Anatomy Flashcards
Percentage of population that have a cilioretinal artery supplying the eye
20%
What is the effect of the cilioretinal artery
allows blood supply of the eye when there is a CRAO
Location of eye the cilioretinal artery
between macula and OD from a posterior ciliary artery source
What does the cilioretinal artery supply
foveal photoreceptors
what percentage of people have the ophthalmic BELOW the optic nerve?
15%
what percentage of people have the ophthalmic medially ABOVE the optic nerve?
85%
What form the circle of Zinn
where the short ciliary nerves penetrate the globe around ON to form the arterial circle of Zinn.
Short ciliary nerve supplies ?
The Optic Head nerve and the choroid up to the equator
What is the thinnest Cranial nerve ?
Trochlear nerve
Trochlear nerve exits the skull ?
SOF
SOF is located ?
between the greater and lesser wing of the sphenoid
Trigeminal V2 nerve exits the skull ?
Forman rotundum
Trigeminal V3 nerve exits the skull ?
Foramen ovale
Contents of the foramen ovale?
O- Optic ganglion
V - V3 of the trigmenial nerve
A - Accessory meningeal
L- lesser petrosal
E - Emissary vein
Branches of the Ophthalmic division V1
Frontal
Lacrimal
Nasociliary
Blood supply of the optic nerve ?
Intraocular: short ciliary artery
Intracranial: pial vessels of the short ciliary
IOF is located
lies between greater wing of sphenoid and maxilla
Medial wall of the orbital ?
SMEL
The medial orbital wall comprises four bones (anterior to
posterior):
● the frontal process of the maxilla
● lacrimal
● ethmoid
● lesser wing of sphenoid.
Floor of the orbital ?
MY ZIPPED PANTS are on the floor
- orbital plate of maxillary bone
- small orbital process of palatine bone
- orbital surface of zygomatic bone.
Lateral wall of the orbital ?
Zara is a great wing woman
Zygomatic
Greater wing of sphenoid
Roof of the orbital ?
FRONT - LESS
● the orbital plate of the frontal bone
● the lesser wing of sphenoid bone (posterioly).
Foramen that the internal carotid enters the Skull ?
Foramen Lacerum
Veins that drain INTO the cavernous sinus ?
Superior and inferior orbital veins
Veins that drain OUT of the cavernous sinus
- Superior and inferior petrosal –> internal jugular
- Emissary vein –> Pytergoid plexus
Inferior optic radiations are responsible for what Visual Field
Meyers loop
Superior visual field - pass through the temporal bone and terminate the visual cortex inferior to the calcarine sulcus
Borders of the cavernous sinus ?
Anterior - pituarity gland
Posterior - apex of petrosal part of the temporal bone
Medially - pituraity fossa
Roof - Pituarity gland
Floor - sphenoid
Superior optic radiations
Inferior visual field - pass through the Parietal bone and terminate the visual cortex superior to the calcarine sulcus
Visual cortex area responsible is at the cortex level
17
optic nerve fibre layers of the retina that are responsible for the temporal retina ?
ipsilateral 2,3,5 -
T for Temporal, T- for team 5 a side
optic nerve fibre layers of the retina that are responsible for the nasal retina ?
contralateral 1,4,6
Lesion anterior to the Willebrand’s Knee?
Superior quandrantopia in the contralateral eye and ipsilateral junctional scotoma
Lesion at the retina ?
Scotoma of the ipsilateral eye
Lesion at the lateral chiasm?
Ipsilateral hemianopia
Lesion at the visual cortex - occlusion at the calcarine artery po the posterior cerebral artery
bilateral homonymous hemianopia with macular sparring
EOM which is the shortest to longest ?
MR 5.5
IR 6.5
LR 6.9
SR 7.5
EOM tendon length shortest to longest ?
MR
IR
SR
LR
Day 26 the which EOM develop?
