Ocular Structures Flashcards
(39 cards)
Cornea
transparent, connective tissue membrane
set into the sclera
Average diameter of Cornea
Vertical 11.5mm
Horizontal 12.0mm
Average thickness of the Cornea at the limbus
0.7-0.9mm
How many layers make up the Cornea?
5 Epithelium Bowman'membrane Stroma Descemet's membrane Endothelium
Where does the Cornea receive its nourishment from?
Tear film that covers and the aqueous humor that flows beneath it.
The cornea has no blood vessels.
What is the junction between the sclera and cornea called?
Limbus
What is the main function of the cornea?
To focus light rays reflected to the eye
Pars Plana
external periphery of the retina
Zonule Fibers
resemble fibers of a spider’s web spread out between the ciliary body and the crystalline lens and fix the crystalline lens in a central position - behind the iris and the pupil.
Pupil
circular opening in the center of the iris.
the eye can adapt rapidly to changes in light by opening and closing the pupil.
Sclera
white outer layer of the eye
stabilizes the eye
starts at the front edge of the limbus and covers the eye to the posterior optic nerves
What does the Sclera comprise of?
dense, white fibrous tissue
What is the main function of the Sclera?
to protect the contents of eyeball.
it also helps to prevent the scattering of light rays
What are the six extra-ocular muscles that have their insertions on the sclera?
Lateral Rectus (LR) Medial Rectus (MR) Superior Rectus (SR) Inferior Rectus (IR) Superior Oblique (SO) Inferior Oblique (IO)
Conjunctiva
thin, translucent mucous membrane that lines the inner surface of the top and bottom eyelids and the outer surface of the eyeball except for the cornea.
What helps the eyelids to slide easily against the outer surface of the eyelid?
the slippery nature of the conjunctival tissue and the folds in the fornix
Limbus
the transition from the transparent cornea to the white opaque sclera
Iris
comparable to the aperture of a camera
coloured part of the eye
situated behind the cornea and in front of the lens
Eye colour is determined by?
the number of brown pigment cells on its surface - blue eyes have very few pigment cells
Two Iris muscles
the actions of the muscles are either to contract or dilate the pupil, controlling the amount of light entering the inner part of the eye.
sphincter muscle
the circular muscle in the iris that constricts the pupil.
parasympathetic nerve activity that normally innervates this muscle.
dilator muscle
the radial muscle in the iris that dilates the pupil
sympathetic nerve activity that normally innervates this muscle.
What divides the anterior and posterior chambers of the eye?
the iris
What do both the anterior and posterior chambers of the eye contain?
aqueous humour