Njds Histology - Eye And Ear

Front 1

The Eye

Back 1

Photosensitive organ partially surounded by orbits

Front 2

How is the eye derived?

Back 2

- Surface ectoderm

- Outpocketing of prosencephalon

Front 3

What are the anatomic components of the eye?

Back 3

1. globe
2. lens
3. photosensitive cells
4. neurons

Front 4

GLOBE

Back 4

Provides support for the outer part of the eye

Front 5

LENS

Back 5

Image focus

Front 6

PHOTOSENSITIVE CELLS

Back 6

Receives visual stimuli and found in the retina

Front 7

NEURONS

Back 7

Transmit visual information to the brain (neurons coalesce into optic nerve)

Front 8

What are the three structural layers of the eye?

Back 8

1. Outer Layer (tunica fibrosa)
2. Middle (vascular) layer
3. Inner

Front 9

Outer Layer (Tunica Fibrosa)

Back 9

Consists of...
- cornea (anterior) and sclera
- majority
- modified connective tissue

Front 10

Middle Vascular Layer

Back 10

Consists of...
- choroid
- ciliary body
- iris (uveal tract)

Front 11

Inner Layer

Back 11

- This layer consists of the retina
- The retina posterior to the ora serrata is sensitive to light

Front 12

What are the three components of the eye?

Back 12

1. Anterior Chamber
2. Posterior Chamber
3. Vitreous Space

Front 13

Anterior chamber

Back 13

This compartment is...
- found between the cornea, and iris and lens
- filled with aqueous humor

Front 14

Posterior Chamber

Back 14

This compartment is...
- between the iris, ciliary body, zonule, and lens
- filled with aqueous humor

Front 15

Vitreous Space

Back 15

This compartment...
- is bounded by lens and retina
- is the largest
- contains gelatenous vitreous body which maintains eye shape and protects retina from tauma due to rapid movements

Front 16

What are the components of the tunica fibrosa?

Back 16

1. Sclera
2. Cornea

Front 17

SCLERA

Back 17

- known as the "whites of the eyes"
- composed of dense fibrous CT where many are multidirectional collagen bundles parallel to eye surface

Front 18

Episclera

Back 18

- This component is the outer surface of the sclera
- It is made of loose CT

Front 19

CORNEA

Back 19

This eye component...
- is the anterior, transparent part of globe
- is a multilayered avascular structure
- has outer nonkeratinized SSE
- has lots of mitotic activity
- is richly innervated

Front 20

Vascular supply of Cornea

Back 20

- This vascular supply lies along the periphery
- Vessels merge into SCHLEMM'S CANAL

Front 21

Schlemm's Canal

Back 21

This structure...
- drains the anterior chamber of aqueous humor
- empties into regional venous system

Front 22

Middle Vascular Layer

Back 22

This contains structures that comprise of the UVEAL TRACT
- choroid
- ciliary body
- iris

Front 23

CHOROID

Back 23

deeply pigmented (many melanocytes)
many blood vessels
loose connective tissue - contains many collagen and elastic fibers and leukocytes

Front 24

Choriocapillary layer

Back 24

very vascular
provides nutirtion of retina
damge can cause extensive retinal damge

Front 25

CILIARY BODY

Back 25

widening of choroid next to lens, triangular in c. sexn
- contains loose CT encasing CILIARY MUSCLE

Front 26

Ciliary Muscle

Back 26

smooth muscle
- inserted on both sclera and ciliary body
- allow for stretching of choroid amd releasing tension on lens
- causes proper visual accomodation

Front 27

Ciliary Processes

Back 27

evaginations of ciliary body
- loose CT core with simple columnar epithelium covering
- cells create AQUEOUS HUMOR

Front 28

Oxytalan (zonule) Fibers

Back 28

from cilary processes insert on lens capsule
holds lens in place

Front 29

IRIS

Back 29

projection of choroid that partially covers the lens leaving aperture
PUPIL
-rough anterior surface covering CT with melanocytes
-below is highly vascularized CT
-Posterior surface is smooth with 2 layers of epithelium
1) Inner Layer - melanocytes and pigmented
2) Outer Layer -myofilaments creating DILATOR PUPILLAE

Front 30

Dilator Pupillae

Back 30

along with melanocytes
regulate light that enters pupil (adaptation)

Front 31

LENS

Back 31

ovoid highly elastic structure

Front 32

What are three parts of the lens?

Back 32

1. Lens Capsule
2. Subcapsular Epithelium
3. Lens Fibers

Front 33

Subcapsular Epithelium

Back 33

simple columnar or cuboidal found only on ANTERIOR SURFACE

Front 34

Lens Fibers

Back 34

majoroty of lens
found below epithelium
elongated subcapsular epithelium cells w/o organelles
contain proteins (CRYSTALLINS)

Front 35

RETINA (Inner Layer)

Back 35

photosensitive elements in posterior portion

Front 36

What are the 2 distinct layers of the retina?

