Anatomy Flashcards
Describe first order sympathetic innervation
pre-ganglionic fibers begin in the hypothalamus -> descend to C8-T2 region of the spinal cord to synapse in the ciliospinal center of budge
Describe 2nd order sympathetic innervation
2nd order pre-ganglionic fibers leave the ganglion and travel around the clavicle across the apex of the lungs before entering the chain of ganglia along the neck > fibers ascend the chain and synapse in the superior cervical ganglion
Post-ganglionic fibers from the superior cervical ganglion form a plexus around the internal carotid artery and enter the skull via carotid canal
What causes Horner’s syndrome?
Pancoast tumor of the lungs can affect pre-ganglionic sympathetic fibers
What does the sympathetic fibers innervate?
- Mueller’s muscle
- Follows V1 and branch with either SPCNs or LPCNs
LPCNs carry sympathetic innervation to iris dilator and the ciliary muscle
sympathetic fibers passes CG and exit w/ SPCNs to innervate choroidal and conjunctival blood vessles
- blood vessels of lacrimal gland through vidian nerve
What synapses at the CG?
parasympathetic
What are the 3 roots that enter the CG
- parasympathetic (the only one that synapses
- sympathetic (passes only)
- sensory (pass only)
Hyperactive sympathetic innervation of blood vessels can develop what?
Central serous chorioretinopathy
contributes to localized damage of bruch’s membrane
What is the optic nerve composed of?
axons of ganglion cells
what are the 4 destinations of the optic nerve
midbrain, LGN, superior colliculus and hypothalamus
Which space contains the cerebrospinal fluid?
subarachnoid space - between the arachnoid and pia sheaths
Why does disc margins appear blurry with papilledema
increase intracranial pressure (ex. space occupying lesion, malignant HTN) that causes CSF within the subarachnoid space to leak over the superficial optic disc. Disc margins are blurred because the CSF spreads over the margins surrounding the RNFL
Oligodendrocytes
provide myelination to the axons posterior to the lamina cribosa
Astrocytes
provide structural support to the optic nerve axons
Optic nerve sheath is also attached to which EOMs?
SR and MR which is probably why pts with optic neuritis experiences pain with eye movements
Retinal RNFL is supplied by what?
SPCAs and CRA
Intraocular ON (pre-laminar layers) are supplied by what?
Circle of Zinn (formed by anastomoses of SPCAs) and other branches of SPCAs
Intraorbital ON (post-laminar) is supplied by what?
CRA and pial mater arterial plexus
Intracranial ON is supplied by what?
branches of the ophthalmic, anterior cerebral, anterior communicating, and internal carotid arteries
Autoregulation occurs where?
optic nerve and retina
What is the disc size vertically and horizontally?
1.75mm vertically
1.50mm horizontally
Why does the ON acts as a blind spot?
because it does NOT contain photoreceptors
Which cells are not present in the optic nerve?
Mueller cells, instead astrocytes cover the optic disc and forms the ILM of elschnig
how long is the optic nerve?
50-60mm long
intraocular, intraorbital, intracanalicular,
intracranial
How long is the intraocular portion of the ON?
1mm
What separates the retinal tissue from the optic nerve?
intermediary tissue of kuhnt
scleral ring that defines the margin of the ONH
border tissue of elschnig
How long is the intraorbital portion of the ON?
30mm
S-shaped, myelinated by oligodendrocytes
How long is the intracanalicular ON
6-10mm
How long is the Intracranial ON?
10-16mm
Fibers in the ON travel to which 4 locations?
LGN, superior colliculus, pretectal nucleus, hypothalamus
Papillomacular bundle damage can cause what kind of VF defects?
central, centralcecal, and paracentral VF defects
Which rim of the ON is thinnest to thickest?
ISNT
inferior rim is thickest
Anterior knees of willbrand
Inferior nasal fibers that cross through the optic chiasm and then loop anteriorly into the contralateral optic nerve before entering the optic tract
Posterior knee of willbrand
superior nasal fibers that loop posteriorly into the ipsilateral optic tract before crossing through the chiasm
Where is the optic chiasm located?
within the circle of willis and above the pituitary gland
Where does the optic tract extend from?
optic chiasm to the LGN
Where is the LGN located?
thalamus
Which layers contain the following?
- Magnocellular layer
- Parvocellular layer
- Koniocellular layer
- 1 and 2
- 3-6
- contain small cells between each layer
Crossed fibers of the optic tract synapse to which LGN layer?
1,4,6
Uncrossed fibers of the optic tract synapse to which LGN layers?
2,3,5
Where do superior, inferior and macular fibers synapse in the LGN?
SMIL
Superior synapse in the medial LGN
Inferior synapse in the lateral LGN
Macular fibers form a wedge of synapse at the dorsal edge of the LGN and extend throughout its entire thickness
LGN receive fibers to help fine tune visual information that is related to the primary visual cortex
fibers from the subcortical areas and the primary visual cortex
optic radiations
fibers that leave the LGN and travel to the primary cortex
Where does the inferior radiations travel?
Inferior radiation is composed of inferior retinal fibers from the lateral side of the LGN
These fibers travel through the temporal lobe and around the tip of the lateral ventricle into the parietal lobe (forming meyers loop) before terminating in V1 in the occipital lobe
“Lower fibers = Laterally & forms meyers loop before ending in the lingual gyrus “
Superior radiations travel where?
Superior radiations are composed of superior retinal fibers from the medial side of the LGN These fibers course directly posterior through the inferior parietal lobe before terminating in V1 in the posterior portion of the occipital lobe
What divides the occipital lobe to inferior and superior portions?
What are the 2 portions called?
calcarine fissure
cuneus gyrus superior retinal fibers terminate here
Lingual gyrus (inferior retinal fibers terminate here)
Where does the macula fibers project to in the occipital lobe?
outer surface of the apex of the occipital lobe and make up 50% of the fibers within V1
superior macular fibers project to cuneus gyrus and inferior projects to lingual gyrus
Layer 4 of V1
location of synapse between the optic radiation and neurons of the striate cortex
fibers from the parvo and magnocellular layers of LGN synpase in different strata within layer 4
Axons projecting from the neuron within this layer of V1 travel to higher cortical areas (V2-V5) for further visual information processing
Layer 5 of V1
sends axon to superior colliculus for control of saccadic eye mvmts
Layer 6 of V1
provides feedback info back to LGN
Binocular processing of visual info begins at which level?
primary visual cortex
What is the optic chiasm supplied by?
circle of willis and branches of the ICA
What is the optic tract supplied by?
anterior choroidal branch of middle cerebral artery
What is the LGN supplied by?
anterior choroidal and posterior cerebral arteries
What is the optic radiations supplied by?
anterior choroidal, middle cerebral, and posterior cerebral arteries
What is the primary visual cortex supplied by?
posterior cerebral artery and the middle cerebral artery
What serves as the dual blood supply in the primary visual cortex?
posterior cerebral and medial cerebral
Tumor = knocks out both
stroke = macular sparing
postchiasmal lesions will cause what kind of VF defect?
homonymous
What is the VF defect if the lesion is located more posterior and post-chiasmal
congruous
Ex. occipital lobe lesions
Where are incongruous VF defects usually located
anterior to the chiasm
Temporal lobe lesions cause what kind of VF defects?
superior, pie in the sky
remember that a lesion in the temporal lobe damages the inferior retinal fibers forming meyer’s loop
PITS
Parietal lobe lesions cause what kind of VF defects?
pie on the floor
remember that lesions in the parietal lobe damages the superior retinal fibers (also associates with asymmetric OKN response)
PITS
Lesion in the optic chiasm can result in which 2 VF defects?
