Eye and Ear Flashcards Preview

Histology > Eye and Ear > Flashcards

Flashcards in Eye and Ear Deck (39):

Structure of the eye

3 layers
1. Outer layer (CT layer) = Tunica Fibrosa
- Sclera = CT
- Conea

2. Uvea
- Choroid - vascular layer which provides nutrients to the retina
- ciliary body
- Iris

3. Retina (innermost part)
- consists of rods and cones and neruons that will become the optic nerve
- mainly nerual (5/6)
- non neural retina lines the ciliary body and the iris


Tunica Fibrosa

- outermost layer
- fibrous layer
- Sclera - covers most of the back of the eye
- Cornea - in contact with air on one side and fluid on the other



- CT layer
- acting as a capsule to hold the eye in place
- has typical CT materials - fibroblasts, amorphous components, etc.



- Has 5 layers
1. corneal epithelium (outermost layer)

2. Bowman's membrane
- thick layer of extracellular material
- noncellular

3. Stromal layer
- thickest layer

4. Descemel's membrane

5. Endothelium Layer
- squamous

Light must pass through all 5 layers of cornea before it gets inot the anterior chamber


Canal of Schlemn

- Facilitates equilibrium of pressure within the eye
- Equilibrates the pressure in the anterior chamber
- if you have pressure that builds up in the anterior chamber, it can drain out through this canal



3 layers
1. choroid - vascular
2. ciliary body
3. iris



- Blood vessels providing nutrients to the sclera (CT) and the retina

Choriocapillary layer - close to the retina
- subdivision of choroid
- blood vessels are much smaller - filled with capillaries
- immediately adjacent to the retina


Ciliary Body

- contain muscle that can contract and change shape of lens for visual accommodation
- folds of epithelium = ciliary processes
- from the processes, you have zonule fibers

- by changing the shape of the muscle, you will pull or relax on the lens to change its shape for visual acuity


Ciliary Processes

- Contain a double layer of low columnar to cuboidal epithelium
- Inner layer is pigmented with melanin granules
- outer layer is non pigmented



- Double layer of epithelium continues from the ciliary processes to line the posterior iris
- eye color is due to amount of pigment in the epithelium


Zonule Fibers

- from the ciliary processes, you get zonule fibers attached to the lens
- oxytalin fibers - first component of elastic fibers
- bridge between ciliary body and lens
- Pull on the lens - change lens shape


Vitreous Chamber

- like a sponge
- a lot of hyaluronic acid
-- glycosaminoglycans - hyrophobic - absorb a lot of water
--holds a lot of water



5/6 of the back of the eye ball is neural retina

forward 1/6 is non neural
- double layer epithelium that projects forward to line the ciliary body and iris


3 Layers of the Retina

1. Outer most/ deepest layer
- consists of rods and cones embedded in pigmented epithelium
- receive photons of energy in the form of light
- stimulate some visual stimulus

2. Bipolar neurons
- one side on the rods and cones
- the other on a ganglian cell
- Muller cell - sustantacular cell (support cell)

3. Ganglain Cell layer
- one end attaches to the bipolar neuron layer
- the other end forms axons and project to become the optic nerve


Ora serrata

- Transition form the neural retina to the non neural retina
- non neural is double layer epithelium that lines the ciliary body and back of the iris



- most sensitive to light
- only give you black, white and shades of grey
- Rhodopsin - responsible for perceptions of black, white and grey
- under low light conditions, the rods are able to pick up light that the cones cannot



- give you color vision
- have iodopsin - gives perceptions of color
- cones need a good bit of light to be stimulated
- in the light they are able to pick up more photons of light


Fobea Centralis

- macula
- only cones
- located at the back of the eyeball
- responsible for central vision and visual acuity


Optic Nerve

- blind spot
- central artery of the retina runs through the optic nerve
- no rods or cones



- outermost layer is lens capsule - CT, non cellular

- lens epithelium - simple cuboidal to columnar

- Differentiating lens fibers

- mature lens fibers

- light has to go through all of these layers plus the anterior chamber before reaching the rods and cones



Innermost layer is the conjunctiva
- in contact with the eye ball
- layer of epithelial cells

Tarsal plate gives rigidity to the eye
- so you can move your eye

Meibomian Gland
- sebaceous glands

Orbicular Muscle
- contract to allow movement of the eye

- prevents things from getting in the eye



- Layer in contact with part of the eyeball
- predominantly stratified columnar to stratified squamous


Lacrimal Apparatus

Lacrimal Gland
- produces tears
- secretes fluid onto the eye


Extraocular Muscles

- Pull on the eye to that it can move around and to focus


Structure of the Ear

3 Layers
1. Outer ear
- eardrum

2. Middle ear
- articulating bones
- create a sound wave for inner ear

3. Inner ear
- cochlea (hearing)
- vestibular apparatus (balance and motion)



- Contains a lot of CT and elastic fibers


External Auditory Meatus

- ear canal
- lined by epidermis
- Continuous with the ear lobe
- contains the ceruminous glands - gives rise to ear wax



- Tympanic membrane (eardrum)
- 3 layers
1. Epidermis continuous with the canal
2. middle layer of fibrous CT
3. Inner layer of simple cuboidal and/or squamous


Middle Ear

Malleus, incus, and stapes
- articulating bones
- transmit a sound wave from eardrum to the oval window
- when they articulate, they amplify the signal of sound

- stapes has a pad that pounds on the oval window of the inner ear


Bony and Membranous Labyrinth

Bony Labyrinth
- bone "shell" around the membranous labyrinth

Membranous labyrinth
- the tissue within the bony labyrinth

- nerves are quite large and attach to the three components of the inner ear


Inner Ear Sensory Regions

Vestibular Apparatus
- utricle and the saccule
- maculae is the sensory structure within - responsible for the perception of motion

Semicircular canals
- 3 of them in different orientations (x,y,z)
- cristae ampullares - responsible for 3D orientaion and motion

- Oran of Corti - responsible for hearing



- sea shell shaped
- Oval window is being baned on by the stapes
- pressure wave passes down through cochlea
- causes the organ of Corti to vibrate, causing sensation of sound
- pressure goes back down and pushes on the round window

- vibration of the tectorial membrane is responsible for stimulating the hair cells of the of the organ of corti


Middle Duct of Cochlea

- called scala media
- organ of corti is on the scala media
- one the back of the scala media, there is a layer of cells called the scala vascularis - secrete endolymph (maintains the viability of the cells of the organ of corti)

- surrounded by vesibular membrane


Organ of Corti

- As the fluid within the canal is pushed by a pressure wave the tectorial membrane rubs against the hair cells
- vibrating due to sound creating a pressure wave
- the hair cells perceive the movement of tectorial membrane
- projects that on the cochlear nerve which then goes to the auditory nerve which is how you hear


Stereocilia Bundles

- Hair cells - in a v shaped row
- Tectorial membrane rubbing on the hair cells transduces a signal perceived as sound


Vestibular Apparatus

- within the utricle and the saccule there is a sensory structure called the macula



- contains stereocilia and one long true cilia
- embedded in a gelatinous layer - has calcium carbonate crystals on top of it - otoliths or otoconia

- otoliths provide for inertia

- cilia and stereocilia bend with the movement of the gelatinous layer which provides for perception of linear acceleration

- sensory cells containing stereocilia and one true cilia at the end of the escalating ramped up bundle of stereocilia


Cristae Ampullares

- at the base of semicircular canals perceive rotation
- The gelatinous layer rubs against the other side of the canal
- inertia is provided by the rubbing against the other side of the canal


Semicircular canals

- canals are in X, Y, Z orientation allowing for perception of rotation