Back 36

1. Pigment epithelium
2. neural (optical) retina

Front 37

Pigment Epithelium

Back 37

simple columnar
-transmit Vitamin A to photo. cells
-produce melanin
-absorbs light after photo. stimulation

Front 38

What are the layers of the neural retina?

Back 38

1.outer layer of rods and cones
2.external plexiform layer
3.bipolar neurons
4.internal plexiform layer
5.ganlion cells

Front 39

Outer layer of rods and cones

Back 39

dendrite - sensitive to light
inner and outer segments
nuclear region
synaptic region

Front 40

External Plexiform Layer

Back 40

1. contains synapses btw rods and cones, and bipolar neurons

Front 41

Bipolar Neurons

Back 41

aka LINKING CELLS
integrate rods and cones with ganglion cells

Front 42

Internal Plexiform Layer

Back 42

contains synapses btw bipolar neurons and ganglion cells

Front 43

Ganglion Cells

Back 43

transmits visual info to brain thru axons
axons merge to become OPTIC NERVE

Front 44

Path of light in retina

Back 44

1. ganglion cells (closest to vitreous body
2. bipolar neurons
3. rods and cones

Front 45

What are the cells of the retina?

Back 45

1. Rods
2. Cones
3. Diffuse bipolar cells
4. monosynaptic bipolar cells
5. ganglion cells
6. horizontal cells
7. amacrine cells
8. supporting cells

Front 46

Rods

Back 46

-responsive to low light conditions
-light sensitive portion
-elongated outer segment contains many stacked membranous disks
-disks contain rhodopsin

Front 47

Rhodopsin

Back 47

In disks of rods
interaction with light is first step to vision

Front 48

Cones

Back 48

elongated conical process
-responsive to color and high intensity light
- less than 5% of photoreceptors
- disks formed by invaginations cell membrane
-thought to provide better visual perception than rods

Front 49

Iodopsin

Back 49

Visual pigment of cones
sensitive to RGB light

Front 50

Diffuse Bipolar Cells

Back 50

synapse with 2 or more photoreceptors

Front 51

Monosynaptic Bipolar Cells

Back 51

synapse with one photoreceptor

Front 52

Ganglion Cells

Back 52

neurons whose axons form OPTIC NERVE
-may be diffuse or monosynaptic

Front 53

Horizontal Cells

Back 53

connect photorecptors together

Front 54

Amacrine Cells

Back 54

connect ganglion cells together

Front 55

Supporting Cells

Back 55

microglia, astrocytes, Muller Cells

Front 56

Muller Cells

Back 56

provide nutrition and structural support to cells of retina

Front 57

FOVEA

Back 57

highest visual acuity

Front 58

What are the accessory structures of the eye?

Back 58

1. Conjunctiva
2. Eyelids
3. Lacrimal Glands

Front 59

Conjunctiva

Back 59

mucous membrane covering cornea and inner surface of eyelid.
-stratified columnar w/ goblet cells

Front 60

What are the three glands of the eyelid?

Back 60

1. Meibomian glands
2. glands of Zeis
3. glands of Moll

Front 61

Meibomian Glands

Back 61

produces lipid rich surface that prefvents tear film evaporation
-does not enter into hair follicle

Front 62

Glands of Zeis

Back 62

sebaceous glands that enter into eyelash follicle

Front 63

Glands of Moll

Back 63

modified sweat glands that empty into eyeash follicles

Front 64

Lacrimal Glands

Back 64

secrete tears
-serous and rich in lysozyme (kills bacteria)
-compound tubuloacinar gland

Front 65

The Ear

Back 65

aka vestibulocochlear apparatus
-concerened with perception of sound and balance

Front 66

What are the three general parts of the ear?

Back 66

1. External ear
2. Middle ear
3. Inner ear

Front 67

What are the components of the EXTERNAL EAR?

Back 67

* collects sound waves
Pinna
external auditory meatus
temporal bone
ceruminous glands
tympanic membrane

Front 68

Pinna

Back 68

most obvious feature
convoluted elastic cartilage covered with skin
leads to EXTERNAL AUDITORY MEATUS

Front 69

External Auditory Meatus

Back 69

-outer third has supporting wall made of elastic caritlage
-remainder is temporal bone
-fibrous elastic CT
-lined on outer surface skin
lined on inner surface by simple cuboidal epithelium
-lined by hairy mucosa and contains CERUMEN GLANDS

Front 70

Ceruminous glands

Back 70

simple coiled tubular glands
secrete ear wax for protection

Front 71

What structures make up the borders of the MIDDLE EAR?

Back 71

1. tympanic membrane
2. temporal bone
3. inner ear

Front 72

What two structures does the middle ear communicate with?

