A3 - Orbit and nasal cavity Flashcards by beth elliott

List the 7 bones contributing to the walls of the orbit

Maxilla
Zygomatic
Frontal
Ethmoid
Lacrimal
Sphenoid
Palatine

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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

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What is the difference between palpebral and bulbar conjunctivae?

Palpebral - covers the eyelids (lines inside of them)
BUlbar - lines the sclera

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What are the recesses called that are formed by the palpebral conjunctiva?

Superior and inferior conjunctival fornices

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What is the orbital septum?

Superior and inferior orbital septum = fibrous membrane from the orbital magins to the tarsi

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Where does the medial palpebral ligament attach?

Anterior lacrimal crest of maxilla to the superior and inferior tarsus

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Where does the lateral palpebral ligament attach?

From orbital tubercle on zygomatic bone, to superior and inferior tarsus

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What cranial nerves pass within the orbit?

Optic
Oculomotor
Trochlear
Trigeminal
Abducens

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What is the superior and inferior tarsi?

Bands of dense connective tissue that strengthen the superior and inferior eyelids (respectively)

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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

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What passes through the optic canal?

Optic nerve and ophthalmic artery

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What passes through the superior orbital fissure?

Oculomotor nerve
Trochlear nerve
Abducens nerve
Ophthalmic nerve
Superior ophthalmic vein

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What passes through the inferior orbital fissure?

Maxillary nerve
Infraorbital vessels

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What passes through the infraorbital foramen?

Infraorbital nerve (branch of the maxillary)

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What are the 3 layers of the eyeball?

Fibrous - outer
Vascular - middle
Neuroretinal - inner

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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

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What is the area called where the sclera and cornea meet?

Corneal limbus

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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

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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

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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)

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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

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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)

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What pierces the optic disc?

Central retinal artery, a branch of the ophthalmic artery

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What area in the eye has the highest number of cones?

Fovea - within the macula

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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?

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