Bitemporal hemianopsia and junctional scotoma
Lesion in the pituitary gland causes what kind of VF defect?
bitemporal hemianopsia
Lesion in the anterior knee of willbrand will cause what kind of VF defect?
junctional scotoma = central vision loss and superior temporal loss in the fellow eye
Glaucoma respects which VF midline?
horizontal, anterior the chiasm
Neurological conditions respects which VF midline?
Vertical
Ex. strokes
90% of homonymous hemianopsia are secondary to strokes except macula only homonymous hemianopsia which are rarely caused by strokes (think compressive lesion
What hormones are released from the anterior pituitary?
FAT PiG
FSH/LH
ACTH
TSH
Prolactin
GH
What is the pituitary gland stimulated by?
Hypothalamus
Important role for T3 & T4
metabolism, released by the thyroid gland
Prolactin
milk production, released but anterior pituitary
Oxytocin
- milk ejection
- released by posterior pituitary
Gonadotropins
- FSH/LH
- released by anterior pituitary
- Testes = FSH and LH help produce testosterone
- Ovaries = FSH and LH help produce estrogen and progesterone ( FSH stimulate menstruation cycle, LH ejects egg from ovary)
Adrenocorticotropic hormones (ACTH)
Stimulates release of
- Mineralcorticoids (aldosterone) = helps reabsorb sodium into the body, water follows (stress to raise BP)
- Glucocorticoids (cortisol) = release glucose into blood stream to utilize as energy (as well as growth and development, etc)
Growth hormone
- bones and muscles to grow
- IGF-1 release from liver = strong muscle growth
What does the posterior pituitary release?
Oxytocin = uterine contraction + milk ejection
ADH = stop release of water, hold on to water, maintain hydration
Rectus insertion farthest to closest to the limbus
SLIM
SR = 7.9
LR = 6.9
IR = 6.8
MR = 5.3
What causes an autoimmune response against the connective tissue and adipose tissue within the orbit?
Thyroid-related ophthalmopathy
What symptoms does thyroid-related ophthalmopathy cause?
ptosis, EOM restrictions, & possible optic nerve compressions
Adipose tissue is separated into what 2 compartments relative to the location of the EOMs?
-
Intraconal - adipose tissue located WITHIN the muscle cone of the four recti muscles & serves to separate them from the optic nerve
- Extraconal - adipose tissue located OUTSIDE the muscle cone between EOMS & walls of the orbit
Where do the EOMs attach to?
sclera
What are the 3 unique characteristics of EOMs compared to typical skeletal muscle fibers?
- Blood supply is denser in EOMs
- Nerve supply is denser and more finely tuned in EOMs
- EOM mvmts are faster & more fatigue-resistant due to a unique combination of white (fast) and red (slow but sustaining) muscle fibers
Where does the superior rectus originate from?
Common tendinous ring (aka annulus of zinn) - inserts 7.7mm from the limbus
The sheath of the superior rectus is connected to what, why is this important?
superior levator palpebrae & the superior conjunctival fornix, this ensures that the lid is raised when the eye is in upgaze
Where does the inferior rectus originate from?
Common tendinous ring at the infraoptic tubercule and inserts 6.5mm from the limbus
The inferior rectus sheath combines with ___ and forms ____, why is this important?
IO sheath to form the suspensory ligament of Lockwood. It attaches to the inferior tarsal plate and extends from the zygomatic bone of the lateral wall to the lacrimal bone of the medial wall to provide support for the globe
Where does the medial rectus originate from?
Common tendinous ring and inserts 5.5 mm from the limbus. The medial check ligament anchors the MR to the medial orbital septum, the bone behind the posterior lacrimal crest, the caruncle, and the plica semiluminaris
Spiral of Tillaux
SLIM (Furthest to closest from the limbus)
Where does the superior oblique originate?
lesser wing of the sphenoid bone & the CTR - it travels anteriorly before looping through the trochlea to insert on the superior lateral globe behind the equator. The trochlea is considered the physiologic origin of the SO because it changes its direction of action.
Where does the inferior oblique originate?
Originates ANTERIORLY at the maxillary bone posterior to the medial orbital rim and lateral to the nasolacrimal canal. It inserts on the inferior lateral globe behind the equator.
All the EOMs originate at the CTR EXCEPT?
IO
All EOM tendons pierce what?
Tenon’s capsule, which sends a “sleeve” of connective tissue with the tendon for a short distance before it merges with the sclera
Name the primary, secondary, and tertiary actions for each EOM
SIN RAD
What are the primary actions for obliques?
torsion
The eyes always ADduct __ degrees towards the midline
60 deg
The eyes always ABducts __ degrees away from the midline
23 deg
If the patient has a RIGHT MLF lesion, what should you see?
Right eye CANNOT ADDuct
left eye nystagmus (opposite side of lesion)
MLF lesions are typically seen in which patients?
MS
Which artery supplies the EOM?
- Superior lateral branch supplies the SR, LR, SO
- The inferior medial branch supplies the MR, IR, and IO
- The lacrimal, supraorbital, and infraorbital arteries may provide a minor blood supply to the EOMs
What is the orbital fascia (aka periorbita or orbital periosteum) composed of?
It is composed of dense connective tissue that covers the bones of the orbit
What is the purpose of the orbital fascia?
provides support to the blood vessels within the orbit and serves as a point of attachment for muscles, tendons, and ligaments
The orbital fascia continues with..?
- periosteum of the skull and bones of the face, within the optic canal is continuous with the dura mater surrounding the brain & optic nerve and also contributes to the formation of CTR
- A portion of the fascia covers the lacrimal gland, lacrimal sac, and contributes to the lining of the nasolacrimal canal
The anterior of the orbital fascia forms what?
orbital septum within the upper and lower eyelids and acts as a barrier, preventing prolapse of orbital fat and orbital infections
Where does the optic nerve lie relative to the sphenoid bone?
laterally
Where is the sphenoid bone located?
Center & forms the base of the cranium
Center & forms the base of the cranium
sella turcica - depression body of the sphenoid
Where does the optic chiasm lie relative to the pituitary gland?
superior to the pituitary gland
Tumor of the pituitary gland can cause what visual field defect?
Bitemporal hemianopsia
What projects from each side of the body of the sphenoid?
Greater wing & lesser wing
The greater wing contains what three foramina?
- Foramen Rotundum (Rotwondum) - passage for the maxillary division (V2) of the trigeminal nerve
- Foramen Ovale (Ov3ale) - Passage for the mandibular division (V3) of the trigeminal nerve and the lesser superficial petrosal nerve
- Foramen Spinosum - Passage for the middle meningeal artery
Opening between the greater and lesser wing?
Superior orbital fissure (SOF) - located btw the posterior lateral wall and the superior wall of the orbit
Where does the cavernous sinus lie?
posterior to the SOF within each eye and travels on the sides of the sphenoid body
Where is the common tendinous (aka annulus of Zinn) ring located?
just anterior to the superior orbital fissure - and serves as the origin of the recti muscles
What passes through the SOF and CTR?
“NOA NERVES” - Nasociliary, oculomotor, abducens nerve - the sympathetic root of the ciliary ganglion travels with the nasociliary nerve as it passes through SOF and CTR
What passes ABOVE the SOF and CTR?
“LFTs”
Superior ophthalmic vein, frontal nerve, lacrimal nerve, and the trochlear nerve
What passes through the inferior orbital fissure and the inferior to the CTR?
