Special Senses Flashcards
(39 cards)
What components make up the periorbital region?
Superior and Inferior Palpebra - eyelids
Eyelashes
Supraorbital ridge - diverts fluids
Lacrimal caruncle - directs tears into opening to drain
Extrinsic Eye muscles
What is the lacrimal apparatus and what are the components?
Produces and brings tears to surface of eye and reabsorbs tears
Components
- Lacrimal Gland - produce tears
- Lacrimal Ducts - bring tears to eye
- Lacrimal Puncta - entry into lacrimal canals
- Lacrimal Canals - brings tears to nasolarcimal duct
- Nasolacrimal Duct - takes tears to nasal cavity
How does the eyelid blink and what is the purpose?
Blink from lateral to medial and helps spread tears
What kind of antimicrobial is contained in tears?
Lysozyme
What are the components of the fibrous tunic?
Continuous w/ dura mater of brain
- Cornea - clear part of eye
- Sclera - white of eye
- conjuctiva is the mucous membrane of sclera
- Canals of Schlemm - edge of cornea/sclera
- where you drain fluid from eye
What are the components of the vascular tunic?
- Choroid
- blood vessels provide nutrients for retina
- Ciliary Body
- ciliary muscle - connects to lens to change shape
- ciliary processes - make aqueous fluid
- Iris
- sphinctor pupillae - constrict pupil
- dilator pupillae - dilate pupil
How is the lens held in place?
With suspensory ligaments
What is the accommodation reflex?
The lens changes shape for near/far vision
- Near vision lens = more biconvex (round)
- Far vision lens = less biconvex
What makes up the nervous tunic or retina?
- Pigmented Layer - absorbs light to prevent from bouncing
- Nervous Layer - photoreceptors, bipolar and ganglion cells
- Optic Disk - blind spot where retina connects to optic nerve
- Ora Serrata - where retina connects to ciliary body
What are the different nervous layers of the retina or nervous tunic?
- Photoreceptor layer
- rods - dim light and black/white
- cones - color vision
- Bipolar layer
- bipolar cells
- Ganglion layer
- axons that compose optic nerve
What is the central fovea?
Central fovea - only photoreceptors=sharpest vision
-100% cones in central fovea and more rods as you move away
What are the characteristics of the lens?
- biconvex
- made of crystallin proteins
- suspensory ligaments
- change shape with accomodation reflex
- focuses light on the retina
How does the ciliary body and suspensory ligaments interact with eachother to change shape of lens?
Ciliary body relaxes = more tension on suspensory ligaments
-lens is less biconvex for far vision
Ciliary body contracts = less tension on suspensory ligaments
-lens is more biconvex for near vision
What are the different cavities and chambers of the eye?
Anterior Cavity
- posterior chamber
- anterior chamber
Posterior Cavity
What fluids fill up the different cavities of the eye? How is intraocular pressure and turgor maintained?
Anterior Cavity = aqueous humor
-constanty produced and reabsorbed
Posterior Cavity = vitreous humor
-not continuously produced/reabsorbed
Intraocular pressure maintained with aqueous humor
Turgor (shape) maintained with vitreous humor
What three processes are involved in formation of images on the retina?
- Refraction of light rays
- accomodation of lens
- constriction of pupil
How much light is refracted by the cornea and lens?
cornes = 60%
lens = 40%
How does accomodation work for lens?
Biconvex lens
Far object = less convex
Near object = more convex
ciliary muscles change shape of lens
How does constriction of the pupil affect vision?
Part of the accomodation reflex that limits peripheral light
-near vision = pupillary constriction
How do photoreceptors act as neurons in different light conditions?
What are the characteristics of rod cells?
- not present in central fovea
- increase in concentration to ora serrata
- dim light and peripheral vision
- 6 – 600 rod cells converge on 1 bipolar cell, as well as amacrine and
- horizontal cells.
What are the characteristics of cone cells?
- 100% cone cells in central fovea
- diminish in number toward ora serrata
- three different types: blue, red, green cone cells
- bright light required to break pigments
- 1:1 relationship with bipolar cells
- visual acuity and color vision
Walk through the visual pathway.
Begin when bipolar neurons initiate action potential after receiving signal from photoreceptors
-Ganglion cell axons converge in blind spot = optice nerve
Optic Chiasma = some crossing over
- medial retina pathway = contralateral
- lateral retina pathway = ipsilateral
What is the anatomy of the external ear?
