Week 6: The Eye Flashcards
Fibrous Tunic
Sclera
Outermost layer
Vascular Tunic
Middle layer
Iris, Ciliary Body, Choroid
Retina
Innermost layer
Pigmented layer and neural layer.
Sclera
White of eye
Shape to eyeball
Protects inner parts
Continues as cornea anteriorly.
Cornea
Transparent, non-vascular.
Covers Iris
Principal Refractive Medium of eye.
Choroid
Pigmented (absorbs rays so they dont bounce)
Highly vasularised
Anterior choroid (ciliary body and iris)
Ciliary Body
Alters shape of lens (with muscles), allows eye to focus on objects.
Zonule
Ciliary Muscles
Iris
Coloured part of eye
Diaphragm between lens and cornea
Alters pupil size.
Bright Light
Circular mucles of iris contract = constriction (para)
Dim Light
Radial muscles of iris constrict = dilate (symp)
Retina
Nervous tissue and pigment
Photoreceptors
Role in image formation
Ora Serrata
Junction between retina and ciliary body
Where retina transitions from non-photosensitive to multilayered photosensitive region.
Mucla Lutea
Center of retina
Depression called fovea
Highest visual acuity
High concentration of cone receptors
Optic Disc
Retina where ganglion neurons bend posteriorly to form optic nerve
Blind spot.
Lens
Posterior to iris
Focuses light rays on retina
Refractory apparatus of eye
Suspensory ligaments attach lens to ciliary body
Anterior Cavity
Aqeuous humor (from blood capillaries in ciliary body)
Maintains introcular pressure
Supplies nutrients to lens and cornea
Posterior Cavity
Vitreous humor (jelly)
Intraocular pressure
Holds retina against choroid
Conjuctiva
Thin mucous membrane
Lines eyelid, covers front surface of eyeball (minus cornea)
Produces lubricant, keeps eyeball moist.
Refraction of Light Rays
Cornea - principle and fixed
Lens - varied
Lens during distant viewing
Light rays at cornea are parallel
Ciliary muscles relaxed
Suspensory ligaments tight
Lens is stretched
tall, thin shape
Lens during near viewing
Light rays divergent
Ciliary mucles contracted
Suspensory ligaments loose
Lens short, bugled, convex.
Convergence of Eyes
Six extrinsic muscles
Ensures image falls on fovea
Constriction of Pupil
During near vision
Limits amount of light through periphery of bulging lens
Light through thickest part of lens
Prevents blurred vision
Rods
20 times more numerous than cones
Dim light, high sensitivity and peripheral
Does not provide sharp images
Cones
Less numerous than rods
Bright light, low sensitivity, central receptors
High clarity and colour vision.
Fovea Centralis
Only cones
# of rods increase and cones decrease with further distance from fovea.
Rhodopsin
photopigment - rods
Pigment (Retinal) from Vit A
Protein (Opsin)
Only one pigment
What happens when light strikes Rhodopsin
Pigment breaks down, causes nerve impulse in the neuron.
Cone Photopigments
Cone Opsins (red, green, blue)
Pathway of Images (From Retina to Brain)
Photoreceptors - Bipolar Neurons - Ganglion Neurons - Optic Nerve (CN II) - Optic Tract - Thalamus - Visual Cortex
Lacrimal Apparatus Location
Gland and duct above eye, below outer eyebrow
Function of Lacrimal Apparatus
Tears
Tears
Watery solution containing: salts, mucous, Lysozyme
Functions of Tears
Clean, lubricate, moisten eyes.
Protect against bacterial infections.