Inferior ophthalmic vein (and occasionally the central retinal vein if it has not yet joined with the ophthalmic vein)
What goes through the optic canal (optic foramen)
optic nerve and ophthalmic artery
what goes through the carotid canal?
ICA and sympathetic plexus
What goes through the supraorbital foramen?
supraorbital nerve (part of V1) and vessels (supraorbital artery & vein)
What goes through the infraorbital foramen?
Infraorbital nerve (part of V2) and vessels (infraorbital artery & vein)
What goes through the mandibular foramen?
Inferior alveolar nerve and vessel
What goes through the stylomastoid foramen?
facial nerve
What makes up the roof of the orbit?
“FRONT LESS” - Frontal bone (majority of roof) & lesser wing of the sphenoid bone
What makes up the floor of the orbit?
“My pal gets his z’s on the floor” = maxillary (majority of orbital floor), palatine, zygomatic
What is the weakest wall of the orbit?
Floor - orbital floor fractures can cause eye to drop down into the maxillary sinus, leading to muscle entrapment and enophthalmos
What is the medial wall comprised of?
“SMEL” - ethmoid, lacrimal, and maxilla bones and the body of the sphenoid
Thinnest and smallest wall of the orbit?
Medial wall
What can cause orbital cellulitis?
ethmoid bone (aka lamina papyracea) - infection in the sinus cavity can often spread to the orbit through very thin lamina papyracea
Strongest wall of the orbit?
Lateral wall - “GREAT-Z” - greater wall & zygomatic
All walls have sphenoid EXCEPT?
Floor; remember “2-2-3-4 all have sphenoid except the floor”
- The superior and lateral walls are comprised of 2 bones, the floor by 3, and the medial wall has 4 bones.
What is the most common benign orbital tumors in adults?
Cavernous hemangioma
What is the most common benign orbital tumors in children?
Capillary hemangioma
The common carotid artery divides into what?
Internal and external branch
The external carotid supplies which structures?
Head, neck, and a small portion of the eye
Facial artery travels (external carotid) where? what does it supply?
branches at the angle of the mandible and travels across the mandible and cheek towards the medial canthus of the eye - the angular artery is the terminal branch of the facial artery that communicates with the dorsal nasal artery (from the ophthalmic artery) and supplies the medial canthus
Maxillary artery (external carotid) travels where, what does it supply?
- A terminal branch of the external carotid artery that begins just anterior to the ear in the parotid gland
- The infraorbital branch of the maxillary artery enters the orbit through the inferior orbital fissures and supplies the IR and IO.
Branches of the external artery
“Some ancient lovers find old positions more stimulating”
- superior thyroid
- ascending pharyngeal
- lingual
- facial
- occipital
- posterior auricular
- maxillary
- superficial temporal
Where does the Maxillary artery exit?
through the infraorbital foramen and supplies the lower eyelid and the lacrimal sac before joining the angular artery (from the facial artery of the external carotid) and the dorsal nasal artery (from the ophthalmic artery)
Where does the superficial temporal artery arise?
The second terminal branch of the external carotid artery that arises within the parotid gland
What does the superficial temporal artery supply?
It has 3 branches that supply the superficial skin, muscles, and soft tissue around the face and orbit - communicate with branches from the ophthalmic artery
Giant cell arteritis (aka temporal arteritis) is an inflammation of..?
large and medium-sized vessels
Damage to the short posterior ciliary arteries (SPCA/circle of Zinn) leads to what?
AAION
- suffocation and irreversible damage to the optic nerve head and results in a significant loss of vision. This can quickly spread to the fellow eye if not promptly treated with oral corticosteroids and is considered an ocular emergency.
What branches of the internal carotid artery?
Ophthalmic
Where does the ICA travel?
Through the petrous portion of the temporal bone and travels directly into the cavernous sinus
Which CN surrounds the ICA? (3)
CN 6 travels alongside ICA as it courses through the cavernous sinus, CN 3 is lateral, and CN 2 is medial to the ICA just before it exits the sinus
What is the first branch of the ICA?
Ophthalmic artery
An internal carotid artery aneurysm will most likely affect which CN?
CN 6
What are the branches of the ophthalmic artery?
DR MCLESSI or CL MS LSE
- Central retinal artery (CRA)
- Lacrimal Artery
- Muscular Artery
- SPCA
- LPCA
- Supraorbital Artery
- Ethmoid Artery
What does the CRA supply?
inner 2/3 of the retina - enters the optic disc slightly nasal to the center
What does the lacrimal artery supply?
LR and lacrimal gland - terminates at the lateral palpebral artery, which supplies the lateral inferior and superior lids - the lateral palpebral ateries anastomose with the medial palpebral arteries (from dorsal nasal artery) to from the palpebral arcades of the eyelids
What does the muscular artery supply (2 branches)?
- Provides blood to the extraocular muscles via 2 branches
1. superior lateral muscular artery supplies LR, SR, SO, and the levator muscle
2. The inferior medial muscular artery supplies the MR, IR, and IO.
SPCA is also known as.. and supplies what?
Circle of Zinn, also supply the posterior choroid and the macula
What supplies the optic disc?
Circle of Zinn
What does the LPCA supply?
anterior choroid and then travel to join the ACA to form the major arterial circle of the iris, overall LPCAs supply the iris, ciliary body, and anterior region of the choroid
Where is the major arterial circle of the iris located?
Ciliary body - it contains fenestrated capillaries that allow plasma to leak out, which ultimately contributes to aqueous humor formation
What does the supraorbital artery supply?
Provides blood structures within the orbit (SR, SO, and levator muscle) before exiting the orbit through the supraorbital notch to supply the superficial scalp and forehead
What does the ethmoid artery supply?
Sphenoid, frontal, and ethmoid sinuses
What are the 2 Terminal branches of the ophthalmic artery, and what do they each supply? (2)
- Supratrochlear artery - supplies the skin of the forehead and scalp, as well as the muscle of the forehead
- Dorsal nasal artery - supplies the lacrimal sac and then travels along the side of the nose to join the angular artery (from the facial branch of the external carotid artery) - dorsal nasal artery branches into the medial palpebral artery that supplies the medial superior and inferior eyelid. Remember, these arteries join with the lateral palpebra arteries to form the palpebral arcades
What causes occlusion of the internal carotid or the ophthalmic artery?
Ocular ischemic syndrome
What are the 10 layers of the retina?
RPEIIOOGNI
- RPE
- Photoreceptors
- ELM
- ONL
- OPL
- INL
- IPL
- GCL
- NFL
- ILM
Which retinal layers does the SPCA/LPCA supply?
RPE, Photoreceptors, ELM, ONL, OPL
Which of the following retinal layers does the CRA supply?
ILM, GCL, IPL, INL, OPL
Which retina layer has dual blood supply?
OPL
Which veins drain the inner 6 layers of the retina?
Central retinal vein —> exits through ON —> enter the cavernous sinus (either directly or after joining the superior ophthalmic vein)
What causes CRVO and BRVOs?
Thrombus formation within the veins
What is the major threat to vision in patients with CRVO?
neovascular glaucoma
What does the anterior ciliary veins drain, where do they drain into?
- Drain blood from the anterior structures of the eye
- outer portion of the ciliary body
- the conjunctiva
- Schlemm’s canal.
The anterior ciliary veins follow the path of the anterior ciliary arteries across the tendons of the 4 recti muscles. They drain into the superior and inferior ophthalmic veins.
What drains blood from choroid?
vortex veins
typically each quadrant contains at least one vortex vein (although multiple may be present). The vortex vein drains into the superior and inferior ophthalmic veins
What is the largest vein in the orbit, what does it drain?
