Download The nasolacrimal duct

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1. Orbit and Ocular Adenexa
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Orbit
1: Sinuses
The paranasal sinuses are cavities in the interior of the maxilla, frontal, sphenoid and ethmoidal bones.
They vary considerably in size and shape in different individuals and at different ages. They are lined with
mucoperiosteum and filled with air, they communicate with the nasal cavity through relatively small
apertures.
All sinuses are lined by pseudostratified columnar ciliated epithelium.
Maxillary sinuses
The largest of the paranasal sinuses. Located in the body of the maxilla. The cavity is pyramid shaped. Its
base forms part of lateral wall of the nose. The maxilla, the uncinate process of the ethmoid, the inferior
concha and the perpendicular plate of the palatine bone all contribute to the lateral
wall of the
nasal cavity, part of which is the medial wall (base) of the maxillary sinus.
The apex extends laterally into the apex of the zygomatic bone. The roof of the sinus is formed by the
orbital plate of the maxilla and contains the infraorbital nerve and blood vessels. The floor is formed
by the alveolar process. Sometimes, the bone that is separating the teeth from the sinus is missing. The
anterior wall is related to the face and contains the canals for the anterior and middle superior alveolar
nerves and blood vessels. The posterior wall is related to the infratemporal fossa and contains the posterior
superior alveolar nerves and blood vessels.
The maxillary sinus communicates with the nose through an opening, the
ostium,in
the superior part of
its medial wall and discharge into the middle meatus of the nose.
It reaches full size after the eruption of all permanent teeth.
-Nerve supply: The mucous membrane is supplied by the infraorbital nerve ,from
the ophthalmic
V and the anterior, middle and posterior superior alveolar nerves, from the maxillary V2.
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-Blood supply: This is from the anterior and posterior superior alveolar branches of the infraorbital and
maxillary arteries respectively. Also the facial artery and the greater palatine artery is involved.
The veins drain the ostium and join the venous plexuses in the nose.
-Lymphatic drainage: The vessels pass through the ostium and drain into the submandibular nodes
Frontal sinuses
The two frontal sinuses lie within the frontal bone, separated by a bony septum. Both of the sinuses are
triangular in shape extending upward above the medial end of the eyebrow and backward into the medial
part of the roof of the orbit. The frontal sinus is usually incompletely divided into a number of recesses by
bony partitions.
The anterior wall of the sinus is related to the fore head skin and the supraorbital and supratrochlear
nerves. The posterior wall is related to the Anterior Cranial
of the brain. The floor is related to the orbit and nose.
fossa,
meninges,and the frontal lobe
There is a communication with the nose via the infundibulum or the frontonasal duct. It opens into
the hiatus semilunaris in the middle meatus, close to the openings of the anterior ethmoidal sinuses and the
maxillary sinus.
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These sinuses are rudimentary or absent at birth and are generally well developed between 7th and
8th years, but reach full size only after puberty.
-Nerve supply: The mucous membrane is supplied by a branch from the supraorbital nerve,
from
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the ophthamic V , as it passes through the supraorbital foramen.
-Blood supply: The arterial supply is from the supraorbital and anterior ethmoidal arteries. The veins drain
into the venous plexuses of the nose and into the supraorbital vein.
-Lymphatic drainage: The lymphatic vessels drain into the submandibular nodes
Sphenoidal sinuses
These two sinuses lie within the body of the sphenoid bone. Of all the sinuses these vary most in their
extent and development. Extension can be found as far as into the pterygoid processes or the greater wing
of the sphenoid. It can partly surround the optic canal in the lesser wing of the sphenoid.
Most of the time the two sinuses are separated by a median septum. However, this septum usually is
deviated to one side and makes that one of the sinuses is larger than the other.
The anterior wall is related to the nasal cavity and the ethmoidal sinuses. The posterior wall is related to the
posterior cranial fossa and the pons. The cavernous sinus is located laterally to the sinuses. This
contains the internal carotid artery and the abducent nerve. In front of the cavernous sinus, the
sphenoid sinus is related to the orbital cavity. Superiorly the sinus is related to the Turkish saddle, sella
turcica, which contains the hypophysis cerebri or the pituitary gland. Superior to this are the
optic nerve and the Optic Chiasma. Inferiorly the sinus is related to the nasopharynx and the
pterygoid canal.
These are minute cavities at birth and main development is after puberty.
The sphenoid sinus opens into the nasal cavity in the sphenoethmoidal recess above the superior concha.
-Nerve supply: The mucous membrane is supplied by the posterior ethmoidal nerves and the orbital
branches of the pterygopalatin ganglion.(all
from V2)
-Blood supply: The arterial supply is from the posterior ethmoidal arteries. The veins drain into the
posterior ethmoidal veins.
-Lymphatic drainage: The lymphatic vessels drain into the retropharyngeal nodes.
Ethmoidal sinuses
These aircells lie within the ethmoidal bone between the nose and orbital cavity. Sometimes there’s an
extension into the maxillary, sphenoidal, lacrimal, frontal and palatine bones. These aircells are usually
grouped together into an anterior, middle and posterior group.
Inferiorly they are related to the nose. Superiorly they are related to the anterior cranial fossa and the frontal
lobe of the cerebrum. Laterally they are related to the orbital cavity and medially they are related to the
nose. The anterior group communicates with the nose through one or more openings into the ethmoidal
infundibulum or the frontonasal duct. The opening is into the middle meatus of the nose. The middle group
of aircells opens by one ore more orifices on or above the ethmoidal bulla into the middle meatus of the
nose. The posterior group of aircells, which lie close to the optic canal, open by one orifice into the superior
meatus of the nose above the superior concha.
