Orbit I and II Flashcards
1
Q
What bones make up the outer rim of the orbit?
A
- Frontal
- Zygomatic
- Maxillary
2
Q
Inside of the orbit, which two bones make up the medial wall.
A
- Lacrimal bone is located on the anterior aspect of the medial wall
- Ethmoid bone makes up the majority of the medial wall.
3
Q
What makes up the Apex of the orbit?
A
The Optic Canal
4
Q
What makes up the Lateral Wall of the orbit?
A
Zygomatic Bone
Sphenoid Bone
Frontal Bone
5
Q
What makes up the Roof of the orbit?
A
Frontal Bone
Sphenoid Bone
6
Q
What makes up the Medial wall of the orbit?
A
Ethmoid Bone Lacrimal Bone Frontal Bone Maxillary Bone Sphenoid Bone
7
Q
What is the mucocutaneous junction?
A
Is a junction where the outermost layer of the skin around the eyelid becomes continuous with the palpebral conjuctiva.
8
Q
What is the palpebral conjuctiva?
A
It is the mucos membrane on the inside of the eyelid.
9
Q
What is the function of the orbital (bulbar) conjuctiva?
A
It serves as a protective covering for the eye itself.
10
Q
Does the palpebral conjunctiva become continous with the orbital (bulbar) conjuctiva?
A
Yes.
11
Q
What is the palpebral fissure?
A
It is the space between the upper and lower lids, bounded by the upper an lower palpebral margins.
12
Q
Where do the palpebral margins meet?
A
At the canthi (angles)
Medial canthus
Lateral canthus
13
Q
What are the seven layers associated with the eyelid?
A
- Skin
- Subcutaneous connective tissue
- Muscular layer
- Submuscular layer
- Tarsal Plate
- Tarsal Glands
- Palpebral Conjunctiva
14
Q
What is Horner’s Syndrome?
A
It is a lesion to the superior cervical sympathetic ganglion.
15
Q
What does Horner Syndrome result in? What will the patient present with?
A
It results in paralysis of the Tarsal muscles on the effected side.
The patient will present with:
Ptosis
Meiosis
Anhydrosis
16
Q
What is Ptosis?
A
Drooping of the eyelid
17
Q
What is Meiosis?
A
Small pupil
18
Q
What is Anhydrosis?
A
Lack of sweating and reddening of the skin on the affected side.
19
Q
What is the larger medial angle of the eye known as?
A
The lacrimal lake
20
Q
What is the lacrimal caruncle?
A
It is the fleshy elevation seen in the medial angle of the eye within the lacrimal lake.
21
Q
What does the lacrimal caruncle contain?
A
Sweat glands
Sebaceous glands
Cilia
These glands are responsible for the yellow and white secretion sometimes found in the eye upon arising after a nights sleep.
22
Q
Plica semilunaris
A
A connective tissue band that separates the sclera from the lacrimal lake
23
Q
Where is the lacrimal gland located?
A
At the superolateral aspect of the orbit
24
Q
Components of the lacrimal gland?
A
Palpebral portion - lies close to the eye on the inner surface of the eyelid. it can be seen if the eye is everted.
Orbital portion- Portion that contain the interlobular ducts.
25
What is the route of tear secretion.
Tears secreted from the gland collect in the superior fornix of the upper lid, and pass over the eye surface.
Blinking aids in this process.
26
What kind of cells exist in the lacrimal gland. What do they secrete? What is the function?
Serous cells that secrete a watery solution of bacteriocidal enzyme lysozymes.
It provides nutrients and dissolved oxygen to the cornea
27
1. Puncta larimali
2. Lacrimal canaliculus
3. Lacrimal sac
4. Nasolacrimal duct
1. Drain opening
2. Duct
3. Collection of fluid
4. Drainage to nasal sinus
28
The motor fibers to the lacrimal gland are what in nature? Where do these fibers arise from?