Superior ophthalmic vein - responsible for the majority of venous drainage of the eye, receiving blood from the CRV, the superior vortex veins, muscular veins draining the SR, SO, and MR (also receive blood from the ACA), and the lacrimal vein.
Where does the superior root of the superior ophthalmic vein (SOV) originate?
Superomedial orbital rim from branches of the supraorbital and supratrochlear veins (drain blood from forehead & scalp)
Where does the inferior roof of the superior ophthalmic vein (SOV) originate?
branches of the angular vein (branch of the facial vein)
Where does the SOV exit and drain into?
exits the orbit through the SOF and drains into the cavernous sinus
Where does the inferior ophthalmic vein originate? What does it drain?
- originates from a diffuse network of veins along the anterior medial orbital floor between the globe and the IR
- drains IR,IO, LR
The IOV forms which 2 branches?
- inferior branch (drains to pterygoid plexus)
- superior branch (drains to cav sinus)
Where does the supraorbital veins originate?
forehead
Where does the frontal vein originate?
venous plexus on the forehead
Where does the angular vein originate?
side of the nose and the medial angle of the orbit
Where does the anterior facial vein receive its blood from?
branch of the pterygoid venous plexus, as well as the superior and inferior palpebral veins (drains into internal jugular vein)
Where does the infraorbital vein arise and where does it travel?
arises from several superficial veins that drain the face - it enters the orbit via the infraorbital foramen and travels along the floor of the orbit within the infraorbital groove and canal.
What goes through the cavernous sinus?
3,4,6,V1,V2
What does the cavernous sinus drain into?
SOV/IOV —> Cav sinus —> Sigmoid sinus —> Internal Jugular Vein
Where is the pterygoid venous plexus located?
infratemporal fossa
Where does the superficial temporal vein originate?
venous plexus on the side of the skull
Where does the middle temporal vein receive its blood from?
orbital vein that originates from lateral palpebral venous branches
The posterior facial vein is formed by what?
The union of the superficial temporal vein and the maxillary vein within the parotid gland
The posterior facial vein divides into what 2 branches?
- Anterior branch - unites w/ the anterior facial vein to form the common facial vein. The common facial vein drains into the internal jugular vein
- Posterior branch - joins with the posterior auricular vein (which communicates with the occipital and superficial temporal veins) to form the external jugular veins
Where does the occipital vein originate?
at the posterior vertex of the skull. It may drain directly into the internal jugular vein or join the posterior auricular to drain into the external jugular vein
The external jugular vein is formed by the union of which 2 veins?
Retromandibular and posterior auricular vein drains blood from the superficial face
The internal jugular vein is a continuation of which sinus?
sigmoid sinus and drains blood from the common facial, occipital, lingual, and superior medial thyroid veins
What are dural sinuses responsible for?
draining blood from the head back to the heart
What lines the dural sinuses?
endothelium
Where is the cavernous sinus located?
behind the SOF
What is located inferior and superior to the cavernous sinus?
The sphenoid sinus is inferior and the optic chiasm is superior to the cavernous sinus
From where does the cavernous sinus receive its blood from?
Superior and inferior ophthalmic veins, as well as the superficial middle cerebral vein (via the sphenoparietal sinus) and inferior cerebral veins
Where does the cavernous sinus drains into?
superior and inferior petrosal sinuses —> which ultimately drains into the internal jugular vein to carry blood to the heart
The cavernous sinus can also communicate with..?
pterygoid plexus
The area of the face from the corners of the mouth to the bridge of the nose is sometimes referred to as the… and why?
Triangle of death - infection in this area can gain access to the brain through the cavernous sinus because of venous communication between the facial vein and the ophthalmic vein
Which CN is mostly affected by an ICA aneurysm?
CN 6
Inflammation of the SOF and/or cavernous sinus is called what, what are the associated symptoms?
Tolosa-Hunt Syndrome - which affects CN 3,4,5,6, resulting in painful external opthalmoplegia and diplopia
What causes carotid-cavernous fistula (CCF), and what are the associated symptoms?
abnormal communication between arterial and venous blood supplies within the cavernous sinus. It is associated with a painful red eye, orbital bruit, and pulsatile proptosis
Meeting point for the superior sagittal, straight, occipital, and transverse sinuses, where is it located?
confluence of the sinuses
The sigmoid sinus receives the ___.
inferior petrosal sinus (which communicates with the cavernous sinus). It exits the skull through the jugular foramen and becomes the internal jugular vein.
Where does the Transverse sinus travel?
Travels on the surface of the tentorium along the occipital bone and the petrous portion of the temporal bone. The transverse sinuses receive blood from the superior petrosal sinus, inferior cerebral veins, and inferior cerebellar veins. They eventually travel inferiorly to form the sigmoid sinuses.
The superior petrosal sinus drains blood from where?
inferior cerebral veins and some cerebellar veins. It communicates with the cavernous sinus and the transverse sinus
The inferior petrosal sinus originates and receives blood from where?
Originated from the posterior inferior portion of the cavernous sinus. It receives blood from the internal auditory veins, as well as veins from the brainstem and cerebellum. The inferior petrosal sinus exits the skull through the jugular foramen and drains into the jugular vein
The superior sagittal sinus is located where?
within the superior falx cerebri (strong folds of dura mater that separate the right and left hemispheres of the brain) on the upper petrous portion of the temporal bone
Where does the superior sagittal sinus drain into?
drains blood from the superior cerebral veins. It travels posteriorly to the internal occipital protuberance, where it drains into the right transverse sinus.
The inferior sagittal sinus travels where?
within the inferior portion of the falx cerebri between the occipital bone and the petrous portion of the temporal bone. It receives blood from the inferior cerebral veins. The inferior sagittal sinus travels posteriorly to join the great cerebral vein to form the straight sinus.
Where does the straight sinus originate from and where does it drain?
originates at the junction of the falx cerebri and the tentorium (CT separating the brain and cerebellum). It drains blood from the superior cerebellar veins before draining into the left transverse sinus.
Where does the occipital sinus originate and where does it receive blood from?
Originates at the margin of the foramen magnum and travels within the falx cerebri along the occipital bone. It receives blood from the vertebral veins before draining into the left transverse sinus
3 different sections of the eye
- Fibrous outer layers: Cornea/Sclera
- Vascular Inner Layers: Iris, Ciliary body, and Choroid
- Neural Layers:Retina and RPE
What is the refractive power of the cornea?
43D
What is the function of the cornea?
Transmits and refracts light, serves as a barrier against pathogens and edema
Which layer is the main refracting element?
air/tear film, contributes 44D to the refractive power of the cornea
Axial length of an emmetropic eye?
24mm
Horizontal and vertical diameter of an emmetropic eye
23.5mm H, 23mm V
The tear/cornea interface contributes __ and the cornea/aqueous contributes __to the total refractive power of the cornea.
5D, -6D
The central radius of curvature is __mm for the anterior corneal surface and __mm for the posterior corneal surface.
7.8, 6.5 —> steeper in the back
The average anterior horizontal diameter is __mm and the anterior vertical diameter is __mm
11.7, 10.6 - anspheric anterior
The average posterior horizontal AND vertical diameter is __mm, resulting in the cornea appearing spherical if viewed from behind
11.7
What is the thickness of each corneal layer? (Rule of 5’s)
- Epithelium - 52um
- Basement membrane
- Bowmans layer - 8-14um
- Stroma - 450um
- Descement’s membrane - 5 —>15
- Endothelium — 5um
What kind of cells does the epithelium consist of?
stratified squamous non-keratinized epithelium
How many cell layers are in the epithelium
5-6 cell layers, 52um thickness total
What are the 3 different layers of the epithelium.
