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102 Cards in this Set

  • Front
  • Back
What are the orbits?
Bony cavities in facial skeleton resembling quadrangular pyramids
How are the orbit axes related?
How are the optical axes related?
-Orbit axes diverge @ 45 degrees
-Optic axes are parallel
What is the function of the orbits?
To contain and protect the eyeballs and accessory visual structures.
What are the accessory visual structures?
-Extraocular muscles
-Orbital fascia
-Conjunctiva/Lacrimal apparat.
What is the function of orbital fat?
To fill any space not occupied by the eyeball or accessory visual structures, forming a matrix that supports them.
What are the general features of the pramidal orbit?
-Four walls
What is the base made up of?
The orbital margin sourrounding the orbital opening.
What is the function of the base?
To reinforce the orbit margin, protect its contents, and provide attachmnet for orbital septum.
What is the orbital septum?
Interrupted fibrous sheet extending into the eyelids.
What forms the roof of the orbit?
The orbital part of the frontal bone.
What special feature of the frontal bone resides in the roof?
Fossa for the lacrimal gland - shallow depression for it.
What constitutes the medial wall of the orbit?
The ethmoid bone, along with fronta/lacrimal/sphenoid contributions.
What 2 indentations are found on the medial orbit wall?
-Fossa for lacrimal sac
-Lacrimal groove
Why is the medial wall paper thin?
B/c the ethmoid bone is highly pneumatized
What forms the orbital floor?
Maxillary orbital plate
What important feature is found in the orbit floor maxilla?
Inferior orbital fissure
What forms the lateral orbit wall?
-Greater wing of sphenoid
-Zygomatic bone
What is the apex of the orbit?
The optic canal.
Where is the widest part of the orbit?
At the equator of the eyeball
What lines the orbit bones?
What is the function of eyelids?
To protect the eyeballs and spread lacrimal fluid over them.
What covers the eyelids?
-Externally = skin
-Internally = palpebral conjunctiva
What is palpebral conjunctiva?
a transparent mucous membrane that is reflected onto the eyeball too
What is the conjunctiva of the eyeball that is continuous with the palpebral conjunctiva?
What does the bulbar conjunctiva adhere to?
The cornea.
What is a conjunctival fornix?
A deep recess created where the palpebral conjunctiva reflects to form the bulbar.
what is the conjunctival sac?
The space formed between the palpebral and bulbar conjunctiva when the eyelid is closed.
What is the conjunctival sac called when the eyelid is open?
The palpebral fissure
What forms the 'skeleton' of the eyelids? What type of tissue?
Superior/inferior tarsi - connective tissue bands.
What secretory glands are found within the eyelids?
Tarsal glands - secrete lipid substance that's immiscible with tears; makes them spill onto cheeks when you cry.
What are the sebaceous glands associated w/ eyelashes called?
What are the corners of the eyes called where the eyelids meet?
Med/Lat Palpebral commissures (kanthos -- acanthamoeba)
What are the medial/lateral palpebral ligaments?
Ligaments that attach the tarsi to orbit margins.
-orbic. oculi inserts on medial
what is the orbital septum?
a weak membrane spanning from the tarsi to orbit margins; continuous with periosteum.
What 4 things does the lacrimal apparatus consist of?
1. Lacrimal glands
2. Lacrimal ducts
3. Lacrimal canaliculi
4. Nasolacrimal duct
What do the lacrimal glands produce?
Lacrimal fluid - moistens and lubricates conjunctiva and cornea
What is lacrimal fluid made up of?
-Physiological H2O-based saline -Bacteriocidal lysozyme
-Dissolved O2
What do the lacrimal ducts do?
Convey lacrimal fluid to the conjunctival sac.
What are lacrimal canaliculi?
Small ducts that drain lacrimal fluid from the lacrimal lake to the lacrimal sac.
What is the lacrimal lake?
a triangular space at the medial eye angle where tears collect.
What is the lacrimal sac?
The upper portion of the nasolacrimal duct
What does the nasolacrimal duct exist for?
Conveying tears from the lacrimal duct to the inferior nasal meatus.
How does the levator palpebrae superioris interact with the lacrimal gland?
Separates it into superior (orbital) and inferior (palpebral) portions.
What are lacrimal puncta?
Small openings on the lacrimal papilla near medial angle of eye; when eye contracts tears drain into them to be carried to lacrimal sac.
What nerve stimulates lacrimal fluid production?
Parasympathetic fibers of CN VII
Where does lacrimal fluid initially get secreted?
From 8-12 excretory ducts in the lateral superior conjunctival fornix.
In what manner do eyelids come together when one blinks?
Lateral to medial; facilitates pushing of fluid from excretion site to drainage site.
What happens to tears ultimately?
They drain into the inferior nasal meatus, to nasopharynx, and get swallowed.
What type of nerves supply the lacrimal apparatus in general?
both sympathetic and parasymp.
What are the 2 components of loose connective tissue around the eyeball called?
