The Orbit

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The Orbit Its Contents
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The Bony Orbit

• Lateral Wall
• zygoma
• frontal (zygomatic process)
• sphenoid (greater wing)
• Roof
• frontal
• sphenoid (lesser wing)
• Medial Wall
• maxilla (frontal process)

• lacrimal
• ethmoid (lamina papyraceae)
• sphenoid (lesser wing)
• palatine (orbital plate)
• Floor
• maxilla
• zygoma
• palatine

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Foramen and Fisssures

• Lateral
• Zygomatico-orbital foramen
• Roof
• supraorbital notch (foramen)
• Posterior
• optic canal
• superior orbital fissure

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Foramen and Fissures (cont)

• Medial
• anterior ethmoid foramen
• posterior ethmoid foramen
• nasolacrimal canal
• Floor
• inferior orbital fissure
• infraorbital canal

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Contents of the Orbit

• Globe of the Eye and the attached Optic Nerve
• Extraocular Muscles (move the globe)
• levator palpebre (elevates upper eyelid)
• superior rectus
• superior oblique
• medial rectus
• inferior rectus
• lateral rectus
• inferior oblique
• Lacrimal Gland

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Structures of the Eye

• Globe is a multilayer structure supported by
  connective tissue and small muscles.
• Consists of Three Layers
• Outer Layer (Sclera) collagenous and mostly
  avascular and acellular. Tough yet thin ( 1mm).
• Provides attachment for muscles.
• Perforated by the optic nerve and opthalamic
  vessels.

• Cornea the anterior clear portion of the
  sclera. Its stroma is sandwiched in between an
  outer epithelial layer and an inner endothelial
  layer. Contains few cells and no blood vessels.
• Protects inner eye
• Refracts light into the eye.
• Surface innervated by V1.
• Receives nourishment from tears and aqueous
  humor. Consistently pumps fluid into aqueous
  humor.

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Structures of the Eye

• Iris consists of connective tissue, muscle and
  pigment. It controls light entry onto retina.
• Dilation sympathetic control
• Constriction parasympathetic control
• Pigment controls intra- ocular light scatter.
• Ciliary Body unites the Iris with the choroid.
  Makes aqueous humor and anchors the lens. Ciliary
  muscles control the lens thickness.
• Vitreous 90 water with collagen fibrils and
  hyaluronic acid, has a gel-like consistency.
  Degenerates with increased age.

• Middle Layer (Choroid) consists of blood
  vessels, connective tissue and pigmented cells.
  Provides nutrients and oxygen to outer retinal
  surface.
• Inner Layer (Retina) converts focused light
  into nerve impulses. Light has to pass into the
  inner retina to reach photoreceptors (Rods and
  Cones).
• Other areas
• Uvea consists of the iris , ciliary body and
  choroid

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Extra-Ocular Muscles
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Actions of Extraoccular Muscles
Muscle Origin Insertion
Action Innervation Levator
Tendinous Skin of elevate upper
III Palpebre Ring upper
eyelid eylid Superior Tendinous
Superior Portion Rotate Globe Rectus
Ring Sclerocorneal Superiorly
III
Junction (SCJ) Medial Tendinous
Medial Portion Rotate Globe Rectus
Ring SCJ
Medially III Inferior
Tendinous Inferior Portion Rotate
Globe Rectus Ring SCJ
Inferiorly III
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Muscle Origin Insertion
Action Innervation Lateral Tendinous
Lateral Portion Rotate Globe Rectus
Ring SCJ
Laterally VI Superior
Tendinous Posterior to Rotate
Globe Oblique Ring Superior
Portion Down and Out IV
SCJ Inferior
Maxilla of Posterior to Rotate
Globe Oblique Orbital Floor Superior
Portion Up and Out III
SCJ Movement of the
globe of the eye envolves the synergistic
activity of all extraoccular muscles and is a
bilateral process.
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Cranial Nerves in the Orbit

• II Optic (SSA)
• III Occulomotor
• GSE Components
• GSA Components
• GVE Components
• IV Trochlear
• GSE Components
• GSA Components
• V Trigeminal
• Ophthalmic br.s
• Frontal
• Lacrimal

• Nasociliary
• GSA Components
• Maxillary br.s
• Zygomatic
• Infraorbital
• GSA Components
• VI Abducens
• GSE Components
• GSA Components
• VII Facial
• GVE Components

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Vascular Structures in the Orbit

• Arteries
• Branches of Internal Carotid A.
• Central Retinal A.
• Ophthalmic A.
• Supraorbital br.
• Lacrimal br.

• Veins
• Ophthalmic Veins
• Superior
• Inferior
• can drain into cavernous sinus and receive
  drainage from facial vein.

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The Ear
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Regions of the Ear

• External Ear
• Auricle
• helix
• anti-helix
• tragus
• External Acoustic Meatus
• Tympanic Membrane
• Middle Ear
• ear ossicles (malleus , incus stapes)

• Muscles
• tensor tympani
• stapedius
• Oval Window
• Inner Ear
• Cochlear Apparatus
• Vestibular Apparatus

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The Boundaries of the Ear
The bony boundries of the ear are located within
the temporal bone . There are several openings
in the temporal bone which support or transport
structures into this region. -
External Acoustic Meatus - supports the tympanic

membrane. - Internal Acoustic Meatus -
transports the cranial nerves VII
VIII. - Stylomatastoid Foramen - transports the
Facial
Nerve proper. - Petrotympanic
Fissure - transports Chorda Tympanic
branch of
VII. -Tympanomastoid Fissure transports
auricular branch of X.
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Oval Window - supports the membrane over the
opening to the scala
vestibuli. Round Window - supports the membrane
over the opening
from the scala tympani. Tympanic Canaliculus -
transports the tympanic
branch of IX. Cochlear
Canaliculus - transports perilymph from
the labyrinth to the

subarachnoid space. Auditory (Eustschian) Tube -
interconnects the nasal
pharynx with the middle ear.
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Nerves which Pass through or to the Regions of
the Ear

• Trigeminal V
• Nerve to Tensor Tympani m. (SVE)
• Auriculotemporal (GSA) - sensory to external
  acoustic region.
• Glossopharyngeal IX
• Tympanic Br. (GSA)
• Lesser Petrosal (GVE)
• Vagus X Auricular Br. (GSA)

• Facial VII
• Facial N. Proper (SVE, GSA)
• Chorda Tympani (GVE SVA)
• Greater Petrosal (GVE SVA)
• Vestibulochoclear VIII (to the organs of hearing
  and equilibrium)

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Structures of the Auditory System

• External Ear consists of the auricle and the
  external acoustic canal.
• Functions like an antenna, funneling sound waves
  toward the tympanic membrane.
• Middle Ear consists of the tympanic membrane,
  the ear ossicles and the oval window.
• Functions to amplify ( 20X)
• Tensor Tympani muscle which connects to malleus
  and Stapedius muscle which connects to stapes
  help to control extraneous sound vibrations (
  inervated by trigeminal and facial nerves
  respectively).

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Structures of the Auditory System

• Inner Ear also provides some amplification but
  is most concerned with reception and transmission
  of sound.
• Sound vibrations are transmitted from the stapes
  through the oval window to the scala vestibuli.
• The scala vestibuli is a perilymph filled channel
  in the cochlea which transmits sound waves
  through a small slit, the helicotrema, to the
  scala tympani.
• The scala tympani transmits sound out the round
  window back into the middle ear.
• Between the scala vestibuli and the scala tympani
  is the scala media, also known as, the cochlear
  duct. The cochlear duct contains the sensory
  receptive layer for sound, the Organ of Corti.

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