Grow rapidly between 6 and 8 years old and after puberty.
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-Nerve supply: The mucous membrane of the ethmoidal airsinuses is supplied by the anterior and posterior
ethmoidal nerves and by branches of the pterygopalatine ganglion.
-Blood supply: The arterial supply is from the anterior and posterior ethmoidal arteries and the
sphenopalatine artery. The veins correspond the arteries.
-Lymphatic drainage: The lymphatic vessels of the anterior and middle group of aircells drain into the
submandibular nodes. The lymphatic vessels of the posterior group of aircells drain into the
retropharyngeal nodes.
2: Bones comprising the orbital walls
Fig 1
Orbit
7 individual bones form the orbit:
1: The maxilla
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2: The palatine bone
3: The zygomatic bone
4: The sphenoid bone
5: The frontal bone
6: The ethmoidal bone
7: The lacrimal bone
The orbital margin (rim) has a quadrilateral shape with rounded corners. In the adult the orbital
margin is less high (35mm) than it is wide (45mm).
Supraorbital margin
-is formed by the frontal bone.
-at the junction of the rounded medial third and the sharp lateral two thirds you can find the supraorbital
notch or foramen. This transmits the supraorbital nerve and blood vessels.
Medial margin
-
formed above by the maxillary process of the frontal bone and below by the frontal process of the
maxilla.
the frontal process of the maxilla forms the anterior lacrimal crest.
lower part of this margin is easily felt, because it is sharp, whereas the upper part is indistinct
Infraorbital margin
- is formed medially by the maxilla and laterally by the zygomatic bone.
Lateral margin
-
is formed by the process of the frontal bone above and the process of the zygomatic bone below.
the suture between these bones, the frontozygomatic suture, can be easily felt in the living subject.
this is the strongest part of the orbital margin.
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The walls of the orbital cavity are lined with periosteum and consist of a roof, medial wall, floor, and
lateral wall. The apex is formed by the optic canal, at the medial end of the superior orbital fissure.
Aid:
Roof, Floor, Lateral wall, Medial wall
R
M
No. of bones
2
4
F
3
L
2
Roof
The concave roof or superior wall of the orbit is formed by 2 bones:
1: the orbital plate of the frontal bone
2: the lesser wing of the sphenoid bone
-the fossa for the orbital part of the lacrimal gland is located anterolaterally behind the zygomatic process
of the frontal bone.
-medially the fovea trochlearis, that is located approximately 4 mm from the orbital margin, forms the
pulley of the superior oblique muscle
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-the frontal lobe of the cerebral hemisphere and the anterior cranial fossa are separated from the orbit by the
roof.
-the frontal sinus is located within the frontal bone.
Medial wall
The medial walls are almost parallel to each other.
The medial wall is the thinnest wall (lamina papyracea) and is formed by 4 bones, anterior to posterior:
1: the frontal process of the maxilla
2: the lacrimal bone
3: the orbital plate of the ethmoid bone
4: small part of the body of the sphenoid bone
Frontal Process of maxilla
-forms the anterior lacrimal crest
`forms the anterior part of the lacrimal fosa for the lacrimal sac.
Lacrimal bone
-lies posterior to the frontal process of the maxilla
-the anterior ½ contributes to the formation of the fossa for the lacrimal sac
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Orbital plate of the ethmoid bone
- is largest bone, that forms the medial wall
- is a very thin and fragile bone,
- border the nasal cavity anteriorly and the ethmoid air cells and the sphenoid sinus posteriorly
Sphenoidal Bone
-a small portion is formed by the body of the sphenoid
-the sphenoidal sinus may reach this portion
On the anterior part of the medial wall is the lacrimal groove ( fossa) for the lacrimal sac.
-groove is formed by the lacrimal bone posteriorly and the frontal process of the maxilla anteriorly.
- groove is bounded in front and behind by the anterior and posterior lacrimal crests.
Floor
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The thin floor of the orbit is formed by 3 bones:
1: the orbital plate of the maxilla
2: the orbital plate of the zygomatic bone
3: the orbital process of the palatine bone
The orbital plate of the maxilla separates the orbit from the maxillary sinus. The floor is continuous with
the lateral wall anteriorly, but is separated from it by the inferior orbital fissure posteriorly. From this
fissure the infraorbital grove is running forward and becomes the infraorbital canal about halfway the floor.
This canal opens onto the face as the infraorbital foramen.
The floor slopes downward from posterior to anterior at approximately 20 degrees from the horizontal
plane.
Lateral wall
The lateral wall is the thickest and strongest wall and is formed by 2 bones:
1: the zygomatic bone
2: the greater wing of the sphenoid bone
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The lateral tubercle, (=Whitnall’s tubercle, marginal tubercle ), which is a small elevation of the orbital
margin of the zygomatic bone, lies approximately 11mm below the frontozygomatic suture. This tubercle is
the site of attachment , from before backwards, for:
- the aponeurosis of the levator muscle
- the lateral palpebral ligament
- the lateral check ligament and below it, the suspensory ligament of the eyeball
The zygomatic bone which forms the anterior third of the lateral wall, separates the orbit from the temporal
fossa. The greater wing of the sphenoid bone which forms the posterior two thirds of the lateral wall,
separates the orbit from the temporal lobe of the brain in the middle cranial fossa.
