Orbit and the Eye Flashcards
Identify the bones in the bony orbit
Identify features of the bony orbit
What is the apex of the bony orbit?
Optic canal
What are the sides of the orbital rim?
Superior, inferior, medial and lateral orbital margins
What kind of fracture can affect the medial wall and orbital floor?
Orbital blowout fracture
Which muscle forms the external layer of the eyelid?
Orbicularis oculi
What are the parts of the orbicularis oculi?
Orbital and palpebral
What are tarsal glands embedded in tarsi responsible for?
Lipid secretion
The iris is covered by conjunctiva/cornea and the sclera and lower eyelid is covered by conjunctiva/cornea
Cornea
Conjunctiva
What is the junction between cornea and sclera better known as?
The limbus
Outline the path of lacrimal fluid in the eye
Produced by lacrimal gland before washing over eye and being pushed toward the medial angle. Drain through lacrimal punctae before reaching inferior meatus
Which nerve provides parasympathetic innervation to the lacrimal gland?
CN VII (facial)
What are the three layers of the eye?
Fibrous
Uvea (vascular layer)
Retina (photosensitive)
What are the two parts of the fibrous layer?
Sclera and cornea
What are the three parts of the uvea?
Iris
Ciliary body
Choroid
What divides the eye into anterior and posterior segments?
Lens
The anterior segment contains vitreous/aqueous humour while the posterior segment contains vitreous/aqueous humour
Anterior contains aqueous while posterior contains vitreous
Outline the circulation of aqueous humour
Ciliary body secretes aqueous which nourishes lens within posterior chamber then cornea in anterior chamber. Passes into scleral venous sinus (canal of Schlemm) and is reabsorbed
What is the main arterial supply to the eye and what is it a branch of?
Ophthalmic artery - branch of internal carotid
The central artery of the retina is wholly encapsulated by what?
Optic nerve
The majority of venous drainage of the eye comes from which vein?
Superior ophthalmic vein
What is the importance of the danger triangle of the face?
Bacteria in this area can enter the venous system which can enter the cavernous sinus and meninges
What is found within the fundus?
Optic disc
Macula
Fovea (centre of macula)
The optic disc is the point of CN III formation. True/false?
False - site of CN II formation (optic nerve)
Where is the blind spot of the eye? Why?
Optic disc - there are no photoreceptors
The fovea within the macula has the greatest density of cones/rods
Cones
From anterior to posterior, what are the layers of the retina?
Axons of ganglion cells
Ganglion cells
Photoreceptors
Complete ischaemia of the central artery of the retina can lead to what?
Monocular blindness
What are the 7 extraocular muscles of the eye?
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Levator palpebrae superioris
Where do all rectus muscles originate and insert?
Originate from common tendinous ring and insert onto sclera
What is the somatic motor innervation of the extraocular muscles?
LR6 - Lateral rectus CN VI
SO4 - Superior oblique CN IV
AO3 - All others CN III
What are the only two eyeball muscles not to have a secondary movement?
Medial and lateral rectus
The lateral rectus muscle can only abduct/adduct the eyeball and bring line of gaze into the same plane as superior and inferior rectus/oblique
Abduct
Rectus
When in abduction, the superior rectus can only elevate/depress while the inferior rectus can only elevate/depress
Elevate
Depress
The medial rectus can only abduct/adduct the eyeball and bring line of gaze to the same plane as superior and inferior rectus/oblique
Adduct
Oblique
When in adduction, the superior oblique can only elevate/depress while the inferior oblique can only elevate/depress
Depress
Elevate
Pure elevation of the eyes is carried out by which muscles acting synergistically?
Superior rectus and inferior oblique
Pure depression of the eyes is carried out by which muscles acting synergistically?
Superior oblique and inferior rectus