Back 72

1. mastoid air cells (poseriorly)
2. nasopharynx (anteriorly
- via auditory (eustachian) tube

Front 73

What are the two structures in the medial wall of the middle ear?

Back 73

1. oval window
2. round window
*Both are membrane covered structures w/o underlying bone

Front 74

What are the three ossicles and where are they located?

Back 74

*bridging the tympanic membrane and the oval window

1. malleus
2. incus
3. stapes

Front 75

What are the functions of the ossicles?

Back 75

transmit vibratory stimuli to oval window and then to inner ear

Front 76

What are structural characterisitics of the ossicles?

Back 76

1. They have synovial joints
2. covered by simple SE
3. malleus and stapes
have muscle attachment
for regulating sound
passage

Front 77

What are the two labyrinths of the INNER EAR?

Back 77

1. bony labyrinth
2. membranous labyrinth

Front 78

Bony Labyrinth

Back 78

casing within temporal bone housing membranous labyrinth
*contains widenin known as VESTIBULE

Front 79

Vestibule

Back 79

contains dilated utricle and saccule

Front 80

MEMBRANOUS LABYRINTH

Back 80

simple squamous epi attached to peiosteum of bony labyrinth

Front 81

What are the component parts of the membranous labyrinth?

Back 81

1. saccule and utricle
2. semicircular canals
3. endolymphatic duct and sac
4. cochlear duct

Front 82

Saccule and utricle

Back 82

cavities containing neuroepithelial cells that communicate with vestibulocochlear nerve
***MACULA

Front 83

What are the locations of the macula in the saccule and utricle respectively?

Back 83

Sacule - floor
Utricle - lateral wall
* macula oriented perpendicular to each other

Front 84

What are the macula composed of?

Back 84

1) 2 kinds of receptor hair cells
2) supporting cells
3) efferent and afferent nerve endings

Front 85

What are the components of the hair cells of the macula?

Back 85

up to 80 sterocilia and 1 cilium
* a geltainous layer covers hair cells

Front 86

What is the function of otoliths?

Back 86

cause displacement when head changes acceleration, bends stereocilia and sends message to brain via VESTIBULOCOCHLEAR NERVE

Front 87

SEMICIRCULAR CANALS

Back 87

helps determine body position

Front 88

Where are the receptors in the semicircular canals located?

Back 88

dilated areas adjacent to utricle
*ampullae

Front 89

How are they arranged and what is their name?

Back 89

They are arranged in long ridges
-CRISTAE AMPULLARES

Front 90

What are the 2 structural differences between the maculae and the ampullae?

Back 90

1) thicker gelatinous layer and conical in shape
*CUPULA
2) NO OTOLITHS

Front 91

How do the semicircular canals function?

Back 91

determines body position by movement of endolymph
tilts cupula, bends stereocilia, leads to signals depending on direction of tilt

Front 92

ENDOLYMPHATIC DUCT AND SAC

Back 92

-absorb endolymph
-scavenge debris present in endolymph

Front 93

COCHLEAR DUCT

Back 93

aka cochlea
-responsible for reception of sound
-has 3 spaces in cross sxn

Front 94

What are the 3 spaces of the cochlea?

Back 94

1. scala vestibuli
2. scala media
3. scala tympani

Front 95

Scala vestibuli

Back 95

superior, contains perilymph

Front 96

Scala Media

Back 96

contains endolymph, terminates at end of cochlea

Front 97

Scala tympani

Back 97

inferior, contains perilymph

Front 98

What do the vestibuli and tympani connect?

Back 98

oval window to round window

Front 99

Describe the sturcture of the cochlear duct?

Back 99

1. double layer of of simple SE separates vestibuli and media
*REISSNER'S MEMBRANE
2. lateral wall of media
- simple cuboidal epi
*STRIA VASCULARIS
-transports and modifies endolymph
- No cilium
-long hair cells contact TECTORIAL MEMBRANE

Front 100

What does the organ of Corti consist of?

Back 100

hair cells and supporting cells

Front 101

What are the 2 hair cell patterns in the organ of Corti?

Back 101

1. outer layer
- 3-5 rows in cuved pattern of stereocilia
2. inner layer
- linear pattern of stereocilia

Front 102

What are the innervations of the hair cells?

Back 102

Afferent and Efferent
-parakaryons of afferent neurons make up spiral ganglion

Front 103

What are the supporting cells of the cochlear duct?

Back 103

PILLAR CELLS
-line inner tunnel (space important for sound transmission)

Front 104

Describe the path of sound perception

Back 104

External Ear > external auditory meatus > tympanic membrane > ossicles > oval window > perilymph of vestibuli > vestibular membrane > endolymph of scala media > perilymph of scala tympani > displacement of basilar membrane (under hair cells) > tectorial membrane > bending stereocilia > AP generated > cochlear branch of vestibulocochlear nerve