- Squamous - 2 layers of non-keratinized squamous cells
- Wing cells - 2-3 cell layers joined by desmosomes to each other and to surrounding layers
- Basal cell layer - the only mitotic layer in the corneal epithelium, composed of 1 layer, the basal layer of the epithelium secretes its own basement membrane, the basal lamina
The BM attaches to the basal layer via ___.
Hemidesmosomes - ALWAYS attach basement membrane to something
At approximately what age does the epithelium double?
60yo
The basement membrane consists of what 2 layers?
- basal lamina (secreted by epithelial cells)
- reticular lamina (produced by the underlying stromal cells in the cornea)
3 factors that increase the risk of recurrent corneal erosion (RCE)?
-
Poor hemidesmosomes attachment
- Epithelial basement membrane dystrophy
- Age-related thickening of the BM
Where do stem cells originate?
Palisades of Vogt, 0.5mm - 1.0mm band around the limbus at the same level as the basal layer, allowing for an easy transition as stem cells migrate circumferentially to become basal cells
Stem cells become __ cells which produce __?
Basal which produce wing cells that migrate anteriorly to eventually become the surface layer of the epithelium
Limbal stem cell deficiency has been shown to contribute to poor corneal epithelial maintenance in individuals with…?
Aniridia, Stevens-johnson syndrome, and alkali corneal burns
What has type 1 collagen?
“Bowman’s bones, stroma, sclera”
What causes damage to type 1 collagen?
- Osteogenesis imperfecta
- Ehlers danlos
Bowman’s layer has which 2 types of collagen?
Type 1 and 5 (3 and 7 found at lesser extent)
T/F Bowman’s layer is a basement membrane
FALSE! It is a transition layer from epithelium to stroma
How thick is Bowman’s layer?
8-14um (10um)
Can Bowman’s layer regenerate?
No, causes scarring
T/F Bowman’s may play a role in the correct curvature of the cornea
True
What are some clinical conditions related to Bowman’s layer?
- Band Keratopathy - calcium deposits (swiss-cheese pattern)
- Pterygia - Destroy bowman’s layer as they progress onto the cornea
- Crocodile shagreen - Bilateral gray-white polygonal stromal opacities that may involve Bowman’s layer
- Reis-Buckler’s dystrophy - rare corneal epithelial dystrophy that appears early in life and is secondary to damage to bowman’s layer
- Keratoconus - INITIAL damage occurs in Bowman’s layer. Advanced keratoconus may result in hydrops due to damage to descemet’s membrane
- Refractive surgery - The flap created during LASIK consists of epithelium AND Bowman’s layer; PRK involves the application of laser THROUGH Bowman’s layer, resulting in post-op corneal haze
How thick is the stroma?
450um of uniformly spaced 30nm lamellae IS ESSENTIAL
Which part of the stroma has a higher incidence of cross linking between collagen fibers?
Anterior 1/3 stroma - creates more rigidity and help maintain corneal curvature
Which part of the stroma is more likely to have corneal edema?
Posterior 2/3 stroma - lamella that are large and have less branches and less cross-linking compared to the anterior 1/3 stroma
T/F Descemet’s membrane can regenerate
TRUE - very resistance to trauma and damage
Descemet’s membrane is composed of type __ collagen
4
How thick is descemet’s layer?
5-15um
Where does Descemet’s membrane terminate?
Limbus and become schwalbe’s line
What are some clinical conditions that occur in Descemet’s membrane?
- Hydrops - occurs in keratoconus as a result of ruptures within Descemet’s membrane
- Haab’s striae are folds in Descemet’s membrane that occur in congential galucoma
- Hassall-Henle bodies are small areas of thickened Descemet’s membrane in the corneal periphery that protrude toward the anterior chamber. They increase in number with age and have no visual significance
- Arcus - START at descemet’s
Where is Dua’s layer located?
Between stroma & Descemet’s membrane
How thick is the endothelium?
5um
Endothelium cell contains what pumps, what are the importance of these pumps?
Na+/K+ - helps maintain corneal hydration and transparency by regulating water and ion flow between the aqueous humor and corneal stroma
Endothelial cells are rich in __ and __
organelles and mitochondria (which decrease with age)
The endothelium are linked together by…?
macula occludens
T/F endothelial cells do NOT replicate
TRUE! They decrease in number with age, neighboring cells change shape (pleomorphism) and size (polymegathism) to compensate for decrease endothelial cell density
Where does the cornea obtain its nutrients (3)?
- Diffusion from aqueous humor
- Limbal conjunctival and episceral capillary networks
- Palpebral conjunctival networks
What is the main source of oxygen under OPEN eye conditions?
Tear film
What is the main source of oxygen under CLOSED eye conditions?
palpebral conjunctival blood vessels (eyelid)
Defense response to oxygen deprivation of the cornea?
Corneal neovascularization - new vessels arise from endothelial cells of the limbal capillary network in response to cytokines and growth factors (including VEGF)
Corneal innervation is responsible for ___ and ___?
Pain sensation and proper wound healing
LPCNs and SPCNs form a myelinated network of 60-80 nerves that enter where?
mid stroma, after traveling 2-4mm inside the stroma, the corneal nerves lose their myelin sheath as they penetrate through Bowman’s layer to enter the epithelium. These nerves are now “naked” nerves packed with nocireceptors that mediate the pain
What is characterized by poor corneal sensitivity and wound healing and is secondary to damage to V1 of the trigeminal nerve? What are some examples?
Neurotrophic keratitis (ex. herpes simplex, herpes zoster, CVA, diabetes mellitus)
Nerve networks are found in what 3 places?
- Epithelium - referred to as the intraepithelial plexus
- Anterior stroma/Bowman’s layer - subepithelial plexus
- Mid stroma - referred to as the stromal plexus
where do the corneal nerve enter?
at the level of the mid-stroma
Main functions of the conjunctiva? (4)
- Protection of the soft tissues of the eyelid and orbit
- Allows extensive mvmt of the eye without damaging soft tissues
- Serves as a source of antimicrobial and other immunological agents
- Produces mucin layers of the tears
The conjunctiva is composed of what 2 layers, what are they composed of?
- ratified non-keratinized epithelial layer - composed of cuboidal/columnar cells in the palpebral conj that become squamous cells in the bulbar conjunctiva. The superficial cells contain melanin granules, microvilli, and goblet cells
- Submucosa - Loose CT layer that is separated into 2 layers - Outer lymphoid layer & Deep fibrous layer
What is the outer lymphoid layer composed of?
IgA, macrophages, mast cells, lymphocytes, leukocytes, eosinophils, and Langerhans cells (migrate through the conjunctiva)
What is the deep fibrous layer composed of?
collagen fibrils, fibroblasts, blood vessels, lymphatic vessels, nerves, and accessory lacrimal glands. In general, this layer is loosely attached to underlying structures
The palpebral conj covers what 3 structures?
eyelid margin, tarsal plate, fornices
The marginal conjunctiva is composed of.. ?
stratified columnar epithelial cells
The tarsal conjunctiva is composed of…?
stratified columnar epithelium
The bulbar conjunctiva is composed of…?
stratified squamous cells
What are the 3 main functions of the limbus?
- provide nutrients for neighboring structures
- provides a passageway for aqueous humor to drain
- supplied by blood from capillary loops of the conjunctiva and the episcleral vessels
Bowmans and descemet’s end at what structure?
limbus
Descemet’s become __ in the anterior chamber angle?
