Orbit Overview Flashcards
What does the orbit socket contain?
the globe, connective tissue,
extraocular muscles (EOMS),
orbital nerves, blood vessels,
and fat
What three coats (tunics) does the globe
consist of?
Outer fibrous layer (cornea &
sclera), middle vascular layer
(iris, ciliary body, choroid), and
inner neural layer (retina)
What three chambers are filled with fluid in
the globe?
Anterior, posterior, and vitreous
What is the sheet of dense connective tissue
that covers the sclera?
Tenon’s capsule (Bulbar fascia)
Describe the attachment of Tenon’s capsule
Anteriorly merges with sclera/
conjunctiva at the limbus.
Posteriorly is continuous with
the dural sheath of the optic
nerve.
What is the purpose of Tenon’s capsule?
-provides a strong barrier
-separates the globe from
contents of orbit
-prevents orbital infections
from entering the globe
What is the transition between the cornea
and tenon’s capsule/sclera referred to?
Limbus
Why is Tenon’s capsule continuous with
dura sheath posteriorly?
The optic nerve must pierce
sclera and tenon’s capsule to enter the globe
Sheet of dense connective tissue that extends
the entire rim of the orbit to the tarsal
plate
Orbital septum (Palpebral fascia)
Describe the attachment of the orbital septum
Continuous with the periosteum
at the superior and inferior
orbital rim
What is the purpose of the orbital septum?
Anterior barrier of the orbit
-separates the eyelids and
lacrimal sac from the orbit and
keeps the orbital fat in place
What does the orbital septum prevent from
entering the orbit?
Facial/eyelid/nasolacrimal
system infections
Rim where the orbital septum originates
Arcus margins
Sheet of dense connective tissue that covers
the bones of the orbit
periorbital (orbital fascia, periosteum)
Describe the attachment of periorbita
anteriorly- continuous with the
periosteum of facial bones
and orbital septum
posteriorly- continuous with
dural sheath of the ON and
forms the common tendinous
ring
Cranial nerve II
optic nerve
cranial nerve III
oculomotor
cranial nerve IV
Trochlear
cranial nerve V and its branches
Trigeminal
-V1 ophthalmic
-V2 maxillary
-V3 mandibular
cranial nerve VI
abducens
What blood vessels are in the orbit?
-Ophthalmic artery and its
branches
-superior and inferior ophthalmic
vein and its branches
Transverse dense connective tissue located
in the superior orbit and courses from
lateral orbital wall to medial orbital wall
Whitnall’s ligament
What is the function of Whitnall’s ligament?
Provides support and maintains
spatial movement between
anatomic structures in
the superior orbit
How is the Whitnall’s Ligament formed?
By condensation of the levator
muscle and is the point where
the levator muscle fibers end
and the levator aponeurosis
begins
What is the function of levator aponeurosis?
moves the eyelid
Transverse dense connective tissue located
in the inferior orbit and courses from
lateral orbital wall to medial orbit wall
Lockwood’s ligament
What is the function of Lockwood’s Ligament?
-provides support and maintains
spatial relationships between
anatomic structures in
the inferior orbit
-contributes to the formation
of the capulopalpebral fascia
What is the function of the capulopalpebral
fascia?
dense connective tissue that
acts as a muscle to move the
lower eyelid
Transverse dense connective tissue that is
an expansion of the sheath of the medial
rectus and attaches to the lacrimal bone
Medial check ligament
What is the function of medial check ligament?
Prevents overaction of the medial
rectus
Transverse dense connective tissue that is
an expansion of the sheath of the lateral
rectus and attaches to the zygomatic bone
Lateral check ligament
What is the function of the lateral check
ligament?
prevents overaction of the lateral
rectus
Which ligaments come together to form
the supporting hammock-like structure for
the globe?
-Whitnall’s
-Lockwood’s
-Medial check
-Lateral check
Web of interconnecting connective tissue
septa that organizes the orbital space surrounding
the globe
Orbital septal system
What is the function of the orbital septal
system?
Anchors and supports EOMS
(muscles), nerves, and blood
vessels
What are the extraocular muscles?
-Recti muscles: medial, lateral,
superior, and inferior
-Oblique muscles: superior
and inferior
What muscles play a role in eyelid retraction?
levator palpebrae, Müller’s
muscle (Tarsal), capsulopalpebral
fascia (not actually
a muscle)
Space not occupied by orbital structure
and filled with adipose tissue
orbital fat
What is the purpose of orbital fat (adipose)?
-surrounds the ON and separates
it from the EOMs
-separates muscles in the orbit
from the orbital walls
In the anterosuperior orbit, what 2 pads are
anterior to the levator aponeurosis?
nasal, central
What 3 fat pads are posterior to the orbital
septum and anterior to the capsulopalpebral
fascia?
nasal, central, temporal
hole or opening in bone that allows entrance
and exit of nerve and vessels in and
out of the orbit
foreamen
long, narrow opening in bone that allows
entrance and exit of nerves and vessels in
and out of the orbit
fissure
shallow depression in bone that contains
anatomical structures
fossa
What are the foramen of the orbit?
optic foramen (canal), supraorbital
foramen, supratrochlear
foramen, and infraorbital
foramen
What are the fissures located in the orbit?
superior and inferior orbital fissure
What fossa are located in the orbit?
two lacrimal fossa
Where is the optical canal?
