Orbit And Content Flashcards
What are the four walls of the bony orbit?
Roof: Frontal bone, Lesser wing of sphenoid
Floor: Maxilla, Zygomatic, Palatine bone
Medial Wall: Frontal process of maxilla, Lacrimal bone, Orbital plate of ethmoid, Lesser wing of sphenoid
Lateral Wall: Zygomatic bone, Greater wing of sphenoid
What structures pass through the optic canal?
Optic nerve
Ophthalmic artery
Meninges
Sympathetic fibers
What are the three tunics of the eyeball?
Fibrous Tunic: Sclera and cornea
Vascular Tunic (Uveal tract): Choroid, ciliary body, iris
Nervous Tunic: Retina
What is the function of the ciliary body?
Accommodation: Adjusts the shape of the lens for near vision.
Production of aqueous fluid.
What is the macula lutea, and what is its significance?
A small, yellowish area of the retina, 3mm lateral to the optic disc.
Contains the fovea centralis, the most sensitive part of the retina for detailed vision (cones only).
What is glaucoma, and what causes it?
Glaucoma is increased intraocular pressure.
It is caused by blockage of aqueous fluid flow(Canal of schlemm) or overproduction of aqueous humor.
Function of medial rectus
Adduction
Function of lateral rectus
Abduction
Function of Superior rectus
Elevation, adduction, medial rotation
Function of Inferior rectus
Depression, adduction, lateral rotation
Function of Superior oblique
Depression, abduction, medial rotation
Function of inferior oblique
Elevation, abduction, lateral rotation
Levator palpebrae superioris
Elevates the upper eyelid.
What is Horner’s Syndrome, and what are its symptoms?
Horner’s Syndrome is caused by damage to the sympathetic nerves.
Symptoms:
Partial ptosis (drooping eyelid)
Miosis (pupillary constriction)
Anhydrosis (reduced or absent sweating on the face)
What is the lacrimal apparatus, and what are its components?
Lacrimal gland (orbital and palpebral parts)
Lacrimal papilla
Lacrimal punctum
Lacrimal canaliculus
Lacrimal sac
Nasolacrimal duct
What is the difference between a stye (hordeolum) and a chalazion?
Stye (Hordeolum): Infection of the oil glands associated with eyelash follicles.
Chalazion: Blockage of a meibomian gland, causing a cyst.
What is the Tenon’s capsule, and what is its function?
Tenon’s capsule is a fascial sheath surrounding the eyeball.
It is attached anteriorly to the sclera at the corneoscleral junction and blends posteriorly with the sheath at the entrance of the optic nerve.
Function: Provides a smooth surface for eye movement and supports the eyeball.
What is the optic disc, and why is it called the “blind spot”?
The optic disc is the point where the optic nerve enters the retina.
It is called the “blind spot” because it lacks photoreceptors (rods and cones) and is insensitive to light.
What is the canal of Schlemm, and what is its function?
The canal of Schlemm is a circular channel at the corneoscleral junction.
It drains aqueous fluid from the anterior chamber into the venous system.
What is retinal detachment, and what are its consequences?
Retinal detachment occurs when the retina separates from the underlying choroid layer.
Consequences: Loss of vision in the affected area, which can lead to blindness if not treated.
What is the ciliary ganglion, and what is its role?
The ciliary ganglion is a parasympathetic ganglion located behind the eye.
It receives preganglionic fibers from the Edinger-Westphal nucleus and sends postganglionic fibers to the ciliary muscle and sphincter pupillae for accommodation and pupil constriction.
What structures pass through the superior orbital fissure
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Ophthalmic division of the trigeminal nerve (CN V1)
Abducens nerve (CN VI)
Superior ophthalmic vein
What is the inferior orbital fissure, and what structures pass through it?
The inferior orbital fissure is an opening between the greater wing of the sphenoid and the maxilla.
Structures passing through it:
Infraorbital nerve
Zygomatic nerve
Inferior ophthalmic vein
What is the conjunctiva, and what are its two parts?
The conjunctiva is a transparent membrane covering the front of the eye and lining the eyelids.
Its two parts:
Palpebral conjunctiva: Lines the eyelids.
Orbital conjunctiva: Covers the eyeball.
What is the lens, and what is its role in vision?
he lens is a transparent, biconvex structure in the eye.
Its role: Refracts light to focus it on the retina, allowing for clear vision.
What is the orbital fascia (periorbita), and what is its function?
The orbital fascia is the periosteum lining the orbital bones.
Function: Provides attachment points for muscles, tendons, and ligaments.
What are the main arteries supplying the orbit, and what do they supply?
Central Artery of the Retina: Supplies the retina.
How does venous drainage occur in the orbit?
Superior Ophthalmic Vein: Drains into the cavernous sinus.
Inferior Ophthalmic Vein: Drains into the pterygoid plexus of veins.
There is communication between the two veins for alternative drainage pathways.
What are the layers of the eyelids, and what structures are found in each layer?
Skin: Outermost layer.
Subcutaneous Tissue: Contains loose connective tissue.
Orbital Septum (Tarsal Plate): Provides structural support.
Tarsal (Meibomian) Glands: Secrete oils to prevent tear evaporation.
Palpebral Conjunctiva: Lines the inner surface of the eyelids.
What is the hyaloid artery, and what happens to it after birth?
he hyaloid artery is a fetal structure that supplies blood to the developing lens and retina.
After birth, it disappears, leaving behind the hyaloid canal in the vitreous humor.
What is the visual cortex, and where is it located?
The visual cortex is the part of the brain that processes visual information.
It is located in the occipital lobe.
What nerve innervates the conjnctiva?
Lacrimal nerve
What is the pupillary light reflex, and which nerves are involved?
he pupillary light reflex is the constriction of the pupil in response to light.
Nerves involved:
Afferent: Optic nerve (CN II).
Efferent: Oculomotor nerve (CN III)
What are the orbital relations, and what structures are adjacent to each wall of the orbit?
Roof: Anterior cranial fossa and frontal lobe of the brain.
Floor: Maxillary sinus.
Medial Wall: Nasal cavity and ethmoidal air sinuses.
Lateral Wall: Temporal fossa.
What is a blowout fracture, and what are its symptoms?
A blowout fracture is a fracture of the orbital floor or medial wall, often caused by blunt trauma.
Symptoms: Diplopia (double vision), enophthalmos (sunken eye), and infraorbital nerve damage.
