Dissection 4-The Orbit And It's Contents Flashcards
Relative Osteology
Frontal Bone
-Supraorbital notch (foramen): name accordingly
-orbital surface
-lacrimal fossa
Ethmoid bone
Lacrimal bone
Lacrimal groove
Nasolacrimal canal
Maxilla
-infraorbital groove
-infraorbital foramen
Zygomatic bone
Sphenoid bone
-optic canal
-lesser wing
-superior orbital fissure
-greater wingAnterior and Posterior Ethmoid Foramina
On the medial wall of the orbit
Typically small and absolute identification may not be possible
Inferior orbital fissure
Gap between the maxilla and greater wing of the sphenoid bone
Lamina Papyracea
Name for the part of the ethmoid bone that forms the medial wall of the orbit because it’s paper thin
Lateral wall is stout and strong
Roof of the orbit
Related to the anterior cranial fossa
Floor of the orbit
Is related to the maxillary sinus
Medial wall of the orbit
Is related to the ethmoidal air cells
Eyelashes (cilia)
Feature of the living eye
Palpebral fissure (rima)
The opening between the eyelids
Medial and Lateral Palpebral Commissures
Where the upper and lower eyelids join
Medial and Lateral angles (canthi)
The medial and lateral corners of the eye
Sclera
The whitish posterior five-sixths of the exterior coat of the eyeball
Cornea
The transparent anterior one-sixth of the exterior coat of the eyeball
Iris
The colored diaphragm seen through the cornea
Pupil
The aperture in the center of the iris
Lacrimal caruncle (medial angle of the eye)
A pink fleshy bump
Lacrimal lake
The area surrounding the lacrimal caruncle
Lacrimal Papilla
A small bump on the medial end of each eyelid
Lacrimal Puncta
A small opening at the apex of each lacrimal papilla
Bulbar Conjuctiva
The membrane that lines the surface of the eyeball
Palpebral Conjuctiva
The membrane that lines the inner surface of the eyelid
Superior and inferior conjunctival fornices
The regions where the bulbar conjunctiva becomes continuous with palpebral conjunctiva
Conjunctival Sac
The potential space between the bulbar conjunctiva and the palpebral conjunctiva
Orbital Septum
A sheet of connective tissue that’s attached to the periosteum at the margin of the orbit and to the tarsal plates
Separates the superior superficial fascia of the face from the contents of the orbit
Tarsal Plates
Give shape to the eyelids
Tarsal glands are embedded in the posterior surface of each tarsal plate. They drain by small orifices that are located posterior to the eyelashes. They secrete an oily substance onto the margin of the eyelid that prevents overflow of lacrimal fluid
Lacrimal Gland
Occupies the lacrimal fossa in the frontal bone.
Drains into the superior conjunctival fornix by 6 to 10 short ducts
Lacrimal Groove
Medial side of the orbital margin
Lacrimal Fluid Drainage
2 lacrimal canaliculi drain lacrimal fluid from the medial angle of the eye into the lacrimal sac
nasolacrimal duct extends inferiorly from the lacrimal sac and enters the inferior meatus of the nasal cavity
lacrimal fluid flows from the lacrimal gland across the eyeball to the medial angle of the eye
-during crying, excess lacrimal fluid cannot be emptied through the lacrimal canaliculi and tears overflow the lower eyelids. Increased drainage of tears into the nasal cavity results in sniffling (characteristic of crying)
In the Clinic: Tarsal Glands
If the duct of a tarsal gland becomes obstructed, a chalazion (cyst) will develop. A chalazion will be located between the tarsal plate and the conjunctiva. In contrast, a hordeolum (stye) is the inflammation of a ciliary gland, which is a sebaceous gland associated with the follicle of an eyelash
Frontal Sinus
May extend into the roof of the orbit
Contained in the frontal bone
Ehtmoidal air cells
May extend into the roof of the orbit (medially)
Periorbita
Lines the bones of the orbit
Membrane just inferior to the roof of the orbit
Frontal Nerve
May be visible through the periorbita (pass superior to the Extraocular Muscles)
(A branch of cranial nerve V1)
Courses from the apex of the orbit toward the supraorbital margin. Trace the frontal nerve anteriorly and observe that it divides into the Supratrochlear nerve and supraorbital nerve