SR, MR, IR and IO
Day 27 which EOM develop?
LR
Day 28 which EOM develops ?
SO
Each rectus muscle receives blood supply from 2 ciliary arteries except?
Lateral rectus
First nerve to suffer compression in the cavernous sinus ?
6th cranial nerve
Circle of zinn is incomplete in what percentage of people ?
23%
Nasociliary artery branches into the
Ethomidal anterior
Ethmoidal posterior
Infratrochlear
Longest unprotected nerve ?
Trochlear
Only nerve to exit the brainstem dorsally ?
Trochlear
Smallest cranial nerve in terms of axons?
Trochlear
Orientation of the lateral rectus to the IC in the cavernous sinus ?
Lateral
Oculomotor functions ?
Motor - somatic and visceral
Sensory
Somatic -
Contralateral innervation of SR
Ipsilateral of IO, IR, MR
Visceral - pupillary light reflex
bilateral levator superioris
Snesory
What nerve fibres pass anteriorly in the optic chiasm ?
inferonasal
The Roof of the posterior fossa
.
Tentorium cerebelli
The contents of the posterior fossa
Cerebellum
Pons
Medulla oblongota
Anterior border of the posterior fossa
Superior border of petrous temporal bone and dorsum sellae
The cerebellum lies in the cerebellar fossa, in the squamous part of occipital bone.
Cornea endothelium: Thickness, organisation of layers, amount of cells, function
- Thickness 4-6um
- It is a monolayer of interdigitating hexagonal cells joined by tight junctions
- At birth: 1 million cells with approximately 3800 endothelial cells/mm2; these cells are loss with ageing. Cornea endothelium do not regenerate but rather stretch to fill gaps left by cell loss
- Function of the cornea endothelium is to keep cornea dehydrated and clear. If cell count < 500cells/mm2, pump action will be insufficient and this could lead to corneal oedema
Schwalbe’s line
Schwalbe’s line is the termination of the Descemet’s membrane and delineates the outer limit of the cornea endothelium -it is a structure that can be seen usually only on gonioscopy
Posterior embryotoxon
Posterior embryotoxon is the thickening and anterior displacement of the Schwalbe’s line
The lacrimal sac measures
12-15mm
The nasolacrimal duct measures
12-18
Location of the Hasner valver?
At inferior meatus - congenital lacrimation irritation
Length of the vertical part of caniculi
2mm
Location of Rosenmuller valve?
Mucosal tissue fold, prevents reflux into the nasolacrimal sac
length of the horizontal part of caniculi
10mm
A critical gene in the development of surface ectoderm?
PAX6 is a critical gene in the development of surface ectoderm.
Lipid layer diameter
0.1 um
Mucin layer diameter
0.2-0..5um
Layers 1, 2 of the lateral geniculate represent what pathway and what are they useful for ?
represent magnocellular pathway, concerned with detection of movement
Layers 3-6 of the lateral geniculate represent what pathway and what are they useful for
represent parvocellular pathway, concerned with colour vision and visual acuity
Sherrington’s law
Sherrington’s law of reciprocal innervation states that the contraction of an extraocular muscle occurs together with the relaxation of the ipsilateral antagonist muscle.
Hering’s law
Hering’s law of equal innervation states that there are equal contractions of the contralateral ( in the fellow eye) yoke muscles.
The nuclei of the Trigeminal nerve are located ?
Main sensory
sensory
Mesencephalic
Motor
The nuclei of the Oculomotor nerve located?
In the superior colliculus of the midbrain and runs between the poster cerebral artery and superior cerebellar artery to the cavernous sinus.
The nuclei of the Trochlear nerve located?
In the inferior colliculus, in the anterior part of the grey matter surrounding the midbrain
The nuclei of the abducens nerve located?
At the pontomedullary junction, lies in the subarachnoid space, crosses over the petrosal part of the temporal bone through an osteofibrous canal called Dorello’s canal. It runs in the cavernous sinus lateral to the internal carotid
Relationship between the trochlear and oculomotor nerve?