The superior orbital fissure separates the lateral wall from the roof posterior in the orbit.
3. Orbital foramina, ducts, canals and fissures
Foramina
The optic foramen
(optic nerve, the ophthalmic artery, sympathetic fibers from the carotid plexus)
The supraorbital foramen (blood vessels, supraorbital nerve)
The anterior ethmoidal foramen
-opens into the anterior cranial fossa at the lateral edge of the cribriform plate of the ethmoid bone
-transmits the anterior ethmoidal nerve and artery
- located in the frontoethmoidal suture.
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The posterior ethmoidal foramen
-traverse the ethmoidal bone
-transmits the posterior ethmoidal artery and nerve, which supply the ethmoidal sinuses
-is located in the frontoethmoidal suture
The zygomatic foramina
-
located in the zygomatic bone in its lateral aspect
zygomaticfacial and zygomatictemporal nerve and artery
The nasolacrimal duct
-Travels inferiorly from the lacrimal fossa into the inferior meatus of the nose
-runs downward, backward and laterally
-is about 18mm long
The infraorbital canal
This is the anterior continuation of the infraorbital groove and exits 4mm below the inferior orbital margin.
It transmits the infraorbital nerve.
The optic canal
-
lies in the lesser wing of the sphenoid, medial to the body of the bone
situated at the apex of the orbit
measures 4 to 10 mm long ( for MCQ 5mm)
connects the middle cranial fossa with the orbit
transmits
1 the optic nerve
2 meningeal sheaths and extension of the subarachnoid space
3 ophthalmic artery
4 sympathetic plexus
-the sphenoidal sinus lies close to it
-sometimes the ethmoidal sinus also lies very close to it.
Fissures
The superior orbital fissure
-
lies between the lesser and greater wings of the sphenoid.
lies below and lateral to the optic foramen.
connects the middle cranial fossa with the orbital cavity.
lies between the roof and lateral wall of the orbit.
the widest part is at the medial end.
about halfway the fissure on the greater wing of the sphenoid is a small sharp spine for the lateral
rectus muscle
the common tendinous tendon is attached to this spine on the greater wing.
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Passing through the superior orbital fissure, laterally, outside the common tendinous ring are, from lateral
to medial
1 lacrimal nerve
2 frontal nerve
3 trochlear nerve
( remember this as LFT= Liver Function Test)
4 superior ophthalmic vein ( drains into the cavernous sinus)
Passing within the common tendinous ring
1 upper and lower divisions of the oculomotor nerve,
2 nasociliary nerve and
3 abducens nerve
Passing medial to the common tendinous ring
The inferior orbital fissure
-lies between the greater wing of the sphenoid and the orbital plate of the maxilla
-connects the pterygopalatine and infratemporal fossae with the orbit
- is closed in the living subject by the periorbita and the muscle of Muller
-transmits
1 maxillary nerve, which immediately changes its name to infraorbital nerve.
2 transmits the zygomatic nerve, branches of the pterygopalatine ganglion
3 inferior ophthalmic vein, which drains into the pterygoid venous plexus.
After you have studied this chapter,
1correct any mistake you see with ‘italics, size 14’
2add anything else that you think might be asked in MCQ
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and return it to me
A
Orbit
1: Sinuses
Paranasal sinuses
- are cavities in maxilla, frontal, sphenoid and ethmoidal bones.
- most sinuses are rudimentary or absent birth
- enlarge during the eruption of the permanent teeth.
- are lined with pseudostratified columnar ciliated epithelium mucoperiosteum.
Maxillary sinuses (Fig 2A & 2B)
- is the largest of the paranasal sinuses and is pyramid shaped, with the base forming
part of lateral wall of the nose.
- the anterior wall is related to the face.
- its roof is formed by the orbital plate of the maxilla and it contains the infraorbital
nerves and blood vessels.
- the inferior orbital canal usually ridges the sinus from the roof to the anterior
wall.
- the apex of the root of the two premolar and three molar teeth may produce a conical
projection on the sinus floor.
- the posterior wall is related to the infratemporal fossa and it contains the posterior
superior alveolar nerves and blood vessels.
- opens at the posterior end of the hiatus semilunaris situated in the middle
meatus
- a second opening may lie posteriorly.
- it reaches full size after the eruption of all permanent teeth.
Nerve supply
- the mucous membrane is supplied by the infraorbital nerve and the anterior, middle
and posterior superior alveolar nerves.
Blood supply
- is from the anterior and posterior superior alveolar branches of the infraorbital and
maxillary arteries respectively.
- is also from the facial artery and the greater palatine artery.
- the veins drain through the ostium and join the venous plexus in the nose.
Lymphatic drainage
- the vessels pass through the ostium and drain into the submandibular nodes
Frontal sinuses
- the two frontal sinuses lie within the frontal bone, separated by a bony septum.
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-
are triangular in shape, each extends upward above the medial end of the eyebrow
and backward into the medial part of the roof of the orbit.
- posteriorly, a sinus may reach the lesser wing of the spenoid bone.
- the anterior walls are related to the fore head skin and the supraorbital and
supratrochlear nerves.
- posterior walls are related to the anterior cranial fossa in which are the
meninges and the frontal lobe of the brain.
- floors are related to the orbit and nose.
