Eyes Flashcards
What receptors are found in the eye?
Photoreceptors.
Which area of the brain processes visual information?
The Occipital lobe.
What is the function of the Lacrimal apparatus?
Production of Lacrimal fluid/tears.
State the flow of Lacrimal passage from the apparatus to the nasal cavity.
Lacrimal apparatus,
Lacrimal gland,
Lacrimal ducts to canal,
Lacrimal sac,
Nasolacrimal duct,
Nasal cavity.
What is the function of Lacrimal fluid?
Contains lysozyme which protects and cleanses the eyes.
What are the THREE tunics of the eye?
Fibrous tunic,
Vascular tunic,
Retina.
What does the fibrous tunic consist of?
Cornea & Sclera.
What does the Vascular tunic consist of?
Choroid, Ciliary body, Iris & Pupil.
What does the Retina consist of?
Photoreceptors- Rods & cones,
Optic disc,
Macula lutea,
Fovea Centralis
What is the function of the Cornea?
The transparent layer over the iris, protects the eye and has a curved shape to focus light. Accounts for 75% of refraction.
What is the function of the Sclera?
The white of the eyes,
Covers the entire eye except the cornea,
Provides shape & support.
What is the function of the Choroid?
Contains Melanocytes which produce melanin to absorb light.
Highly vascular.
What is the function of the Ciliary body?
Secretes aqueous humor,
ciliary muscles alter shape of the lens to focus image - Accomodation.
What is the function of the Iris?
The coloured portion of the eye - determined by melanin count.
Regulates the amount of light entering the eye.
Contains circular and radial smooth muscle.
What is the function of the Pupil?
The hole in the centre of the iris,
Point where light enters the eye.
What is the function of the Retina?
Forms the beginning of the visual pathway, Contains photoreceptors.
Contains the optic disc which is the location where the optic nerve exists the eye.
What is the function of the Macula Lutea?
The exact centre of the posterior retina, contains the Fovea Centralis which contains only cones - highest area of visual activity.
What is the difference between rods & cones?
Rods are specialised for black and white vision, aswell as shapes and movement. 120million in each eye.
Cones are specialised for colour vision. 6 million in each eye.
What are the TWO cavities of the eye?
Anterior cavity,
Posterior cavity.
What is the Anterior cavity?
Anterior to the lens,
Contains two chambers- Anterior chamber: between cornea & iris.
Posterior chamber: between iris & lens - contains aqueous humor which nourishes the lens and cornea.
What is the Posterior cavity?
Lies between the lens and retina,
contains the vitreous body- a jelly like substance which maintains the shape of the eye.
What is Intraocular pressure?
The pressure from Aqueous humor and Vitreous body.
What are the FOUR steps of image formation?
Refraction,
Accomodation,
Pupil Constriction,
Convergence of the eyes.
What is Refraction?
The Cornea & Lens bend light rays to focus an image on the Central fovea.
What is Accomodation?
The change in shape of the Lens to allow sharp focusing of light into the Retina.
What is Pupil constriction?
The smooth muscle of the Iris controls the amount of light entering the eye & helps prevent light scattering.
What is Convergence of the eyes?
Medial movement of both eyes to focus on an object.
What is the definition of Refraction?
A bending of light as it passes from one substance into another with a different density.
Where does Refraction occur? and at what percent?
75% of Refraction occurs in the Cornea,
25% of Refraction occurs in the Lens.
What is a potential abnormality that affects Refraction?
Presbyopia: Loss of lens elasticity which results in a decreased ability to focus on near objects.
What is the process for focusing on a DISTANT object?
Ciliary muscles relax - pulls on suspensory ligament - which pulls on the Lens. Flat lens = reduced refraction.
What is the process for focusing on a NEAR object?
Ciliary muscles contract - lessens tension on suspensory ligaments - lens thickens - increased curvature of lens= increased refraction.
What is meant by Binocular vision?
Both eyes focus on the same object.
What is the first step of vision transduction?
Absorption of light by photopigments in rods & cones.
This initiates an action potential.
What is the flow of Visual pathway?
Visual info in the Optic nerve travels to the: Hypothalamus - establishes sleep patterns based on circadian rhythm.
Midbrain: Contains some visual reflex centres that control movement of the head, eyes & trunk in response to visual stimuli.
Primary Visual area: Location in which visual imagery is processed and associated.
What are the THREE cranial nerves involved in the movement of Extrinsic eye muscles.
Oculomotor,
Abducens,
Trochlear.
What are the accessory structures of the eye?
Eyelid,
Eyebrow,
Eyelash,
Canthus,
Lacrimal Caruncle.
