Anatomy of the Eye and Orbit Flashcards
What is the sclera?
Is the opaque posterior 5/6 which gives attachment to muscles moving eyeball
What is the cornea?
Is the anterior 1/6 which is transparent and is a window to allow light rays to enter the eyeball
What is the ciliary body?
Suspends the lens and produces Aqueous Humor
What is the choroid?
Supplies blood to outer layers of retina
What is the iris?
Controls the diameter of the pupil and thereby controls the amount of light rays entering the eyeball
What is the retina?
Has light sensitive rods and cones which enables us to see.
What is the crystalline lens?
Is a transparent, crystalline biconvex structure which is suspended by zonules (suspensory ligaments) from the ciliary body. It can change shape (i.e. become less or more convex.)
What should you understand about the ciliary body and suspensory ligaments?
The ciliary body and the suspensory ligaments of the lens are present in 360o
What is the anterior segments?
Front of the lens Contains a watery fluid called Aqueous Humor
What is the posterior segment?
Behind the lens Filled with a gel called Vitreous Humor
What is aqueous humor?
A watery fluid anterior to the lens.It helps maintain intraocular pressure.
What is a vitreous humor?
A transparent gel posterior to the lens.It helps cushion the retina.
What is the anterior chamber?
In front of the iris
What is the posterior chamber?
Behind oros but in front of the lens
What is A?
Trabecular meshwork
What is B?
Schlemm’s canal
What is A?
Cornea
What is B?
Sclera
What is C?
Iris
What is D?
Pupil
What is A?
Frontal bone
What is B?
Zygomatic bone
What is C?
Sphenoid bone
What is D?
Maxilla bone
What is E?
Lacrimal bone
What is F?
Ethmoid bone
What is A?
Frontal sinus
What is B?
Ethmoidal air sinuses
What is C?
Maxillary air sinus
What is the AP length of eyeball?
24mm
What is the AP length of orbit?
40 mm
What is the orbital fat cushion globe important for?
Support
What do the lids do?
Skin on the outside, mucous membrane on the inside (conjunctiva)
What do eyelashes have?
Sebaceous glands
What do hard plates do?
Keep shape by tarsal plate
What do oily secretory glands do?
Tear film
What is A?
Skin
What is B?
Orbicularis oris
What is C?
Levator palpebrae superioris
What is D?
Tarsal plate
What is E?
Meibomian glands
What is F?
Conjunctiva
What is G?
Eyelash with sebaceous glands
What is conjunctiva?
Thin vascular membrane that covers inner surface of eyelids and loops back over sclera.
Does not cover the cornea
Where is the lacrimal gland situated?
In the orbit laterally
What is the parasympathetic innervation of the lacrimal glands done by?
Facial nerve
Where do lacrimal glands ducts open into?
Conjunctival sac
What happens during each blink?
During each blink, eyelids spread tears evenly on the surface of cornea
Tears drain through punctae on the medial side of each eyelid
Drains into lacrimal sac which sits over the lacrimal bone
Then drains through nasolacrimal duct into the inferior meatus of the nasal cavity.
What do intrinsic muscles do?
Control pupil diameter & helps alter lens curvature to enable us to see near objects
What do extrinsic muscles do?
Move the eye
What are the intrinscic muscles that affect parasympathetic nerve?
Ciliaris muscle and constrictor pupillae
What intrinsic eye muscles are involved in the sympathetic response?
Dilator pupillae
Plexus around blood vessels
What are the 4 straight muscles of the rect?
Medial rectus
Lateral rectus
Inferior rectus
Superior rectus
What are the 2 oblique muscles?
Superior oblique
Inferior oblique
What do the recti muscles do?
Arise from the apex of the orbit from an annular fibrous ring
What do the superior oblique muscles arise from?
Roof of the orbit posteriorly
What do the superior oblique muscles arise from?
Floor of the orbit anteriorly
What does the levator palpebrae superior do?
A muscle running to the upper eyelid to elevate it
Where does the recti muscle insert into the sclera?
Anteriorly
Obliques insert posteriorly
Where does the LPS originate and insert?
Origin is roof of orbit
Inserts in upper eyelid
Where do all recti originate and insert?
Origin is tendinous ring
Inserts sclera anteriorly
Where does the SO originate and insert?
Origin is lesser wing of sphenoid
Inserts in the sclera posteriorly
Where does the IO originate and insert?
Origin is the medial part of orbit floor
Insers in the sclera posteriorly
What does the trochlear (IV) nerve supply?
Supplies muscle with trochlea (SO)
What does the abducent nerve supply?
What is everything but the SO and LR supplied by?
Oculomotor nerve (III)
What is A?
Optic (II) nerve: carries visual impulses from the eyeball. Leaves orbit through Optic foramen
What is B?
Oculomotor (III) nerve – supplies all the muscles going to the eye except 2 and also supplies levator muscle of the eyelid.
It carries parasympathetic fibres which synapse at the ciliary ganglion in the orbit
What is C?
The Abducent (VI) nerve also supplies just one muscle the lateral rectus
What is D?
The Trochlear (IV) nerve arises from the dorsal part of the midbrain and supplies 1 muscle the superior oblique
What does the nasociliary nerve do?
Small branch of the Ophthalmic division. Goes medially and its branches supply medial part of orbit, ethmoidal air sinus, nasal cavity
What does the lacrimal branch of trigeminal nerve do?
Smallest branch of the Ophthalmic division, travels laterally and supplies lateral part of orbit and lacrimal gland
What does the frontal branch of the trigeminal nerve do?
Largest branch of Ophthalmic division. Divides into supraorbital and supratrochlear branches
What does the maxillary branch of the trigeminal nerve do?
Passes through the inferior orbital canal in the floor of the orbit, and exits through the infraorbital foramen as the infraorbital nerve
What is the opthalmic artery?
A large branch of the Internal Carotid artery. It supplies all structures in the orbit, and also some branches to the nasal cavity and forehead.
What does the central retinal artery do?
Travels within the substance of the optic nerve, supplies inner layers of the retina
What do short posterior ciliary arteries supply?
The posterior part of the choroid (and outer retina)
What does the long posterior ciliary artery supply?
Anterior choroid, ciliary body, iris
What is the optic disc?
Start of the optic nerve, physiological blind spot.
Do you know the four parts of this diagram, hmmmmmmm
Yessir
What do the superior and inferior ophthalmic veins which drain into
Cavernous sinus
What is the caverous sinus immediately posterior to?
The apex of the orbit
What does the eye develop from?
The nreural tube
What do optic vesicles do?
Grow outwards from diencephalic part of neural tube towards surface ectoderm.
How does the lens placode form?
Optic vesicles reach surface ectoderm
Cells of surface ectoderm thicken
How does the optic cup form?
The lens placode starts to push inwards (invaginate), which causes the optic vesicle too to form the optic cup
How does the 2 layered optic cup form?
The lens vesicle ultimately looses its connection with the surface ectoderm.
As the optic cup is forming, blood vessels that pass through form a fissure in its inferior wall called as the choroid fissure
What is the mesenchyme derived from?
derived from mesoderm and neural crest cells
What does the surface ectoderm form from?
Eyelids, conjunctiva, corneal epithelium
What does the mesenchyme form?
Choroid, stroma of cornea, sclera and extraocular muscles.
What does the lens fibre form from?
Epithelium of lens vesicle & later loose their nucleii.