Parasympathetic. They arise from the 7th cranial nerve
29
What is the specific branch of CN VII that travels to the lacrimal gland?
The greater petrosal nerve.
30
What is the course of the greater petrosal nerve?
The greater petrosal nerve courses within the hiatus for the facial nerve to the middle cranial fossa.
It continues across the foramen lacerum where it is met by the deep petrosal nerve. Together these two nerves form the nerve to the pterygoid canal.
The nerve to the pterygoid canal passes through the pterygoid canal it then courses into the pterygoid fossa to the pterygoplatine ganglion.
The postganglionic parasympathetic fibers then rejoin with the sympathetic fibers and then join the maxillary nerve (V2) and follows its zygomaticotemporal branch anteriorly.
These fibers then join the lacrimal branch of (V1) and follow it to the lacrimal gland.
31
What type of fiber does the deep petrosal nerve carry?
Sympathetic fibers
32
What two nerves make up the nerve to the pterygoid canal?
The greater petrosal nerve and the deep petrosal nerve.
33
What nerve synapses in the pterygopalatine ganglion?
Only the parasympathetic fibers of the greater petrosal nerve.
34
Which muscles originate from the anulus tendineus?
The recti muscles:
1. Superior rectus
2. Inferior rectus
3. Medial rectus
4. Lateral rectus
The anulus tendineus is medially placed and therefore the muscles must travel laterally as well as anteriorly to reach the eye.
35
Which muscles do not originate from the anulus tendineus? Where do they originate from
1. Superior oblique : Sphenoid
2. Inferior oblique : Maxilla
3. Levator palpebrae supeiroris : Sphenoid
36
What is the anulus tendineus?
A fibrous ring which encircles the junction of the superior and inferior orbital fissures and the optic canal (optic nerve).
37
Are all 6 extraocular muscles functioning at all times?
Yes!
38
What are the division of the occulomotor nerve?
Superior division
| Inferior division
39
What muscle does the superior division of the occulomoter nerve innervate?
1. Levator palpebrae superioris
| 2. Superior Rectus
40
What muscle does the Inferior division of the occulomoter nerve innervate?
1. Medial Rectus
2. Inferior Rectus
3. Inferior Oblique
It also carries parasympathetic fibers to the ciliary ganglion.
41
Which division of the occulomotor nerve carries parasympathetic fibers to the ciliary ganglion?
Inferior division
42
What oculomotor muscle does the trochlear nerve innervate?
Superior oblique muscle
43
What oculomotor muscle does the abducent nerve innervate?
Lateral rectus muscle
44
What is the "chemical" mneumonic for occulomoter muscles and their nerve innervations?
LR6, SO4, AO3
45
Which occulomoter muscle abducts the eye?
The Lateral rectus muscle
46
What type of information does the optic nerve provide?
Sensory information for vision from the retina to the CNS
47
What nerve is the largest nerve in the orbit.
Hint: It is covered by meninges
The optic nerve
48
What type of information does the opthalmic nerve provide?
It supplies sensory information to the orbit and external eye.
49
What are the three main branches of the opthalmic nerve?
1. Lacrimal nerve
2. Frontal nerve
3. Nasociliary nerve
50
What are the two branches of the frontal nerve?
1. Supratrochlear nerve
| 2. Supraorbital nerve
51
What are the branches of the Nasociliary nerve?
1. Communicating branch to the ciliary ganglion
2. Long ciliary nerves
3. Posterior ethmoidal nerve
4. Anterior ethmoidal nerve
5. Infratrochlear nerve
52
What type of information does the lacrimal nerve provide?
1. sensory innervation to the lacrimal gland
2. Sensory innervation to the lateral aspect of the eye
3. Sensory information to the upper and lower palpebrae
53
What type of information does the supratrochlear nerve provide?
supplies sensory innervation to the skin above the medial canthus and a portion of the scalp.
