Bones of Orbit and Skull

Which orbital wall is most prone to damage?

Floor

What are 4 sides of orbit?

Floor (base), Roof (apex), medial orbital walls & lateral walls.

Where are the sinuses located

Found on 3 sides of orbit. All sinuses are located medially, no lateral structures are involved.

Which bones contain sinuses?

Frontal Ethmoid Sphenoid Maxillary (largest sinus)

Orbital Roof has which bone(s)?

Frontal bone & Sphenoid bone (lesser wing)

Foramen

Hole or passage through a bone (note through one bone not joining bones)

Fossa

Indentation, typically where organs sit

Preseptal cellulitis/periobital cellulitis

Infection of the eyelid glands. Can cause inflammation of the surrouding tissue. **Limited by the orbital septum. treatable with oral antibiotics.

What are sutures

Junctions between bones

Characteristics of Palatine bone

L-shaped Horizontal plate Vertical plate Orbital process

Which wall is the strongest wall

Lateral wall

Which part of the sphenoid bone is part of the orbital roof?

Lesser wing of the sphenoid bone.

What is another term for the frontal process?

Marginal process part of zygomatic bone making up the lateral wall.

List important landmarks on the maxillary bone that are found on the medial wall.

Medial wall - frontal process - fossa for the lacrimal sac - anterior lacrimal crest

Fissure

Opening between bones. Passageways that pass through or connect bones

Features of ethmoid bone composing the medial wall

Orbital plate: Lamina papyracea Frontoethmoid suture - foramina (anterior and posterior ethmoidal foramina)

What are other names of the Periorbita and where is it found

Periorbita or Periosteum of the orbit or orbital fascia covers the bones of the orbit

Process

Projection from a bone. Often connective tissue or muscles that attach here.

Exophthalmos/proptosis

Protrusion of the eye caused by: - Thyroid eye disease (most common) - Tumors - Inflammation - Injury

Orbital Cellulitis

Serious infection of teh orbital contents. Onset of pain, edema, proptosis, diplopia, fever. Tenon's capsule may prevent infection from entering the globe. Treatment: IV antibiotics, usually requires hospitalization, CT scan. -> Pressure on the optic nerve can lead to irreversible vision loss, very serious condition.

Important landmarks of sphenoid bone

Superior orbital fissure Inferior orbital fissure both found near greater wing of sphenoid which composes the lateral wall

What is the function of Tenon's capsule

Tenon's capsule protects the GLOBE from orbital infections. Also provides attachment for extraocular muscles.

What bony structure does the optic nerve enter through?

The optic foramen (apex of the orbit) found in sphenoid bone. It is formed by the optic strut connecting the lesser wing to the body of the sphenoid bone.

Function of the orbital septum

The orbital septum acts as a strong barrier to prevent facial infections from entering the orbit. It also maintains orbital fat positioning.

What is another name for the orbital septum

The orbital septum is also known as the septum orbitale or the palpebral fascia

Name two properties of the paranasal sinuses

These air filled sacs 1. add resonance to voice 2. Mucosa lines for protection (acts as an air filter)

What is the function of orbital connective tissue

To cover, protect, separate orbital structures

Features of Zygomatic bone on lateral wall

foramina for nerves and vessels Marginal orbital tubercle - bony prominence providing attachment for ligaments and most extraocular muscles.

Name features of the Lacrimal bone composing the medial wall

- Smallest orbital bone - Along with the frontal process of the maxilla, forms the fossa for the lacrimal sac -> Posterior lacrimal crest

Suspensory Ligament (of Lockwood) (function, location, formation)

- Tenon's capsule and inferior extracocular muscles contribute to the formation - hammock like sheet from the medial to lateral orbit below the globe The suspensory ligament supports the globe.

Orbital septum location at the medial canthus

- anterior to the check ligament of the MR - posterior to the medial palpebral ligament, Horner's muscle, and lacrimal sac.

Orbital septum location at the lateral canthus

- anterior to the lateral palpebral ligament - anterior to the check ligament of the LR

Features of the orbital septum

- circular tissue surrounding the anterior orbital margins to the tarsal plate in the eyelids - tendon of the levator muscle passes through it.

Name 3 important boney landmarks on frontal bone in the orbital roof

1. Fossa for the lacrimal gland 2. Supraorbital notch/foramen 3. Trochlea - (ligamentous sling) U-shaped cartilage allowing passage of superior oblique muscle.

What bones make up the orbital margins?

1. Frontal bone (Supraorbital notch, supratrochlear notch) 2. Zygomatic bone 3. Maxillary bone (Infraorbital foramen)

Name two landmarks on the maxillary bone located on the orbital floor

1. Infraorbital groove 2. Infraorbital foramen

What makes up the orbital floor?

1. Maxillary bone (makes up majority of the floor) 2. Zygomatic Bone (makes up large portion) 3. Palatine bone (only top portion)

Name orbital connective tissue

1. periorbita 2. orbital septum 3. Tenon's capsule 4. Suspensory ligament (of Lockwood)

What bones make up the lateral wall?

2 bones make up the lateral wall 1. Zygomatic bone 2. Sphenoid bone

What makes up the medial wall

4 bones make up the medial wall which is the thinnest wall. 1. Maxillary bone 2. Lacrimal bone 3. Ethmoid bone (majority of wall) 4. Sphenoid bone

What is the function of the Periorbita?

Allows attachment for muscles, ligaments, tendons. Also carries blood and nerves to the orbital bones.

Tenon's Capsule location and description

Also known as bulbar fascia Tenon's capsule is dense connective tissue encircling the globe - Outer to the conjuctiva - outer to the sclera

Common Tendinous ring (or Annulus of Zinn) (location, landmarks, attachment)

Attachement of 4 rectus muscles Anterior to the optic foramen and superior orbital fissure (anterior to sphenoid) Oculomotor foramen (inner portion) openeing within the ring. **Note not part of bone, is tendon

Which part of the sphenoid bone is part of the medial wall?

Body of the sphenoid

Name the bones bordering the inferior orbital fissure

Bordered by 4 bones. 1. zygomatic 2. maxillary 3. greater wing of the sphenoid 4. Palatine

How many orbital bones are there? Name them

Each orbit has 7 orbital bones. 3 of which are shared between the two eyes: Sphenoid, Ethmoid & Frontal Each eye also has: Lacrimal, Maxillary, Zygomatic, Palatine bones

What is the difference between the globe and the orbit?

The globe is the eyeball itself and the orbit is the bony structure around it.

What borders the superior orbital fissure?

The greater and lesser wing of the sphenoid bone.

What is unique about the orbital margins?

The margins overlap but the bones don't make a full circle. Sort of a spiral shape.