Schwalbe’s line
What begins at the limbus?
conjunctival stroma, tenon’s, episclera, tenon’s capsule
What is the source of stem cells at the limbus?
Palisades of Vogt
Plica semiluminaris is composed of..?
stratified squamous bulbar conjunctiva that folds medially at the medial canthus, providing slack in the conjunctiva during lateral eye movements. It also serves as the floor for the lacrimal lake
The caruncle contains…(3)
Sebacous, sweat, and goblet cells - located at the medial side of plica semilunaris, collects debris
The conjunctival blood supply consists of which 2 networks and what is it supplied by??
- Palpebral conjunctiva (including marginal, tarsal, and forniceal conjunctiva) are supplied by the marginal and peripheral palpebral arcades
- Posterior bulbar conjunctiva is by the peripheral palpebral arcades. Anterior bulbar conjunctiva is supplied by the ACA. The peripheral palpebral arcades combine with the anterior ciliary arteries at the posterior bulbar conjunctiva
Where do the lateral lymphatic vessels of the bulbar and palpebral conjunctiva drain into?
partoid lymph nodes
Where does the medial lymphatic vessels drain into?
Submandibular lymph nodes
The bulbar conjunctiva is innervated by what nerve?
LPCN (form nasociliary nerve V1)
The superior palpebral conjunctiva is innervated by what nerve?
Frontal & lacrimal nerve of V1
The inferior palpebral conjunctiva is innervated by what nerve?
lacrimal nerve of V1 and infraorbital nerve of V2
What is the main function of the lens
transmission and focusing of light onto the retina
What is the refractive power of the lens?
20D (1/3 the total refractive power of the eye)
Anterior lens radius of curvature
8-14mm
The posterior lens of curvature
5-8mm, steeper
pH of the lens
6.9, more acidic compared to the aqueous humor (pH=7.2) and the blood plasm (pH=7.4)
Is the lens flatter in the periphery or centrally?
The lens is aspherical, flatter in the periphery
The space between the posterior lens and the anterior vitreous face is called what?
Berger’s space
Peripheral flattening and a gradient index of refraction of the lens helps reduce ___?
Spherical aberration
The lens is composed of what 3 parts?
- Lens capsule
- Lens epithelium
- Lens cortex
The lens capsule is secreted by …?
The anterior lens epithelium
The lens capsule is thinnest where? and thickest?
Thinnest at the post pole and thickest at the anterior pole of the lens
What is the thickest BM in the body?
lens capsule
What part of the lens serves as a barrier against large molecules (albumin, RBCs, WBCs, etc)?
Lens capsule
The lens zonules extend from the ____ and insert into the ___?
NPCE and insert into the anterior capsule of the lens
What is the lens epithelium made up of?
a single layer of cuboidal epithelial cells adjacent to the anterior lens capsule, there is NO posterior lens epithelium (used to form the primary lens fiber during embryonic development)
The lens epithelium cells are joined with ___ and ___?
maculae occludens & gap junction
Which layer serves as the main site of lens metabolism?
lens epithelium
The pre-equatorial region of the lens (just anterior to the lens equator and known as the ____)
germinal zone - contains mitotic epithelial cells that become secondary lens fibers. The production of new lens fibers is continuous throughout life
What is the lens cortex composed of?
65-70% water, 30-35% protein, and 1% other - 80-90% of lens proteins are water soluble alpha, beta, and gamma crystallins that are tightly packed within the cytoplasm of lens fiber cells
What acts as molecules chaperones in the lens?
Alpha crystallins - by helping beta & gamma crystallins recover from injuries, thus preventing degradation of lens fibers and loss of lens transparency
index of refraction for the nucleus and anterior lens?
1.41 and 1.38
Index of refraction for the aqueous and vitreous humor
n=1.336
Zonules are produced by what?
basement membrane of the NPCE in pars plana and pars plicata
What are zonules composed of?
microfibrils that contain fibrillin and extracellular matrix but NO true elastic fiber
Where does primary lens zonules attach directly to?
lens capsule in the pre-and post-equatorial regions of the lens - very few primary lens zonules attach directly at the lens equator
Where does the secondary lens zonules attach?
connect primary lens zonules to each other or to the NPCE of the pars plana
Where do tension zonules connect?
Connect the primary lens zonules to the valleys between the ciliary processes of the pars plicata
What is the main function of the sclera?
forms the posterior 5/6 of the protective connective tissue coat of the eye (the cornea forms the remaining 1/6 protective CT coat) and helps to maintain the shape of the globe and to protect intraocular structures
The scleral serves as a point of attachment for??
EOMS
Radius of curvature for sclera
11.5
Thickest area of the sclera?
posterior pole 1.0mm
The thinnest area of the sclera?
0.3mm under the recti tendon insertions - clinically relevant during strabismus surgery to avoid inadvertent globe penetration
Weakest area of the sclera?
lamina cribosa (optic nerve)
Scleral is vascular/avascular
avascular - receives minimal blood supply from episcleral vessels, choroidal vessels, and branches of the long posterior ciliary arteries
The sclera is minimally innervated by ___ and ___?
LPCN and SPCN
Layers of the sclera (3)
- Episclera - loose CT layer that contains capillary network that surrounds the cornea. Inflammation of CB or iris will cause dilation anterior ciliary arteries, leading to the characteristic ciliary flush
- Sclera proper - thick, dense, avascular CT that is continuous with the corneal stroma. Composed of irregular collagen bundles that provide strength but NO transparency. The sclera contains less fibroblast and GAGs but similar ground substance compared to the corneal stroma
- Lamina fusca - innermost layer of sclera, adjacent to the choroid that contains elast fibers & numerous melanocytes
Where do the anterior ciliary arteries form networks?
anterior conjunctiva and episclera
What is the difference between episclera vs scleral proper?
Episclera is composed of LOOSE CT and HIGHLY vascular vs scleral proper is composed of dense CT and is relatively AVASCULAR
What can cause blue sclera?
- Osteogenesis imperfecta
- Ehlers Danlos
- Minocycline
- Steroids
A yellow sclera can indicate what?
liver disease or lipids trapped over time in adults
Layers of the eye from anterior to posterior
- Remember “CONJ, TENON’s”
- Conj, tenons, episclera, sclera proper, lamina fusca
Where does Tenon’s capsule begin?
2mm posterior to the limbus and extends posteriorly to encircle the rest of the globe separating it from the surrounding orbital adipose tissue
What does Tenon’s capsule cover
a CT that covers the episclera
What is the anterior scleral foramen?
area occupied by the cornea (11.7mm)
What is the posterior scleral foramen?
area where optic nerve enters the eye. The optic nerve is supported by the lamina cribrosa (i.e. scleral tissue sieve), which is composed of scleral collagen and elastin fibers that associate with axon bundles and astrocyte within the optic nerve
What is the most likely area to be damaged with an elevation IOP?
lamina cribrosa - weakest area of the sclera
The sclera contains multiple channels for arteries, veins, and nerves that are passing through to reach other ocular structures.. these are called what?
Emissarias
Emissarias are divided into 3 sections
- Anterior emissaria
- Middle emissaria
- Posterior emissaria
The anterior emissaria includes what?
- deep and intrascleral venous plexi travel through the sclera to connect with the ciliary vein within the ciliary body
- Anterior ciliary arteries provide blood to most anterior structures of the eye
- Branches of the episcleral arteries travel through the sclera to reach the anterior chamber angle
- Aqueous veins of Ascher drain aqueous humor from schlemm’s canal
The middle emissaria include what?
vortex veins that drain the choroid
The posterior emissaria include what?
channels for the LPCAs, SPCAs, LPCNs and SPCN that travel through the sclera to reach the supra choroidal space
What is the anterior chamber depth?
