Orbital Canal Flashcards
Bones making up the orbit… Lateral? Medial? roof? Floor
Roof- mainly frontal and some Sphenoid Medial- (MELS) maxilla, ethnoid, lacrimal, sphenoid Lateral- Zygomatic and Sphenoid Floor- Maxilla (mainly) zygomatic and palatine
What are the 3 sinuses?
Frontal- superior and medical to the orbit Ethmoid Air Cells- medial to oribit Maxillary sinus- below the floor of the orbit
What is the orbital Septum? What are the attachments for the upper and lower eyelid
Orbital septum is an extension of the perisosteum in the upper and lower eyelid which lie deep to the orbicularis oculi. Upper eyelid attached by the tendon of Levator palpebrae Lower eyelid by tarus
What is the conjunctiva?
Covers the posterior surface of the eyelid and reflects onto the outer surface of the sclera of the eyeball. When eyelids are closed the conjunctiva form a sac anterior to the eye.= conjunctival sac
Function and location of the tarsus
Superior and infeior tarus provide support for the eyelids. BOth are made of dense CT which is attached to the bone of the orbit by the medial and lateral palpebral ligament. Within the tarsal plates are sabecous glands that empty into the free margins of the eyelids and increase viscosity of the eyes.
What muscle is associated with the superior tarsus?
The levator palpebrae superioris. In companion to the levator palpebrae superioris is a collection of smooth muscle fibers passing from the levator to the superior tarsus. This muscle, the superior tarsal muscle, is innervated by postganglionic sympathetic fibers.
What nerves give MOTOR innervation to the eye? Through wh5at muscle? Functin?
CN 3- Levator Palepbrae Superioris- HOlds eyelids open
CN 7- Orbicularis Oculi (Closure)
Postganglioinc sympathetic Fibers- Superior Tarsal Muscle -holds eyelids open– Remember this is Smooth muscle
Explain the lacrimal apparatus?
The lacrimal gland is superior lateral region of the orbit. Numerous ducts empty secretions which are moved across the eyeballs as the eyelids blink. Fluid accumulates and enters the lacrimal canaliculi which join togethrer to form the lacrimal sac posterior to the medical palpebral ligament.
A small part of the orbiularis oculi muscle, the lacrimal part, lies psterior to the lacrimal sac. When it contracts during blinking, the lacrimal part compressed on the lacrimal sac forcing fluids into the nasolacrimal duct which drains into the inferior meatus of the nasal cavity.
Innervation of the Lacrimal Apparatus
V1 lacrimal branch sends Sensory bacnk to the CNS
Parasympathetic secretomotor fibersstimulate fluid secretion from thisgland.
oThepreganglionic fibersleave the CNS in CN VII, enter the
greater petrosal nerveand continue as the nerve of the pterygoid canal.
o This nerve carries the preganglionic fibers to the pterygopalatine ganglion where they synapse on postganglionic neurons.
oThe postganglionic fibers travel with the maxillary nerve (V2)
and continue with its zygomatic branches and eventually reach
the lacrimal gland via the zygomaticotemporal branc
Sympathetic innervation follows a similar path:
o except the postganglionic fibers originate in the superior
cervical ganglion, follow blood vessels to reach the head, and
form the deep petrosal nerve prior to joining the
nerve of the pterygoid canal
.
oThese sympathetic fibers then follow the parasympathetic fibers with the exception that they do not synapse in the pterygopalatine ganglion, but rather just pass through it.
Main Movement of each muscle of the eye
Superior Rectus- Look laterally and Upward
Inferior Rectus- Look laterally and downward
Medial Rectus- Look medially
Lateral Rectus- look laterally
INferior Oblique- Look medially and upward
Superior Oblique- look medially and downward
Obliques do Opposite and abduct
Rectus do the same and Adduct (except medial rectus)
What muscle is describe as the book reading/walking down stairs muscle?
Superior Obliques- medially and down.
Also accompanied by the medial rectus.
Arteries of the orbit and eyeball
Branches of the Opthalmaic Artery (whcih is a branch of the internal carotid)
Lacriaml Artery- Supplies the lacrimal gland, laterally located muscles, and parts of the eyeball and lid
Central artery of retina- enters the optic nerve. Seen in ophthalmoscope and if occuluded causes blindness
Long and short cillary arteries- enters posteriorally and pierces the sclera to supply internal structures.
Veins of the orbit and eyeball
Superior and inferio Opthalmic Veins
Because opthalmic veins communicate ith veins of the face and the cavernous sinus, they aremeans that infection can spread from outside to inside the crnaial cavity. w
Nerves of the Orbit and Eyeball
CN3- innervates the levator palpebrae and superior rectus (via superior branch) and medial erctus, inderior rectus and inferior oblique (via inferior branch)- this nerve also carries preganglionic parasym fibers to the cillary ganglion
CN 4- innervates the superior oblique muscle
CN 6- lateral rectus
What are the branch of V1
V1 is a branch of CN 5 called opthalamic. Its branches are
- Lacrimal- lateral and recieves postganglionic sym and parasym from the zygomaticotemporal nerves. Also carries sensory info from the lacrimal gland, conjunctiva and upper eyelid
- Frontal Nerve- largerst of V1. Sensroy from outside the orbit like scalp, skin of forehead, skin of upper eyelid, conjunctiva via its supraorbital and supratrocheal branch
- Nasocilliary- most deep of Va- Via its branches nerves provide sensory innervatio to the eyeball and sympathetic innervation for dilation; sensory innervation to the nasal cavity and ethmoid ari cells.