- communicate with the nose via the frontonasal duct or the ethmoidal
infundibulum to a opening at the front end of the hiatus semilunaris in the
middle meatus. (Fig 2B).
- the only sinus absent at birth and are generally well developed between 7th and 8th
years, but reach full size only after puberty.
Nerve supply
- mucous membrane is supplied by a branch from the supraorbital and supratrachlear
nerves.
Blood supply
- arterial supply is from the supraorbital, supratrochlear and anterior ethmoidal
arteries.
- veins drain into the venous plexuses of the nose and into the superior ophthalmic and
diploic vein.
Lymphatic drainage
- lymphatic vessels drain into the submandibular nodes
Sphenoidal sinuses
-
-
are two sinuses lie that within the body of the sphenoid bone.
of all the sinuses, these vary most in their extent and development.
partly surround the optic canal in the lesser wing of the sphenoid.
are separated by a median septum.
it may invade the greater wing of sphenoid and the basi-occipital bone to the foreman
magnum
anterior walls are related to the nasal cavities and the ethmoidal sinuses.
posterior walls are related to the posterior cranial fossa basilar artery and the
pons.
- related laterally to the cavernous sinuses which contains the internal carotid
artery and the abducens nerve. (Fig 2C).
- are also related laterally to the orbital cavity.
- superiorly, are related to pituitary fossa which contains the pituitary gland and
superior to this is the, optic nerve and the chiasma.
- Inferiorly, is related to the nasopharynx and the pterygoid canal.
- are minute cavities at birth and main development is after puberty.
- open into the nasal cavity into the sphenoiethmoidal recess above the superior
concha.
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Nerve supply
- supplied chiefly by branches from the maxillary nerve.
Blood supply
- arterial supply is from the posterior ethmoidal arteries.
- veins drain into the posterior ethmoidal veins.
Lymphatic drainage
- lymphatic vessels drain into the retropharyngeal nodes.
Ethmoidal sinuses
-
lies between the orbit and the nose
of each ethmoidal sinus is made up of numerous small cavities called air cells, lying
within the ethmoidal bones
are named according to their opening into the nasal cavity as anterior, middle and
posterior groups.
consists of 3-18 air cells.
they may show extension into the maxillary, sphenoidal, lacrimal, frontal and palatine
bones.
the posterior group of air cells may surround the optic canal.
inferiorly they are related to the nose
superiorly they are related to the anterior cranial fossa, meninges and the frontal lobe
of the cerebral hemisphere.
laterally they are related to the orbital cavity, forming its medial wall, which is
paper-thin, (lamina papyracea)
medially they are related to the nose.
Drainage(Fig 2B)
anterior group drains to middle meatus into the hiatus semilunaris through openings
in the frontonasal duct or the ethmoidal infundibulum.
middle group-middle meatus
posterior group- superior meatus
grows rapidly between 6 and 8 years old and after puberty.
Nerve supply
- the mucous membrane of the ethmoidal air sinuses is supplied by the anterior and
posterior ethmoidal nerves and by orbital branches of the pterygopalatine ganglion.
Blood supply
-
is from the branches of the internal and external carotid arteries
the arterial supply is from the anterior and posterior ethmoidal arteries and the
sphenopalatine artery.
the veins correspond the arteries.
Lymphatic drainage
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-
the anterior group drain into the submandibular nodes.
the middle group drain into the submandibular lymph nodes
the posterior group of air drain into the retropharyngeal nodes.
2: Bones comprising the orbital walls
- The orbit
-
the orbital cavities are a pair of large bony sockets that contain the eyeballs, their
associated muscles, nerves, vessels and fat, and most of the lacrimal apparatus.
each cavity is pear or pyramidal shaped and its apex is directed posteriorly, medially
and slightly upward (Fig 3)
Bones Comprising the orbital wall.
- is made up of 7 bones (Fig 4)
- it has roof, medal wall, floor and lateral wall.
- is widest , floor approximately 1 to 1.5 cm behind the orbital margin.
- medial wall is oblong is shape and parallel to the sagittal plane (Fig 5)
- lateral wall are oriented at an angle of approximately 45 degrees to the this plane and
meet at the pituitary fossa.
- In adults measures 40 mm in height, 45 mm in width and 40 mm in depth (Fig 6).
- volume is about 30 ml.
7 individual bones form the orbit (Fig 4)
1: The maxilla
2: The palatine bone
3: The zygomatic bone
4: The sphenoid bone
5: The frontal bone
6: The ethmoidal bone
7: The lacrimal bone
The orbital margins (rim) (Fig 7)
- has 4 margins, superior, medial, inferior and lateral
- has a quadrilateral shape with rounded corners.
- is made up of three bones; the frontal, zygomatic, and the maxilla.
- the lateral margin is thickest and concave forward and does not reach as far anteriorly
as the medial margin. (Fig 5)
- medial margin is sharp and distinct in its lower half due to the anterior lacrimal crest,
- but indistinct superiorly.
- in the adult the orbital margin is less high (35mm) than it is wide(45mm).
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Supraorbital margin
-is formed by the frontal bone.
-at the junction of the sharp lateral two thirds and the rounded medial third is
the supraorbital notch or foramen. (Fig 7)
- the supra-orbital foreman transmits the supraorbital nerve and blood vessels.
- medially to the supra orbital foramen, is crossed by the supratrochear nerve and
vessels.
