Orbit Flashcards
The bony orbits are bounded by
medially- ethmoid paranasal sinuses
inferiorly- maxillary paranasal sinuses
Accessory structures of the eye
eyebrows
eyelids
Eyelids
separated by a palpebral fissure and reinforced by dense CT
Levator palpebrae superioris lifts the superior eyelid
orbicularis oculi closes the eyelid
Conjunctiva
a transparent mucous membrane that covers the inner surfaces of the eyelids and anterior surface of the eyeball
Lacrimal apparatus
keep the surface of the eyelid moist
Lacrimal gland
produces lacrimal fluid, lies in a fossa in the superolateral orbit
Lacrimal ducts
convey fluid to the conjunctival sac
Lacrimal canaliculi
connect to the nasolacrimal duct- a passage that conveys lacrimal fluid to the nasal cavity
Lacrimal production is stimulated by parasympathetic impulses of
CN VII
7 extra-ocular muscles of the orbit
levator palebrae superioris
4 recti- superior, inferior, medial, and lateral
2 obliques- superior and inferior
Common tendinous ring
origin of the 4 recti
surrounds the optic canal
Levator palpebrae superioris
elevates the superior eyelid
innervated by CN III
4 recti muscles
mainly run anteriorly to attach to the superior, inferior, medial, and lateral aspects of the eyeball
Superior oblique
originates posteriorly, runs anteriorly along the medial orbital wall, and loops thru the trochlea in the anteromedial part of the orbital roof insert on the posterolateral eye surface
out and down
Inferior oblique
abducts and elevates the pupil
out and up
Nerves of orbit
general sensory- CN V1
Special sensory- CN II for vision
brachial motor- CN VII to orbicularis oculi
somatic motor- CN III, CN IV, CN VI
arteries of the orbit
receives arterial blood supply from branches of the ophthalmic artery off the internal carotid artery
the central retinal artery is a terminal branch
Nasal cavity
lined with mucosa continuous with the lining of all chambers that communicate with the nasal cavity
Nasopharynx posteriorly
paranasal sinuses superiorly and laterally
lacrimal sac and conjunctiva superiorly
Nasal cavity boundaries
roof (frontal)-
ethmoid
sphenoid bones
floor-
maxilla
palatine
lateral walls-
nasal conchae
Lateral nasal wall
3 mucosa covered scrolls of bone form the lateral nasal walls-
superior, middle, and inferior nasal conchae
Paranasal air sinuses
air-filled extensions of the respiratory part of the nasal cavity located within the frontal, ethmoid, sphenoid, and maxillary
spheno-ethmoidal recess
opening of the sphenoidal sinus
Superior meatus
entrance to the posterior ethmoidal sinuses
Middle meatus
entrance to the frontal, ethmoidal, and maxillary sinuses