Orbit Flashcards
What portion of the orbit is the weakest? What 3 bones is it composed of?
medial wall composed of the maxilla, lacrimal, and ethmoid
What portion of the orbit is the most reinforced?
lateral wall is reinforced anteriorly by the zygomatic bone and posteriorly by the greater wing of the sphenoid
What is the floor of the orbit formed by?
the orbital process of the maxilla and some palatine bone
What separates the floor from the lateral wall of the orbit?
inferior orbital fissure
The roof of the obit is nearly horizontal and is formed by what?
the orbital part of the frontal bone
What is a shallow depression in the orbital part of the frontal bone? (houses the lacrimal gland)
the fossa for the lacrimal gland
The optic canal goes through the lesser wing of the sphenoid and allows for the passage what what 2 things into the orbit?
optic nerve (CN II) and opthalamic artery
What is located between the greater and lesser wings of sphenoid and allows for the passage of the nerves that supply the extraocular muscles, 3 branches of the opthalmic nerve (CN V1) and opthalmic veins? What nerves pass though this?
Superior orbital fissure
CN III, IV, VI, and V1
What provides passage for the maxillary nerve (CN V2) and infraorbital vessels?
Inferior orbital fissure
What travels anteriorly to become enclosed in bone and form the infraorbital canal that opens below the orbital rim as the infraorbital foramen?
infraorbital groove
What does the infraorbital foramen contain?
infraorbital nerve and vessels
What provides communication between the orbit and ethmoid for the passage of anterior and posterior ethmoidal nerves and vessels?
ethmoidal foramina
What provides lubrication for the conjunctiva and the eyeball?
lacrimal apparatus
What are the 3 layers of the eyeball?
fibrous layer- outer
middle layer- vascular
retinal layer- inner
Which layer of the eyeball forms the fibrous skeleton and provides the shape and resistance?
fibrous layer
What forms the tough fibrous layer covering the posterior 80% of the eyeball?
sclera- the anterior part of it is visible as the “white of the eye” and provides attachment for the extrinsic and intrinsic muscles of the eye
What is located in the anterior part of the eyeball and is highly sensitive to touch? Innervation
cornea, ophthalmic nerve (V1)
What does the middle vascular layer include?
choroid, ciliary body, iris
What lines most of the sclera and contains an extremely rich capillary bed with the smallest vessels located next to the retina?
choroid
What connects the choroid with the circumference of the iris?
ciliary body- muscular and vascular
What is a thin contractile diaphragm with a central aperture, the pupil, for transmitting light?
iris
What are the two involuntary muscles that control the size of the pupil?
sphincter- parasympathetic, constricts the pupil
dilator- sympathetic, dilates the pupil
What is the sensory neural part of the eyeball?
retina
What is the neural layer a continuation of? What is this layer sensitive to?
the optic nerve (CN II), light-sensitive
What is the oval-shaped area of acute vision called?
the macula- near the optic disk
What layer is attached to the choroid and helps absorb the light reducing the scattering of light in the eyeball?
the pigmented layer
What area is investigated during the fundus examination?
ocular fundus- posterior part of eyeball where the light is focused after going through the compartments of the eyeball
What chamber is directly posterior to the cornea and anterior to the iris? What is it filled with? What produces the fluid?
the anterior chamber is filled with a clear watery solution called aqueous humor produced by the ciliary body
What chamber is between the iris and the lens?
posterior chamber- also filled with aqueous humor
What is posterior to the iris and anterior to the vitreous body?
lens- a transparent biconvex structure enclosed in a capsule
The lens is attached to the ciliary processed by what?
the suspensory ligament
Sphincter-like contraction of the _______ relaxes the lens making it more _____ which brings _____ objects into _____.
ciliary muscle, convex, near, focus
this process is called accommodation
The ______ occupies the posterior 80% of the eyeball and is filled with the gelatinous substance called the _______.
vitreous body, vitreous humor
this is irreplaceable unlike the aqueous humor
What are the layers (anterior to posterior) of the eyelids?
- thin skin- loose CT
- skeletal (voluntary) muscle fibers
- orbital septum is a fibrous membrane
- superior and inferior tarsi made of dense CT
- conjunctiva
- muscles of superior eyelid
What is continuous with the periosteum of the bony part of the orbital rim on one end and with the tarsi on the other?
orbital septum
What do the superior and inferior tarsi represent?
the skeleton of the eyelids
What are embedded in the tarsi and produce an oily secretion that lubricates the edges of the eyelids and prevents them from sticking together?
tarsal glands- modified sebaceous glands whose secretions increase the viscosity of tears and slows down evaporation
Paralysis of either superior eyelid muscles results in what? What are these muscles?
ptosis- drooping eyelid
- levator palpebrae superioris
- superior tarsal muscle
What is involved in the production and delivery of lacrimal fluid that lubricates the eyeball?
lacrimal apparatus- it also has an antibacterial and nutritive function
What carries the lacrimal fluid to the superior fornix of the conjunctiva?
excretory ducts
Lacrimal fluid accumulates in the medial corner of the eye and is drained via superior and inferior ______ (one in each eyelid) into the ______.
Lacrimal canaliculi, lacrimal sac
What conveys the lacrimal fluid to the inferior nasal meatus?
nasolacrimal duct
Production of lacrimal fluid is stimulated by (parasympathetic/sympathetic) innervation through fibers of the ____ nerve (CN ? ) which synapse in the pterygopalatine ganglion to eventually form the ______ nerve (off the _______). Postsynaptic (parasympathetic/sympathetic) fibers from the superior cervical ganglion are vasoconstrictive.
parasympathetic, facial, VII, lacrimal, ophthalmic, sympathetic
Elevation (pupil)
moves up
Depression (pupil)
moves down
Adduction (pupil)
moves medially
Abduction (pupil)
moves laterally
Intorsion (pupil)
internal rotation- rotates medially towards the nose
Extorsion (pupil)
external rotation- rotates laterally away from nose
All recti muscles originate from what?
the common tendinous ring around the optic nerve (annulus of Zinn) near the optic foramen and intsert onto the anterior part of the eyeball
Oblique muscles originate from the orbital walls and attach to the ______ part of the eyeball.
posterior
Which muscle abducts the eye and is innervated by the abducens nerve?
lateral rectus
Which muscle adducts the eye?
medial rectus
Which muscle mainly elevates the eye and slightly adducts? Also when the eye is adducted, it will intort.
superior rectus
What muscle mainly depresses the eye and slightly adducts? When the eye is adducted, it will also extort.
inferior rectus
What muscle originates from the sphenoid bone near the apical region of the orbit and then passes along the medial wall of the orbit upon reaching a fibrocartilaginous pulley the trochlea, where it makes a sharp bend and inserts onto the superior and posterior part of the eyeball?
superior oblique
If the gaze is directly laterally and the eyeball is abducted, this muscle will mainly adduct and intort the eyeball. When the eyeball is adducted and the visual axis is more parallel with the long axis of the distal portion of this muscle, it becomes the depressor of the eyeball.
superior oblique
What innervates the superior oblique?
trochlear nerve (CN IV)
What is the only extraocular muscle that originates from the anterior part of the orbit (near the lacrimal fossa) and inserts onto the posterior and inferior part of the eyeball?
inferior oblique
If the gaze is directed laterally and the eyeball is abducted this muscle mainly adducts and extorts the eyeball. When the eyeball is adducted and the visual axis is more parallel with the long axis of the distal portion of this muscle it elevates the eyeball.
inferior oblique
What muscles are innervated by the oculomotor nerve (CN III)?
inferior oblique, inferior rectus, superior rectus, medial rectus
