Glossary of ANATOMY OF ORBIT - 45
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- What is the orbit?
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated
- What are the 4 walls of the orbit and what are the bones that make up these walls?
The 4 Walls of orbit are:
1. Roof – frontal bone
2. Floor – maxillary and
Today we are talking about the orbit. The roof of the orbit is formed by the orbital plate of the frontal bone. The first thing you see is the extension of the dura mater called periorbita. The red is the lesser wing of the sphenoid. The optic nerve and ophthalmic go through the optic canal. Ethmoid is a huge bone and here you see only a part of it. It forms part of the eye and nasal cavity. There are sinuses in the ethmoid bone.
3. Lateral – sphenoid and
4. Medial – ethmoid, lacrimal, maxilla, and lesser wing of the sphenoid
- What are the 8 foramina of the orbit?
a. Optic canal – apex
b. Superior orbital fissure – roof
c. Inferior orbital fissure – floor
d. Infraorbital groove and foramen – floor
e. Supraorbital notch or foramen – margin of roof
f. Nasolacrimal canal – medial
g. Anterior and posterior ethmoid foramen – medial
h. Zygomatic foramen – lateral
- What passes through the anterior and posterior ethmoid foramen?
The small holes in the back are the anterior and posterior foramen. Nerve and artery of the same name pass through this.
- What passes through the superior orbital fissure?
The superior orbital fissure: you have CN 3, 4, V1, V1 and the superior ophthalmic vein.
- What passes through the inferior orbital fissure?
In the inferior orbital fissure, you have a continuation of the nerve called d V2. V2 comes out of the infra orbital groove, with an artery and vein
- What comes out of the zygomatic foramen?
The zygomatic nerve comes out of the zygomatic foramen.
- What is the significance of the nasal lacrimal duct?
There is a hole called the nasal lacrimal duct that communicates with the nasal cavity. This causes the nose to run when you cry goodbuddis. Don’t feel bad about it. It is going to be ok.
- How do you get headaches and what can happen if you get a sinus infection and you get a direct hit on the face?
Openings in the head are called sinuses. This is where you get sinus headaches. You have them behind the ethmoid bone. A sinus infection can break trough the ethmoid bone and you can go blind. A direct hit on the eyeball can break that bone.
The little hole in front is the ethmoid fossa. In the lateral wall you see the red greater wing of the sphenoid. If you go up through the frontal bone you go into the anterior cranial fossa. If you go straight into the eye you are in the middle cranial fossa.
- What are the 5 main structures of the eyelids?
1. Skin, connective tissue, and glands
a. levator palpebrae superioris
b. superior tarsal muscle
c. orbicularis occuli
4. Tarsal plate and gland
The eyelids have skin on the outside, the epidermis. This is the obicularis oculi that comes. This comes from the 2nd brachial arch so this is innervated by facial nerve. On top is the levator palpebri superioris innervated by CN3. There e is involuntary muscle that goes into the tarsal plate: the muscle is superior tarsal muscle. It is involuntary and innervated by the 3rd nerve. This is involuntary and has sympathetic innervations. In the bottom, you see the small hair and the lashes that have sweat and sebaceous glands associated with it. The inside of the eyelid is the conjunctiva. And infection called pink eye is of the conjunctivas. The ballbar conjunctiva palpebral. There is the superior and inferior fornix associated.
- Describe the role of the lashes and the sebaceous glands of the eyelids?
Closer you have the lashes and the sebaceous gland, and they secrete the substance that is the lipid that goes across the opening of the eye and that will prevent the tears that run down your face constantly. “Sleep” is the secretions of the tarsal plate. On the inside is the palpebral conjunctiva.
- What is conjunctivitis?
Conjunctivitis (commonly called "pinkeye") is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), often due to infection.
- What is the role of tarsal plate and tarsal gland?
-Tarsal plate is the plate of strong dense connective tissue that forms the supporting structure of the eyelids.
- Tarsal gland is one of the long sebaceous glands of the eyelids that discharge a fatty secretion that lubricates the eye. This lipid secretion prevents tears from flowing down the face, except for when you cry.
- Describe the lacrimal apparatus?