- only the medial part of the margin is covered by the eye brow, laterally, the eye brow runs above the
margin (Fig 8)
Medial margin (Fig 9)
- formed above by the maxillary process of the frontal bone and below by the frontal
process of the maxilla.
- the frontal process of the maxilla forms the anterior lacrimal crest.
- the supra-orbital margin can be traced downward toward the posterior lacrimal
crest on the lacrimal bone.
- the anterior lacrimal crest gives attachment to the medial palperbral ligament
the lacrimal part of orbicularis oculi.
Infraorbital margin (Fig 10)
- is formed medially by the maxilla and laterally by the zygomatic bone.
Lateral margin (Fig 11)
-
this is the strongest part of the orbital margin
-
is formed by the zygomatic process of the frontal bone above and the frontal process
of the zygomatic bone below.
the frontozygomatic suture, the suture between these bones, can be easily felt in the
living subject.
the Whitnall tubercle lies on the zygomatic bone 10 mm below the
frontozygomatic the suture.
the Whitnall tubercle gives attachment to the lateral palpebral ligament-
-
Orbital walls
-the walls of the orbital cavity are consist of a roof, medial wall, floor, and lateral wall.
-the apex is formed by the optic canal at the medial end of the superior orbital fissure.
Roof (Fig 12)
-
the orbital plate of the frontal bone and the lesser wing of the
sphenoid bone
is concave in shape
-the fossa for the orbital part of the lacrimal gland is located anterolaterally
behind the zygomatic process of the frontal bone.
the fovea trochlearis, is located approximately 4 mm from the orbital margin, at
its supero-medial angle and it forms the pulley of the superior oblique muscle.
is made up of 2 bones,
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-
superiorly the frontal lobe of the cerebral hemisphere lies and the anterior
cranial fossa
the frontal sinus is located within the frontal bone.
Medial wall (Fig 13)
- almost parallel to each other.
- is the thinnest wall (lamina papyracea of the ethmodial bone)
- is formed by 4 bones, anterior to posterior are, the frontal process of the maxilla, the lacrimal
bone, the orbital plate of the ethmoid bone and a small part of the body of the sphenoid
bone
- anterior to posterior, are boarded by nasal cavity, ethmoidal air cells and sphenoidal
sinus.
- the frontal process of maxilla forms the anterior lacrimal crest, which forms the anterior
part of the lacrimal fossa for the lacrimal sac.
Lacrimal bone (Fig 14)
-lies posterior to the frontal process of the maxilla
-the anterior ½ contributes to the formation of the fossa for the lacrimal sac
Lacrimal sac fossa (Fig 15)
-on the anterior part of the medial wall is the lacrimal (groove) fossa for the
lacrimal sac.
-the fossa is formed by the lacrimal bone posteriorly and the frontal process of the
maxilla anteriorly.
- groove is bounded in front and behind by the anterior and posterior lacrimal crests and
is continues below with the nasolacrimal canal.
Ethmoidal Bone
- The orbital plate forms the largest part of the medial wall
- is a very thin and fragile bone (lamina pupracea).
Sphenoidal Bone
-a small portion of the medial wall is formed by the body of the sphenoid
-the sphenoidal sinus may reach this portion
Floor (Fig 15)
- is formed by 3 bones, the orbital plate of the maxilla, the orbital plate of the zygomatic
bone, and the orbital process of the palatine bone
The orbital plate of the maxilla
- separates the orbit from the maxillary sinus.
- is continuous with the lateral wall anteriorly, but is separated from it by the
inferior orbital fissure posteriorly.
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-forms anterior margin of the inferior orbital fissure.
- the infraorbital groove runs forward and becomes the infraorbital canal about
halfway in the floor.
-the infraorbital canal opens onto the face as the infraorbital foramen, 1cm below
the infraorbital margin.
-the floor slopes downward from posterior to anterior at approximately 20 degrees
from the horizontal plane.
-lateral to the opening of the nasolacrimal canal, inferior oblique muscle takes
origin.
Zygomatic bone
-forms the lateral part of the floor
-is continues with the lateral wall anteriorly.
Palatine bone
- forms a small posterior most part of the floor
Lateral wall
-
is formed by 2 bones, the zygomatic bone and the greater wing of the sphenoid
bone.
- is the thickest and strongest wall
- the zygomatic bone, which forms the anterior third of the lateral wall, separates the
orbit from the temporal fossa,
-the greater wing of the sphenoid bone forms the posterior two third of the lateral wall,
and it separates the orbit from the temporal lobe of the brain in the middle cranial
fossa.
-anterior to posterior, borders temporal, pterygoplatine and middle cranial fossa.
-the lateral tubercle, (Whitnall’s tubercle, marginal tubercle), is a small elevation of
the orbital margin of the zygomatic bone, lies approximately 10mm below the
frontozygomatic suture. (Remember it as 1cm)
- the Whitnall tubercle is the site of attachment, from before backward, for:
a) the lateral palpebral ligament
b) the aponeurosis of the levator muscle
c) the check ligament of lateral rectus muscle
d) the suspensory ligament of the eye ball.
-posteriorly, the superior orbital fissure separates the lateral wall from the roof.
- anteriorly, separates the orbital cavity from the temporal fossa containing the
temporalis muscle, posteriorly separates the orbital cavity from the middle cranial
fossa, the meninges and the temporal lobe of the cerebral hemisphere.
3. Orbital foramina, ducts, canals and fissures (Fig 18)
Foramina
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The optic foramen
-is situated at the apex of the orbit between the roots of the lesser wing of the
sphenoid.
