Anatomy - Orbit Flashcards
What bones form the roof and floor of the orbit?
Floor
- orbital process of maxilla
- palatine bone
Roof
-orbital part of frontal bone
What bones form the walls of the orbit?
Medial walls
- Orbital plate of ethmoid
- Frontal process of maxilla
- Lacrimal
- Sphenoid
Lateral walls
- frontal process of zygomatic bone (ant)
- greater wing of sphenoid (post)
The apex of the orbit is at the __
Optic canal in the lesser wing of the sphenoid
What separates the floor of the orbit from the lateral wall?
Inferior orbital fissure
What houses the lacrimal gland?
Fossa for the lacrimal gland in the orbital part of the frontal bone
Fissures and foramina of the orbit
- Optic canal
- Superior orbital fissure
- Inferior orbital fissure
- Infraorbital groove
- Ethmoidal foramina
The optic canal goes through ___ and allows for passage of ___
Goes through the lesser wing of the sphenoid
Allows for passage of
Optic n. (CN II)
Ophthalmic a.
Superior orbital fissure is located ___ and allows for passage of ___
Between the greater and lesser wings of sphenoid
Allows for passage of: CN III IV VI V1 Ophthalmic v.
Inferior orbital fissure is located ___ and allows for passage of ___
At the right angle to the superior orbital fissure
-between greater wing of sphenoid and maxilla
Allows for passage of CN V2 (maxillary n.) Infraorbital vessels
Travel of the infraorbital groove?
What does it contain?
Begins from inferior orbital fissure Travels anteriorly Becomes enclosed in bone Forms infraorbital canal Opens below orbital rim as the infraorbital foramen
Contains infraorbital n. and vessels
Ethmoidal foramina allows for passage of __
Anterior and posterior ethmoidal nerves and vessels
____ humor is irreplaceable and more dense than ___
Vitreous
Aqueous
The aqueous humor is located in the (anterior/posterior) chamber of the eye
Anterior
Which is between cornea and iris
The posterior chamber is located between ___ and ___
Iris and lens
3 layers of the eyeball and what they contain
- Fibrous
- sclera, cornea
- Vascular
- choroid, ciliary body, iris
- Retinal
- optic disc, macula, ocular fundus
Tough fibrous layer covering the posterior 80% of the eyeball.
The anterior part is visible as the white of the eye
Sclera
Transparent part of the fibrous layer located in the anterior part of the eye.
Cornea
The cornea is more ___ than the sclera and projects ___
Convex
Anteriorly
Blinking and tears are elicited by touching what? and innervation of what nerve?
Cornea
Ophthalmic n. (V1)
The ____ lines most of the sclera and contains a rich capillary bed, with the smallest vessels located next to the ___, which is avascular
Choroid
Retina
The ____ connects the choroid with the iris. It is both ___ and ___
Ciliary body
Muscular
Vascular
The ___ is a thin contractile diaphragm with a central aperture, the ___, for transmitting ___.
Iris
Pupil
Light
Two involuntary muscles control the size of the pupil:
- system
- fibers
- action
- speed
Sphincter pupillae
- parasympathetic
- circular fibers
- constriction
- fast
Dilator pupillae
- sympathetic
- radial fibers
- dilation
- slow
The optic part of the retina consists of 2 layers:
- Neural layer
- light sensitive
- continuation of the CN II - Pigmented layer
- attached to choroid
- helps reduce scattering of light through absorption
During a retinal detachment, which layer of the retina becomes dislodged?
Neural layer only
Where the Optic Nerve (CN II) enters the eyeball, the retina contains the __
Optic disc
True or false:
the optic disc has photoreceptors
False
The oval-shaped area of acute vision is called the __
Macula
The posterior part of the eyeball wig its retina is called the ____.
This is where light is ___
Ocular fundus
Focused
Light traveling to the retina passes through the following structures:
Cornea Anterior chamber Posterior chamber Lens Vitreous humor
The anterior chamber is filled with ___, which is produced by ___
Aqueous humor
Ciliary body
The posterior chamber is filled with __
Aqueous humor
The lens is attached to the ciliary processes by __
The suspensory ligament
Explain accommodation
- passive stretching and thinning of the lens brings far objects into focus
- sphincter like contraction of ciliary muscle relaxes the lens, bringing near objects into focus (parasympathetic)
Layers of the eyelids, anterior to posterior
- thin skin with loose CT layer
- Skeletal muscle fibers
- Orbital septum
- Tarsi (dense CT, eyelid “skeleton”)
- Conjunctiva
- Muscles of superior eyelid
Skeletal muscle fibers on the second layer of the eyelids:
Action
Innervation
Palpebral part of orbucularis oculi
- involuntary (orbital part is voluntary)
- gently close eyelid
- innervates by CN VII
What is the orbital septum?
Attachments?
- Fibrous membrane
- Continuous with periosteum of the orbital rim and the tarsi
- in the upper eyelid it also attaches to levator palpebrae superioris tendon
The superior and inferior tarsi are made of ___. Attachments?
