Lecture 7: Eye And Adenxa Flashcards
Know how to label the picture on slide 4
Do it nigs
Know the 6 muscles of the eye slide 7
Their innervation and muscle action
Superior rectus- oculomotor nerve, elevates, and laterally rotates the eyeball
Inferior rectus- CN 3- depresses, adducts, and rotates eyeball laterally
Lateral rectus- CN 6- abducts eyeball
Medial rectus- CN 3- adducts eyeball
Superior oblique- CN 4 (trochlear)- abducts, depresses, and medially rotates eyeball
Inferior oblique- CN 3- abducts, elevates, and laterally rotates eye
Levator palpebrae superioris- CN3- elevates superior eyelid
All eye muscles are the oculomotor nerve except?
Torochlear (4) superior oblique (goes through a trochlear)
Abducent CN 6: lateral rectus
What muscles are used to close eyelids?
To open eyelids?
Orbicularis oculi contracts and levator palpebrae relaxes
To open: levator palpebrae superioris contracts
What are the glands that secrete oily substance into tears?
Tarsal glands
What is the syndrome were you have a drooping superior eyelid cause by loss of sympathetic innervation to superior tarsus muscle.
Ptosis: in Horners syndrome
Be able to label the diagram in slide 21
Ya
Be able to label the bones making the orbit on slide 22
Ljdbc
What are the parts that make u the lacrimal apparatus?
Picture on slide25
Consist of the:
Lacrimal gland: secretes lacrimal fluid (watery physiological saline containing lysozyme and O2)
Excretory ducts: lacrimal fluid from gland to conjunctival sac
Lacrimal canaliculi (small canals)
Lacrimal punctum (opening)
Lacrimal papilla
Lacrimal lake (where tears collect)
Lacrimal sac (diluted superior part of duct)
Nasolacrimal duct –> inferior nasal meatus
What is the parasympathetic innervation of the lacrimal gland?
Secretomotor parasympathetic fibre from facial nerve (CN 7) via pterygopalatine ganglion
Sympathetic: inhibits tears
Parasympathetic: creates tears
Development
Were do the retina, iris and optic nerve originate from?
What forms from the ectoderm?
Mesenchyme?
The brain. Reason why the optic nerve is coated in the 3 layers of the cranial meninges!
Surface ectoderm –> lens, cornea, conjunctiva, eyelashes, lacrimal glands.
Mesenchyme–> choroid, sclera, tarsal plates, orbicularis oculi
Describe the optic tract
The optic nerves meet at the optic chiasm then to the optic tract and end at the lateral geniculate body (midbrain)
Rods and cones. What do they specialise in?
Rods: dim light, peripheral vision receptors
Cones: bright light, high acuity colour receptors
Normal retina
What is the optic disc
Fovea centralis
Optic disc: blind spot, where retinal ganglion cell nerve axons leave retina in optic nerve and pass to brain
Fovea centralis: area of macula with most accurate vision, only comes
What used to be in the hyaloid canal?
Because when we are an embryo less than 10 weeks old we have an artery that is supplying the lens and letting it grow. It regresses and it no longer gets supplied from blood vessels. Instead lens will get nutrients from the vitreous fluid
What is the function of the vitreous body?
- holds the eye in shape
- vision, it is a high density substance which magnifies and refracts the light to focus it onto the fovea centralis
Tunic of the eyeball
Label diagram on slide 35
Fibrous: sclera (white): tough, opaque, supplied by arteries cornea (clear): transparent, avascular, highly innervated by nerves from CN5-V1
Vascular: choroid, ciliary body, and iris
Nervous coat: retina (2 layers, neural layer and retinal pigmented epithelium) important because it changes the colour of our eyeball
Corneal blink reflex: Afferent limb (sensory) ie which nerve is sensory to brain Efferent limb (motor from brain)
Afferent: opthamic branch from trigeminal
Efferent: facial
Cataract
Clouding of lens
Scatters light entering the eye ie light can’t focus so will make vision blurry
- fixed by removing lens and replacing it
Aqueous humour
Fills and shapes anterior and posterior chambers of eye
- provides nutrients to avascular lens and cornea, removes wastes
- secretion from ciliary processes
- ciliary processes –> posterior chamber –> through pupil –> anterior chamber
- circadian rhythm of flow: higher in morning than at night
Glaucoma. What is this condition
Impaired aqueous humour outflow
Elevated intracellular pressure
Optic nerve damage
Ciliary body and iris
Ciliary body connect choroid to iris
Ciliary body processes secrete aqueous humour
Autonomic innervation of muscles of iris.
What is the disease when there is a hole in the iris?
Coloboma
Pupillary reflexes
Slow sympathetic response ie dilation
Fast parasympathetic fibres by ciliary nerves ie constriction
Under autonomic control
What happens when there is an absence of nerve stimulation to the eye?
The ciliary muscle relax, the k
Zonular fibres are under tension
Lens is stretched then to refract light for distant vision
What happens when parasympathetic stimulation causes ciliary muscle to contract?
Zonular fibres relax.
In the absense of stretching, internal tension causes lens to become more spherical (thicker) to refract light for near vision
What happens when the aqueous humour pressure decreases?
It may cause the retina to separate slide 50.
Vision impairment and blindness
Macula degeneration
Chronic disease no cure,
Leading causes of blindness