3.6mm
What are the boundaries of the anterior chamber?
corneal endothelium (ant boundary), TM, schlemm;s canal, ciliary body, and iris root (peripheral boundaries) and the ant iris surface (posterior boundary)
Structure of the internal scleral sulcus (angle) from posterior to anterior, becker-shaffer grading system
- “I Can See The Stupid Line”
- Iris
- Ciliary body (grade 4)
- Scleral spur (grade 3)
- TM (grade 2)
- Schlemm’s canal (grade 1)
- Schwalbe’s line
Van Herick grading system
- rade 4 = 1/2 or greater
- Grade 3 = 1/4-1/2
- Grade 2 = 1/4
- Grade 1 = <1/4
- Grade 0 = no structures visible
What is the origin site for the ciliary muscle fibers (posteriorly) and the TM lamellae
Scleral spur
What areas of the sclera contain elastin?
the innermost layer of the sclera that is shared with the choroid, scleral spur, lamina cribrosa and lamina fusca
Major site for aqueous humor filtration
TM
Which one is pressure DEPENDENT? Uveoscleral or Corneoscleral?
- Corneal scleral (80% of outflow) - major site for aqueous humor outflow - pressure dependent
- Uveoscleral (20% of outflow) - minor site for aqueous humor outflow - pressure independent
If episcleral venous pressure increases, what happens to IOP?
increase
What can cause a congested vein?
Sturge weber, unilateral glaucoma, portwine stain
What is the base and apex of the TM?
Base is the SS and apex is the cornea
What are the 2 divisions of the TM?
- Corneoscleral
- Uveoscleral
What are the three drugs that increase outflow
- Pilocarpine (corneoscleral ouflow)
- a2 agonist (uveoscleral outflow)
- Prostaglandin (uveoscleral outflow) - relaxes ciliary muscle and cause changes within the extracellular matrix
What are the 2 drugs of a2 agonist
- Apraclonidine and brimonidine - remember a2 = 2 drugs and 2 MOA
- MOA: increase uveoscleral outflow and decrease aqueous production
What is an alpha 1 drug?
Phenylephrine
How does pilocarpine work?
- it pulls on the longitudinal ciliary muscle
- increases accommodation, myopic shift and brow ache
Where is the JXT located?
- in the TM closer to schlemm’s canal - aka cribriform layer
- It is the site of the most resistance to aqueous outflow
How does the aqueous penetrate endothelial tight junctions that line the schlemm’s canal?
- high to low pressure gradient
- IOP has to be higher than episcleral venous pressure
Describe the layers of the TM from inner to outer
uveoscleral meshwork, corneoscleral meshwork, JXT
What is the major site for aqueous humor filtration?
Schlemm’s canal (up to 90%) - contains multiple channels formed by CT septae that increases the surface area for aqueous filtration, channels are known as internal collector channels
Schlemm’s canal inner border and outer border
- Inner border = TM and scleral spur
- Outer border = against the sclera near the limbus
How does the aqueous humor transport from the JXT into Shlemm’s canal?
giant vacuoles
2 major routes that aqueous humor can drain out of?
- External collector channels (efferent vessel) —> deep scleral venous plexus —> intrascleral venous plexus —> episcleral venous plexus
- Aqueous veins of ascher —> episcleral venous plexus
Where does the episcleral venous plexus drain into?
anterior ciliary veins —> muscular veins —> superior/inferior ophthalmic veins —> cavernous vein —> cavernous sinus —> superior/inferior petrosal sinus —> internal jugular vein —> brachiocephalic vein —> superior vena cava —> right atrium of the heart
Where is the termination of descemet’s membrane?
schwalbe’s line
What is the pigmented line called in schwalbe’s line?
Sampolesi line
Anterior displaced schwalbe’s line is called?
Posterior embryotoxin
What is the average size pupil?
3-4 mm but can range 1-8mm
What does the iris pupil margin contain?
Schwalbe’s contraction furrows - variations of thickness of the posterior pigmented epithelium
What is the thickest part of the iris?
- collarette - served as the attachment for the fetal pupillary membrane during embryonic development
- and contained remnants of old fetal vessels and fetal vessels
- 1.5mm of the pupillary margin
What is the thinnest part of the iris?
iris root
2 zones of the collarette
- Ciliary zone
- Pupillary zone
Anridia
- bilateral condition characterized by partial or absence of the iris
- highly associated with glaucoma due to angle closure from PAS
- Pts often have poor vision due to foveal hypoplasia with subsequent nystagmus
- Other ocular associates include micro cornea, lens subluxation, and optic nerve hypoplasia
What are the layers of the iris?
- Anterior border layer
- Iris stroma
- Anterior epithelium and dilator muscle
- Posterior pigmented iris epithelium
Iris color is determined by?
- the amt of melanin NOT melanocytes
- Brown eyes have thicker ABL and more melanin
Lack of pigment within the iris epithelial layers are called what?
oculoocutaneous albinism
Collagenous columns in the ABL that serves as passageways for the aqueous humor to enter the iris stroma
iris crypts - it gives iris surface a rough appearance
Heterochromia
difference of eye color between the eyes
What does the iris stroma consist of?
- cells - fibroblasts, melanocytes, lymphocytes, macrophages, mast cells, and clump cells
- nerves - LPCNs and SPCNs (parasympathetic fibers are carried within the SPCNs)
- Blood vessels - nonfenestrated iris capillaries (zonula and occluden junctions), forms part of the BAB
Where is MACI (Major) located and what supplies it?
CB - LPCA and ACA
Where is MACI (Minor) located?
- Iris stroma - non fenestrated
- Forms the BAB
Where does the iris drain into?
iris > CB > choroidal veins > vortex veins > SOV and IOV
Where is the sphincter muscle located and what innervates it?
- iris stroma, CN III parasympathetic traveling w/ SPCNS
- Parasympathetic causes pupil constriction
What innervates the dilator muscle?
- sympathetic
- it extends radially from the iris root
What is the pupillary ruff formed by?
posterior and anterior iris epithelial layer curling towards the ABL
What is an iris cyst?
separation between the anterior and posterior epithelial layers of the iris
Total volume of the posterior chamber
0.060
What are the 3 regions of the posterior chamber?
- Posterior chamber proper
- Canal of Hannover
- Canal of Petit
What medication works on the dilator muscle
alpha 1 phenylephrine
What innervates the ciliary body?
CN III parasympathetic fibers in the SPCNs allowing for accommodation
What are the 2 regions of the ciliary body?
Pars plana and pars plicata
What is the Valley of Kuhnt?
Heavily pigmented areas between the ciliary processes
Which part of the ciliary body produces and secretes aqueous humor?
NPCE
What 2 areas have fenestrated capillaries?
MACI and choroid
Describe the flow of aqueous humor
Pars plicata > posterior chamber > pupil > anterior chamber > TM
Len zonules arise where and are produced by
- tertiary vitreous
- produced by the pars plana
- zonules extend to the valleys of Kuhnt of pars plicata before inserting into the lens capsule
What are the layers of the ciliary body?
- Supraciliaris - outermost layer
- Ciliary muscle - contains 3 types of muscle (longitudinal, radial, mullers)
- Ciliary stroma - contains MACI (non-fenestrated)
- Ciliary epithelium - contains zonula occludens to form part of the BAB, 2 layers PE and NPCE
Which areas of non-fenestrated capillaries?
MACI (minor) and retina
Blood supply of the ciliary body?
