Chapter 3: The Orbit Study Guide
updated August ‘08
Part 1: basic vocabulary
Canal: (pipe or channel) Optic canal contains Optic nerve, ophthalmic artery
Suture: (Latin – sutura meaning seam)
Foramen (plural foramina) Latin forare – a hole in the bone for nerves and blood vessels to pass
through
Fossa – an anatomical pit or depression in bone for nerves or blood vessels to pass through
Tubercle [tube Latin: lump] a small prominence; used as an attachment site for muscle or ligament
Fissure - a natural cleft between body parts, narrow slit-like opening
Notch
Zygomatic – to join or bridge
Ethmoid – sieve, like a strainer
Trochlear – U-shaped pulley for the tendon of the superior oblique muscle
Sphenoid - wedge shaped or wing like
(Pterygoid – shaped like a wing)
Sinus – air pocket in bone, or common pooling area for drainage
(There are four sinuses: Frontal, Ethmoid, Sphenoid, and Maxillary)
Part 2: Eleven Bones that make up the orbit are:
Single: Frontal
Paired: Maxillary
Ethmoid
Zygomatic
Sphenoid
Lacrimal
Palatine
Part 3:
Optic Canal (or Optic foramen) – the tunnel in the sphenoid bone through which the optic nerve
and the ophthalmic artery passes
Superior Orbital Fissure – the opening between the greater and lesser wings of the sphenoid
bone at the back of the orbit; most of nerves and major veins pass
through except the optic and zygomatic nerves, and ophthalmic artery
Inferior Orbital Fissure – the opening in the orbit between the posterior part of the orbital floor
and the lateral wall
Ethmoid Foramina (anterior & posterior) – the openings in the medial wall of the orbit through
which the ethmoidal arteries and nerves pass
Infraorbital foramen – the opening in the maxillary bone below the orbital rim through which
the infraorbital artery and nerve pass
Infraorbital groove – the groove in the orbital floor that becomes the infraorbital canal leading to
the infraorbital foramen
Supraorbital Notch – the notch, sometimes a foramen, near the middle of the superior margin of
the orbital; it contains the supraorbital artery and nerve
Supraorbital Margin Zygomatic foramen – innervates the cheek
Pterygoid canal (of sphenoid bone)
Infraorbital canal
Nasolacrimal canal – the tunnel that leads from the lacrimal fossa to the nasal cavity
Greater and lesser wing of Sphenoid bone
Trochlear spine or trochlear fossa – the small depression in the frontal bone at the site of the
Trochlea
Palantine – smallest contribution to the orbital structure (the orbit floor)
Orbital plate of ethmoid bone is in which orbital wall? How about the frontal or maxillary
bones?
What is a blowout fracture? Where does it occur?
A blowout fracture is caused by force trauma to the orbit. Due to the sheer strength of the orbital
bones, the force of the trauma is transmitted to the orbital plate of the maxillary wall, where the
thin layer of bone is “blown out.”
How about a comminution fracture?
It is the breakage of one or more of the bones forming the margin (frontal, zygomatic, or
maxillary).
Part 4: Know and be able to identify bones of the orbit floor, ceiling, lateral and medial walls.
What are the sutures that connect them? What are the fossas, fissures and foramina on these
walls?
Orbit Ceiling
Frontal
Bits of sphenoid
Lacrimal Fossa, trochlear fossa
Orbit Floor
Maxillary
Zygomatic
Palantine
Inferior orbital groove, inferior orbital fissure, nasolacrimal canal
Lateral Wall
Zygomatic
Sphenoid (greater wing)
Lateral Orbital Tubercle (Whitnall’s tubercle)
Medial Wall
Maxillary (anteriorly)
Sphenoid (posteriorly)
Ethmoid &
lacrimal bones fill the gap between them
Nasolacrimal fossa
Lacrimal crests (anterior & posterior)
Nasolacrimal canal
Periosteum – a thin layer of connective tissue that adheres to the surfaces of bones
Periobita – the periosteum that lines the orbital bones
Tenon’s capsule – a sheet of connective tissue that lines all of the eye out to the limbus and
ensheathes the extraocular muscles, it fits like a glove.
Whitenall’s ligament – a sling of connective tissue attached to the orbital ceiling through which
the levator muscle passes; also called superior transverse ligament
Lockwood’s ligament – suspensory ligament
Medial and lateral check ligament
Septum orbitale (aka orbital septum and palpebral fascia) – the sheet of connective tissue that is
attached to the orbital margin and runs into the eyelids
Exophthalmos – a condition in which the eye protrudes farther forward from its normal position
in the orbit; also called proptosis
Enophthalmos - a condition in which the eye is placed farther back in the orbit than normal