54
What type of information does the supraorbital nerve provide?
supplies the superior palpebra and the scalp above. Note that the supraorbital nerve is a direct continuation of the frontal nerve that exits the orbit via the supraorbital foramen
55
What foramen does the supraorbital nerve exit through?
The supraorbital foramen
56
What nerve is the terminal branch of the nasociliary nerve?
Infratrochlear nerve
57
Where is the ciliary ganglion located?
Between the optic nerve and the lateral rectus muscle.
58
What type of fibers run through the ciliary ganglion?
1. Sensory and sympathetic fibers run through the ganglion without synapsing in it.
2. Parasympathetic fibers from the oculomotor nerve also reach the ganglion and they are the ONLY ones that synapse there.
59
What connects the cilliary ganglion to the posterior aspect of the eye?
Hint: They therefore supply all three modalities to the eye: parasympathetic, sympathetic, and sensory)
The short ciliary nerves
60
How do sympathetic fibers reach the eye?
short and long ciliary nerves
61
Where do parasympathetic fibers originate?
| Where do sympathetic fibers originate?
1. Edinger-Westphal nucleus
| 2. Superior Cervical ganglion
62
What innervates the dilator pupillae muscle (dilate pupil)
Sympathetic fibers
63
What is the parasympathetic function in the eye?
Constriction of the pupil (Spincter muscle)
| Focus on near objects (Contraction of the ciliary muscle)
64
What are all of the nerves of the orbit?
```
Optic nerve II
Oculomotor III
Trochlear IV
Trigeminal V1
Abducent VI
Sympathetics
Parasympathetics
```
65
What arteries supply the orbit?
```
Lacrimal
Central Retina
Long and shorty ciliary
Supraorbital
Anterior ethmoidal
Posterior ethmoidal
Supratrochlear
```
Meningeal branches
Medial and Lateral palpebral
Dorsal nasal
66
Venous drainage of the orbit?
Venous drainage takes place through the superior and inferior opthalmic veins. They pass through the superior orbital fissure and enter the cavernous sinus.
67
What is the function of the cornea of the eye?
It is responsible for primary refraction and focusing of light entering the eye.
It roughly focuses an image on the eye.
68
What is the function of the lens of the eye?
It is responsible for secondary focusing of objects onto the retina.
69
What is the function of the iris of the eye?
It controls the amount of light falling onto the retina
70
What is the function of the autonomic nervous system of the eye?
It controls focusing of images onto the retina, and the amount of light entering the eye via its connections to smooth muscles located in the iris and the ciilary body.
71
How many chambers do we have? Where are they located?
1. Anterior Chamber - located between the cornea and iris
2. Posterior Chamber- located between the iris and the lens
3. Postremal (vitreous) Chamber- Is located behind the lens.
72
Which chamber of the eye is filled with aqueous humor?
The anterior and posterior chambers
73
Which chamber of the eye is filled with vitreous humor?
The postremal chamber
74
What are the three layers of the eye? In order from superficial to deep.
1. Sclera
2. Choroid
3. Retina
75
Which eye layer is the posterior 5/6ths of the eye
| Hint: It is opaque?
The sclera
76
Which portion of the eye provides insertion for the extra-ocular muscles?
The sclera
77
Where is the sclera thickest? Where is it thinnest?
It is thickest at the posteriorly and thinnest at the coronal equator of the globe.
78
Which eye layer is the anterior 1/6ths of the eye?
| Hint: It is transparent
The cornea
79
What is the cornea-scleral junction known as? What is it marked by?
The limbus. It is marked by a shallow depression
80
If the cornea is an avascular structure, how is it maintained?
It is maintained by diffusion of metabolites from the aqueous humor and by the blood vessels of the limbus.
Some oxygen is also derived directly from the external environment.
81
What is the Tenon's capsule?
a dense layer of connective tissue that comes in contact with the cinjunctiva at the junction of the sclera and the cornea.
82
Which part of the eye has a smaller radius or curvature? The sclera or the cornea?
