Download The Orbit: Bone structures

Ocular Anatomy
V.S. 111
UAB School of Optometry
Timothy W. Kraft, Ph.D.
975-2885
[email protected]
Goals for the Term
• Solid base of knowledge
• Comfort with Ocular terminology
• Basics of tissue structure & function
– At the end of the course you can give
yourself a 3D guided tour of the eye and
orbit within your mind’s eye.
Exam Schedule & Grading
• Midterm 45%
• Lab work sheets & hw (5%)
• Quizzes: Six, pick your best 5 for 10%
• and Final Exam 40%
• some of Final is review
There will be 4 or 5 Lab sessions, attendance is mandatory
Sources of information
• The Human Eye structure and Function
by Clyde Oyster
• Hand-outs, outlines including additional
figures.
• CD’s of power point presentations for out
of class review
Come to Class
Texts and Supplements
• Oyster (you buy this one) The Human
Eye
• Williams & Warwick Functional
Neuroanatomy of Man (copy provided)
• Snell & Lemp: Clinical Anatomy of the
Eye (copy of selected figures provided)
Broad-based learning
• Power point presentations
– Almost all lectures available on CD
• Hand out outline the lecture
• Study Guides
• When all else fails: RTB
Go to Class
Overview
• When the structure seems complicated , think
FUNCTION
– Imaging : OPTICAL CLARITY
– Information processing: pathways, adaptation
– Mobility: balance, strength, speed, MECHANICS
– Biological System: respiration, pain, protection
Terminology
• Rostral (toward top of head - rooster)
• Caudal (toward tail) cauda equina - horses tail
• Anterior - front - ventral
• Posterior- back - dorsal (dorsal fin)
• Medial (midline) {Nasal}
• Lateral away from midline (Temporal)
• Central • Peripheral- away from center
Basic components of eyeball
Scleral
outer
Vitreal
Inner
Eyeball: Optical Pathway
• Cornea
• Anterior Chamber
• Iris/Pupil
• Posterior Chamber
• Lens
• Vitreous
• Retina
Figure by Snell & Lemp
Eyeball: Layered tissues
• Protective epithelium
• Cornea/Sclera
• Choroid
• RPE
– All to protect/nourish the
nervous tissue of
retina/optic nerve
• Scleral/Vitreal
Figure by Snell & Lemp
The Orbit: Bone structures
Bones: Those
Latin names
Protecting the
eye while
serving its
needs.
•VS111
•Aug 11, 2008
•Lect 1-2
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?
Skull has 22+ bones
• Cranium
– Parietal (2)
– Occipital
– Temporal (2)
• Face
– Maxillary (2)
– Nasal (2)
– Inferior chonchae (2)
– Lacrimal (2)
– Sphenoid
– Palatine (2)
– Ethmoid
– Zygomatic (2)
– Mandible
– Vomer
•Frontal bone is part of both cranium & face
11 bones make up the orbits
• Single Bones
• Paired Bones
– Frontal Bone
– Maxillary
– Ethmoid Bone
– Zygomatic
– Sphenoid Bone
– Lacrimal
– Palatine
Bones
of the
skull
Lateral View of Skull
• Frontal
• Zygomatic
• Note temoral aspect
of Sphenoid
• Maxillary
• Lacrimal
• Ethmoid
Sinuses exist in 4 Orbital Bones
• Air filled
• Mucosa lined
• Lighten bone
• Acustic
• Possible infection
site
The basic shape of the orbit is
a pyramid:
•The medial walls are parallel
•The depth is 1.5 x base
• The margin of the
orbit {VERY STRONG}
– 4 cm wide
– 3.5 cm high
– 3 BONES
• Frontal
• Zygomatic
• Maxillary
•4.5 cm deep
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)
A key figure of Chap 3
Let me help
you get a 3D
understanding
of the
structures
summarized
by this figure
•Naso
The orbital ceiling
•Frontal
•Bits ofSphenoid
Lacrimal Fossa
Trochlear Fossa
Supraorbital Notch
The Lateral Wall
•Not shown are:
•Zygomatic foramen
•Whitnall’s Tubercle
•Zygomatic
•Sphenoid
Bones
of the
skull
Now look
at the
Sphenoid
The Sphenoid Bone
• Butterfly
• (Owl like)
– Greater Wing
– Lesser Wing
– Pterygoid process
• Many Foramina
– Optic Foramen
– Sup. Optic Fissure
Lateral View of Skull
• Frontal
• Zygomatic
• Note temoral
aspect of
Sphenoid
• Maxillary
• Lacrimal
• Ethmoid
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
The Lateral Wall
•Not shown are:
•Zygomatic foramen
•Whitenalls Tubercle
•Zygomatic
•Sphenoid
The Medial Wall
• Ethmoid
• Lacrimal
• Sphenoid
• Maxillary
The Orbit Floor
• Maxillary
• Zygomatic
• Palatine
Main components of fissures
Let me help
you get a 3D
understanding
of the
structures
summarized
by this figure
•Fig 3.2
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
Blowout fracture of the floor of
maxillary bone.
Blowout fracture of the floor of
maxillary bone. CT image
Blowout fracture of the
ethmoid bone. CT image.
•esf
ethmoid sinus fracture
•mwf
medial wall fracture
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.
Two
Views
• Tenon’s capsule
• Periorbita
A better view
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)
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.
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
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
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