Anatomy Flashcards
Layers of the eyeball
Outside in
- Fibrous coat/outer layer
- Vascular coat/middle layer
- Nervous coat/inner layer
Segments of the eyeball
- Anterior segment
2. Posterior segment
Characteristics & Function of Cornea
- Transparent
- Centrally positioned at the front of the eye
- Makes up anterior 1/6th of fibrous coat
- Light refraction
Sclera’s functions
- Provides shape to the eye
- Provides attachment to extraocular muscles
Components of fibrous coat
- Sclera
- Cornea
Junction where sclera ends and cornea begins
Limbus
Components of vascular coat
Anterior -> Posterior
- Iris
- Ciliary body
- Choroid
Function of fibrous coat
Protects intraocular contents
Function of vascular coat
Supplies nutrition to various structures of the eyeball (Cornea and lens are avascular)
Describe sclera
- White part of the eye
- Makes up posterior 5/6th of the fibrous coat
- Several vessels penetrate through the sclera including the optic nerve
Another name for vascular coat
Uvea
What is choroid?
A layer of connective tissue and blood vessels
Function of choroid
Provides nourishment to the outer layer of the retina
Parts of the ciliary body
- Ciliary muscle
2. Ciliary processes
What is ciliary muscle made of?
A collection of smooth muscle fibres arranged in 3 orientation (radial, circular, longitudinal)
Briefly explain the role of ciliary muscle in accommodation reflex
Accommodation reflex : adjusting lens for near vision
Ciliary muscle contracts -> Circular ciliary body reduces in size -> Zonnular fibres/suspensory ligament of lens slack -> Lens become more rounded
What are ciliary processes?
Function?
Ciliary processes project from the surface of the ciliary body
Attach the lens to the ciliary body via zonnular fibres/suspensory ligament of lens
What is iris?
- Circular structure with an aperture in the center called the pupil
- Gives the eye colour as iris is strongly pigmented
Function of iris
- give the iris colour
- has a two fiber arrangement which help control the pupil size
Explain the layers of fibres in the iris
- Circular fibres give rise to sphincter pupillae
- Under parasympathetic control -> miosis - Radial fibres give rise to dilator pupillae
- Under sympathetic control -> mydriasis
Name the layers of the nervous coat
2 cellular layers
- neural
- pigmented
Location of pigment cell layer of retina
- Beneath the neural layer
- Attached to the choroid layer
What is optic disc?
- Optic nerve head
- Retinal ganglion cell axons exit the eye to become optic nerve
- Site of entry of central retinal artery into the retina
- Blind spot (no light detecting cells)
Name the two chambers of the anterior segment
- Anterior chamber
- Posterior chamber
Boundary of anterior segment
Cornea -> Lens (included)
Boundary of posterior segment
Lens -> Retina
Boundary of anterior chamber
- Anterior boundary : Back of cornea
- Posterior boundary : Anterior surface of iris and part of ciliary body
Depth of anterior chamber in hypermetropes and myopes
Hypermetropes : Slightly shallower than normal
Myopes : Deeper than normal
Almost equal in both eyes of the same individual in any case
Secretion of aqueous humour
By ciliary body in the posterior chamber
Function of aqueous humour
- Nourishes and protects the eye (cornea and lens are avascular)
Boundaries of posterior chamber
Anterior boundary - posterior of surface of iris and part of ciliary body
Posterior boundary - crystalline lens
Lateral body - ciliary body
