The Orbits Flashcards
Purpose of the orbits
Contain and protect the eyeballs and their muscles, nerves and vessels, together with most of the lacrimal apparatus
All space in the orbits not occupied by structures is filled with:
Orbital fat
What is the periosteum that is lines with the bones of the orbit called
Periorbita
What is the sup wall of the orbit formed by?
Mainly by the orbital part of the frontal bone and lesser wing of the sphenoid
The sup wall anterolaterally consists of:
Lacrimal fossa that’s occupied by lacrimal gland
The medial wall of the orbit is formed by:
Ethmoid bone
Frontal
Lacrimal
Sphenoid
The medial wall anteriorly is indented by the:
Lacrimal groove and fossa for the lacrimal sac
The medial wall of the orbit is (THICK/THIN)
Paper-thin
In the medial wall of the orbit, the ethmoid air cells are often:
Visible through the bone of a dried cranium
The lateral wall of the orbits is formed by:
It is:
Frontal process of zygomatic bone
And greater wing of sphenoid
The strongest and thickest wall
The inf wall of the orbits is formed by:
Mainly by the maxilla
Partly by the zygomatic and palatine bones
The inf wall (floor) is demarcated from the lateral wall by the:
Inf orbital fissure
The inf wall of the orbit (floor) is shared by:
The orbit superiorly
And maxillary sinus inferiorly
Where is the apex of the orbit located?
At the optic canal in the lesser wing of the sphenoid— just medial to the sup orbital fissure
The base of the orbits is formed by:
Orbital openings
The eyelids are movable folds that are covered externally by __ ___ and internally by:
Thin skin
A transparent mucous membrane— palpebral conjunctiva
Palpebral conjunctiva is reflected onto the ____, where it is continuous with the
Bulbar conjunctiva
What are the lines of reflection of the palpebral conjunctiva onto the eyeball?
Superior and interest conjunctival fornices
What are superior and inferior tarsi
Dense connective tissue that strengthens the upper and lower eyelids
What are the tarsal glands
Lipid secretion of which lubricates the edges of the eyelids and prevents them from sticking together when they close.
Eyelashes are located:
In the margins of the eyelids
What are the ciliary glands
Large sebaceous Glands associated with the eyelashes
The lacrimal glands lie in the _____ part of each orbit. They secrete:
Superolateral
Tears
Production of lacrimal fluid is stimulated by:
Parasympathetic impulses from facial nerve
What conveys lacrimal fluid from the lacrimal glands to the conjunctival sac?
Lacrimal ducts
Lacrimal canaliculi each begins at a ____ ____ on the ____ ___ near the ___ angle of the eye.
Lacrimal punctum (opening)
Lacrimal papilla
Medial
Lacrimal canaliculi convey the lacrimal fluid from the ___ ____ to the _____ ___ (____).
Lacrimal lake
Lacrimal sac (the dilated sup part of the nasolacrimal duct)
What conveys the lacrimal fluid to the nasal cavity
Nasolacrimal duct
the eyeball is suspended by (#) extrinsic muscles that control movements
6
3 layers of eyeball muscles
Fibrous layer (outer coat)
Vascular layer (middle coat)
Inner layer (inner coat)
What does fibrous layer of eyeball muscles consist of
Sclera and cornea
The vascular layer (middle coat) of the eyelid consists of what
Choroid
Ciliary body
Iris
The inner layer (inner coat) of the eyeball consists of what
Retina
Which has both optic and non-visual parts
What is the sclera of the eyeball
Tough opaque part of the fibrous layer of the eyeball
Covers the post 5/6 of the eyeball.
The white of the eye
The sclera is relatively _____.
Avascular
What is the cornea
The transparent part of the fibrous layer covering the ant 1/6 of the eyeball.
The cornea is completely ______, receiving its nourishment from the ____ ___ and the _____ ___
Avasular
Lacrimal fluid
Aqueous humor
What is the choroid
Dark reddish brown later between the sclera and retina
Forms the largest part of the vascular layer of the eyeball aaaaand lines most of the sclera
The choroid attaches firmly to the ____ later of the ____ and is directly continuous with:
Pigment
Retina
The ciliary body
The ciliary body is ___ as well as ____
Muscular
Vascular
The ciliary body connects the ____ with the ____
It provides attachment for the ____
Choroid
Iris
Lens
What controls thickness of the lens
Contraction/relaxation of the circularly arranged smooth muscle of the ciliary body
Ciliary processes secrete ____ ______.
This fills the:
Aqueous humor
Anterior segment of the eyeball (ant to the lens, suspensory ligament and ciliary body
The Iris lays:
Just on the ant surface of the lens
What is the iris
Thin contractile diaphragm with a central opening (pupil) for transmitting light
Muscles controlling the size of the pupil
Sphincter pupillae
Dilator pupillae
The sphincter pupillae is ____ stimulates, _____ arranges and works to _____ the pupil (___ ___)
Parasympathetically
Circularly
Constrict
Pupillary miosis
The dilator pupillae is _______ stimulated ____ arranged and _____ the pupil
Sympathetically
Radically
Dilates
The retina consists of what two functional parts?
