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
Give the actions of the superior rectus
Elevation, adduction, medial rotation
Give the actions for the medial and lateral rectus
Medial = adduction
Lateral = abduction
Give the actions of the inferior rectus
Depression, adduction, lateral rotiation
Give the origin and insertion of the superior oblique muscle
O= body of sphenoid
I= through trochlear ring, onto posterior surface of sclera deep to the superior rectus muscle
Give the actions of the superior oblique muscle
Depression, abduction, medial rotation
Give the origin and insertion of the inferior oblique muscle
O: anterior floor of orbit
I: posterior surface of sclera, deep to the lateral rectus
Give the actions of the inferior oblique muscle
Elevation, abduction and lateral rotation
What innervates the LPS?
Occulomotor nerve (III)
What innervates the 6 extra-ocular muscles?
SR, MR, IR, IO = oculomotor nerve (CN III)
LR = abducens (VI)
SO = trochlear (IV)
What cells in the lacrimal gland secrete lacrimal fluid?
Acini - contains serous cells that secrete the fluid
Where is the lacrimal gland located?
Superolateral aspect of orbit, in lacrimal fossa (depression in orbital plate of frontal bone)
What enzyme does lacrimal fluid contain?
Lysozyme
What are the 2 parts of the lacrimal gland?
Orbital = larger, sits on lateral margin of LPS (more superior)
Palpebral= smaller, sits on inner surface of eyelid
What is the blood supply and drainage of the lacrimal gland?
Blood supply: lacrimal artery (branch of ophthalmic)
Venous drainage: superior opthalmic vein –> cavernous sinus
What innervates the lacrimal gland?
Lacrimal nerve - branch of ophthalmic nerve (V1)
Describe the flow of tears through the lacrimal apparatus
1- lacrimal glands secrete fluid, moves across the eyes when you blink
2- accumulates in lacrimal lake (medially)
3- fluid drains into lacrimal punctum
4- drained by superior and inferior lacrimal canaculi, which then join to form the common lacrimal canaculi
5- drains into the lacrimal sac
6- drains into the nasolacrimal duct
7- drains into the inferior meatus of the nasal cavity
What forms the external nasal septum?
Nasal bone
Maxilla - frontal processes
Frontal bone - nasal part
Cartilage: septal, 2x lateral and 2x alar (major and minor)
What forms the internal nasal septum?
Nasal, maxillary and palatine (paired bones)
Ethmoid (perpendicular plate) and vomer
What bones contribute to the nasal cavity?
Nasal - paired
Maxilla - paired
Sphenoid
Vomer
Palatine - paired
Lacrimal - paired
Ethmoid
What 4 channels are present in the nasal cavity?
Superior, middle and inferior nasal meatus’
Sphenoethmoidal recess (between superior concha and nasal roof)
Where do the 4 channels open into?
Common nasal meatus
Where are the 4 sinuses of the face located?
Sphenoidal - within body of sphenoid (either side of nose, superiorly)
Maxillary - either side of nose under cheeks
Frontal - most superior, on forehead
Ethmoidal - within ethmoid bone, just lateral to sphenoidal (3 ethmoidal sinuses)
What sinus is at risk of spread of infection?
Maxillary
Where does the frontal sinus drain?
Via frontonasal duct into middle meatus
What are the functions of the sinuses?
- lighten weight of head
- support immune defence
- humidify air
- Increase resonance of voice
What innervates the sinuses?
Trigeminal nerve
What nerve provides parasympathetic innervation to the lacrimal gland?
Facial nerve (CN VII)
What bones form the nasal septum?
Ethmoid (perpendicular plate)
Vomer
What 4 bones form the roof of the nose?
Frontal, sphenoid, ethmoid, nasal
What 2 bones form the floor of the nose?
Palatine (horizontal process) and maxilla (palatine process)
What drains into the inferior meatus?
Nasolacrimal duct
Where do the maxillary sinuses drain into?
Middle meatus
What type of epithelium lines the paranasal sinuses?
Pseudostratified ciliated columnar epithelial cells with goblet cells
Where do the frontal sinuses drain into?
Middle meatus
Where do the sphenoid sinuses drain into?
Sphenoethmoidal recess
What gland can be approached surgically through the sphenoid sinuses?
Pituitary
The superior wall of the orbit separates the orbital cavity from which cranial fossa?
Anterior
The inferior wall of the orbital cavity separates it from which sinus?
Maxillary
What movements do the medial and lateral check ligaments limit?
Medial - limits abduction
Lateral - limits adduction
What does the inferior check ligament do when the gaze is directed downwards?
Retracts the lower eyelid
What is the term for when the eyeballs are retracted into their sockets during disease, dehydration or starvation?
Enophthalmos
What type of secretion do the tarsal glands secrete to stop the eyelids sticking together when closed?
Lipid
What is the name given to the SM fibres located within the levator palpebrae superioris?
Superior tarsal
What structure produces aqueous humour?
Ciliary processes
Where is aqueous humour secreted?
Into the posterior chamber, then passes the pupil to enter the anterior chamber
What is the role of the vitreous humour?
Refracts light, holds the retina in place and supports the lens
What structures are responsible for the refraction of light?
Cornea, lens, aqueous humour, vitreous humour
What are the boundaries of the nasal cavity?
Roof: frontonasal, ethmoidal, sphenoidal (named according to bones forming)
Floor: maxilla (palatine process) and palatine (horizontal plate)
Medial wall: nasal septum (ethmoid perpendicular plate and vomer)
Lateral wall: 3 nasal concha, medial surface of maxilla, vertical plate of palatine, medial pterygoid plate of sphenoid, labyrinth of ethmoid
Where is olfactory mucosa located?
Above the superior nasal concha
What is the name of the arterial plexus in the nose?
Kiesselbach’s plexus
