Anatomy Flashcards
What two layers make up the fibrous outer layer?
Sclera
Cornea
What attaches to the sclera?
Muscles
How much of the refractive power of the eye comes from the cornea?
Around 2/3rds
What makes up the Uvea?
Iris
Ciliary Body
Choroid
What is the function of the ciliary body?
Controls the size of the iris and the shape of the lens.
Secrets Aqueous humour
What is the function of the choroid?
A highly vascularised area which supplies the avascular areas of the eye with nutrients and is the place where gas exchange takes place.
What is the retina?
The photosensitive innermost layer of the eye.
What can the eye be divided up into?
The Anterior and Posterior segments
Where is the anterior segment of the eye to be found?
Lies superior to the lens.
What can the anterior segment of the eye be further broken down into?
Anterior chamber- between cornea and iris
Posterior Chamber - Between iris and suspensory ligaments.
What is the main differentiation between the anterior and posterior segments?
The anterior contains Aqueous humour
The posterior contains Vitreous humour
Where is the posterior segment to be found?
Behind the lens
Floaters seen within the vision are made up of what?
Bodies of vitreous humour
Where is aqueous humour produced?
Within the ciliary bodies
How does the aqueous humour enter the anterior segment of the eye?
Passes through the posterior chamber and though the iris it is drained away at the edge of iris.
What artery supplies the eye?
Ophthalmic
The ophthalmic artery is a branch of which artery?
Internal carotid artery.
How do the central artery and vein supply the retina?
They are inserted inside the optic nerve and travel intrinsically.
What are the main two veins for they eye and where do they drain into?
Superior and Inferior ophthalmic vein
Drain into the cavernous sinus
What cranial nerve in CN II
Optic
What are the three main regions of a fundus within the eye?
Optic disc
Macula
Fovea
What is the optic disc?
Formed of the optic nerve entry
Why is the optic nerve a blind spot within our vision?
There are no photoreceptor cells within the optic disc
What is the macula?
Area with the greatest density of cones.
Appears as a darker region
What is the fovea?
Area of most acute vision
Seen as a depression at the centre of the macula.
The retina could be divided into what three layers, give them from most inferior to anterior.
Photoreceptor cells
Ganglion cells
Axons of the ganglion cells
In order for the inferior oblique or the superior oblique muscles to operate what must first happen to the eye?
It must be Adducted by the medial rectus
In order for the Superior and Inferior rectus to operate what must first happen to the eye?
It must be abducted by the lateral rectus.
Which two muscles cause elevation though they aren’t active at the same time.
Superior rectus
Inferior oblique
Which two muscles cause depression though they aren’t active at the same time.
Inferior rectus
Superior oblique
All of the muscles of the eye attach on the anterior apart from which two muscle
Inferior and superior oblique
Attach on the posterior aspect
What is special about the inferior and superior oblique muscles?
They have a trochlear attachment which serves as a pully.
What is the motor innervation of the superior rectus?
CN III Oculomotor
What is the motor innervation of the lateral rectus?
CN VI Abducens
What is cranial nerve CN III?
Oculomotor
What is cranial nerve CN VI
Abducens
What nerve innervates the superior oblique?
CN IV Trochlear
What is cranial nerve CN IV?
Trochlear
What is the easy what to remember what cranial nerves innervate what eye muscles?
LR6 SO4 O3
Lateral Rectus CN VI
Superior Oblique CN IV
Other muscles CN III
What nerve innervates the Medial Rectus?
CN III Oculomotor
What nerve innervates the Inferior Rectus?
CN III Oculomotor
What nerve innervates the Inferior Oblique?
CN III Oculomotor
In terms of sensory innervation what does CN V1 do?
Upper eyelid
Cornea
Conjunctive
In terms of sensory innervation what does CN V2 do?
Lower eyelid
Maxilla
In terms of sensory innervation what does CN V3 do?
Mandible to TMJ
EXCEPT the angle of the mandible.
In terms of modality what is the corneal reflex?
Somatic
What nerve carries afferent AP from the cornea to the pons? Corneal Reflex
CN V1 - Ophthalmic
What nerve carries efferent motor AP from the pons to the eyelid? Corneal reflex
CN VII Facial
What is cranial nerve CN VII
Facial
What muscles is in charge of closing the eye in the corneal reflex?
Orbicularis Oculi
What muscle is in charge of opening the eye in the corneal reflex?
Levator Palpebrae Superiolis
What s the corneal reflex?
Blinking when cornea is irritated of threatened
What nerve is in control of the levator Palpebrae superiolis?
CN III Oculomotor
What is mullers muscle?
Adjoined to the Levator palpebrae superiolis it is involved with the opening of the eyelid.
What is the innervation for mullers muscles?
Sympathetic
What kind of reflex is pupillary constriction?
Autonomic
Under parasympathetic control the pupils do what and under what circumstances?
Constrict
Under bright light and during rest and digest
What is non physiologically constricted pupil called?
Miotic
A miotic pupil along with a drooping eyelid and a raised eyebrow, indicating a facial palsy, is indicative of what condition?
Horners syndrome
What is drooping eyelid called?
Ptosis
A fixed pinpoint pupil could indicate what?
Use of opiate drugs
A fixed dialled pupil could indicate what?
CN III pathology
What muscles encircle the pupil and cause constriction of the pupil?
Sphincter pupillae
Under sympathetic control the pupils do what and under what circumstances?
Dilation of the pupil
Darkness and during fight or flight
What is a non physiologically dilated pupil called?
Mydriatic pupil
What muscles radiate out from the pupil and cause dilation of the pupil?
