the orbit: bone structures bones: those latin names protecting the eye while serving its needs....
TRANSCRIPT
![Page 1: The Orbit: Bone structures Bones: Those Latin names Protecting the eye while serving its needs. VS112 Sept 5, 2007 Lect 2-3](https://reader035.vdocuments.mx/reader035/viewer/2022062519/56649c815503460f949384c0/html5/thumbnails/1.jpg)
The Orbit: Bone structuresBones: Those Latin names
Protecting the eye while serving its needs.
•VS112
•Sept 5, 2007
•Lect 2-3
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Reasonable Goals
• Overall function is simple, but the details..– Name the bones,
– Know the construction of the orbit walls,
– Know the strong and weak points,
– What is in the orbit, what holds it there?
– What comes into, goes out of the orbit?
– What are holes (fissures, foramina) used for?
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Skull has 22+ bones
• Cranium
– Parietal (2)
– Occipital
– Temporal (2)
– Sphenoid
– Ethmoid
• Face– Maxillary (2)
– Nasal (2)
– Inferior chonchae (2)
– Lacrimal (2)
– Palatine (2)
– Zygomatic (2)
– Mandible
– Vomer
•Frontal bone is part of both cranium & face
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11 bones make up the orbits
• Single Bones
– Frontal Bone
– Ethmoid Bone
– Sphenoid Bone
• Paired Bones
– Maxillary
– Zygomatic
– Lacrimal
– Palatine
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Bones of the skull
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Lateral View of Skull
• Frontal
• Zygomatic
• Note temoral aspect of Sphenoid
• Maxillary
• Lacrimal
• Ethmoid
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Sinuses exist in 4 Orbital Bones
• Air filled
• Mucosa lined
• Lighten bone
• Acustic
• Possible infection site
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The basic shape of the orbit is a pyramid:
•The medial walls are parallel
•The depth is 1.5 x base
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• The margin of the orbit {VERY STRONG}
– 4 cm wide
– 3.5 cm high
– 3 BONES• Frontal• Zygomatic• Maxillary
•4.5 cm deep
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Terminology
• Fossa: shallow depression in bone
• Foramen (pl. foramina): hole(s) in bone
• Fissure: hole between adjacent bones
• Tubercle: bump attachment site
• Groove, canal, notch (as they sound)
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A key figure of Chap 3
Let me help you get a 3D understanding of the structures summarized by this figure
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Reasonable Goals
• Overall function is simple, but the details..– Name the bones,
– Know the construction of the orbit walls,
– Know the strong and weak points,
– What is in the orbit, what holds it there?
– What comes into, goes out of the orbit?
– What are holes (fissures, foramina) used for?
![Page 16: The Orbit: Bone structures Bones: Those Latin names Protecting the eye while serving its needs. VS112 Sept 5, 2007 Lect 2-3](https://reader035.vdocuments.mx/reader035/viewer/2022062519/56649c815503460f949384c0/html5/thumbnails/16.jpg)
The orbital ceiling
•Frontal
•Bits of-
Sphenoid
Lacrimal Fossa
Trochlear Fossa
Supraorbital Notch
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The Lateral Wall
•Not shown are:•Zygomatic foramen•Whitnalls Tubercle
•Zygomatic
•Frontal
•Sphenoid
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Bones of the skull
Now look at the Sphenoid
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The Sphenoid Bone
• Butterfly
• (Owl like)
– Greater Wing
– Lesser Wing
– Pterygoid process
• Many Foramina
– Optic Foramen
– Sup. Optic Fissure
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Lateral View of Skull
• Frontal
• Zygomatic
• Note temoral aspect of Sphenoid
• Maxillary
• Lacrimal
• Ethmoid
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The Sphenoid Bone &
Occipital (at back)
Ethmoid (yellow)
Palatine (small red)
Maxillary(straight on view of structure shown on hand out - page 42)
•Now go back to lateral wall slide
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The Lateral Wall
•Not shown are:•Zygomatic foramen•Whitenalls Tubercle
•Zygomatic
•Frontal
•Sphenoid
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The Medial Wall
• Frontal (?)
• Ethmoid
• Lacrimal
• Sphenoid
• Maxillary
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The Orbit Floor
• Maxillary
• Sphenoid
• Zygomatic
• Palatine
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Main components of fissures
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Let me help you get a 3D understanding of the structures summarized by this figure
•Fig 3.2
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Weakest bones are in the floor and medial wall of the orbit.
• Transmitted pressure through the tissues(?) or the sturdier bones causes blowout fractures.
•Lamina papyracia
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Blowout fracture of the floor of maxillary bone.
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Blowout fracture of the floor of maxillary bone. CT image
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Blowout fracture of the ethmoid bone. CT image.
•esf ethmoid sinus fracture •mwf medial wall fracture
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Connective tissues in the orbit
• All of the structures within the orbit have a connective tissue sheath– Around the Globe & muscles it’s call Tenon’s capsule
• If the globe is the palm and EOM fingers, then Tenon’s capsule is the glove.
– Lining the bones, it’s the periosteum• periorbita- a special name for orbit bone lining
– nerves, blood vessels have them too
• And they are interconnected making for a web of sheaths.
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Two Views
• Tenon’s capsule
• Periorbita
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A better view
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Terminology
• Fossa: shallow depression in bone
• Foramen (pl. foramina): hole(s) in bone
• Fissure: hole between adjacent bones
• Tubercle: bump attachment site
• Groove, canal, notch (as they sound)
![Page 36: The Orbit: Bone structures Bones: Those Latin names Protecting the eye while serving its needs. VS112 Sept 5, 2007 Lect 2-3](https://reader035.vdocuments.mx/reader035/viewer/2022062519/56649c815503460f949384c0/html5/thumbnails/36.jpg)
Soft tissue covering
• Surrounding the sclera is the episclera
– Connective tissue and blood vessels.
• Surrounding the episclera is Tenon’s capsule
– Another layer of connective tissue protecting the globe and making it slippery for movement within the orbit.
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Soft tissue covering
• Check ligaments
– medial and lateral are most prominent but the inferior rectus and levator have them too.
• Superior transverse ligament
– Supports levator muscle (Whitnall’s Ligament)
• Suspensory ligament (of Lockwood)
– Connective tissue underneath the globe
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Orbital infection
• Orbital cellulitis: infection of the tissues and fat pads behind/surrounding the eye, but not the eye itself
– 60% of orbital cellulitus is a secondary infection due to a sinus infection
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Bone development• Dermal Bones, most of orbit
– Foci of osteoblasts differentiated from with the mesoderm
• Cartilage pre-formed bones: ethmoid and part of sphenoid. (Endochondral bone)– Chondrocytes form cartilagenous template of the final
bone
– Osteoblasts invade and differentiate into osteocytes
• Bone can restructure/repair itself– Osteoclast cell can breakdown boney matrix
• Permits growth of the skull and orbits