Lacremal gland is on the lateral inside of the orbit. Tears are secreted all the time, blinking moves it across the cornea. The puncta, superior and inferior drain the eyelids. They lead into the canonical and the lacrimal sack. The lacrimal sack sits in that depression, and from there you have the lacrimal duct that drains into the cavity. Bells palsy patients can’t blink their eyes. So they get ulcerated corneas.
The lacrimal glands are paired glands, one for each eye, that secrete lacrimal fluid. Each gland is about the size of an almond (2 cm) and sits alongside the eyeball within the orbit, nestled in the lacrimal fossa of the frontal bone.
The glands produce lacrimal fluid when stimulated by parasympathetic fibers of the facial nerve via the pterygopalatine ganglion. The lacrimal fluid flows through the lacrimal ducts which exit in the space between the eye and the upper eyelid. The lacrimal gland receives its blood supply from the lacrimal artery, a branch of the ophthalmic artery.
- What is tarsal chalazion?
A small circumscribed tumor of the eyelid formed by retention of secretions of the tarsal (meibomian) gland and sometimes accompanied by inflamation.
The Meibomian glands (Glandulae tarsales) are a special kind of sebaceous glands at the rim of the eyelids, responsible for the supply of sebum, an oily substance that prevents evaporation of the eye's tear film. There are approximately 50 glands on the upper eyelids and 25 glands on the lower eyelids.
Dysfunctional Meibomian glands often cause dry eyes, one of the more common eye conditions. They may also cause blepharitis, as the dry eyeball rubs off small pieces of skin from the eyelid, which can get infected. Inflammation of the Meibomian glands (also known as meibomitis, Meibomian gland dysfunction, or posterior blepharitis ) causes the glands to be obstructed by thick secretions, the resulting swelling is termed a chalazion. Besides leading to dry eyes, the obstructions can be degraded by bacterial lipases, resulting in the formation of free fatty acids, which irritate the eyes and sometimes cause punctate keratitis.
- What is a sty?
A stye (also spelled sty) is an inflammation of the sebaceous glands at the base of the eyelashes. They are harmless but can be very painful. They are generally caused by a Staphylococcus bacteria infection. They are particularly common in infants.
The stye may form on either the inside or the outside of the eyelid.
* An external stye (external hordeolum) will show as a tender, red swelling on the edge of the eyelid and will tend to drain itself quickly.
* An internal stye (internal hordeolum) will also be tender and may show external red swelling. Internal styes often take longer to heal because the abscess cannot drain as easily. These types of styes can also cause blurred vision and irritation.
- Describe bell's palsy and its effects on blinking?
Bell's palsy (facial palsy) is characterised by facial drooping on the affected half, due to malfunction of the facial nerve (VII cranial nerve), which controls the muscles of the face. Named after Scottish anatomist Charles Bell, who first described it, Bell's palsy is the most common acute mononeuropathy (disease involving only one nerve), and is the most common cause of acute facial nerve paralysis. The paralysis is of the infranuclear/lower motor neuron type. Bells palsy patients can’t blink their eyes. So they get ulcerated corneas.
- Describe the lacrimal puncta?
This is the left eye of a female. The lacrimal gland is in the upper left for the person. Kenneth corer is the carnicale. You have the palpebral and bulbar conjunctiva. The tiny hole is the inferior puncta that go to caniniculi to the lacrimal sack. You can not see the cornea; you see the iris and the sclera. The cornea has no blood vessels and it has a regular collagen arrangement. This is easy to transplant due to no blood vessels. So you have no immune response. You can transplant the cornea from anyone to anyone with no problem. Lacremal gland is lateral. The lacremal sack drains to nose as well.
Can’t see the cornea because it covers the iris and it is transparent and it has blood no vessels
Why is the cornea easy to transplant? It has no blood vessels so no immune response to it
We also see the inferior Pump duct
Lacrimal gland is lateral, so tears come across your eye in a medial manner , go inside the canaliculi, then go into the nasal lacrimal duct
- What are the 3 layers of the eye and its constituents?
