00:01
Welcome to today's
anatomy lecture.
00:03
In this lecture,
we will discuss the bony ocular orbit
and accessory structures
of the visual apparatus.
00:11
So without further ado,
let's dive straight into it.
00:15
The bony ocular orbits
or skeletal cavities
located on either
side of the nose.
00:22
These orbits house protect
and support the functioning
of the eyes themselves.
00:29
Accessory visual apparatus
such as the extra
ocular muscles,
the nasal lacrimal apparatus,
associated neuro vasculature,
as well as stromal
connective tissue and fat.
00:44
The bony orbits are
roughly pyramidal in shape,
with the orbital base located
anteriorly at the orbital opening
and the orbital apex
located posteromediately.
00:59
The orbits themselves are formed
by the frontal, maxillary, ethmoid,
sphenoid, lacrimal, zygomatic,
and the palatine bones.
01:12
Furthermore, the ocular orbit
is said to have four surfaces.
01:16
These include a roof,
a floor, a medial wall,
and a lateral wall.
01:24
The roof of the orbit
is formed primarily
by the concave orbital
plane of the frontal bone,
and by the lesser wing
of the sphenoid bone
near the apex of the orbit.
01:37
Here two landmarks of
significance can be found,
the trochlear fovea,
located anteromedially,
which is the site of attachment
for the cartilaginous trochlea
for the superior
oblique muscle
and the lacrimal fossa,
which is located
anterolaterally
in houses the orbital part
of the lacrimal gland.
01:58
The medial wall the orbit
is formed by three bones,
from the base to the apex they
include the lacrimal bone,
the orbital plate
of the ethmoid bone,
and the body of
the sphenoid bone.
02:11
Here are several additional landmarks
of significance can also be found.
02:15
At the junction the orbital
plate of the ethmoid bone
and the orbital plate
of the frontal bone,
anterior and posterior
ethmoidal foramina can be seen.
02:24
The lacrimal bone contains a
fossa for the nasolacrimal sac.
02:30
The floor of the orbit
is formed largely
by the orbital plate
of the maxilla.
02:35
Additionally,
the zygomatic bone
and orbital process
of the palatine bone
also contribute
to its formation.
02:44
Two passages of neuro
vasculature can be found
in the floor of the orbit.
02:48
Posteriorly located we find
the inferior orbital fissure
medially located the
infra orbital canal,
which then opens into the infra
orbital foramen onto the face.
03:01
A direct blow in the front of
the orbit with a blunt object
larger than the
orbital aperture,
for example,
a baseball, a fist,
may cause a rapid increase
in intraorbital pressure
and a resulting blowout fracture
of the thin orbital floor.
03:19
The lateral wall the orbit is formed
by the zygomatic bone anteriorly
and the greater wing of the
sphenoid bone post early.
03:29
And lastly,
the landmarks of importance
located in the
lateral wall include:
The zygomaticofacial,
and zygomaticotemporal
foramen,
located interiorly,
posterosuperiorly located is
the superior orbital fissure,
and it exists between the greater and
lesser wings of the sphenoid bone.
03:51
In the previous slides,
we have mentioned
various openings within
the bony orbit of the eye
that permit the passage of
various neurovascular content.
04:00
The first of these passages
is the optic canal.
04:03
This canal is formed
between the lesser wing
and the body of
the sphenoid bone.
04:08
It connects the orbit to
the middle cranial fossa,
and permits the passage
of the optic nerve
which is the second cranial
nerve and the ophthalmic artery.
04:19
The next two passages are the superior
and inferior orbital fissures.
04:24
The superior orbital fissure,
as I already mentioned,
is formed between the greater and
lesser wings of the sphenoid bone
and it permits the
passage of ocular motor,
trochlear and the
abducens nerves,
which are also going
to be cranial nerves
three,
four and six respectively.
04:45
The nasal ciliary, lacrimal
and frontal branches of
the ophthalmic nerve,
which is the first
division of the trigeminal
and the trigeminal is known as
the fifth cranial nerve also pass.
04:59
And then lastly, we passage of
the superior ophthalmic vein.
05:04
The inferior orbital fissure
lies between the greater weighing
of the sphenoid bone above
and the palatine and
maxillary bones below.
05:13
And it permits
the passage of:
The zygomatic, infraorbital
branches of the maxillary nerve,
which is the second division,
the trigeminal nerve,
also the infraorbital
vein and artery,
and lastly,
the inferior ophthalmic vein.
05:30
And lastly, there are the
ethmoidal, infraorbital
and zygomaticofacial in
zygomaticotemporal foramen,
which permit the passage of neuro
vasculature are of the same name.
05:43
One additional structure
I'd like to touch upon
before moving on to the next topic
is the common tendinous ring.
05:50
This is a fibrous band,
which surrounds
the optic canal
and the superior
orbital fissure
and it gives attachment
to the four recti muscles
at the apex of the orbit.
06:02
And atomically, this ring is
often used to divide the content
entering both the optic canal
and superior orbital fissure
as lying within the
common tendinous ring
or line outside the
common tendinous ring.
06:16
Additionally, all structures entering
via the inferior orbital fissure
will all lie outside the
common tendinous ring.
06:24
Next I'd like to discuss
supportive structures
located within the orbit which
include the connective SEPTA,
sheaves, ligaments and fat.