The cornea
83
What layer of the eye is the Uveal layer considered? What three components is it made up of?
It is considered the middle layer: It is a highly vascular layer which is made up of three components
1. Choroid
2. Ciliary body
3. Iris
84
The sphincter pupillae muscle and the dilator pupillae muscles are muscles within what structure? What nervous system are they regulated by?
The exist in the iris:
Sympathetic = dilator pupillae
Parasympathetic = Sphinctor pupillae
85
What structure of the eye divides the anterior chamber from the posterior chambers
Largely the Iris
86
Which ligament adjust the shape of the lens?
The suspensory ligament of the lens aka Zonular fibers
87
What are the two structures that are attached to the suspensory ligament?
The cilliary body and the capsule of the lens
88
What is the main function of the ciliary muscles?
It permits the fine focusing of images onto the retina by adjusting the suspesory ligaments which are attached to the lens of the eye
89
What nerve innervates the ciliary muscles?
The parasympathetic nerve fibers of CN III via ciliary ganglion.
90
What type of muscle is ciliary muscle?
Smooth muscle
91
How is the ciliary muscle arranged around the lens?
Circumferentially
92
What happens when the ciliary muscles contract?
When the ciliary muscles contract the tension on the suspensory ligaments is actually reduced. Which means it allows the lens to take on a more globular, thickened and rounded form. (i.e parasympathetic)
93
If we want near vision instead of far vision what will happen to the ciliary muscles?
The ciliary muscles will contract. Causing less tension to be applied to the suspensory ligaments thus thickening the lens.
94
There is a double layer of cuboidal epithelium around the ciliary body.
Which layer is highly pigmented.... and is a continuation of pigmented epithelial layer of the retina
Deep layer
95
There is a double layer of cuboidal epithelium around the ciliary body.
Which layer is not pigmented. Non-photosensitive and is an extension of the receptor layer of the retina
Surface layer
96
What are ciliary processes?
Ciliary processes are epithelial folds of the ciliary body that contain a connective tissue core rich in fenestrated capilaries
97
What is the function of a ciliary process?
They function to produce aqueous humor which circulates into the anterior chamber via the pupil.
98
Why are balanced rates of secretion and absorption of aqueous humor important?
It is responsible for the maintenance of a constant intra-ocular pressure of about 15mm off mercury which stabalizes the lens and cornea.
The flow also provides for a continuous exchange of metabolites to the cells of the AVASCULAR cornea and lens
99
How is the aqueous humor reabsorbed?
It is reabsorbed at the angle of the anterior chamber into the canal of schlemm.
100
Character of Aqueous humor fluid
Similar in composition to the CSF and hypotonic with respect to the plasma.
101
what is the most common cause of blindness?
Glaucoma
102
What is Glaucoma a result of?
Increases intraocular pressure that compresses the retina, optic nerve and blood vessels. If chronic this can result in eventual blindness.
103
What are the symptoms of Glaucoma?
Blurred vision or halos around bright objects
104
What is the most anterior part of the uveal layer of the eye? Where does it arise from?
The Iris. It arises from the ciliary body and forms an adjustable diaphragm in front of the lens.
105
Where does the pupillary edge of the iris rest on the lens?
The anterior edge of the lens
106
What orientation does the constrictor muscles of the pupil consist of? What autonomic innervation exist? What is the name of the muscle?
Circumferentially oriented smooth muscle with parasympathetic innervation.
Constrictor pupillae muscle
107
What orientation does the dilator muscles of the pupil consist of? What autonomic innervation exist? What is the name of the muscle?
Radially oriented with sympathetic nerve innervation
Dilator pupillae muscle
108
From what structure does the Dilator pupillae muscle originate?
The deep layer pigmented in the ciliary body is transformed in the iris into non-pigmented Myoepithelial cells.
109
What is the lens enclosed by?
A homogenous capsule rich in glycoprotein which is a specialized remnant of the epithelial basement membrane.
