Lecture 27- Microanatomy of the eye Flashcards
What are the 3 layers of the eyeball
Sclera/ cornea (outer) UVea (vascular)- middle -choroid - ciliary body - iris RetINa- inner
What are the roles of the sclera and cornea
Protect inner structures and together with intraocular fluid the shape of the eyeball
What are the roles of the sclera and cornea
Protect inner structures and together with intraocular fluid the shape of the eyeball
S- protection, Cornea- bending light onto fovea (visual acuity)
What is the appearance of the sclera and cornea
S- tough, dense ct
Cornea colourless and transparent, parallel arrangement of CT
Limbus- boundary between s+c, zone of transition of epi of conjuctiva w cornea
What is the uvea
Vascular, pigmented to lightproof the eye and reduce reflection
Comprises of choroid, ciliary body (melanocytes absorb light) and iris
Ant. portion contains SM (CB, constrictor/dilator of iris)
Macular degeneration(age)/ lipid deposits in choroid prevent nutrients reaching retina
What is the role of the ciliary body muscle?
Regulate tension of suspensory ligaments of lens (Accomodation of light onto fovea)
What is the structure and role of retina
outer pigmented and inner retinal layer
post. 2/3 light sensitive and contain photoreceptor neurons: rods and cones
anterior 1/3 not light sensitive, separated by posterior portion by ora serrata (no neural component)
Simple pigmented cuboidal epithelium
Where are the anterior and posterior chambers of the eye located
Anterior chamber- between cornea and iris, filled w/ aqueous humour
Posterior chamber- between posterior iris + anterior lens
What are the transparent components of the eye
Cornea (avascular)
Aqueous humour- watery fluid produced by ciliary processes (shape)
Lens (avascular)- focuses light onto fovea
Vitreous humour- found posterior to lens- hydrated gel, mostly hyaluronic acid/ some collagen fibrils
What are the 5 layers of the cornea
Epithelium (SSNK- most anterior, interacts w/ tear film, free nerve endings) continous w/ conjunctival epithelum at limbus (CS junction)
Bowmans layer- SSNK, damage leads to scar formation and loss of VA
Stroma- bend light: T1 collagen, uniform parallel arrangement so transparent
Descemet’s membrane
Corneal endothelium- non regenerative
What are the 5 layers of the cornea
Epithelium (SSNK- most anterior, interacts w/ tear film, free nerve endings) continous w/ conjunctival epithelum at limbus (CS junction)
Bowmans layer- SSNK, damage leads to scar formation and loss of VA
Stroma- bend light: T1 collagen, uniform parallel arrangement so transparent
Descemet’s membrane
Corneal endothelium- non regenerative
Where is the iris found and what is its role
Delineates ant/post chambers- heavily pigmented so blocks light apart from at pupil, controls how much enters
Ant limiting layer- fibroblasts/ melanocytes
Stroma (bv/ melanocytes)
Pupil dilator muscle- sphincter inc/dec pupil diameter
Pigmented epithelium
Where is the iris found and what is its role
Delineates ant/post chambers- heavily pigmented so blocks light apart from at pupil, controls how much enters
Ant limiting layer- fibroblasts/ melanocytes
Stroma (bv/ melanocytes)
Pupil dilator muscle- sphincter inc/dec pupil diameter
Pigmented epithelium
Where is the iris found and what is its role
Delineates ant/post chambers- heavily pigmented so blocks light apart from at pupil, controls how much enters
Ant limiting layer- fibroblasts/ melanocytes
Stroma (bv/ melanocytes)
Pupil dilator muscle- sphincter inc/dec pupil diameter
Pigmented epithelium
Where is the iris found and what is its role
Delineates ant/post chambers- heavily pigmented so blocks light apart from at pupil, controls how much enters
Ant limiting layer- fibroblasts/ melanocytes
Stroma (bv/ melanocytes)
Pupil dilator muscle- sphincter inc/dec pupil diameter
Pigmented epithelium
What is the role of the ciliary body?
Aqueous humour produced by CP epithelium- passes from post > ant chamber and drains through canal of schlemm : blockage leads to ^ IO pressure and glaucoma> damage to retina and blindness
Contraction of ciliary muscle causes relaxation of lens
What is the structure of the lens
Avascular, outer capsule of type iv collagen and layer of cuboidal (lens) epi on ant. face only
Centre of tightly packed anucleate cells with crystallins form lens fibres
What are the 2 layers of nerve cells in the retina?
Derived from neuroectoderm ( extension of brain)
Inner sensory retina- neurons/ glial cells
Outer retinal pigmented epithelium- simple cuboidal melanin containing cells
What are the 4 groups of cells found in the sensory retina?
Photoreceptor neurons- rods and cones
Conducting neurons- bipolar and ganglion cells
Association neurons- horizontal and amacrine cells
Neuroglial cells- muller cells
Where are rods and cones found?
rods- light intensity, concentrated at periphery of retina
cones- colour, concentrated in fovea: arranged at an angle so outer nuclear layer and other retinal layers dont block light pathway
between fovea there is a mixture of rods and cones
How is the optic nerve formed?
At optic disk, axons from ganglion cells merge to form ON
Blind spot, no photoreceptors present
How is the optic nerve formed?
At optic disk, axons from ganglion cells merge to form ON
Blind spot, no photoreceptors present
What are the components of the eyelid/ surrounding glands?
Eyelash, skin, orbicularis muscle ( close eyelids and pump tears)
Accessory lacrimal glands- aqueous portion of tear film
Conjunctiva- protection/ lubrication- microbial barrier and immune surveillance
Tarsal plate- dense fibroelastic tissue
Meibomian gland- lipid rich secretion preventing tears from evaporating
Cornea