-lies between the lesser wing
and body of sphenoid
-at the orbital apex
What is the function optical canal?
opening between the orbit and
cranial cavity that allows CN II
and ophthalmic artery to pass
through
What is the common tendinous ring (annulus
of zinn)?
band of connective tissue that
lies anterior to optic canal
What is the function of annulus of zinn?
origin for the 4 EOMs (muscles)
If a patient has an orbital infection, why
must they be treated immediately?
Because the optic canal connects
the orbit and cranial cavity
so the infection can easily
spread to brain
Where is the superior orbital fissure?
-Lies between the greater and
lesser wings of the sphenoid
-inferior portion at the orbital
apex
What nerves pass through the superior orbital
fissure through the annulus of zinn?
-Superior and inferior division
of oculomotor nerve (CN III)
-nasociliary nerve (CN V1)
-abducens nerve (CN VI)
What nerves and vessels pass through the
superior orbital fissure and above the annulus
of zinn?
-superior ophthalmic vein
-trochlear nerve (CN IV)
-lacrimal nerve (CN V1)
-frontal nerve (CN V1)
Which cranial nerve provides sensory of
touch that results in discomfort when you
touch your superior orbit?
CN V -trigeminal
Where is the inferior orbital fissure (infraorbital
fissure)?
Lies between the floor of the
orbit and lateral wall
What nerves and vessels pass through the
inferior orbital fissure?
-inferior ophthalmic vein
-zygomatic nerve (CN V2)
-infraorbital nerve (CN V2),
artery, and vein
Where do the infraorbital nerve (CN V2),
artery, and vein go after passing through
the inferior orbital fissure?
Continue along the infraorbital
groove to pass through the infraorbital
canal and infraorbital
foramen
Where is the lacrimal fossa (for lacrimal
gland) located?
located in the frontal bone
temporally
Where is the lacrimal fossa (for the
lacrimal sac) located?
-medially
-formed by the lacrimal bone
(posterior lacrimal crest) and
the frontal process of maxillary
bone (anterior lacrimal
crest)
Which canal extends from the maxillary
bone from the lacrimal fossa to open into
the nasal cavity?
nasolacrimal canal (nasolacrimal
duct within this canal)
Why is the lacrimal fossa (for the lacrimal
sac) not consider apart of the orbit?
It is considered medial to the
orbit because it is separated
by the orbital septum
How does an infection spread when it occurs
within the lacrimal sac?
Can spread to nasal cavity but
not the orbit because of the
barrier protection from orbital
septum
Where is the superior orbital (supraorbital)
foramen/ notch located?
Located in the frontal bone
medially
Why can the supraorbital foramen also be
called a notch?
Varies among individuals,
could be a notch or hole
What is the function of the supraorbital
foramen?
-opening between the orbit
and facial surface
-supratrochlear nerve (CN
V1), artery, and vein pass
through
Where is the inferior orbital (infraorbital)
foramen located?
maxillary bone
What is the function of the infraorbital foramen?
opening between orbit and facial
surface
-infraorbital nerve (CN V2),
artery, and vein pass through
skeleton of head
skull
What two parts make up the skull?
-cranium
-face
Bones meet at _______________________,
a seam-like immovable joint
suture
Exception to bones forming sutures
movable temporomandibular
junction (TMJ)
Air-filled cavities within several of the skull
bones
sinuses
What are the bones of the cranium?
frontal, parietal, temporal, occipital,
sphenoid, ethmoid
Bone that forms the anterior portion of the
cranium, anterior floor, and superior part
of the face
frontal
Bone that forms the roof of cranium and
lateral sides of skull skull
parietal
Bone that forms the floor of cranium and
lateral sides of skull
temporal
Bone that forms the posterior portion of
the cranium and posterior floor of cranium
occipital
Where is the foramen magnum located?
inferior aspect of the occipital bone
Bone that forms the floor of cranium
sphenoid
What are the three portions of sphenoid
bone?
-body
-lesser wing
-greater wing
What is housed in the sella turcica of the
body of sphenoid?
Pituitary gland
What are the four parts of the ethmoid
bone and what are their functions?
-Vertical (perpendicular) plate
forms nasal septum
-horizontal (cribriform) plate
allows olfactory nerves to
pass through
-Labyrinths (2) house ethmoidal
sinuses
What are the bones of the face?
frontal, palatine, lacrimal,
nasal, inferior conchae,
vomer, zygomatic bone (2),
maxillary (2), and mandible
Bone that forms the forehead and orbital
roof
frontal
Bone that extends from the hard palate at
the of the mouth to the orbital floor
palatine
Bone that forms the bridge of the nose
nasal
Bone that is located along the lateral wall
of nasal cavity
inferior conchae
Bone that forms the posterior part of nasal
septum
vomer
Bone that forms the lateral part of cheekbone
and the lateral wall and floor of orbit
zygomatic
Bone that forms the upper jaw, cheek, hard
palate, lateral wall of nasal cavity, and floor
of orbit
maxillary
Bone that forms the moveable lower jaw
mandible
What does the orbit contain?