Optic and non-visual
Which part of the retina is sensitive to visual light rays?
The optic part
2 layers of the optic part of the retina
Neural layer (light receptive)
Pigmented layer (reduces the scattering of light in the eyeball)
The non-visual retina is an anterior continuation of what?
The pigmented layer
Posterior part of the eyeball where light enters. Part of the retina
Fundus of the eyeball
The optic disc (part of retina) is where ___ ___ and ___ are located. They are conveyed by the ___ nerve.
It is _____ to light
Sensory fibers
Vessels
Optic
Insensitive (bling spot)
Macula lutea (yellow spot) of the retina is lateral to the ___ ___. It is a ___ ___ area of the retina with special ____ _____ that is specialized for ____ of vision
Optic disc
Small oval
Photoreceptor cones
Acuity
Depression at the center of the macula of the retina. Area of most acute vision
Fovea centralis
What changes the shape of the lens
Accommodation of the ciliary muscle
What causes contraction of the ciliary muscle (sphincter)?
Parasympathetic stimulation via the oculomotor nerve (CN III)
What happens to the lens as it becomes smaller
Becomes more convex, bringing near objects into focus
In absence of nerve stimulation, what happens to the lens
Becomes less convex and brings more distant objects into focus (far vision)
What are the extra-ocular muscles of the orbit
What do they do?
Levator palpebral Superioris
Four recti
Two obliques
Work together to move the sup eyelids and eyeballs
Eyeball rotates around was axes?
Vertical
Transverse
Anteroposterior
What axis causes the eyeball to move medially (toward the midline, adduct ion) or laterally (away from midline, abduct ion)?
Vertical axis
What axis does the pupil move superiorly (elevation) and inferiorly (depression)?
Transverse axis
Movements around the anteroposterior axis
Moves the sup pole of the eyeball medially (medial rotation or intorsion) or laterally (lateral rotation, or extortion)
The four recti muscles run ____ to the eyeball, arising from the ___ ___ ___
Anteriorly
Common tendinous ring
The common tendinous ring surrounds the ___ ___ and part of the ___ ____ fissure at the ____ of the orbit
Optic canal
Superior orbital
Apex
What are the primary actions of the four recti?
Elevation
Depression
Adduction
Abduction
The apex of the orbit is _____ placed relative to the orbit, so that the ____ of the orbit foes not coincide with the ___ ___.
Medially
Axis
Optical axis
Position of the superior and inferior rectus muscles when the eye is in the primary position
Approach the eyeball from its medial side.
Line of pull passing medial to the vertical axis
OINA for levator palpebrae superioris
OR: lesser wing of sphenoid. Sup and ant to optic canal
INS: sup tarsus and skin of sup eyelid
NS: Oculomotor nerve; deep layer (sup tarsal muscle) supplies by sympathetic fibers
AC: elevates sup eyelid
Antagonist to the sup half of the orbicularis oculi
Superior tarsal muscle- smooth muscle fibers supplied by ____ nerve
Produces additional ____ of the _____ fissure
Interruption of sympathetic supply produces:
Sympathetic
Widening
Palpebral
A constant ptosis (drooping of the upper eyelid)
OINA for sup oblique
OR: body of sphenoid bone
INS: through trochlea to insert into sclera, deep to SR
NS: trochlear nerve (CN IV)
AC: abducts, depresses and rotates eyeball medially (intorsion)
OINA for inf oblique
OR: ant part of the floor of orbit
INS: sclera deep to lateral rectus muscle
NS: Oculomotor nerve (CN III)
AC: Abducts, elevated, and rotates eyeball laterally (extortion)
OINA for sup rectus
OR: Common tendinous ring
INS: Sclera just post to corneoscleral junction
NS: Oculomotor nerve (CN III)
AC: Elevates, adducts and rotates eyeball medially (intorsion)
OINA for inf rectus
OR: common tendinous ring
INS: sclera post to corneoscleral junction
NS: Oculomotor nerve (CN III)
AC: depresses, adducts and rotates eyeball laterally
OINA for medial rectus
OR: Common tendinous ring
INS: sclera post to corneoscleral junction
NS: Oculomotor (CN III)
AC: Adducts eyeball
OINA for lateral rectus
OR: Common tendinous ring
INS: Sclera just post to corneoscleral junction
NS: Abducent Nerve (CN VI)
AC: abducts eyeball
Nerves of orbit
Optic nerves
Oculomotor
Trochlear
Abducent
Opthalamic
Ciliary ganglion
Optic nerves are purely ___ nerves that transmit impulses generated by ___ ___ and develop as paired ____ ____ of the _____
Sensory
Optical stimuli
Anterior extensions
Forebrain
Optic nerves are surrounded by extensions of the ____ _____ and ___ ____, the latter occupied by a thin layer of ____
Cranial meninges
Subarachnoid space
CSF
Oculomotor (CN III) divides into what branches?
