The orbit Flashcards
What forms the roof and floor of the orbit?
Roof= orbital plate of the frontal bone Floor= maxilla
What forms the lateral and medial walls of the orbit?
Lateral wall= greater wing of sphenoid and zygoma
Medial wall= ethmoid and lacrimal bones
What does the superior orbital fissure contain?
Oculomotor nerve, trochlear nerve, abducent nerve, branches of opthalmic nerve
What does the inferior orbital fissure contain?
Maxillary nerve and sympathetic nerves
What does the optic canal contain?
Optic nerve and opthalmic artery
What does the lacrimal groove become?
Nasolacrimal canal-> inferior meatus of nasal cavity
What is the sclera?
The outer fibrous coat of the eye- the white of the eye
Continuous with cornea and dura
Covered by conjunctiva
Describe the cornea
Avascular, richly innervated, transparent
Covered by non-keratinised stratified squamous epithelium
Continuous with conjunctiva
What is the middle vascular coat of the eyeball?
Choroid
What is the choroid?
Highly vascular middle coat of the eyeball
Continous with iris by the ciliary body
What is the ciliary body?
Ciliary processes which project inwards towards the lens, connected by suspensory ligaments
Responsible for changes in lens convexity
Contraction relaxes suspensory ligaments-> increased lens convexity
Parasympathetic activation causes what to happen in the eye?
Contraction of ciliary muscles to make lens more convex and adjust for near-sightedness Sphincter pupillae (circular) contract and constricts pupil
Sympathetic activation causes what to happen in the eye?
Dilator pupillae to contract, pupil dilates
What is the optic disc?
Blind spot where fibres of optic nerve converge
What is the macula lutea and where is it found?
Site of highest visual resolution on retina
Surround fovea centralis
What is papilloedema?
Oedema of the vessels entering the eyeball around the optic disc
Caused by increased ICP
What is the contents of the eyeball?
Vitreous body (clear gel) behind lens and aqueous humour infront of lens
What nerves are involved when focusing on a near object?
Eyes converge (oculomotor), pupils constrict and lenses increase in convexity (Parasympathetic from ciliary ganglion)
What is the small elevation on the medial margin of the lower eyelid called?
Lacrimal papilla
What is the small orifice in the lacrimal papilla called? Where does it lead?
Lacrimal punctum, leads to lacrimal sac and nasolacrimal duct-> inferior meatus of nasal cavity
Whats the palpebral fissure?
Area between eyelids
What can lead to sunken eyes?
Cachexia (due to cancer) or severe anorexia
What can lead to popping eyes?
Hyperthyroidism
What inserts into the skin of the eyelids
Obicularis oculi (palpebral part) and levator palpebrae superioris
What are the eyelids strengthened by?
Dense connective tissue= tarsus
Where are the tarsal glands and what do they produce?
Found in the tarsus of the eyelids, lubricates edges of the eyelids
What is found in the medial corner of the eye?
Lacrimal caruncle and just lateral to it is the plica semiluminaris (vertical fold of conjunctiva)
Name the recti and their innervation
Superior, medial and inferior recti= oculomotr
Lateral rectus= abducent
Name the other muscles of the eye (not recti)
Superior oblique= trochlear nerve
Inferior oblique= oculomotor nerve
Where do the parasympathetic nerves to the eye orginate from?
Pre ganglionic from Edinger-Westphal nucleus in brainstem
Travel with oculomotr fibres to ciliary ganglion
Post ganglionic fibres travel in short ciliary nerves to eye
What would pressure on the oculomotor nerve cause?
Diplopia and ptosis (drooping of eyelids)
Large and unresponsive pupil (no PNS innervation)
Down and out eye
What is myopia?
Focused image falls short of retina, lens too round
What is it called when focused image falls short of retina?
Myopia
What is hypermetropia?
When image is in focus behind retina
Lens is too flat
What does the opthalmic nerve supply?
Sensory to eyeball, lacrimal gland, conjunctiva, eyelids, forehead and nasal mucosa
Via lacrimal, nasociliary and frontal branches
What is the supply of the lacrimal gland?
Sensory from opthalmic nerve
Parasympathetic from pterygopalatine ganglion
What nerves and muscles are involved in the blink reflex?
Sensory efferent from conjunctiva= lacrimal nerve of V1
Brainstem
Obicularis oculi closes eyelids= facial nerve (VII)
Describe nasociliary nerve
Branch of V1, divides into anterior ethmoidal nerve (ethmoidal sinus) and infratrochlear nerve (skin&mucous membrane of nose and conjunctiva). Also gives off ciliary nerves (sympathetic and sensory to eyeball)
What is the blood supply of the retina
Central artery= end artery from opthalmic artery
Describe route of blood drainage from retina
Superior and inferior opthalmic veins-? superior orbital fissure-> cavernous sinus
inferior orbital fissure-> terygid plexus
Name the branches of the opthalmic artery
Ciliary branches, anterior and posteiror ethmoidal and central artery
Which branch of the opthalmic nerve is most medial and which is most lateral?
Medial= nasociliary, lateral= lacrimal
