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Anatomy Lecture 7
Orbit
60
Anatomy
Post-Graduate
03/17/2008

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Term

What forms the roof of the orbit?

     
Definition

Orbital plate of frontal bone

Lesser wing of sphenoid

 

Term
Where does the lacrimal gland lie?
Definition
Lacrimal gland lies in the fossa for the lacrimal gland in the anterolateral part of the roof
Term

Roof separates what from the orbit?

Definition

The anterior cranial fossa

Term
Where does the optic canal lie and what does it connect?
Definition
Optic canal lies at the extreme posterior end of the roof. It connects the orbit to the middle cranial fossa
Term
What forms the floor of the orbit?
Definition
Floor is formed by the following:
orbital surface of maxilla
anterolaterally by the zygomatic bone
palatine bone posteriorly
infraorbital groove & canal
Term
What forms the floor of the orbit?
Definition
Floor is formed by the following:
orbital surface of maxilla
anterolaterally by the zygomatic bone
palatine bone posteriorly
infraorbital groove & canal
Term
What is the location of the inferior orbital fissure and what does it connect?
Definition
Inferior orbital fissure lies between the floor and lateral wall & connects orbit & infratemporal fossa
Term
What makes up the medial wall of the orbit?
Definition
Medial wall is formed by the following bones
Frontal process of the maxilla & maxillary process of frontal
Lacrimal bone which has a groove and crest
Orbital plate of ethmoid bone (paper thin)
Sphenoid
Term
What are the 2 foramina in the medial wall of the orbit?
Definition
Posterior ethmoid foramen and anterior ethmoid foramen
Term
What makes up the lateral wall of the orbit?
Definition
Lateral wall is formed by the following bones:
Greater wing of the sphenoid
Orbital surface of the zygomatic bone
Term
What lies between the roof and lateral wall of the orbit?
Definition
Between the roof and lateral wall lies the superior orbital fissure
Term
What forms the apex of the orbit?
Definition
·Apex is formed by the optic canal (in the lesser wing of the sphenoid)
Term
What forms the base of the orbit?
Definition
·Base is the orbital margin
Term
What covers the bony orbit?
Definition
The bony orbit is covered by the orbital periosteum (periorbita)
Term
What are the contents of the orbit
Definition
Contents of the orbit:
Eyeball
Fascial sheath of the eyeball which surrounds the eyeball (Tenons capsule or fascia bulbi)
Muscles of the orbit- 4 recti, 2 oblique, 1 levator palpebrae superioris
Nerves:
Optic N
Oculomotor N-
Trochlear N
Abducent N
Ophthalmic N branches -Lacrimal, Frontal, Nasociliary
Sympathetic nerves
Ciliary ganglion
Vessels :  Ophthalmic A & its branches
                Ophthalmic veins- Superior & Inferior
 Lacrimal gland
 Orbital fat.
Term
What is the frontal nerve and its branches?
Definition
It enters the orbit through the superior orbital fissure. It runs forwards above the levator palpebrae superioris. Frontal gives the following branches:
Supraorbital
Supratrochlear
Term
What is related to the lacrimal nerve along its course?
Definition
It enters the orbit through superior orbital fissure. It runs above the lateral rectus to reach the lacrimal gland. It receives postganglionic parasympathetic fibres from the pterygopalatine ganglion through the zygomatic nerve and supplies the lacrimal gland. It ends in the lateral part of the upper eyelid as palpebral branch
Term
What is the nasociliary nerve and its branches?
     