Superior and inferior
Superior branch of the oculomotor nerve (CN III) supplies what muscles
Sup rectus and levator palpebrae superioris
Inf branch of the oculomotor nerve supplies:
It carries:
medial and inf rectus and inf oblique
Presynaptic fibers to the ciliary ganglion
The trochlear nerve (CN IV) passes directly through the __ ___ fissure and enters the ___ surface of the:
Sup orbital
Superior
Sup oblique muscle
The Abducent nerve (CN IV) passes directly through the ___ ___ fissure and Enters the ___ surface of the:
Superior orbital
Medial
Lateral rectus muscle
The ophtalmic nerve (CN V1) passes through the ___ ____ fissure
Superior orbital
Branches of the ophthalmic nerve
Lacrimal nerve
Frontal
Nasociliary
The lacrimal nerve arises in the ____ wall of the ___ sinus. It passes to the _____ gland, giving sensory branches to the
Lateral
Cavernous
Lacrimal
Conjunctiva and skin of superior eyelid
;the distal part of the lacrimal nerve carries ______ fibers conveyed to it from the _______ nerve
Secretomotor
Zygomatic (CV2)
The frontal nerve enters through the ____ ____ fissure, and divides into the ___ ___ and ____ ___ nerves, providing _____ innervation to the:
Superior orbital
Supraorbital
Supratrochlear
Sensory
Sup eyelid, scalp and forehead
What is the sensory nerve to the eyeball?
Nasociliary nerve
The nasociliary nerve also supplies several branches to:
The orbit
Face
Paranasal sinuses
Nasal cavity
Anterior cranial fossa
Branches of the nasociliary nerve
Infra trochlear nerve
Ethmoidal nerves
Long ciliary nerves
Terminal branch of the nasociliary nerve
Infra trochlear nerve
Infratrochlear nerve supplies:
Eyelids
Conjunctiva
Skin of the nose
Lacrimal sac
The ethmoidal nerves supply:
Mucous membrane of sphenoidal and ethmoidal sinuses
Nasal cavities and dura mater of the ant cranial fossa
Short ciliary nerves are branches of the:
Ciliary ganglion
Small group of postsynaptic parasympathetic nerve cell bodies located between the optic nerve and lateral rectus close to the apex
Ciliary ganglion
The ciliary ganglion receives nerve fibers from what 3 sources?
Sensory fibers from CN V1 via nasociliary nerve
Presynaptic parasympathetic fibers from CN III
Postsynaptic sympathetic from internal carotid plexus
Long ciliary nerves convey _____ ____ fibers to that?
Postsynaptic sympathetic
Dilator pupillae and afferent fibers form the iris and cornea
Arteries of the orbits are from what?
The ophthalmic artery
A branch of the internal carotid artery
ALSO, infra-orbital artery, from the external carotid artery
The ophthalmic artery transverses _____ canal to reach ____ cavity
Optic
Orbital
Branches of the ophthalmic artery
Central retinal artery
Supra-orbital artery
Supratrochlear artery
Lacrimal artery
Short and long post ciliaries
Ant and post ethmoidal art
Infra-orbital artery
Central retinal art arises inf to the _____ nerve, pierces the ___ ___ of the ___ nerve and runs within the ___ to the __.
It emerges at the ___ ____, spread over the internal surface of the ____
Optic
Dural sheath
Optic nerve
Nerve to the eyeball
Optic disc
Retina
The terminal branches of the central retinal artery are _____ arteries, with provide:
End
Only blood supply to the internal aspect of the retina (optic retina except cones and rods)
The Supra-orbital artery passes ____ and ____ from ________ foramen to supply:
Sup and post
Supra-orbital
Forehead and scalp
Supratrochlear passes from _____ margin to:
Supra-orbital
Forehead and scalp
The lacrimal art passes along the _____ border of ____ ___ muscle so supply:
Super
Lateral rectus
Lacrimal gland
Conjunctiva
Eyelids
Short and long post ciliaries art pierces _____ to supply
Sclera
Choroid
Ciliary body and iris
And and Post ethmoidal arteries pass through ant and post _____ foramen to supply:
Ethmoidal
Ant, middle and post ethmoidal cells
The infra-orbital art is the third part of the _____ artery
Maxillary
The infr-orbital art passes along the ______ ____ and ___ to the:
Infra-orbital groove and foramen
Face
Sup and inf ophthalmic veins pass through the ____ fissure and enter the _____ sinus
Sup orbital
Cavernous
The inf ophthalmic vein drains to the:
Pterygoid venous plexus
The central vin of the retinal usually enters:
The cavernous sinus directly,
May join one of the ophthalmic veins
Sclera venous sinus is a vascular structure encircling the ____ chamber of the eyeball through which the ___ ___ is returned to the blood circulation
Anterior
Aqueous humor