a. Fibrous outer tunic: sclera and cornea
b. Vascular middle tunic
1) Choroid – outer pigmented cells; inner vascular portion
2) Cilary body – secretion of aqueous humor and ciliary muscle for controlling lens shape
3) Iris - sphincter and dilator pupillae muscles; pigmentation
c. Inner nervous tunic: retinal layer
1) Pigmented layer
2) Nervous layer including receptor cells
3) Specialized regions:
a) macula lutea and fovea centralis; area of greatest visual acuity
b) optic disk - entry of optic nerve and central vessels; "blind spot"
There Are 3 layers of the eye: fiberous, vascular and neuro. The outer CT layer is the white sclera of the eye. The bump on top is the cornea and you can see through it. The vascular layer is the choroids. That is yellow. Goes to the ciliary body then you have the iris. The vascular is choroids, ciliary is iris. The lens fibers will attach to the sides of the lens. The lens is circular and attaches to the ciliary body. In the ciliary body you have the smooth ciliary muscle that when it contracts, it cause the cilliary body to move closer to the lens, when they do that, the lens fibers relax, and are not as taught. Then the lens rounds up. Far vision is where the ciliary muscles are relaxed. Close vision is when the we accommodate for the near vision, the ciliary muscles contract, bodies move closer to the lens, fibers relax and lens rounds up. This is the parasympathetic system.
- Why can't you accomodate well when you reach 40 yrs?
The lens losses the elasticity. So when the lens fibers relax, it stays there stretched out.
- What are the 3 chambers pf the eye?
a. Vitreous - contains vitreous body
b. Posterior chamber - like anterior chamber contains aqueous humor
c. Anterior chamber
- Describe aqueous humor?
1. Secreted by ciliary process
2. Flow from posterior to anterior chambers, through Canal of Schlemm (sinus venosus) and uptake by ciliary veins
The epithelial cells secrete the aqueous humor that fills up the space between the lens and fiber and the cornea. The lens also is avascular. You always make AH, and you have the canal of schlem that the AH drains into. This is the drain the AH, drains to the scleral veins and the venous system takes it away.
- Describe glaucoma?
Aqueous humour is produced by the ciliary body of the eye, and then flows through the pupil and into the anterior chamber. The trabecular meshwork then drains the humour to Schlemm's canal, and ultimately to the venous system. All eyes have some intraocular pressure, which is caused by some resistance to the flow of aqueous through the trabeculum and Schlemm's canal. If the intraocular pressure (IOP) is too high, (>21.5 mm Hg), the pressure exerted on the walls of the eye results in compression of the ocular structures and you get glaucoma.
- Describe the eye in more detail and mention vitreous humor, and the retinal layer?
Behind the lens is the virtuous humor. 9% water. Glycosylated glycoprotein with a consistency of not well set jell-o. The retinal layer represented by the yellow.
- Describe detached retina?
. At the very bottom, you have pigmented epithelial cells that continue all around. The receptors though stop at the ora serrata. Then the pigmented epithelium. The detached retina, the nerve cell layer detaches itself from the pigmented cell layer. Therefore, Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Without rapid treatment, it can lead to vision loss and blindness.
- Describe the optic disc?
The optic disc (bracket) is the blind spot with all the axons from the nerves that make up the optic nerve. This is where it leaves with the central retina artery and vein. Any problems with these and you will go blind.
- Describe the effects of diabetes on the eye?
- Diabetics have problems with the vascularity on the eye. You get lesions in the retnal artery, and you get blood in the VH and you get more BVs and they leak and the VH had blood in. the blood clouds the VH. What they do is stick a needle in the eye you can replace the vitreous humor.
- What is macula and why is fovea centralis very important?
The depressed area is the macula. That is what Dr.s look for in your eye. The center is the fovea centralis with the highest visual acuity.
- Which layer of the retina is involved in detached retina?
The middle is the separated area where you have the detached retina. The axons of the ganglion cells make up the optic nerve. Ganglion cells are the big lumps at the left side.
- What are the 2 main categories involved in the refraction of light and what are their characteristics?
- Refraction of light
1. Refractory elements
b. Aqueous humor
d. Vitreous body
a. contraction of medial recti and convergence of eye
b. increased curvature of lens with contraction of ciliary muscles and relaxation of suspensory ligaments
c. Constriction of pupil
d. Parasympathetic control of accommodation
- Separate the extrinsic muscles of the eye into 4 categories based on their innervation?
1. Muscles innervated by occulomotor nerve (CN III) superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae
2. Muscle innervated by trochlear nerve (CN IV): superior oblique
The muscles are in this. The levator palpebri superioris is cut. Beneath it is the superior rectus. The superior, medial inferior lateral rectus. On the oblique side, you have the superior oblique muscle of the eye. You also have the inferior oblique and superior oblique. Know the innervations. SO4-LR6 the superior oblique is 4 lateral rectus is CN6, the rest are by CN3.