Lacrimal Nerve
(A branch of cranial nerve V1)
Passes through the superior orbital fissure lateral to the frontal nerve and courses along the lateral wall of the orbit. The lacrimal nerve is much smaller than the frontal nerve. Follow the lacrimal nerve anterolaterally toward the lacrimal gland
Trochlear Nerve
Passes through the superior orbital fissure medial to the frontal nerve. Follow the trochlear nerve to the superior border of the superior oblique muscle which it innervates. The trochlear nerve usually enters the superior border of the superior oblique muscle in its posterior one-third
Levator Palpebrae Superioris
attaches to the upper eyelid which it elevates
Superior oblique muscle
Medial side of the orbit
The tendon passes through the trochlea, bends at an acute angle and attaches to the posterolateral portion of the eyeball
Lateral Rectus Muscle
Lateral side of the orbit
Arises by 2 heads from the common tendinous ring. The common tendons ring surrounds the optic canal and part of the superior orbital fissure and it’s the posterior attachment of 4 rectus muscles
Common Tendinous Ring
Surrounds optic canal and part of the superior orbital fissure
posterior attachment of the 4 rectus muscles
The optic nerve, nasociliary nerve, oculomotor nerve and abducens nerve pass through this
Superior Rectus muscle
Lies immediately inferior to the levator palpebrae superioris muscle
Attaches to the eyeball by a thin, broad tendon
Oculomotor nerve (superior rectus muscle and levator palpebrae superioris muscle)
Branch of the superior branch reaches the inferior surface of the superior rectus muscle
Passes around the medial side of the superior rectus muscle to innervate the levator palpebrae superioris muscle
Nasociliary nerve
Branch of cranial nerve V1
Hopes through the orbit
Much smaller than frontal nerve. Crosses superior to the optic nerve and gives off several long ciliary nerves to the posterior part of the eyeball
Anterior ethmoid nerve
Small branch of the nasociliary nerve that passes through the anterior ehtmoidal foramen
Supplies the mucus membrane in the nasal cavity
Superior branch of the oculomotor nerve
Innervates the levator palpebrae superioris and the superior rectus muscles
Inferior branch of the oculomotor nerve
Innervates the medial rectus, inferior rectus and inferior oblique muscles
Ciliary Ganglion
Parasympathetic ganglion located between the optic nerve and lateral rectus muscle
Short ciliary nerves connect the ciliary ganglion to the posterior surface of the eyeball
Optic Nerve
Actually a brain tract and it is surrounded by the 3 meningeal layers
Ophthalmic Artery
Branches from the internal Carotid artery
In its course through the orbit, note that it usually crosses superior to the optic nerve and reaches the medial wall of the orbit.
Gives rise to posterior ciliary arteries that supply the eyeball
Supraorbital artery
Branch of the ophthalmic artery
Exits the supraorbital foramen in the company of the supraorbital nerve to supply forehead and scalp
Lacrimal Artery
Passes along the superior border of the lateral rectus muscle to supply the lacrimal gland, conjunctiva and eyelids
Superior ophthalmic vein
At the medial angle of the eye, anastomoses with angular vein
Pursues the same course as the ophthalmic artery and receives tributaries corresponding to the branches of that vessel
Passes between the two heads of the lateral rectus muscle and through the medial part of the superior orbital fissure and ends in the cavernous sinus
Medial Rectus Muscle
Can be easily seen along the medial wall of the orbit
In the clinic: Ophthalmic Veins
Anastomoses between the angular vein and superior and inferior ophthalmic veins are of clinic importance. Infections of the upper lip, cheeks and forehead may spread through the facial and angular veins into the ophthalmic veins and then into the cavernous sinus. Thrombosis of the cavernous sinus may result, leading to involvement of the abducens nerve and dysfunction of the lateral rectus muscle