Dense CT
Medially: Maxilla through Medial Palpebral ligament
Laterally: zygomatic bone through lateral Palpebral ligament
Tarsal glands produce ___
Oily secretions Keep eyelids from sticking together Modified sebaceous glands Increase viscosity of tears Decrease evaporation
Mucous membrane that lines the eyelids internally and reflects into the sclera superiorly and inferiorly
Conjunctiva
The upper and lower pockets formed by the reflections of the conjunctiva onto the sclera are called:
Superior and inferior fornices
Muscles of superior eyelid elevation
Levator Palpebrae Superioris
Superior Tarsal Muscle
Origin, insertion, and innervation of levator Palpebrae superioris
Posterior part of Orbital roof
Superior tarsus
CN III
Origin, insertion, and innervation of superior tarsal muscle
Levator Palpebrae Superioris
Superior Tarsus
Sympathetic postganglionic fibers from the superior cervical ganglion
The lacrimal gland is located ___ in the ___ corner of the orbit
Anteriorly
Superolateral
Excretory ducts carry the lacrimal fluid to the ___ of the conjunctiva
Superior fornix
Lacrimal fluid that accumulates in the medial corner of the eye is drained via __
Superior and inferior lacrimal canaliculi
The openings of the canaliculi are the ___, located on the ___ surface of the eyelid
Puncta
Posteromedial
Innervation of the lacrimal gland
Production of fluid = parasympathetic through CN VII
sympathetic fibers re vasoconstrictive
All recti muscles originate from the __ and insert on the __ part of the eyeball
Common tendinous ring around the Optic Nerve (annulus of Zinn)
Anterior
Oblique muscles originate from the ___ and attach to the __ part of the eyeball
Orbital walls
Posterior
Actions and innervation of:
Lateral rectus
Abduction
CN VI (abducens)
Actions and innervation of:
Medial rectus
Adduction
CN III
Actions and innervation of:
Superior rectus
Elevation
Slight adduction
CN III
Actions and innervation of:
Inferior rectus
Depression
Slight adduction
CN III
Actions and innervation of:
Superior oblique
When the eye is abducted:
Abduction and intortion
When the eye is adducted:
Depression
CN IV
Origin and insertion of superior oblique
Sphenoid
Goes to trochlea (pulley) and bends to insert on the superior and posterior eyeball
Actions and innervation of:
Inferior oblique
When the eye is abducted:
Abduction and extortion
When the eye is adducted:
Elevation
CN III
The only extraocular muscle that originates from the anterior part of the orbit (near the lacrimal fossa) is the __
Inferior oblique
The ___ is a large sensory nerve partially ensheathed with the cranial meninges
Optic N. (CN II)
The optic n. passes into the orbit via the ___ and collects sensory info from the ___. It projects to the ___ geniculate nucleus of the ___
Optic canal
Retina
Lateral
Thalamus
The oculomotor n. (CN III) nuclei are in the ___. The nerve exits the brain between the __ and the ___. It passes into the orbit via the ____.
Midbrain
Midbrain and pons
Superior orbital fissure
The superior branch of CN III innervates the __ and ___
Levator Palpebrae Superioris
Superior Rectus
The inferior branch of CN III innervates the ___, ____, and ____.
Medial rectus
Inferior rectus
Inferior oblique
The _____ gives off a branch carrying preganglionic parasympathetic fibers to the ___ ganglion, which continue as ____ nerves to the sphincter pupillae muscle
Inferior branch of CN III
ciliary
Short ciliary
The nucleus of CN IV is located in the ___. CN IV enters the orbit via the ___. It innervates the __
Midbrain
Superior orbital fissure
Superior oblique
The nucleus of CN VI is in the ___. It enters the orbit through the ___ and innervates the ___
Pons
Superior orbital fissure
Lateral rectus
CN V1 is pure ___. It divides into what 3 nerves that pass through what opening into the orbit?
Sensory Superior orbital fissure 1. Nasociliary 2. Lacrimal 3. Frontal
Which branch off of V1 is typically first? What does it supply?
Nasociliary n.
Ciliary ganglion, eyeball, medial eyelids, nose, anterior cranial fossa
What structures does the lacrimal n. supply? Frontal n.?
Lacrimal:
Lacrimal gland
Conjunctiva
Lateral part of upper eyelid
Frontal: Eyelids Conjunctiva Forehead Scalp
What artery supplies most of the orbit? It follows the ___ n. to enter the orbit through the ___
Ophthalmic
Optic
Optic canal
As the ophthalmic a. is passing along the lateral side of the optic n. it gives off the ___, which supplies the ___
Lacrimal a.
Lacrimal gland
Position of the ophthalmic a. relative to the optic n.
Inferolateral but
Upon entering the orbit it crosses superior and medial
Branches of the ophthalmic a.
- Lacrimal
- Central retinal
- Posterior ciliary (6 short and 2 long)
- Muscular branches (anterior ciliary)
- Supraorbital
- Ethmoidal
- Supratrochlear
The floor of the orbit also receives blood supply from the ___, which passes into the orbit via the ___ and is a branch of the ___
Infraorbital a.
Infraorbital foramen
ECA
Venous drainage of the orbit is through the ___ and the ___, which pass through the ___ and enter the __ sinus.
Superior and inferior ophthalmic veins
Superior orbital fissure
Cavernous
The superior ophthalmic v. is formed by the joining of the ___ and the ___.
Supraorbital v.
Angular v.
____ veins from the vascular layer of the eyeball drain into the inferior ophthalmic v.
Vortical