15-A Orbit Contents Flashcards
Describe the bony cavities that surround the orbital along the midline. (3)
ethmoid sinuses, nasal cavity, maxillary sinuses
What is the shape of the orbital, esp. the breadth medially vs. laterally
the medial border is faces directly forward while the lateral allows for significant lateral vision
Which 7 bones contribute to the orbital?
medially: ethmoid, lacrimal, palatine and maxilla, superiorly: frontal bone and laterally the zygomatic and sphenoid bones
Name the foramen that serve several branches of the trigeminal and are directly above and below the orbit.
surpraorbital foramen (notch) and infraorbital groove and foramen
Name the three holes in the back of the orbital
optic canal, superior orbital fissure and the inferior orbital fissure (maxillary branch of trigeminal) (also the ethomidal foramina)
Where is the optic canal located and what does it permit pass?
hole in lesser wing of the sphenoid bone, transmits the optic nerve with menial covering and ophthalmic branch of the internal carotid
Where is the superior orbital fissure and what passes through it?
large crack between the sphenoid rings transmits CN III, IV, VI and V1 as well as the superior ophthalmic vein
Where is the inferior orbital fissure and what passes through it?
elongated hole in the orbital floor between the maxilla and the sphenoid, transmits infraorbtial branch of the maxillary division of the trigeminal nerve
What passes through the supraorbital and infra orbital foramen respectively?
supraorbital nerve and supra orbital branch of the ophthalmic artery, infraorbtial branch V2
What is the lacrimal groove?
space in the maxilla and lacrimal bone where the lacrimal duct sits along the midline
What is defined as a blowout fracture?
serious damage to the orbit which causes the contents of the orbit to herniate into the maxillary sinus (inner parts of the orbit can be somewhat weaker than the rim)
What is the periorbita a continuation of and what does it surround in the eye?
periorbita lines the bony orbit and is continuous with the periosteal dura
What is the role of the meningeal dura in the optic cavity?
the meningeal dura continues to cover the optic nerve up until the back of the eye as the optic nerve sheath (encloses the arachnoid with CSF and pia mater)
What fusion separates the orbital cavity from the orbital?
periorbita and the optic nerve sheath are fused at the optic canal
What are the bulbar fascia and episcleral space?
the fascia that surounds the back of the eyeball is called the bulbar fascia, the space between the sclera and the bulbar fascia is called the episcleral space and allow for the movement of the eye
What are the tarsal plates?
dense connective tissue within the eye lit
Describe the layers of the eyelid from superficial to deep. (5)
skin, thin subcutaneous tissue, 3 muscles, tarsal plates, conjunctiva (palpebral, bulbar is on the eye itself but is continuous with the palpebral conjunctiva)
What are the three muscles involved in movement of the eye lid and describe their action.
levitator palpebrae superioris (ocular motor nerve) opens the eye along with the superior tarsal muscle (sympathetics) and the obicularis oculi which closes the eye (facial nerve)
What are the superior and inferior fornices of the conjunctiva?
they are areas where the conjunctiva reflects on itself, the space between the two conjunctival layers is called the conjunctival sac
Describe the path of tears across the eye.
the lacrimal gland is in the superior lateral corner of the eye and tears are wiped across the eye toward the lacrimal apparatus that collects the tears through puncta to the lacrimal sac and then through the nasolacrimal duct to the nasal cavity
What nerve innervates the lacrimal gland?
the facial nerve
What are the three muscles within the eyeball?
the cilliary muscle which changes the shape of the lens for focus and the pupillary sphincter and pupillary dilator that regulate the light that enters the eye
Describe the enervation of the colliery muscle, the pupillary dilator and the pupillary sphincter.
cilliary muscle (parasympathetic), pupillary dilator *radially oriented (sympathetic) and pupillary sphincter *circularly oriented (parasympathetic)
The superior oblique loops through which fiber cartilage loop at the front of the eye?
trochlea
Which eye movements occur along the following axes: horizontal, vertical and anteriorposterior?
horizontal (elevate and depress), vertical (abduction and adduction) and anterior posterior axis (medial rotation and lateral rotation)
The action of a muscle around a given axis is determined by two things:
the direction of the pull, and where the insertion lays relative to the axis
Which muscles are responsible for adduction and abduction?
medial and lateral rectus (respectively) along with contributions from the superior and inferior rectus to adduct and superior and inferior obliques for abduction
What muscles are used to depress the eye?
the inferior rectus and the superior oblique
What muscles are used to elevate the eye?
the superior rectus and the inferior oblique
What muscles are used in medial rotation of the eye?
superior rectus, superior oblique
What muscles are use din lateral rotation?
inferior rectus and inferior oblique
A muscle that is ________ to an axis can’t function around that axis.
parallel