3. Muscle innervated by abducens nerve (CN VI): lateral rectus
4. Muscle with sympathetic innervation: superior tarsal
- Illustrate the insertion of the 6 extrinsic extraocular muscles?
The 2 obliques are inserted by aponeuroses into the postero - lateral quadrant of the eyeball. When in situ, inferior rectus passes above inferior oblique.
Label the contents of this MRI?
1 is the inferior rectus
2 is lateral rectus
3 is medial rectus
4 is the ethmoid sinuses
5 is the lacrimal gland
Label this MRI?
1 is the levator PS, 2 is superior rectus, 6 is the superior O, 5 is the medial rectus
Label this MRI?
M = Maxillary sinus
E = Ethmoidal sinus
1 = levator palpabrae superioris
2 = suerior rectus
4 = inferior rectus
5 = medial rectus
6 = superior oblique
9 = olfactory bulb
11 = nasal septum
13 = middle concha
14 = inferior concha
17 = frontal lobe
18 = tongue
- Describe the diff types of eye movements?
All of these were derived from the occipital somites. So they were GSE. CN3,4,6. your eyes are not straight forward, they are at an angle, so when they contract, it will pull the pupil up and toward the midline. The questions will bein relation to the way the pupil is looking. Inferior rectus goes down and toward the midline. The Superior oblique rotates it down and out, inferior is up and out. If the eye points down and out CN3 is not working. Lateral rectus pulls it out. On the exam: he will ask what nerve is cut. The patient uses what eye muscles to look a certain direction. you have to know that the right eye and the left eye. Be able to know that.
All the muscles were derived from somites, they are skeletal muscles and yiu have con
So GSE, CHN III, IV, and VI
Which way is the pupil staring?
Medial rectus is towards your nose
Superior oblique rotates the eye down and out
Your patient is staring straight….his right eye will use the superior oblique and
The oblique muscles rotate the eye and pull the eye muscles down and in
- So you have a patient come to you and she cannot raise her eye , can’t open her eye, and you pull open her eye and you look at it, and it is stuck in the down and out position, what cranial nerve is damaged?
(Remeber that superior oblique is still working because it is still down and out, so it is CN III that is affected not CN IV which innervates superior oblique! Because she could not open her eye with the levator palpebrae superiosis, and the only muscle that were working were SO4 LR6, so the SO which pulls the eye down and out and the LR which pulls it out so the eye is stuck to the pupils staring in a down and out position.
- Ask you a question on the exam like your patient is staring straight ahead and without moving his head you ask him to look at his fingers out here or look at a penny on the floor which eye muscles will he use?
Well, his right eye will use the Superior Oblique and lateral rectus and his left eye will use the inferior rectus and the medial rectus to get it down.
The oblique muscles rotate the eye and the pupils ends up staring and rotating down and out since the eye is pulled down and in.
- Clinical scenario where the patient comes in with a closed eye and it is stuck in the down and out position, also this eye, its pupil will be permanently dialated , why?
because the parasympathetic components of CN III are not working
- Describe the 2 classes of autononic innervation supply to the eye?
a. Ciliary ganglion
1) Preganglionic fibers reach ganglion via oculomotor nerve
2) Postsynaptic fibers travel via short ciliary nerve to sphincter pupillary and ciliary muscles
b. Lacrimal gland
1) Preganglionic fibers travel via greater petrosal and Vidian nerves to pterygopalatine ganglion where they synapse
2) Postsynaptic fibers travel via maxillary and zygomatic nerves to reach lacrimal nerve and gland
a. To dilator pupilae muscle: Postganglionic fibers arising from superior cervical ganglion and internal carotid plexus accompany nasociliary nerve and enter eye via long ciliary nerves
b. To superior tarsal muscle: Postganglionic fibers from superior cervical ganglion travel with oculomotor nerve.
c. To lacrimal gland: Postganglionic fibers from cervical ganglion; they travel along internal carotid plexus, form the deep petrosal nerve to reach nerve of pterygoid canal and join parasympathetic fibers to lacrimal nerve
- Describe the 2 categories of sensory innervatuin to the eye?