LPCA and ACA
Innervation of the ciliary body?
- CN III parasympathetic - accommodation
- Sympathetic fibers from superior cervical ganglion which travel with LPCN and SPCNs to innervate arteries within the CB
- Sensory nerve fibers from the trigeminal ganglion of V1
Where is the choroid located?
between the sclera and RPE
Where is the thickest part of choroid located?
Posterior pole 0.2 mm
Where is the thinnest part of the choroid located?
ora serrata 0.1 mm
Describe the layers of the choroid
- Suprachoroid lamina (lamina fusca) - allow passage for LPCAs and LPCNs (extend mid-equatorial to the ora serrata along 3 and 9 o clock regions), it also contains both sclera and choroid
- Choroidal stroma - innervated by sympathetic nervous system which causes vasoconstriction, choroidal melanoma’s can occur here
- Choriocapillaris - concentrated around the macula, surrounded by pericytes for regulation of blood flow
- Bruch’s membrane
2 layers of the choroidal stroma are?
- Hallers (larger vessels) - vortex veins are located here
- Sattlers - smaller vessels, branch to form capillary beds, drains into the vortex veins
What are the 5 layers of bruch’s membrane?
- BM of choriocapillaris
- outer collagenous layer
- Elastic layer - angioid streaks occur here
- Inner collagenous layer
- BM of the RPE
What’s the most important thing about bruch’s membrane?
allow passage of nutrients and waste products - phospholipids can block passage
Where does drusen deposits lie?
inner collagenous layer of bruch’s
What cause’s break in bruch’s?
- CHBALA
- CNVM, histo, wet AMD, pathological myopia, choroidal rupture, best disease, pseudoxanthoma elasticum (Angioid streaks)
What can cause angioid streaks?
- PEPSI
- Pseudoxanthoma elastic, Paget’s, ehlers danlos, Sickle cell, Idiopathic
What supplies the anterior and posterior choroid?
LPCA and SPCAs
What drains the choroid?
vortex veins
What innervates the choroid?
- LPCNs/SPCNs carry parasympathetic, sympathetic fibers from the superior cervical ganglion, sensory fibers
What is the volume of the vitreous chamber?
4mL
Bowl like depression of the anterior chamber is called?
Patellar fossa
What collagen type does the vitreous have?
2
What helps maintain uniform spacing in the vitreous?
Hyaluronic acid which is a type of GAG - located mostly within the vitreous cortex
What does the vitreous mostly consist of?
Water, collagen type 2, hyaluronic acid, fibroblast (mostly in the vitreous base)
What are the 5 attachments of the vitreous? from tightest to weakest attachment
Ora serrata (tightest attachment), lens, optic disc, macula, blood vessels (weakest attachment)
The retina is derived from ?
Neuroectoderm
What are the layers of the retina
RPEOOIIGNI
What is the RPE important for?
- phagocytosis of PR outer segment (lysosome plays a sig role in phagocytosis) - undigested material can cause accumulation of lipofuscin
- Transfer of ions, water, and metabolites
- Vit A storage (all-trans retinol) and metabolism
- Blood retinal barrier (zonula occludens, zonula adherens and maculae adherens)
- Absorbs stray light
- Produces growth factor VEGF essential for choriocapillaris function as well as pigment epithelial derived factor (PEDF) and antiangiogenic factor that counter balances the effects of VEGF
The photoreceptor layers contain how many rods and cones?
- 120 million rods per eye
- 6-8 million cones per eye
What does the inner segment of a PR contain?
- Myoid - inner layer of the inner segment that contains ER and Golgi apparatus for protein synthesis, “myoid make protein”
- Ellipsoid - the outer layer of the inner segment that is packed with mitochondria
- Cilum - connects the outer and inner segments of photoreceptors
What does the outer segment of a PR contain?
- stacks of membranous disc that contain photopigments produced by the inner segments
- these disc surround the photopigments molecule
- 600-1000 discs per rod and 1000-1200 disc per cone
- disc membranes are continuous with the plasma membrane in cones but free-floating in rods
- Disc photopigments are formed in the inner segment, assembled into disc at the base of the outer segment, and are continually shed at the tip of the outer segment for phagocytosis by the RPE
Why are rods important?
used for scotopic vision, used to detect low levels of illumination
Rod disc contain which photopigment?
Rhodopsin
Rods absorb photons max at __ nm?
507
Where do the rods terminate?
at the spherules
Why are cones important?
Used for photopic vision, contains 3 different photopigments (iodopsins) that each contain the same chromophore (11-cis-retinal) but differ in their protein (opsin component)
What are the 3 photopigments for cones? What are the max absorptions?
- Cyanolabe (blue) - max absorb photons at 426nm
- Chlorolabe (green) - max absorb photons at 530nm
- Erythrolabe (red) - max absorb photons at 557nm
Where is the fovea compared to the optic nerve
5mm temporal and 0.4mm inf to the optic nerve and only contains cones
Which layer contains the PR?
ONL
Where does rods spherules/cone pedicles synapse w/ bipolar and horizontal cells occur?
OPL layer
Each rod spherule can synapse with what?
1-4 bipolar cell dendrites
Wernickes vs Broca’s area (Temporal lobe)
Wernicke: produces speech, helps with choice of words
Brocas: understanding of speech but does not produce speech
Label the following structure
MLF connects which CN
3,4,6,8
What does CN 7 wrap around?
CN 6 in the pons
The main branch of CN 7 divides into which 5 branches for facial expression?
” To zanzibar by motor car”
Temporal
Zygomatic
Mandibular
Cervical
What CN provides parasympathetic innervation to the lacrimal gland and submandibular and sublingual.
CN 7
Which CN carries taste fibers to the anterior 2/3 of the tongue?
CN 7 via the chorda tympani nerve, parasympathetic
What should you think of when you see CN 7?
MOTOR, MOTOR, MOTOR with minor sensory component that carries sensation to the ant 2/3 tongue
Bells palsy vs stroke
Bell’s palsy: lower motor lesions causing complete hemifacial paralysis. “ipsi ALL”
Stroke: upper motor lesion causing paralysis of the lower half of the face
Remember: upper neuron is bilateral and lower neuron is contralateral input with ipsilateral innervation
Which CN provides parasympathetic innervation?
3 (iris sphincter for miosis and accommodation) and 7 (lacrimal gland)
Which CN provides sympathetic innervation?
3 = muller’s
V1 = LPCN (iris dilator and ciliary muscle) and SPCN (choroidal and conjunctival blood vessels)
CN 7 = innervation of blood vessels of lacrimal gland via vidian nerve
hyperactive sympathetic innervation of blood vessels of the choroid is thought to play a role in
central serous chorioretinopathy
What forms the ILM over the optic nerve?
astrocyte
there are NO mueller cells over the optic disc
What is the length of the:
Intraocular portion of ON
Intraorbital portion of ON
Intracanicular portion of ON
Intracranial portion of ON
Intraocular portion of ON = 1mm
Intraorbital portion of ON = 30mm
Intracanicular portion of ON = 6-10mm
Intracranial portion of ON = 10-16mm
What separates the ON from the retinal tissue?
What surrounds the glial tissue?
ring of glial tissue known as the intermediary tissue of Kuhnt which continues posteriorly as the border tissue of Jacoby.
sclera collagen fibers surround glial tissue forming the border tissue of elschnig
glial tissue are made with tight junction to prevent fenestration from choroidal vessels
Damage to the papillomacular bundle can cause what kind of VF defect? What is it caused by?
centroceco, paracentral, and central VF defects
- caused by nutritional and toxic optic neuropathy