-transmits optic nerve with its meninges and the extension of the subarachnoid
space, the ophthalmic artery, and the sympathetic fibers from the carotid plexus
The supraorbital foramen
-lies at the junction of sharp lateral 2/3 and the medial rounded 1/3 of the
supraorbital arch .
- transmits the supraorbital nerve and vessels.
The ethmoidal foramen
- lie in the frontoethmoidal suture or in the frontal bone.
- situated where the roof joins the medial wall.
The anterior ethmoidal foramen
-located in the frontoethmoidal suture
-opens into the anterior cranial fossa at the lateral edge of the cribriform plate of the
ethmoid bone
-transmits the anterior ethmoidal nerve and artery
The posterior ethmoidal foramen
-is located in the frontoethmoidal suture
-traverse the ethmoidal bone
-transmits the posterior ethmoidal artery and nerve, which supply the ethmoidal sinuses
The zygomaticofacial foramen
- sometimes 2 in number
- -lies in the zygomatic bone near the junction of the lateral and inferior orbital margin
-transmits the zygomaticofacial artery and nerve from the orbit to the face.
The zygomatico temporal foramen
-lies above the zygomaticofacial foramen, close to the sphenozygomatic suture.
-it transmits the zygomatico temporal nerve and vessels from the orbit to the temple
The nasolacrimal duct
-begins at the antero-medial corner of the floor of the orbit.
-travels inferiorly from the lacrimal fossa into the inferior meatus of the nose
-runs downward, backward and laterally
-is about 18mm long remember it as (2cm)
-formed by lacrimal bone, the maxilla, and the inferior choncha
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The infraorbital canal
- is the anterior continuation of the infraorbital groove and exits 10mm below the
inferior orbital margin.
-it transmits the infraorbital nerve and vessels.
The optic canal
-is at the apex of the orbit
-is at the posterior junction of medial wall and the roof
-it passes anteriorly, inferiorly, and laterally from the middle cranial fossa to the apex of
the orbit.
- is formed bounded by two roots of lesser wing of sphenoid, laterally and the body of
the sphenoid medially.
- measures 4 to 10 mm long (for MCQ 5mm).
- the cranial opening at the cranial end is oval with a prolonged floor.
- connects the orbit to the middle cranial fossa
- the sphenoidal and posterior ethmoidal air sinuses lie medial to it.
- the olfactory nerve lies above to it.
The optic canal transmits:
1 the optic nerve
2 meningeal sheaths and extension of the subarachnoid space
3 ophthalmic artery, which is the first branch of the internal carotid artery, after it
leaves the cavernous sinus.
4 sympathetic plexus
Fissures
The superior orbital fissure
- lies between the lesser and greater wings of the sphenoid.
- lies below and lateral to the optic foramen.
- Is about 25mm long. (remember the length of the orbital port of the optic nerve
is also 25mm long)
- connects the middle cranial fossa with the orbital cavity.
- lies between the roof and lateral wall of the orbit.
- the widest part is at the medial end.
- about halfway the fissure on the greater wing of the sphenoid is a small sharp spine
for the lateral rectus muscle
- the common tendinous tendon is attached to the spine on the greater wing.
Passing through the superior orbital fissure, laterally, outside the common tendinous ring
are, from lateral to medial
1 lacrimal nerve
2 frontal nerve
3 trochlear nerve
(remember this as LFT= Liver Function Test)
4 superior ophthalmic vein ( drains into the cavernous sinus)
Passing within the common tendinous ring
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1 upper and lower divisions of the oculomotor nerve,
2 nasociliary nerve and
3 abducens nerve
Passing medial to the common tendinous ring:
-inferior ophthalmic vein
The inferior orbital fissure
- it lies between the lateral wall and the floor of the orbit.
- is between the greater wing of the sphenoid and the orbital plate of the maxilla
-connects the pterygopalatine and infratemporal fossae with the orbit
-the fissure is narrowest in the center and is covered by the Muller's muscle and
periorbita.
-it ends from the orbital margin at 20mm.
-is limited antero-laterally by the zygomatic bone.
-transmits
1. maxillary nerve, which immediately changes its name to infraorbital nerve on
entering the orbit.
2. infraorbital artery
3. zygomatic nerve,
4. inferior ophthalmic vein, which drains into the cavernous sinus.
Orbit by Prasad
ORBIT and OCULAR ADENEXA
Osteology of the orbit
The two orbital cavities are situated between the cranium and the facial skeleton and are
separated from each other by the nasal cavities, ethmoidal and sphenoidal air sinuses. The
orbit is roughly quadrilateral pyramid in shape. It has floor, roof, medial wall, and lateral
wall. The orbit is widest approximately 1.5 cm behind the orbital margin. The medial
wall is oblong is shape and parallel to the sagittal plane, while the lateral wall are
oriented at an angle of approximately 45 degrees to the this plane. The orbit measures 40
mm in height, 40 mm in width and 40 mm in depth. The volume is about 30 ml.
Roof of the orbit
Is formed by
1. Largely by the triangular orbital plate of the frontal bone.
2. Behind by the lesser wing of sphenoid bone.
The roof is thin and translucent, separates the orbit from the anterior cranial fossa and
frontal lobes of the brain.
Fossa for the lacrimal gland lies in anterio lateral aspect.
Trochlear fossa. Lies in anterio medial aspect of roof, 4 mm from the margin.
