Chapter 17 Special Senses

Front 1

Accessory Structures of Eye

Back 1

** Palpebrae: Eyelids

* Superior and Inferior

* Lateral and Medial Commissures

* Palpebral fissure

** Eyebrows and Eyelashes- Protect from sun, foreign objects, and sweat

** Conjunctiva ** Lacrimal apparatus and Extraocular eye muscles

Front 2

Conjunctiva

Back 2

Thin, transparent, vascular membrane

** Bulbar conjunctiva: begins at edge of Cornea; Covers Sclera anteriorly

** Palpebral conjunctiva: from bulbar conjunctiva to cover inner surfaces of the eyelids

Front 3

Lacrimal Apparatus

Back 3

Lacrimal glands produce lacrimal fluid aka tears to flow in Lacrimal Ducts which empty tears onto surface of Conjunctiva then Tears pass over the anterior surface of eyeball and pass into Lacrimal canals which pass into Lacrimal Sac which passes to Nasolacrimal Duct to Nasal cavity which is below Inferior Nasal Conchae

Front 4

Anatomy of Eyeball

Back 4

Has Three tunics(layers):

1) Fibrous tunic: Outermost

2) Vascular tunic: Middle

3) Nervous tunic: Innermost

There are two cavities of the eyeball:

1) Anterior and 2) Posterior cavity

There are Three Intraocular muscles:

1) Pupillary constrictor

2) Pupillary dilator

3) Ciliary muscle

Front 5

Fibrous Tunic

Back 5

**Cornea: Has a transparent coat, very strong and protective. It helps focus light onto the Retina, Has Aqueous humor

** Sclera: Has a layer of dense irregular CT, strong and protective, it gives shape to eyeball, site of attachment of Extrinsic muscles, Has Vitreous humor

Front 6

Choroid (Vascular tunic)

Back 6

Highly vascularized, Provides nutrients to Retina, and contain Melanocytes that produce Melanin which prevent reflection and scattering of Light within the eyeball (Absorbs light)

Choroid attaches to Sclera

Retina attaches to Choroid

Front 7

Ciliary Body (Vascular Tunic)

Back 7

Has Ciliary muscles

It contains Ciliary processes that contain blood capillaries that secrete Aqueous humor

Front 8

Ciliary Muscles

Back 8

Has Zonular fibers: comes from Ciliary processes; attach to Lens and maintain tension on lens

Contraction of ciliary muscles: Pushes muscle forward to Relax the Zonular fibers which Lens becomes thicker and helps to better focus for near vision- design for short contraction

Front 9

Iris (Vascular tunic)

Back 9

Colored portion of eye that contain melanocytes that produce melanin

Iris contain Radial (Pupillary Dilator) and Circular (Pupillary Constrictor) muscles that changes diameter of pupil to regulate amount of light entering the eyeball

Front 10

Anterior Cavity of Eyeball

Back 10

Contain Aqueous humor

Has 2 chambers: Anterior and Posterior

Includes Scleral venous sinus aka Canal of Schlemm

Front 11

Posterior Cavity of Eyeball

Back 11

Contain Vitreous humor

Front 12

Intraocular Pressure

Back 12

This is pressure exerted by fluids inside the eyeball which is aqueous and vitreous humor

Functions: Maintains shape and prevents collapse

Front 13

Retina

Back 13

Inner, thin sheet of nervous tissue located posterior of eye, continuous with Optic nerve

Front 14

Optic Disc (Blind Spot)

Back 14

No cone or rod cell, area where optic nerve exits eyeball posteriorly

Front 15

Macula Lutea

Back 15

Central region of Retina

Lutea is the yellow color

Front 16

Fovea Centralis

Back 16

Depression in center of Macula lutea; light rays converge on fovea for clearest vision; point of greatest visual cavity

Front 17

Nearsightedness

Back 17

Eyeball is too long; Light converges before fovea

Front 18

Farsightedness

Back 18

Eyeball is too short; Light converges after fovea

Front 19

Layers of Retina

Back 19

1) Pigmented layer: Sheet of Melanin-containing epithelial cells, Helps to absorb light

2) Neural sensory layer: Photoreceptor, Bipolar cell, and Ganglion cell layer

Ganglion layer: Axons from optic nerve

Front 20

Photoreceptor Cells

Back 20

Convert light rays to electrical impulse

Rod cells respond to varying shade of gray

Cone cells respond to colors

Front 21

Hearing Is..

Back 21

Conversion of sound waves into electrical impulses

Front 22

External Ear

Back 22

** Auricle includes: Helix and Lobule

** External auditory canal: Lines temporal bone and leads to eardrum includes Hairs and Ceruminous glands

Front 23

Tympanic Membrane: Eardrum

Back 23

** Thin semitransparent partition between external auditory canal and middle ear

Located in External ear

Front 24

Middle Ear

Back 24

** Small air filled cavity

Includes: Ossicles, Windows, Eustachian tube

Front 25

Ossicles in middle ear

Back 25

Has Malleus which attaches to internal surface of the tympanic membrane

The Incus is the middle bone

The Stapes: fits into the oval window

Front 26

Middle ear has Two windows...

Back 26

1) Oval window

2) Round window: covered with secondary tympanic membrane

Front 27

Middle Ear has Two Muscles...

Back 27

1) Tensor tympani and 2) Stapedius

They protect the inner ear from prolonged loud noises

Front 28

Eustachian (Auditory) Tube

Back 28

Connects Middle ear to the Superior portion of the Throat

Front 29

Cochlea Inner Ear is...

Back 29

** Snail-shaped spiral organ embedded within Temporal bone

Has Three channels:

1) Scala Vestibuli: Filled with Perilymph it ends at Oval Window

2) Cochlear Duct: Filled with Endolymph

3) Scala Tympani: Filled with Perilymph it ends at Round Window

Scala vestibuli and tympani are separated by Cochlear duct, except for Helicotrema the opening at the apex of Cochlea

Front 30

Organ of Corti

Back 30

Rests on Basilar membrane it contains:

** Tectorial membrane: Flexible membrane that covers hair cells

** Inner and Outer Hair cells: their Stereocilia are embedded in Tectorial membrane

** Supporting cells and Sensory fibers in Cochlear branch of Vestibulocochlear nerve

Front 31

External and Middle Ears Sound Conduction

Back 31

** Auricle directs sound waves into External Auditory Canal >> Sound waves strike Tympanic membrane and begins to Vibrate

** Vibrations are transmitted to Ossicles: Malleus to Incus to Stapes

** Stapes moves back and forth against Oval Window

Front 32

Inner Ear Sound Conduction

Back 32

** Bulging of stapes pushes against the Perilymph of Scala Vestibuli

** Pressure waves are transmitted from Scala Vestibuli through Helicotrema to the Scala Tympani

** Vestibular membrane begins to Vibrate and pressure is transmitted to the Endolymph of the Cochlear Duct

** Basilar and Tectorial membranes begin to Vibrate then Pressure is released from Scala Tympani through the Round window into Middle Ear