110
What are some properties of the lens?
Elastic, Biconvex, and almost entirely composed of living cells.
111
What kind of epithelial cells is the mature lens composed of?
Extremely elongated cells that have lost their nuclei but are still able to undergo cytoplasmic metabolism at low rates.
112
What do lens fibers contain?
A crystalline protein which allows cell membranes of adjacent fibers to fuse leaving little intervening extracellular substances to intervene.
113
Are there any action potentials in the rods or the cones?
No.
114
When does the first action potential take place?
In the axon of the ganglion cells
115
How many histologiclly zones are the retina divided into? How many functional groups are there
10 histological zones
| 5 functional groups of neurons
116
What does the outermost cell layer of the retina consist of?
Pigmented epithelial cells that lie on the choroid.
117
Inner limiting membrane of the retina:
| What does the outer layer of the retina consist of?
It lies adjacent to the pigmented epithelial cells and it consist of rod and cone receptor cells.
118
Inner limiting membrane of the retina:
| What does the intermediate layer of the retina consist of?
It consist of a network of interneurons and bipolar cells. It integrates sensory inputs from the receptor cells before transmission to the CNS.
119
Inner limiting membrane of the retina:
| What does the innermost layer of the retina consist of?
Comprises the ganglion cells.. the axons of which combine to form the optic nerve.
120
What integrates sensory inputs from the receptor cells before transmission to the CNS.
The intermediate layer of the retina cells from the Inner limiting membrane of the retina:
121
Rods or Cones?
| High sensitivity specialized for night vision
Rods
122
Rods or Cones?
| Most sensitive to direct Axial stimulation
Cones
123
Rods or Cones?
| More sensitive to scattered light
Rods
124
Rods or Cones?
| Achromatic photopigment
Rods
125
Rods or Cones?
| Saturated in the day light
Rods
126
Rods or Cones?
| Low temporal resolution; slow response, long intergration time
Rods
127
Rods or Cones?
| Less photopigment per cell
Cones
128
Rods or Cones?
| Less amplification per cell
Cones
129
Rods or Cones?
| Low sensitivity specialized for daylight division
Cones
130
Rods or Cones?
| High sensitivity specialized for night vision
Rods
131
Rods or Cones?
| Chromatic. (How many)
Cones
| 3 types of cones each with a pigment sensitive to a different part of the visible spectrum of light.
132
Rods or Cones?
| Saturated only in intense light?
Cones
133
What are Muller Cells?
Muller cells are the fifth function group of cells considered support cells.
134
What cells form the blood-retinal barrier?
The tight junctions between the muller cells.
135
What structure receives direct axial stimulation?
The fovea
136
What are the layers of the retina?
```
Pigment epithelium
Roda and cones
Outer nuclear layer
Inner nuclear layer
Ganglion cell layer
Retinal blood vessels
```
137
The fovea consist of almost exclusively what cell? What is the ratio of ganglion cells to photoreceptors?
Cones.
| There is an almost one to one ration of ganglion cells to photoreceptors.
138
What structure is devoid of photoreceptors and is thus referred to as the blind spot of the eye?
Optic Disc.
139
Afferent fibers from what structure converge to form the optic nerve?
How does the optic nerve leave the eye?
Afferent nerve fibers from the retina.
| They leave through a part of the sclera known as the lamina cribrosa.
140
What is the lamina cribrosa?
An area wof the sclera where the optic nerve leaves the eye.
141
What is the name of the retina overlying the lamina cribrosa?
Optic disc
142
Blood supply of the eye?
opthalmic artery via the Retinal and uveal systems.
143
What artery supplies blood to the retina?
Central artery of the retina
144
What artery supplies blood to the uvea?
Branches of the opthalmic artery
145
Venous drainage of the retina?
via the central vein of the retina which normally drains directly into the cavernous sinus ( but may join the ophthalmic veins)