Posterior: bulbar fascia
Anterior: bulbar conjunctiva (continuous w/ palpebral)
What are the 3 layers of the eyeball proper? What does each consist of?
1. Fibrous = sclera + cornea
2. Vascular = choroid + ciliary body + iris
3. Inner = retina (optic/non)
What is the sclera?
the tough, opaque part of the fibrous layer; covers the posterior 5/6 of the eye.
What is the sclera's function?
-Provides a skeletal structure - shape and resistance.
-Attachment site for muscles
What is the cornea?
transparent fibrous coat that covers anterior 1/6 of eyeball
what's the difference between cornea and sclera?
The pattern of collagen in each, and degree of hydration.
What is another name for the vascular layer of the eyeball?
the uvea or uveal tract.
What does the uvea/vascular consist of again?
1. Choroid
2. Ciliary body
3. Iris
What is the choroid?
Dark red-brown layer between sclera and retina; largest part of the vascular layer.
How does the ciliary body compare to the choroid?
Ciliary = muscle + vascular
Choroid = only vascular
What is the function of the ciliary body?
Connects the choroid to the iris circumference.
How does the ciliary body affect the eyeball lens?
Contraction of its smooth muscle affects the thickness and thus focus of the lens.
What are ciliary processes and what do they do?
Folds on the internal ciliary body surface; secrete aqueous humor
What does aqueous humor fill?
Anterior and Posterior chambers of the eye
Where is the anterior chamber of the eye?
between the cornea and iris/pupil
Where is the posterior chamber of the eye?
Between the iris/pupil and the lens/ciliary body.
Where is the iris located?
Lies on top of anterior surface of the lens - literally!
What is the iris?
A thin contractile diaphragm w/ a central aperture
What is the central aperture in the iris called?
The pupil
What controls the size of the pupil?
The iris - 2 muscles that act on it
What are the 2 involuntary muscles controlling the iris?
1. Sphincter pupillae
2. Dilator pupillae
What is the action of sphincter pupillae? What type of nerve supplies it?
Closes the pupil; makes things dark; parasympathetic
What is the action of dilator pupillae? What type of nerve?
Opens the pupil wide; makes things bright; sympathetic
What nerve innervates the pupillae muscles?
Oculomoter nerve CN III
When testing pupillary light reflex, what happens?
Shine a lite in one eye, but both pupils contract.
What does interruption of parasympathetic fibers to the pupillary muscles result in?
Unopposed constriction by sympathetic fibers, thus failure of pupils to close.
What does the inner layer of the eyball consist of?
The retina.
What are the 2 functional parts of the retina?
-Optic retina (sensitive to light)
-Non-visual retina
What are the 2 parts of the optic retina?
-Neural layer (light sensitive)
-Pigment cell layer
What does the pigment cell layer do?
reinforces lite-absorbing property of choroid to reduce light scatter in the eyeball.
What is the non-visual retina?
An anterior continuation of the pigment cell layer
What are the 2 parts of the non-visual retina, and what do they do?
-Ciliary part
-Iridial part
Provide support to the ciliary body and posterior iris surface.
What is the posterior part of the eyeball called?
the fundus
what is the optic disc?
A circular depressed area at the back of the eyeball where the optic nerve fibers and vessels enter.
What is another name for the optic disc, and why?
The blind spot - contains no photoreceptors.
What is the yellow spot just lateral to the optic disc?
Macula lutea.
What is the macula lutea's function?
To provide acuity of vision via special photoreceptor cones.
What area of the macula lutea provides the best acuity of vision?
Fovea centralis
What is the border between functional and nonvisual retina called?
Ora serrata - just behind ciliary body
What supplies the retina with blood?
Cones/rods of neural layer: capillary network of choroid
Other: central artery of retina (opthalmic branch)
What 4 structures constitute the refractive media of the eyeball?
1. Cornea
2. Aqueous humor
3. Lens
4. Vitreous humor
What innervates the cornea?
V1 - opthalmic branch
What encloses the lens of the eye?
a highly elastic capsule anchored by zonular fibers
What do the zonular fibers attach the lens to?
The ciliary body
What muscle varies the convexity of the lens?
The ciliary muscle
How is the ciliary muscle normally situated?
It stretches the lens fairly flat so the spherical shape is flat enough for far vision.
How does the lens change to accomodate near vision?
Parasympathic stimulation causes the smooth muscle to contract; as the sphincter like muscle tightens, the tension on the lens reduces making it rounder.
Where is the vitreous body?
In the posterior 4/5 of the eyeball.
What is the function of the vitreous humor?
Transmits light, holds the retina in place, and supports the lens.
What are the extraocular muscles? (7)
-Levator palpebrae superioris
-Recti (sup/inf/lat/med)
-Sup/inf Obliques
What are the distal attachments of levator palpebrae sup.?
-Skin of superior eyelid
-Deep lamina of superior tarsus
What opposes levator palpebrae?
-Orbicularis oculi
What is the function of the superior tarsal muscle?
Extra widening of eye during sympathetic response (Fright).