The Eyeball Flashcards
What do the sclera and cornea make up?
Fibrous Outer Layer
What make up the fibrous outer layer?
Sclera and Cornea
What do the Iris, Choroid and Ciliary Body make up?
Vascular Middle Layer / UVEA
What is a name for the Iris, Choroid and Ciliary Body?
The UVEA
What makes up the vascular middle layer?
Iris, Choroid and Ciliary Body
What makes up the Sensory inner layer?
Retina
What is the sclera’s role?
It provides attachment for the extraocular muscles. Venous drainage comes out the sclera and blood vessels have gaps in the sclera to get through.
It’s covered in the same meninges as those from the brain.
How many dioptres of refraction do the cornea and lens provide respectively?
Cornea - 43D
Lens - 10-15D
What are the layers of the cornea?
Epithelium - Anterior layer. Able to repair.
Bowmans
Stroma - majority of cornea, can become filled with fluid that impairs vision
Descements
Endothelium - Fluid resistant, stops fluid from the the eye reaching the cornea
= EBSDE
Describe the Iris
Thin, contractile diaphragm to affect pupil aperture. Split into anterior and posterior:
Anterior Iris - coloured part
Posterior Iris - Behind the eye, the lens is pressed against the posterior surface of the iris
The Iris is peripherally attached to the anterior surface of the ciliary body
The iris sphincter muscle is controlled by the short ciliary nerves which is a branch of CN III whereas the dilator is controlled by the sympathetic long ciliary nerves
Describe the ciliary bodys epithelium in relation to the choroid
Continues posteriorly with the choroid
Describe the ciliary bodys position in relation to the peripheral margin of the iris
Anteriorly
What are the 3 parts of the ciliary body called?
Ciliary Proper, Ciliary Processes, Ciliary Epithelium
Describe the ciliary proper
It’s made up of the ciliary muscle which, when contracted, allows for the lens to thicken
Describe the ciliary processes
Extension of the ciliary body - between the processes are the zonules that attach to the lens
Describe the ciliary epithelium
2 layers and secretes aqueous humour
What is the choroid?
Thin brown lining on the inner surface of the sclera extending from the optic nerve to ciliary body (thick at the back, thin to the front). It’s a vascular structure providing nourishment to the outer retinal layers
What makes up the inner sensory layer?
The retina. One layer of the retinal pigmented layer rests against the choroid
What is the anterior chamber?
The area between the cornea and anterior iris
What is the posterior chamber?
Between the posterior iris and ciliary processes
What’s the role of the vitreous?
To transmit light in transparent gel and supports the posterior surface of the lens
How many bones is the orbit comprised of and what are they?
7 (seven)
Frontal
Maxilla
Lacrimal
Ethmoid
Sphenoid
Palatine
Zygomatic
What are the fissures that run through the sphenoid bone?
3;
Superior Orbital Fissure, Inferior Orbital Fissure & Optic Canal
What bones make up the medial wall of the orbit?
Maxilla, Lacrimal, Ethmoid, Sphenoid Body
What bones make up the superior wall of the orbit?
Frontal & Lesser Wing
What bones make up the lateral wall of the orbit?
Zygomatic & Greater Wing
What bones make up the inferior wall of the orbit?
Maxilla, Zygomatic & Palatine
What passes through the optic canal?
Optic nerve and Ophthalmic artery
What passes through the supraorbital fissure?
Trochlear, Abducens and Oculomotor & Superior Ophthalmic vein
What passes through the inferior orbital fissure?
Zygomatic branch of the maxillary nerve, maxillary nerve, inferior ophthalmic vein and sympathetic nerves
Where does the superior oblique originate?
Through the sphenoid bone; attaches posterior to the superior rectus
Where does the inferior oblique originate?
Anterior of the orbital floor; attaches to the sclera, posterior to lateral rectus
What does the lateral rectus do?
Abducts
What does the medial rectus do?
Adducts
What does the superior rectus do?
Elevates
Intorts
Adducts
What does the inferior rectus do?
Depresses
Extorts
Adducts
What does the superior oblique do?
Intorts
Depresses
Abducts
What does the inferior oblique do?
Extorts
Elevates
Abducts
Where does the LPS originate?
At the lesser wing of the sphenoid and attaches to the superior tarsus
Where is the muller muscle?
Inferior to the LPS
On a fundus image how does central retinal artery occlusion look?
Macula appears pale when it usually is cherry red. The blood supply to the fovea is intact so appears brighter and redder.
Where does venous drainage occur?
At the superior ophthalmic vein to the cavernous sinus; inferior orbital vein to the cavernous sinus
Describe each artery/ the vascular system of the eye?
Internal Carotid Artery
Ophthalmic Artery
Lacrimal Artery
Long Posterior Ciliary Artery
Short Posterior Ciliary Artery
Muscular Artery
Supraorbital Artery
Anterior Ethmoid Artery
Supra-Trochlear Artery
Dorsal Nasal Artery
Medial Palebral Artery
Lateral Palebral Artery
How many layers of the eyelids are there and what are they?
5; C LOTS
Conjunctiva
LPS & Muller Muscle
Orbicularis Oculi (made up of the orbital, palpebral and lacrimal)
Tarsal Plate
Skin
What keeps the eyelids supple?
The glands of moll and glands of Zeis
What does the lacrimal system consist of?
Lacrimal Gland (made up of 12 glands secreting into the superior fornix), Lake, Canaliculi, Sac & Duct
Orbital – larger and sits on the lateral margin of the levator palpabrae superioris muscle.
Palprebral – smaller and is located along the inner surface of the eyelid
When the lacrimal gland is damaged, what small accessory glands can assist?
The conjunctival fornices. They have autonomic and sensory innervation.
What are the tear film layers?
Oil (lipid), water (aqueous) and mucin layer.
How does the Lacrimal System work?
After secretion, lacrimal fluid circulates across the eye, and accumulates in the lacrimal lake – located in the medial canthus of the eye. From here, it drains into the lacrimal sac via a series of canals.
The lacrimal sac is the dilated end of the nasolacrimal duct, and is located in a groove formed by the lacrimal bone and frontal process of the maxilla. Lacrimal fluid drains down the nasolacrimal duct and empties into the inferior meatus of the nasal cavity.
What do the short ciliary nerves control?
The iris sphincter muscle is controlled by the short ciliary nerves which is a branch of CN III
What do the long ciliary nerves control?
The dilator is controlled by the sympathetic long ciliary nerves (part of CN III)
