A3 - Orbit and nasal cavity Flashcards
List the 7 bones contributing to the walls of the orbit
Maxilla
Zygomatic
Frontal
Ethmoid
Lacrimal
Sphenoid
Palatine
The orbit is a quadrangular pyramid shape, list the boundaries.
Superior wall (roof): frontal, sphenoid
Medial wall: ethmoid bone, contributions from maxilla, lacrimal and sphenoid bones
Inferior wall (floor): maxilla, zygomatic and palatine bones
Lateral wall: zygomatic bone (frontal process) and sphenoid
What is the difference between palpebral and bulbar conjunctivae?
Palpebral - covers the eyelids (lines inside of them)
BUlbar - lines the sclera
What are the recesses called that are formed by the palpebral conjunctiva?
Superior and inferior conjunctival fornices
What is the orbital septum?
Superior and inferior orbital septum = fibrous membrane from the orbital magins to the tarsi
Where does the medial palpebral ligament attach?
Anterior lacrimal crest of maxilla to the superior and inferior tarsus
Where does the lateral palpebral ligament attach?
From orbital tubercle on zygomatic bone, to superior and inferior tarsus
What cranial nerves pass within the orbit?
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
What is the superior and inferior tarsi?
Bands of dense connective tissue that strengthen the superior and inferior eyelids (respectively)
What are tarsal glands responsible for?
Located within the tarsi, they secrete lipids for lubrication. This forms a barrier that lacrimal fluid doesnt cross - if production is excessive it spills as a tear
What passes through the optic canal?
Optic nerve and ophthalmic artery
What passes through the superior orbital fissure?
Oculomotor nerve
Trochlear nerve
Abducens nerve
Ophthalmic nerve
Superior ophthalmic vein
What passes through the inferior orbital fissure?
Maxillary nerve
Infraorbital vessels
What passes through the infraorbital foramen?
Infraorbital nerve (branch of the maxillary)
What are the 3 layers of the eyeball?
Fibrous - outer
Vascular - middle
Neuroretinal - inner
What does the fibrous layer of the eye include? List the functions
Sclera - white part of the eye, where extra-ocular muscles attach
Cornea - transparent, allows light to enter
What is the area called where the sclera and cornea meet?
Corneal limbus
What does the vascular layer of the eye include? List the functions
Choroid - connective tissue, highly vascular - nourishes outer layers of retina
Ciliary body - includes ciliary muscle and ciliary processes, controls the shape of the lens and forms aqueous humour
Iris - circular with aperture in middle (pupil), controls diameter of pupil
What are the 2 layers of smooth muscle fibres found in the iris?
Sphincter pupillae: circular fibres that decrease the diameter of the pupil
Dilator pupillae: radial fibres that increase the diameter of the pupil
What is the effect of the sympathetic and parasympathetic nervous system on pupillary dilation/ constriction? What fibres do they each innervate?
Sympathetic = innervates dilator pupillae to increase diameter of pupil (slow)
Parasympathetic = innervates sphincter pupillae to decrease diameter of pupil (fast)
What are the 2 layers of the retina?
Outer pigmented layer - single layer of cells, attached to choroid and helps it absorb light by preventing it scattering
Inner neural layer - consists of photoreceptors
Where is the non-visual part of the retina?
Anteriorly - as the neural layer of the retina doesn’t continue here (only posteriorly and laterally)
What pierces the optic disc?
Central retinal artery, a branch of the ophthalmic artery
What area in the eye has the highest number of cones?
Fovea - within the macula
What type of fluid do the anterior and posterior chambers possess?
Anterior = aqueous humour
Posterior = vitreous humour
What can cause glaucoma?
Obstruction of drainage of the aqueous humour, but normal production so fluid will build up in the anterior chamber. Intraocular pressure can increase and put pressure on the lens, pushing it into the vitreous chamber. Pressure will then be put on the optic nerve and retina = damage and blindness
What maintains pressure of vitreous humour?
Ora serrata
Where is the ophthalmic artery derived from?
Internal carotid artery
What fibres form the suspensory ligament?
Zonular fibres
What shape lens would be ideal to see near vs far objects? How would this affect the tension in the suspensory ligament?
Far objects (long-sight) = flatter lens, thus relaxed ciliary muscle and tight suspensory ligament (holds it flat)
Near objects = rounded lens, thus contracted ciliary muscle and loose suspensory ligament
How does parasympathetic innervation affect accommodation?
Causes contraction of ciliary muscle, relaxing the suspensory ligament and rounding the eye lens = better for near vision
Give the origin, insertion and action for levator palpebrae superioris
O= lesser wing of sphenoid
I= superior tarsus
A= elevates upper eyelids
Give the attachments for the recti muscles
O= Common tendinous ring (superior recti = superior part of ring, etc.)
I= sclera, posterior to sclera-cornea junction