15-A Orbit Contents

Question 1

Describe the bony cavities that surround the orbital along the midline. (3)

Answer 1

ethmoid sinuses, nasal cavity, maxillary sinuses

Question 2

What is the shape of the orbital, esp. the breadth medially vs. laterally

Answer 2

the medial border is faces directly forward while the lateral allows for significant lateral vision

Question 3

Which 7 bones contribute to the orbital?

Answer 3

medially: ethmoid, lacrimal, palatine and maxilla, superiorly: frontal bone and laterally the zygomatic and sphenoid bones

Question 4

Name the foramen that serve several branches of the trigeminal and are directly above and below the orbit.

Answer 4

surpraorbital foramen (notch) and infraorbital groove and foramen

Question 5

Name the three holes in the back of the orbital

Answer 5

optic canal, superior orbital fissure and the inferior orbital fissure (maxillary branch of trigeminal) (also the ethomidal foramina)

Question 6

Where is the optic canal located and what does it permit pass?

Answer 6

hole in lesser wing of the sphenoid bone, transmits the optic nerve with menial covering and ophthalmic branch of the internal carotid

Question 7

Where is the superior orbital fissure and what passes through it?

Answer 7

large crack between the sphenoid rings transmits CN III, IV, VI and V1 as well as the superior ophthalmic vein

Question 8

Where is the inferior orbital fissure and what passes through it?

Answer 8

elongated hole in the orbital floor between the maxilla and the sphenoid, transmits infraorbtial branch of the maxillary division of the trigeminal nerve

Question 9

What passes through the supraorbital and infra orbital foramen respectively?

Answer 9

supraorbital nerve and supra orbital branch of the ophthalmic artery, infraorbtial branch V2

Question 10

What is the lacrimal groove?

Answer 10

space in the maxilla and lacrimal bone where the lacrimal duct sits along the midline

Question 11

What is defined as a blowout fracture?

Answer 11

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)

Question 12

What is the periorbita a continuation of and what does it surround in the eye?

Answer 12

periorbita lines the bony orbit and is continuous with the periosteal dura

Question 13

What is the role of the meningeal dura in the optic cavity?

Answer 13

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)

Question 14

What fusion separates the orbital cavity from the orbital?

Answer 14

periorbita and the optic nerve sheath are fused at the optic canal

Question 15

What are the bulbar fascia and episcleral space?

Answer 15

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

Question 16

What are the tarsal plates?

Answer 16

dense connective tissue within the eye lit

Question 17

Describe the layers of the eyelid from superficial to deep. (5)

Answer 17

skin, thin subcutaneous tissue, 3 muscles, tarsal plates, conjunctiva (palpebral, bulbar is on the eye itself but is continuous with the palpebral conjunctiva)

Question 18

What are the three muscles involved in movement of the eye lid and describe their action.

Answer 18

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)

Question 19

What are the superior and inferior fornices of the conjunctiva?

Answer 19

they are areas where the conjunctiva reflects on itself, the space between the two conjunctival layers is called the conjunctival sac

Question 20

Describe the path of tears across the eye.

Answer 20

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

Question 21

What nerve innervates the lacrimal gland?

Answer 21

the facial nerve

Question 22

What are the three muscles within the eyeball?

Answer 22

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

Question 23

Describe the enervation of the colliery muscle, the pupillary dilator and the pupillary sphincter.

Answer 23

cilliary muscle (parasympathetic), pupillary dilator *radially oriented (sympathetic) and pupillary sphincter *circularly oriented (parasympathetic)

Question 24

The superior oblique loops through which fiber cartilage loop at the front of the eye?

Answer 24

trochlea

Question 25

Which eye movements occur along the following axes: horizontal, vertical and anteriorposterior?

Answer 25

horizontal (elevate and depress), vertical (abduction and adduction) and anterior posterior axis (medial rotation and lateral rotation)

Question 26

The action of a muscle around a given axis is determined by two things:

Answer 26

the direction of the pull, and where the insertion lays relative to the axis

Question 27

Which muscles are responsible for adduction and abduction?

Answer 27

medial and lateral rectus (respectively) along with contributions from the superior and inferior rectus to adduct and superior and inferior obliques for abduction

Question 28

What muscles are used to depress the eye?

Answer 28

the inferior rectus and the superior oblique

Question 29

What muscles are used to elevate the eye?

Answer 29

the superior rectus and the inferior oblique

Question 30

What muscles are used in medial rotation of the eye?

Answer 30

superior rectus, superior oblique

Question 31

What muscles are use din lateral rotation?

Answer 31

inferior rectus and inferior oblique

Question 32

A muscle that is ________ to an axis can’t function around that axis.

Answer 32

parallel