Dissection 4-The Orbit And It's Contents

Question 1

Relative Osteology

Answer 1

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 wing

Question 2

Anterior and Posterior Ethmoid Foramina

Answer 2

On the medial wall of the orbit

Typically small and absolute identification may not be possible

Question 3

Inferior orbital fissure

Answer 3

Gap between the maxilla and greater wing of the sphenoid bone

Question 4

Lamina Papyracea

Answer 4

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

Question 5

Roof of the orbit

Answer 5

Related to the anterior cranial fossa

Question 6

Floor of the orbit

Answer 6

Is related to the maxillary sinus

Question 7

Medial wall of the orbit

Answer 7

Is related to the ethmoidal air cells

Question 8

Eyelashes (cilia)

Answer 8

Feature of the living eye

Question 9

Palpebral fissure (rima)

Answer 9

The opening between the eyelids

Question 10

Medial and Lateral Palpebral Commissures

Answer 10

Where the upper and lower eyelids join

Question 11

Medial and Lateral angles (canthi)

Answer 11

The medial and lateral corners of the eye

Question 12

Sclera

Answer 12

The whitish posterior five-sixths of the exterior coat of the eyeball

Question 13

Cornea

Answer 13

The transparent anterior one-sixth of the exterior coat of the eyeball

Question 14

Iris

Answer 14

The colored diaphragm seen through the cornea

Question 15

Pupil

Answer 15

The aperture in the center of the iris

Question 16

Lacrimal caruncle (medial angle of the eye)

Answer 16

A pink fleshy bump

Question 17

Lacrimal lake

Answer 17

The area surrounding the lacrimal caruncle

Question 18

Lacrimal Papilla

Answer 18

A small bump on the medial end of each eyelid

Question 19

Lacrimal Puncta

Answer 19

A small opening at the apex of each lacrimal papilla

Question 20

Bulbar Conjuctiva

Answer 20

The membrane that lines the surface of the eyeball

Question 21

Palpebral Conjuctiva

Answer 21

The membrane that lines the inner surface of the eyelid

Question 22

Superior and inferior conjunctival fornices

Answer 22

The regions where the bulbar conjunctiva becomes continuous with palpebral conjunctiva

Question 23

Conjunctival Sac

Answer 23

The potential space between the bulbar conjunctiva and the palpebral conjunctiva

Question 24

Orbital Septum

Answer 24

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

Question 25

Tarsal Plates

Answer 25

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

Question 26

Lacrimal Gland

Answer 26

Occupies the lacrimal fossa in the frontal bone. Drains into the superior conjunctival fornix by 6 to 10 short ducts

Question 27

Lacrimal Groove

Answer 27

Medial side of the orbital margin

Question 28

Lacrimal Fluid Drainage

Answer 28

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)

Question 29

In the Clinic: Tarsal Glands

Answer 29

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

Question 30

Frontal Sinus

Answer 30

May extend into the roof of the orbit Contained in the frontal bone

Question 31

Ehtmoidal air cells

Answer 31

May extend into the roof of the orbit (medially)

Question 32

Periorbita

Answer 32

Lines the bones of the orbit Membrane just inferior to the roof of the orbit

Question 33

Frontal Nerve

Answer 33

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

Question 34

Lacrimal Nerve

Answer 34

(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

Question 35

Trochlear Nerve

Answer 35

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

Question 36

Levator Palpebrae Superioris

Answer 36

attaches to the upper eyelid which it elevates

Question 37

Superior oblique muscle

Answer 37

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

Question 38

Lateral Rectus Muscle

Answer 38

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

Question 39

Common Tendinous Ring

Answer 39

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

Question 40

Superior Rectus muscle

Answer 40

Lies immediately inferior to the levator palpebrae superioris muscle Attaches to the eyeball by a thin, broad tendon

Question 41

Oculomotor nerve (superior rectus muscle and levator palpebrae superioris muscle)

Answer 41

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

Question 42

Nasociliary nerve

Answer 42

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

Question 43

Anterior ethmoid nerve

Answer 43

Small branch of the nasociliary nerve that passes through the anterior ehtmoidal foramen Supplies the mucus membrane in the nasal cavity

Question 44

Superior branch of the oculomotor nerve

Answer 44

Innervates the levator palpebrae superioris and the superior rectus muscles

Question 45

Inferior branch of the oculomotor nerve

Answer 45

Innervates the medial rectus, inferior rectus and inferior oblique muscles

Question 46

Ciliary Ganglion

Answer 46

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

Question 47

Optic Nerve

Answer 47

Actually a brain tract and it is surrounded by the 3 meningeal layers

Question 48

Ophthalmic Artery

Answer 48

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

Question 49

Supraorbital artery

Answer 49

Branch of the ophthalmic artery Exits the supraorbital foramen in the company of the supraorbital nerve to supply forehead and scalp

Question 50

Lacrimal Artery

Answer 50

Passes along the superior border of the lateral rectus muscle to supply the lacrimal gland, conjunctiva and eyelids

Question 51

Superior ophthalmic vein

Answer 51

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

Question 52

Medial Rectus Muscle

Answer 52

Can be easily seen along the medial wall of the orbit

Question 53

In the clinic: Ophthalmic Veins

Answer 53

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