Globe, connective tissue,
EOMs, orbital nerves, blood
vessels, fat
What is the shape of the orbit?
Shaped like a 4-sided pyramid
with the apex posteriorly and
the base anteriorly
Where is the apex of the orbit located?
slightly nasal
What are the dimensions of the orbit?
40 mm (width) x 35 mm
(height) x 45 mm (depth)
3 cc (volume)
What bones form the orbit?
frontal, palatine, lacrimal, zygomatic,
maxillary, sphenoid,
ethmoid
What bones form the orbit roof?
frontal bone and lesser wing
of sphenoid
What bones form the floor of the orbit?
palatine, zygomatic, and maxillary
bones
Why is the floor of the orbit the weakest
wall?
-infraorbital groove/canal in
maxillary bone
-maxillary sinus below floor
What are symptoms of patient that break
floor of orbit?
blurred vision and lose of feeling
in cheek because CN
V2 (infraorbital nerve) goes
through infraorbital foramen in
maxillary bone
What bones for the medially (nasal) wall of
orbit?
ethmoid, maxillary, lacrimal,
and body of sphenoid bones
Why is the medial wall the thinnest wall of
the orbit?
Because lamina papyracea of
ethmoid bone is filled with sinuses
What is the disadvantage of the medial
wall being the thinnest wall?
Ethmoid sinus infections can
spread to the orbit
What bones make up the lateral (temporal)
wall of the orbit?
zygomatic and greater wing of
sphenoid bone
Why is it important for the lateral orbital
rim to be the strongest area of the orbit?
Most exposed to possible injury
What is the purpose of paranasal sinuses?
Reduce the weight of the skull
and filter air we breathe
What are the four paranasal sinuses?
maxillary, frontal, ethmoid,
sphenoid
Where is the maxillary sinus in regards to
the orbit?
inferior
Where is the sphenoid sinus in regards to
the orbit?
posterior and medial
Where is the ethmoid sinus in regard to the
orbit?
medial
Where is the frontal sinus in regards to the
orbit?
superior
Infection in the air cavities is called
sinusitis
If a patient comes in and says that their eye
hurts due to pressure around the eye, what
does that mean?
infection in sinus
Why is the eye called a globe?
hollow structure that encloses
cavity filled with fluid
Components of outer fibrous layer of
globe
Sclera and cornea
Characteristics of sclera
-85% of fibrous portion
-opaque white color
Functions of sclera
-provides protection for the
structures within
-maintains the shape of globe
Sclera is divided into:
sclera and episclera
What is the sclera covered by?
-tenons capsule
-conjuctiva
Characteristics of cornea
-15% of fibrous portion
-transparent to allow light rays to enter the eye
What are the functions of cornea?
refraction occurs here, helps
to bring light rays into focus on
the retina
Location where the cornea transitions to
sclera/Tenon’s capsule/conjuctiva
limbus
Vascular layer (Uvea) is composed of
iris, ciliary body, and choroid
Characteristics of iris
-anterior layer of the uvea
-gives eye color
-hole in the center called the
pupil
What are the two muscles of the iris?
Iris dilator and iris sphincter
iris muscle that contractions dilate the
pupil (during dimmer times so allow more
light in eye)
iris dilator
iris muscle that contractions constrict the
pupil (during bright light to let less light in)
iris sphincter
Middle layer of the uvea and continuous of
iris
ciliary body
What does the ciliary body consist of?
ciliary muscle and ciliary
processes
What is the function of the ciliary muscle?
Contracts and relaxes to regulate
the thickness of the lens
and allow accommodation for
near and far vision
What at the zonules?
suspensory ligaments that attach
the ciliary muscle to crystalline
lens
What is the function of ciliary processes?
produce and secrete aqueous
humor (clear fluid that provide
nutrients to structures of the
eye like the lens)
Posterior layer of uvea (continuous of ciliary
body)
choroid
What is the function of choroid?
network of blood vessels that
provide nutrition to the outer
1/3 of retina
What does the inner neural layer consist
of?
retina
What is the function of the retina?
Neural tissue that converts
light energy into an electrical signal that can be transmitted to the brain
Retina creates electrical signal that exits
the eye and enters the brain via the
optic nerve
Anterior portion of the optic nerve is called
the
optic disc or optic nerve head
Small area at the center of the retina responsible
for central vision
macula
located in the center of the macula and
provides highest visual acuity
fovea
Interior of the eye is made up 3 chambers
filled with fluid:
anterior, posterior, and vitreous
chamber
Where is the anterior chamber?
between cornea and iris
Where is the posterior chamber located?
between ciliary body and lens
The anterior and posterior chamber are
continuous of one another through the:
pupil
Anterior and posterior chamber contain:
aqueous humor (produce by
ciliary body and provide nourishment
for surrounding structures)
Where is vitreous chamber located?
between the ciliary body and
reina
Vitreous chamber contains a gel-like substance
that maintains the shape of the eye
called
vitreous humor