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Anterior and posterior ethmoidal canals; positioned at the junction of roof and medial
wall above the frontoethmoidal suture. And transmit the anterior ethmoidal nerves and
vessels.
Floor of the orbit
The floor slopes slightly downwards from the medial to the lateral wall. It is formed by
three bones
1. The orbital plate of maxilla.
2. The orbital surface of zygomatic bone.
3. The orbital process of the palatine bone.
It is crossed by the infra orbital groove, which runs from the inferior orbital fissure. It
ends as infra orbital foramen 4 mm below the orbital margin.
The floor, although thicker than medial wall, is more often involved in blow out
fractures.
The medial wall
Is formed by four bones,
1. The frontal process of maxilla.
2. The lacrimal bone
3. The orbital plate of ethmoid bone.
4. A small part of the body of the sphenoid.
It is thin and transparent wall [0.2-0.4 mm]. Medial to this wall in an anterior to posterior
sequence lie the anterior, middle, posterior ethmoidal and sphenoidal sinus. Lacrimal
fossa for the lacrimal sac; is bounded by anterior and posterior lacrimal crests and is
continuos below with the nasolacrimal canal.
The lateral wall
Is formed by two bones;
1. Posteriorly by the orbital surface the greater wing of sphenoid bone.
2. Anteriorly by the orbital surface of the zygomatic bone.
Features
Spina recti lateralis; a small bony spine near the apex of the orbit on the greater wing of
sphenoid bone gives origin to the part of lateral rectus muscle.
Zygomaticforamen, transmits zygomatic nerve and vessels to the temporal fossa and
cheek.
Lateral orbital tubercle, the origin of the cheek ligament of lateral rectus, suspensory
ligament of the eye, and aponeurosis of levator palpepral superioris.
Orbital margin
It is made up of three bones; the frontal, zygomatic, and the maxilla. The lateral margin is
thickest and concave forward and does reach as far anteriorly as the medial margin. The
medial margin is sharp and distinct in its lower half due to the anterior lacrimal crest, but
indistinct superiorly.
The superior orbital fissure.
It lies between the roof and the lateral wall and is bounded by the lesser and greater wing
of sphenoid. It separated from the optic foramen above by the posterior root of the lesser
wing of sphenoid. It is comma shaped and 22 mm long and connects the orbit with the
cranial cavity. The common tendinous ring lies between the narrow and the wide parts of
the fissure. Above this ring lacrimal nerve, frontal nerve, Trochlear nerve, superior
ophthalmic vein, and recurrent lacrimal arteries lies. The two divisions of oculomotor
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nerve, abducent nerve, nasociliary nerve, sympathetic root of ciliary ganglion and inferior
ophthalmic vein passes pass within the ring.
Inferior orbital fissure.
It lies between the lateral wall and the floor of the orbit. It transmits the infra orbital
nerve, zygomatic nerve, and branches from the pterygopalatine ganglion. The fissure is
narrowest in the center and is covered by the muller muscle. It ends from the orbital
margin at 20 mm.
Optic canal.
The is a bony canal in the sphenoid bone that passes anteriorly, inferiorly, and laterally
from the middle cranial fossa to the apex of the orbit. It formed by two roots of lesser
wing of sphenoid . It is funnel shaped. It has prolonged roof at the opening in to the orbit.
The opening at the cranial end is oval with a prolonged floor. The sphenoidal and
posterior ethmoidal air sinuses lies medial to it. The olfactory nerves lies above to it. The
canal transmits the optic nerve along with the meninges and the ophthalmic artery. The
artery lie below and lateral to nerve. Sympathetic nerve fibers accompany the artery.
ADENEXA
Muscles of the eyelids and adjacent face.
1. Orbicularis oculi -a muscle of facial expression, which is responsible for lid closure.
2. Levator palpebral superioris is an extra ocular muscle which raises the lid.
The muscles of face are supplied by facial nerve. Those of interest of eye are orbicularis
oculi, corrugator supercilii, and the occipitofrontalis.
1. Orbicularis oculi
This is broad, flat, striated muscle with the orbital, palpebral, and lacrimal portions. The
orbital portion arises from the medial palpebral ligament and medial orbital margin above
and below the ligament. They pass around the lateral orbital margin without interruption
to insert into the skin and connective tissue of the eye brow. The palpebral part is
extremely thin and originates from the medial palpebral ligament. It passes anterior to the
orbital septum and tarsal plate and interlace to form the lateral palpebral ligament. The
small lacrimal part passes deep to the medial ligament and is attached to the posterior
lacrimal crest. These fibers inserted laterally in to the tarsi close to the lacrimal
cannaliculi.
2. Levator palpebral superioris
It has origin from the lesser wing of sphenoid and it blends with the origin of superior
rectus at the optic foramen. It passes above the superior rectus, close to the orbital roof. it
becomes aponeurotic 1 cm behind lid or orbital margin. It inserts in to the skin of eye lid
and anterior surface of the tarsal plate. The lateral horn of the aponeurosis form the lateral
palpebral ligament and attaches to the lateral orbital tubercle, the medial horn forms the
medial palpebral ligament which inserts into the fronto/lacrimalsuture. There is no
equivalent muscle in the lower eye lid.
The eye lids
They are thin curtain of skin, muscle, fibrous tissue, and mucous membrane that serve to
protect the eyes from injury and excessive sun light. The upper eye lid, when open,
normally just over laps the corneoscleral junction.