1. Optic nerve (CN II) - meningeal covering, nature of fibers
2. Lacrimal, frontal and nasociliary nerves branches of ophthalamic nerve (of CN V)
Obiques rotate the eye. Superior O. pulls it down and in. the top is the orbital plate of the frontal bone. The first nerve is the frontal nerve branch of the V1. the superorbital and trochliar supply brow. The lacrimal nerve enters the lacrimal gland. On exam: the cut muscle is the lateral rectus by the abducents nerve. This puncture could be on the exam. The + is the 4 recti
- If he pokes Mona in the eye, the reason she is able to feel it because?
Because of the fibers of the ciliary nerves branches of V1 which carry the pain that she will feel after she is poked in the eye.
What does this illustrate?
Distribution of the oculomotor (CNIII), trochlear (CNIV), and abducens (CNVI) nerves to the muscles of the yeball. Note that CN IV supplies the superior oblique, CN VI the lateral rectus, and CN III the remaining 5 muscles.
This is the same for the most part. All of these muscles attach to the sclera of the eye. Recall 3 goes to upper and lower.
What does this illustrate?
1. Optic nerve tithin its pial, arachnoid, and dural sheaths.
2. The 4 recti arising from a fibrous cuff called the anulus tendineus, that encircles : the dural sheath of optic nerve, nerve VI, and the upper and lower divisions of nerve III. The nasociliary nerve, not shown also passes through this cuff, but nerve IV clings to the bony roof of the cavity.
3. Nerves IV and VI supplying one muscle each, and nerve III supplying the remaining 5 orbital muscles: 2 via its upper division , 3 via its lower division.
4. N. III through the ciliary ganglion supplies parasympathetic fibers to the ciliary muscle and spincter iridis.
The lateral rectus is 6 inferior oblique is 4. the upper and lower divisions of cn3 do the rest.
What does this illustrate?
This is the summary of the nerve. there is the parasympathetic component that goes into the eye. The parasympathetic component will travel with the CN3. the first neuron originates in the danger westfall nucleus. This is the preganglionuc neuron. They travel with the OM nerve and synapse with the ciliary ganglia. The fibers coming off are the short ciliary nerve innervating the ciliary muscle and the constrictor pupuli. If a pation’s eye is stuck down and out the eye will be dialated all the time die to inactivity of the CN3. sympathetic nerves fiber on the carotid and go through the ciliary ganglion and do not synapse and go into the eye. In the eye they dialate the pupil and cause the vaso constriction and supply the superior tarsal muscle. The blue is the trigeminal nerve. The stump separates to 3 components. The V1 gives the sensory innervations to the eye. The main branch is the frontal nerve that splits to the supraorbital and trochliar, V2 to lacrimal nerve: sensation. The little nerve that joins it parasympathetic. The third branch of the V1 is the nasal ciliary nerve. The rest are long sensory. If you get poked in the eye, branches of V1 ciliary relay that sense. The interior go into the ethimoid sinuses. In the corner of the eye is the infra trochlior. The v1 is only sensory. The arteries are from the ophthalmic. The nasociliary and anterior and posterior ethmoidal.
This illustrates what?
All the nerve supply to the eye
- What is the artery supply of the eye?
Ophthalmic artery: branch of internal carotid
a. Orbital branches: lacrimal, supraorbital, supratroclear, posterior and anterior ethmoidal, medial palpebral, dorsal nasal, muscular branches
b. Ocular branches: central artery to retina, long and short ciliary arteries
- What is the venous system of the eye?
a. Superior ophthalmic - mainly to cavernous
b. Inferior ophthalmic - mainly to cavernous sinus and pterygoid plexus
c. Anastomoses with facial vein
NOTE: The avascular nature of cornea and lens!!!!
- Say you are picking a pimple that is on your eye, on your skin, what could happen?
you break through the vein while you are doing it, so the puss from the pimple gets into the vein so then the puss travels from the facial vein into the superior ophthalmic vein into your cavernous sinus then the next thing you know, you have inflammation of the cavernous sinus, all this from picking your pimples so this is one of the things you look out for .
Explain this patient's condition?
A patient here who is suffering from horner’s syndrome. There is damage to sympathetics of head and neck the eye has vasoconstriction in a constant state because the dilator pupillae is not working so he only has the defect of the sympathetic nervous system on one side.
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