axis
Highest density of cone cells
Lacks rod cells and capillaries

21
Q

Optic disc

A

Lacks photoreceptors
Point where ganglion cells turn into optic nerve
“blind spot” of retina

22
Q

Types of Photoreceptors

A

Rods

Cones

23
Q

Rods

A

Use rhodopsin as photopigment
Sensitive to low-light intensity
Responsible for black-and-white vision
Lamellae of outer segment are not continuous with plasmalemma
Axons of up to 100 rods synapse with single bipolar cell

24
Q

Cones

A

Use three different kinds of iodopsins as photopigment
Sensitive to high-intensity light
Greater visual acuity than rods
Lamellae of outer segment are continuous with plasmalemma
Each cone cell synapses with a single bipolar cell

25
Q

General architecture of photoreceptors

A

Spherule (rod) and pedicle (cone)
Cell body
Inner segment
Outer segment

26
Q

General architecture of Inner segment of photoreceptors

A

Mitochondria and other organelles

27
Q

General architecture of Cell body of photoreceptors

A

Nucleus and short axons

28
Q

General architecture of Outer segment of photoreceptors

A

Modified cilium
Connected by a stalk to inner segment
Site of stacks of disks containing photoreceptors

29
Q

General architecture of disks of rod cells

A

Disks detach from cell membrane and become free.
Constantly renewed in rod cells
Older disks are phagocytosed by surrounding pigmented epithelial cells

30
Q

General architecture of disks of cone cells

A

Disks remain attached to cell membrane

31
Q

Rhodopsin

A

Transmembrane glycoprotein

Consists of opsin and 11-cis-retinal

32
Q

When photon strikes the 11-cis-retinal (vitamin A derivative):

A

Cis-retinal transforms into 11-trans-retinal
Rhodopsin becomes activated
Activated rhodopsin interacts w/ transducin (G-protein)
Activates cGMP phosphodiesterase
Closing of sodium channels
Hyperpolarizaiton of the rod cell
Reduction in calcium ion influx
Decline in Ca concentration activates recoverin
Stimulate guanylate cyclase
Returns cGMP concentration to normal

33
Q

Bleaching of photopigments

A

Disassembly of rhodopsin into opsin and retinal after light stimulation

34
Q

Regeneration of photopigments

A

11-trans-retinal is converted back into 11-cis-retinal
11-cis-retinal is transported back to photoreceptor
Recombines with opsin
Rhodopsin is regenerated

35
Q

Capsule of the Lens

A

Insertion point for suspensory ligament
Glycoproteins and type IV collagen
Secreted by subcapsular epithelial cells

36
Q

Anterior epithelium of lens

A

Simple cuboidal epithelium

Give rise to cells that become “lens fibers”

37
Q

Lens nucleus

A

Composed of lens cells that mature into fiber-like structures:

  • Devoid of nucleus and organelles
  • Filled with crystalline proteins
38
Q

Anterior surface of the eyelid

A

Covered with skin
Glands of Zeiss
Glands of Moll

39
Q

Glands of Zeiss

A

Sebaceous gland associated with eyelids

40
Q

Glands of Moll

A

Sweat glants

Ducts open into eyelash follicles

41
Q

Palpebral fascia of eyelid

A 
Fibrous core of eyelids
Meibomian glands (tarsal)
42
Q

Meibomian glands

A

Sebaceous glands not associated with hair follicles
Open in front of free edge of eyelid
Secretion keeps normal tear film in eye

43
Q

Palpebral conjunctiva of eyelid

A

Stratified columnar or squamous epithelium with goblet cells
Lines inner surface of eyelids
Continuous with bulbar conjunctiva (covers eyeball)

Whitney - Histology Test 2 (11 decks)

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