Definition
It is a branch of the ophthalmic nerve. It enters the orbit through the superior orbital fissure. It crosses above the optic nerve from lateral to medial side behind the ophthalmic artery and vein. It reaches the medial wall of the orbit between the superior oblique and medial rectus. It ends by dividing into anterior ethmoidal and infratrochlear nerve.
Nasociliary gives the following branches
Sensory connection to the ciliary ganglion
Long ciliary nerves
Posterior ethmoidal nerve
Anterior ethmoidal nerve
Infratrochlear nerve
Term
What is the ciliary ganglion?
Definition
It is a peripheral parasympathetic ganglion situated near the apex of the orbit between the optic nerve and lateral rectus muscle. It has sensory, sympathetic and parasympathetic fibers in it. But only parasympathetic fibers relay in the ganglion.
Term
The ciliary ganglion receives parasympathetic fibers from?
Definition
It receives its parasympathetic fibers through the following route:
Preganglionic fibers:
Edinger westphal nucleus in the midbrain -> oculomotor nerve -> Inferior  division -> nerve to inferior oblique -> ciliary ganglion
The postganglionic fibers pass through the short ciliary nerves and supply the ciliaris muscle and sphincter puplillae.
Term
What does the ciliaris muscle and sphincter pupillae do?
Definition
 Both these muscles are smooth muscles & help in accommodation:
     Ciliaris muscle ( in the ciliary body) contracts and relaxes the suspensory ligament of the lens thereby allowing the lens to become more convex.
     Sphincter pupillae present in the iris helps the iris to become small.
    These two actions help to focus the nearby objects (Accomodation). Both of them are supplied by the   parasympathetic fibers from the ciliary ganglion.
Term
What are the sympathetic fibers and sensory fibers passing through the cilliary ganglion?
Definition
Some sympathetic fibers passing through the long ciliary nerves pass through the ciliary ganglion but are not relayed in this. Similarly some Sensory fibers pass through this ganglion without relaying to the nasociliary nerve.
It contains only the cell bodies of the parasympathetic neurons.
Term
How does the ophthalmic artery begin and what is its course?
Definition
It arises from the internal carotid artery and passes through the optic canal along with the optic nerve
It lies lateral to the optic nerve
It crosses above the optic nerve from the lateral to the medial side between the superior ophthalmic vein in front and the Nasociliary nerve behind.
It reaches the medial wall of the orbit and terminates by dividing into supratrochlear and dorsal nasal arteries
Term
What are the branches of the ophthalmic artery?
Definition
It gives the following branches:
Central artery of Retina which is an end artery, runs in the optic nerve
Posterior ciliary arteries
Muscular branches
Posterior ethmoidal artery
Anterior ethmoidal artery
Lacrimal artery
Supraorbital artery
Supratrochlear artery
Dorsal nasal artery
Term
The blockage of which artery will cause total blindness?
Definition
Clinical correlation: blockage of the central artery of retina results in total blindness.
Term
What veins are located in the orbit?
Definition
There are two ophthalmic veins:
Superior ophthalmic
Inferior ophthalmic
Both of them open into the cavernous sinus
Term
What is the lacrimal apparatus?
Definition
Lacrimal gland
Lacus lacrimalis
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
Term
What is the lacrimal gland?
Definition
It is a serous gland secreting tears or lacrimal fluid
It is located in the Lacrimal fossa on the anterosuperolateral part of the orbit
It has two parts- Larger Orbital part and smaller Palpebral part
The two parts are separated by the lateral border of the Levator palpebrae superioris and are continuous with each other lateral to the muscle.
Orbital part lies between the lacrimal fossa and the levator palpebrae superioris
Palpebral part lies between the levator palpebrae superioris and the conjunctiva
There are 8-20 ducts issued from the palpebral part and they open into the superior conjunctival fornix.
Term
What is the blood supply of the lacrimal gland?
Definition
Blood supply: lacrimal branch of the ophthalmic artery
Term
What is the nerve supply of the lacrimal gland?
Definition
Nerve supply: Parasympathetic pathway: (secretomotor)
Lacrimatory nucleus (in the pons) Facial N Greater superficial petrosal nerve Nerve of the pterygoid canal (Vidian N) Pterygopalatine ganglion (sphenopalatine ganglion)
Postganglionic fibers: Pterygopalatine ganglion Communicating branch to the maxillary N Zygomatic N communicating branch Lacrimal N Lacrimal gland
Term
What are the layers of the eyelid?
Definition
Following layers – from superficial to deep - Skin, superficial fascia, Muscle layer, Tarsal plate, Tarsal glands, Palpebral conjunctiva
Term
What are the muscles of the eye?
Definition
Levator palpebrae superioris
Superior oblique
Inferior oblique
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Term
What are the recti muscles?
     
Definition
All the four recti arise from the common tendinous ring and are inserted approximately 6mm posterior to the sclerocorneal junction.
 
Remember this mnemonic:
SO4, LR6 and AR3
SO4: superior oblique by the 4th cranial, Trochlear nerve
LR6: lateral rectus by the 6th cranial, Abducent nerve
All the rest: by the 3rd cranial, Oculomotor nerve
Term
What is the levator palpebrae superioris?
Definition
It arises from the lesser wing of the sphenoid bone
It is inserted into the upper eyelid and skin.
It raises the upper eyelid. It is antagonistic to orbicularis oculi.
Term
What is the smooth muscle attached to the tarsal plate called?
Definition
The smooth muscle attached to the tarsal plate of the upper eyelid is called the superior tarsal muscle (muller’s muscle) and it is supplied by the sympathetic nerves.
Term
What are two causes of ptosis and what muscles are affected?
Definition
Therefore in Horner’s syndrome there is ptosis with retention of the palpebral fold due to the paralysis of the superior tarsal muscle.
Paralysis of the levator palpebrae superioris causes ptosis with obliteration of the palpebral fold
Term
What is the superior oblique?
Definition
Arises from near the apex of the orbit superior to the common tendinous ring. It is inserted into the posterolateral quadrant on the superior aspect of the eyeball
It hooks around the trochlea. It is supplied by the trochlear nerve
Term
What is the inferior oblique?
Definition
Arises from the anteromedial part of the floor of the orbit.
It is inserted into the posterolateral quadrant on the inferior aspect of the eyeball. It is supplied by the inferior division of the oculomotor nerve.
Term
What is the inferior oblique?
Definition
Arises from the anteromedial part of the floor of the orbit.
It is inserted into the posterolateral quadrant on the inferior aspect of the eyeball. It is supplied by the inferior division of the oculomotor nerve.
Term
What are the movements of the eye by its extrinsic muscles?
Definition
See Table on lecture!
                                                  