Enters the cavernous sinus inferior posterior to the oculomotor nerve and exits the sinus above the oculomotor nerve
Trochlear innervates the superior oblique / contralaterally or ipsilaterally
Contralaterally
What blood vessels supplies the prefrontal cortex?
The anterior cerebral artery (ACA) supplies the premotor frontal cortex which initiates saccades
Where are the FEF located ?
visual cortex 8
Supranuclear pathway
Supranuclear Eye Movements
These are movements controlled by higher centers in the brain (above the nuclei of the cranial nerves), particularly in areas such as the cerebral cortex, brainstem, and cerebellum. These centers generate signals that descend and modulate the activity of the cranial nerve nuclei responsible for eye movements.
Supranuclear pathways include areas like the frontal eye fields (FEF), which are involved in voluntary saccadic (quick) eye movements, and the parietal eye fields for visual attention.
The PPRF (paramedian pontine reticular formation) and MLF (medial longitudinal fasciculus) help coordinate movements like horizontal and vertical gaze.
Disruption in these areas leads to problems such as gaze palsies, nystagmus, or saccadic initiation failure (difficulty starting voluntary eye movements).
Examples of supranuclear movements:
Saccades: Quick, voluntary shifts of the eyes from one target to another (controlled by the cortex).
Smooth pursuit: Slow, continuous tracking of a moving object.
Vestibulo-ocular reflex (VOR): Compensatory eye movements during head motion to stabilize gaze (this has both supra- and infranuclear involvement).
Role of the basal ganglia
The basal ganglia has a number of functions:
Suppresses unnecessary reflexive saccades
Controls voluntary saccades
Dolls head manoeuvre?
Doll’s Head Maneuver (Oculocephalic Reflex)
The doll’s head maneuver is used to test the integrity of the vestibulo-ocular reflex (VOR), which is a key supranuclear reflex. It involves turning the head to one side while observing the eyes’ ability to remain fixed on a stationary target.
Normal response: When the head is turned to one side, the eyes move in the opposite direction to maintain fixation (compensatory movement).
This reflex indicates that the brainstem (supranuclear pathway) is intact and working properly.
Abnormal response: If the eyes do not move (i.e., they move with the head instead of in the opposite direction), it suggests damage to the brainstem, vestibular system, or higher centers responsible for the VOR.
This test is especially useful in unconscious or comatose patients to assess brainstem function, as they cannot voluntarily move their eyes.Relies of the vestibular-ochlear pathway - eyes move with passive movement of the head. This means that the infranuclear pathway is intact and the problem must be supranuclear
Blood supply of the lateral rectus ?
Lacrimal artery
Where does the IO orginate
inferior oblique muscle of the eye originates from the maxillary part of the floor of the orbit. It arises anteriorly from the orbital floor, lateral to the nasolacrimal fossa.
Where does the SO orginate
the periosteum of the sphenoid bone above and medial to the optic canal, inserts into sclera posteriorly and superiorly under the superior rectus behind the equator
isolate the SO at how many degrees ?
54 degrees adduction
Isolate the recti at
23 abduction
Rectus muscle wit the largest arc is
Lateral Rectus with 12 mm
EOM with Smallest to largest tendon length?
So, the order from smallest to largest tendon length is:
Inferior Oblique (IO): 1-2 mm
Medial Rectus (MR): 3.7 mm
Inferior Rectus (IR): 5.5 mm
Superior Rectus (SR): 5.8 mm
Lateral Rectus (LR): 8.8 mm
Superior Oblique (SO): 19 mm
Thinnest EOM ?
Is the LR at 9.2mm
Smallest to largest distance from limbus ?
MR (5.5) – IR (6.5) – LR (6.9) – SR (7.7)
isolate the IO at how many degrees ?
51 degress adduction