Each lid is divided in to orbital and tarsal portion by a horizontal palpebral sulcus. The
upper and lower lids meet at the medial and lateral canthi, and are separated from each
other by an elliptical opening - the palpebral fissure. The medial canthi is separated from
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the eye by a triangular zone, the lacus lacrimalis, a small raised swelling, the curuncula
lacrimalis, is situated.
The lid margins.
Are approximately 30 mm in length, 2 mm in thickness and the medial one sixth is
rounded and lack eye lashes. Eye lashes are modified, thick, stiff hairs that occur as
double or triple rows close to the anterior lid margin.
Features of the lid margin
1. Lacrimal puncta. Located at the medial ends of upper and lower eye lids.
2. The openings of the meibomian glands are visible to the naked eye.
3. The skin/ conjuctival zone mucocutaneous junction occurs at the level of opening of
the tarsal glands.
4. The gray line marks the anterior boundary of the tarsal plate.
Tarsal plates.
They are modified thickenings of the orbital septum. They are approximately 25-30 mm
from the medial to the lateral borders. They are 1 mm thick and the upper plate is greater
in height [10-12mm] than the lower [5 mm]. They are attached to the medial and lateral
palpebral ligaments. Tarsal glands are modified sebaceous glands.
Blood supply.
The pre tarsal portion is supplied by the superficial temporal and facial artery, while the
post tarsal is supplied by the branches of ophthalmic artery. Lymphatics drain to the
superficial temporal and mandibular lymph nodes.
The conjunctiva
The conjunctiva is a thin translucent mucous membrane. Its superficial layer, the
conjuctival epithelium, is continuos with the corneal epithelium at the limbus and with
the skin at the mucocutaneus junction on the lid margin.
When the lids are closed a potential sac, the conjuctival sac is formed. The volume of this
sac is approximately 7 micro liter. The conjunctiva is responsible for the mucous
component of tear film and it has a variety of immunological defense mechanisms.
For descriptive purposes it can be divided into three parts.
1. Palpebral
2. Bulbar
3. Forniceal
1. Palpebral
Lines the inner surface of the eye lids. It is tightly bound to the tarsal plate. A small sub
tarsal sulcus, close to the lid margin, is important in trapping and removing foreign body
particles.
2. Bulbar
It covers the anterior part of the eyeball including the extra ocular muscle insertions and
Tenon’s capsule. It is tightly bound near the limbus. At the medial canthus the
conjunctiva is highly vascular and rich in goblet cells and interstitial immunocompetent
cells. The caruncle, is a highly vascular nodule of modified skin in the medial corner of
the eye containing large nests of accessory and sebaceous glandular tissue.
3. Forniceal
The superior and inferior fornices form a circular cul de sac. The ducts of the main
lacrimal gland and the bulk of accessory lacrimal glands empty into the superiolateral
fornix.
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Structure of conjunctiva.
It varies in structure depending on the location, from a stratified squamous
nonkeratinizing epithelium to a stratified columnar epithelium. It consists of 2 to 7 layers
of epithelial cells that are organized into 3 main types; basal, intermediate, and
superficial. There are numerous other cell types resident within the epithelium.
1. Globlet cells -most numerous in the fornices and plica semilunaris.
2. Melanocytes- present in all eyes.
3. Langerhans cells [MHC class 2- positive dendritic cells.]- responsible for trapping and
internalizing antigens and transporting these signals to the local lymph nodes.
4. Intraepithelial lymphocytes- a feature of normal conjunctiva.
Lacrimal apparatus.
The lacrimal apparatus consists of the lacrimal gland, lacrimal puncta, lacrimal canaliculi,
lacrimal sac, and nasolacrimal duct. The lacrimal apparatus functions to produce tears.
Tears are essentials in maintaining the functional integrity of the eye.
Lacrimal gland
It is divided by the lateral horn of the aponeurosis of the levator palpebral superioris into
a large orbital and small palpebral portion. The orbital portion is lodged in the lacrimal
fossa. In the orbital portion, fine interlobular ducts unite to form 3 to 5 main excretory
ducts which then traverse the palpebral portion joining with it ducts to open in the
superiotemporal conjuctival fornix. As a result of this, removal of the palpebral portion
renders the entire gland non functional.
Histology.
Is a branched tubuloacinar gland of the serous type. It has a poorly developed capsule.
The secretion of the gland is primarily protenaceous. It also contains lysozymes,
lactoferrin, beta-lysin and immunoglobulin A.
Collecting portion of the lacrimal apparatus.
Excessive tears are drained from the medial aspect of the conjuctival sac via the
cannaliculi into the lacrimal sac and nasolacrimal duct, to empty into the inferior surface
of the nasal cavity.
The puncta are small openings at the summit of small swellings, the papillae lacrimalis.
Each cannaliculus is about 10 mm long and has vertical and horizontal component that
unite to form the common cannaliculus before entering the lacrimal sac. The cannaliculi
are lined by stratified nonkeratinizing squamous cells. The lacrimal sac is 12 mm long. It
lies in lacrimal fossa and is protected by the medial palpebral ligament. This is lined by
stratified cuboidal/ columnar epithelium-containing goblet cells. The nasolacrimal duct
opens into the anterior end of the inferior meatus. The duct lies in a bony canal formed by
the maxilla, the lacrimal bone, and the inferior nasal concha. It is lined by a stratified
columnar ciliated epithelium.
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