Dilator Pupillae
What cranial nerve supplies parasympathetic innervation to the sphincter pupillae?
CN III Oculomotor
What is physiologically normal in the pupillary light reflex?
Constriction upon exposure to light.
What reflex occurs in the stimulated eye?
Direct reflex
What reflex occurs in the non stimulated eye?
Consensual reflex
What connects the lens to the ciliary body?
Suspensory ligaments - Zonules
What other function apart from vascular does the ciliary body have?
Contains a ring of smooth muscle and acts like a sphincter.
Describe what happens to the Lens Suspensory Ligaments and the Ciliary Body when you want to focus on an object far away.
Lens - Pulled Flat
Suspensory Ligaments - Pulled tight
Ciliary Body - Dilates
Describe what happens to the Lens Suspensory Ligaments and the Ciliary Body when you want to focus on near by object.
Lens - Rounded
Suspensory Ligaments - Relaxed
Ciliary Body - Constricts
What is the only innervation on the ciliary body?
Parasympathetic - causes constriction of the ciliary body
What are the three types of lacrimation?
Basal
Reflex
Emotional
What is basal lacrimation?
Constantly produced
Lubricates hydrates and cleans
Lysosomes within act as antibacterials
What is reflex lacrimation?
Extra tears produced in response to mechanical or chemical stimuli
What nerves are involved with the reflex lacrimation?
Affert CN V1
Efferent CN VII
What gland is involved with lacrimation and what nerve innervates it?
Lacrimal gland
CN VII
What is cranial nerve CN VII
Facial
Should you see sclera above the iris?
No
If the eyes appear to be bulging as sclera can be seen superiorly to the iris what condition could this indicate?
Graves - Hyperthyroidism
What is Bells palsy?
Palsy of CN VII
Cant close the eye - CNVII is nerve for orbicularis oculi
Why when focusing on a near object does the lens become spherical?
Increases the refractory power of the lens
Why when focusing on a near object does the pupil constrict?
Focuses the light not the most refractory section of the lens
Within the brainstem what is the first region the afferent AP from CN II reach?
The left or right Pre Tectal Nucleus
From the left or right pre tectal nuclei where does the AP head to next.
From either the L/R PTN the AP passes to both the L/R Edinger Westphal Nucleus.
Why is it important that the ipsilateral stimuli is passed bilaterally to the Edinger Westphal Nuclei?
Both eyes have to react in synchrony, direct and consensual response to each stimuli.
What nerve takes the efferent AP from the Edinger Westphal Nuclei?
CN III Oculomotor
What is the direct reflex test?
Shine light in the L/R eye and look at the same eye.
What is the consensual reflex test?
Shine light in the L/R eye and look at the opposite eye.
Where is light from the right visual field picked up?
Left side of the retina
Where is light from the left visual field picked up?
Right side of the retina
Where is light from the upper visual fields picked up?
Lower retina
Where is light from the lower visual fields picked up?
Upper retina
Describe the pathway from the optic nerve that the action potential will take.
Optic nerve Optic chiasma Optic tract Lateral Geniculate Body Optic radiations Visual cortex -Pre Tectal Nucleus -Edinger Westphal Nucleus
Light from the upper visual fields passes through which lobe and on which optic radiation?
Lower optic radiation
Temporal lobe
Light from the lower visual fields passes through which lobe and on which optic radiation?
Upper optic radiation
Parietal lobe
Why do the upper and lower optic radiations diverge?
Upper has to get around the ventricle in the brain.
What neurotransmitter is used by the photoreceptor cells?
Glutimate
What type of lateral connections take place within the retina?
Horizontal cells
Amacrine cells
What is the function of horizontal cells within the retina?
Receive input from photoreceptor cells, transmits signal to other photoreceptor cells and bipolar cells.
What is the function of amacrine cells within the retina?
Receive input from bipolar cells, projects the stimuli to other bipolar cells and amacrine cells.
What do photoreceptor cells do in the absence of light?
They continually release glutamate.
What is the resting membrane potential or a photoreceptor?
-20Vm
What is it within the photoreceptors that maintains the low resting membrane potential?
A cGMP-gated Na+ channel
What pump lies at the synaptic end of the photoreceptor and why is it important?
Na+/K+ channel
Maintains a concentration gradient towards the synaptic end.
Light causes the closure of the cGMP-gated ion channel how is this done?
Rhodopsin is converted into all-trans-retinal
all-trans-retinal activates a G-Protein
G- protein activates a phosphodiesterase
PDE hydrolyzes cGMP decreasing the concentration.
Leads to the closure of c-GMP Na+ channels
What is the light sensitive protein which is converted into its active form?
Rhodopsin
What is the active form of the light sensitive protein?
All-tans-retinal
What dictates visual acuity?
The density and the spacing of the photoreceptors.
What is visual acuity?
Ability to distinguish between two objects
Visual clarity
How are cones distributed throughout the retina?
Highly concentrated within the fovea
What are cones best at?
Seeing in normal daylight
Why are cones more successful during daylight?
They have a low convergence, only a few cones relay to a single ganglion. Makes them far more sensitive.
How are rods distributed throughout the retina?
More evenly distributed throughout.
Why are rods better at seeing in dim light?
They have a higher convergence, so many photoreceptors relay to one ganglion.
As a result many small stimuli cumulatively are enough to trigger an AP.
How are colours picked out?
A colour is produced by a different length wavelength.
Different photoreceptors are more sensitive to varying wavelengths.
What types of cones are found within the retina?
Short wave lengthj
Medium wave length
Long wave length