Term
When do the muscles of the eyeball bring about only one movement?
Definition
The A-P axis of the eyeball is 23 degrees medial to the axis of the orbit. The muscles acting on the eye ball bring about simple action only when the two axes lie at the same plane. If not, the contraction of the muscle brings about combined movements of the eye ball.
Term
What are the three axes of the eyeball and what are the movements associated with each?
Definition
The movements take place around 3 primary axes which pass through the centre of movement at right angle to each other.
Vertical axis- around which the centre of the cornea & visual axis moves laterally ( abduction) or medially (adduction).
2. Transverse axis- around which the centre of the cornea moves up(elevation) or down ( depression)
3. Anteroposterior axis- around which so-called “wheel rotation” takes place, better defined as intorsion or extorsion as the twelve 0' clock on the cornea moves nasally (intorsion) or temporally (extorsion).
Term
Why do the superior and inferior rectus muscles have three actions each?
Definition
Superior and inferior rectus muscles lie in the long axis of the orbit and not in the long axis of the eyeball.
The long axis of the eyeball is not in the long axis of the orbit. The orbit looks forwards and laterally while the eyeball looks directly forwards.  This is responsible for the superior and inferior recti muscles to cross 3 axes as they pass from the common tendinous ring to the eyeball. Therefore each of these muscles has 3 actions.
Term
What is the movement of the superior rectus muscle?
Definition
Superior rectus: It crosses a horizontal axis therefore it elevates the eyeball, crosses the vertical axis therefore adducts, and it also crosses the anteroposterior axis which brings about intorsion  of the eyeball.
Term
What are the actions of the inferior rectus muscle?
Definition
Inferior rectus also has 3 actions: depression, adduction and extorsion.
Term
What are the actions of the medial rectus muscle?
  
Definition
Medial rectus: crosses only one axis and has only one action. It adducts the eyeball towards the median plane.
Term
What are the actions of the lateral rectus muscle?
Definition
Lateral rectus: crosses only one axis and has only one action. It abducts the eyeball away from the median plane.
Term
What is the action of the superior oblique muscle?
Definition
Superior oblique: has 3 actions because of the peculiarity of its insertion.
It lifts the back of the eyeball which results in the depression of the front of the eyeball. It also intorts (medially rotates) the eyeball because it crosses the anteroposterior axis. It pulls the posterior part of the eyeball medially and thus the anterior part of the eyeball turns laterally (abduction)
Term
What are the actions of the inferior oblique muscle?
Definition
Inferior oblique: also has 3 actions because of the peculiarity of its insertion.
It depresses the back of the eyeball which results in the elevation of the front of the eyeball. It extorts the eyeball and abducts.
Term
What are the muscles involved in pure elevation?
Definition
In pure elevation two muscles contract:
Superior rectus: elevation and intorsion and adduction
Inferior oblique: elevation and extorsion and abduction
Opposite torsion movements of these two muscles get cancelled and it results in pure elevation.
Term
What muscles are involved in pure depression?
Definition
Inferior rectus: depression and extorsion
Superior oblique: depression and intorsion. Torsion movements of these two muscles get cancelled and it results in pure depression.
Term
What are synergists?
Definition
Synergists are those muscles which cancel the unwanted movement of another muscle. In this case superior oblique acts like a synergist and cancels the unwanted extorsion of the inferior rectus muscle.
Term
How does one test the superior rectus muscle?
Definition
Superior rectus: it lies in the long axis of the eyeball when the eyeball is abducted. Therefore it has only one action on the abducted eye. That is elevation.
Therefore the subject is asked to look upwards and laterally to test for the superior rectus muscle.
Look at finger at the side of the forehead (temples)
Term
How does one test the inferior rectus muscle?
Definition
Inferior rectus: it lies in the long axis of the eyeball when the eyeball is abducted. Therefore it has only one action on the abducted eye. That is depression.
Therefore the subject is asked to look downwards and laterally to test for the inferior rectus muscle.
Look at finger at the zygomatic
Term
How does one test the superior oblique muscle?
Definition
Superior oblique: it lies in the long axis of the eyeball when the eyeball is adducted. Therefore it has only one action on the adducted eye. That is depression.
So, this muscle is tested by asking the patient to look at the tip of the nose.
Term
How does one test the inferior oblique muscle?
Definition
Inferior oblique: the same description is applicable to this muscle also.
So, the muscle is tested by asking the patient to look upwards and medially.
Look at the finger between the eyebrows
Term
How does one test the inferior oblique muscle?
Definition
Inferior oblique: the same description as the superior oblique applicable to this muscle also.
So, the muscle is tested by asking the patient to look upwards and medially.
Look at the finger between the eyebrows
Term
How does one test the medial rectus muscle?
Definition
Medial rectus: subject is asked to adduct the eye
Look at the finger at the bridge of the nose
Term
How does one test the lateral rectus muscle?
Definition
Lateral rectus: subject is asked to abduct the eye
Term
What is the cheating muscle?
Definition
Clinical: Superior oblique is copying muscle. In trochlear nerve palsy, diplopia occurs on looking downwards! The eyeball rolls upwards when an attempt is made to steal a look into the neighbor’s answers !!!
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