ORBITAL CAVITY A pyramidal space with a base, apex and four walls. Boundaries and Walls: Roof Orbital plate of frontal b. Lesser wing of sphenoid b. Floor Orbital surface of maxilla Zygomatic bone Orbital process of palatine b. Medial wall Lacrimal bone Orbital plate of ethmoid b. Body of sphenoid b. Lateral wall Zygomatic b. Greater wing of sphenoid b. Frontal bone Greater wing of sphenoid Ethmoid bone Lacrimal bone Zygomatic bone Maxillary bone

Some Features of The Orbit Lacrimal fossa (1) (lodges the orbital part of the lacrimal gland) Lacrimal groove and crests (2) (lodges the lacrimal sac) Trochlear fovea (3) (attachment of the trochlea) Ant. and post. ethmoidal canals (4) (ant. and post. ethmoidal nerves and vessels) Zygomatico-facial and Z-temporal canals (zygomaticofacial and z-temporal n. and v.) Optic canal (5) (optic nerve, ophthalmic a. & meningeal sheath) Supraorbital foramen (6) (supraorbital n. and v.) Infraorbital groove, canal and foramen (7) (infraorbital n. and v.) Superior orbital fissure (8) Inferior orbital fissure (9) 6 3 1 4 5 8 2 9 7 7

Communications of the Orbit The orbital cavity communicates with the: Anterior cranial fossa via ant. and post. ethmoidal canals (1) Middle cranial fossa via optic canal and the superior orbital fissure (2, 3) Infratemporal fossa via inferior orbital fissure (4) Nasal cavity via nasolacrimal canal (5) 1 2 3 5 4

Contents of the Orbital Cavity Orbital fat Eyeball Muscles Vessels Nerves Ciliary ganglion Lacrimal gland Muscles of the Orbit Levator palpebrae suprioris Extrinsic muscles of the eye Intrinsic muscles of the eye 4 Recti muscles Superior rectus Inferior rectus Medial rectus Lateral rectus 2 Oblique muscle Superior oblique Inferior oblique Dilator pupillae Constrictor pupillae Ciliary muscle

Levator palpebrae superioris m. O: roof of the orbit in front of the optic canal I : superficial lamella: front of superior tarsus & skin of upper eyelid deep lamella: upper border of superior tarsus & superior fornix of conjunctiva A: elevation of upper eyelid and sup fornix of conjunctiva N: sup division of oculomotor n. Levator palp sup Lev Palp Sup Insertion of lev palp sup Superior tarsus

Recti Muscles: (sup, inf, med, lat) O: common tendinous ring, according to their position (the lateral rectus m. arises by 2 heads) I: into the sclera, at varying distances from the limbus (corneo-scleral junction) A: directing the cornea vertically or horizontally according the their name (sup. and inf. recti produce some medial deviation in addition to the vertical movement) N.S.: -sup rectus (sup division of oculomotor) -inf & med rectus (inf division of oculomotor) -lat rectus (abducent) Levator palp superioris Levator palp superioris Superior rectus Superior oblique Superior oblique Sup. rectus Lateral rectus Med rectus Lateral rectus Inf. rectus Inferior rectus Inf. oblique Inf. oblique

Superior oblique Inferior oblique O: junction of the roof with medial surface of the orbit (in front of the common tendinous ring) I: its tendon passes through the trochlea, inserted into the sclera behind the equator of eyeball A: directs the cornea downwards and laterally N.S.: trochlear n. Inferior oblique O: anterior part of the floor of the orbit I: runs laterally and upwards, inserted into the sclera behind the equator of the eyeball A: directs the cornea upwards and laterally N. S. : inferior division of oculomotor n.

Intrinsic Muscles of the Eye Sphincter pupillae (constrictor of the pupil) Ciliary muscle (accommodation to near vision) Both muscles are supplied by parasympathetic fibers (through the short ciliary nerves) Dilator pupillae (dilator of the pupil) Supplied by sympathetic fibers (through the long ciliary nerves)

Nerves of the Orbit Sensory Motor Superior division Optic nerve Ophthalmic nerve (frontal, lacrimal, nasociliary) Zygomatic nerve Oculomotor CN III Trochlear CN IV Abducent CN VI Inferior division

Sensory Nerves in the Orbit Optic Nerve Origin and course Formed of axons of ganglion cells of the retina Pierces the sclera 4 mm medial to the center of the eyeball Runs backwards and medially and leaves the orbital cavity through the optic canal Ends in the optic chiasma, medial to the termination of ICA The course of the nerve is divided into 3 parts Intraorbital part (2.5cm) Canalicular part (0.5cm) Intracranial part (1cm) The intraorbital part is sinuous, to allow free movement of the eyeball The nerve is enclosed by a complete meningeal sheath In the optic canal, the opthalmic artery runs below and lateral to the optic nerve (and within its meningeal sheath) The nerve is pierced by the central artery and vein of the retina, 12 mm behind the eyeball Ophthalmic artery ICA Optic chiasma

Branches of the Ophthalmic Nerve Lacrimal nerve The smallest branch of the ophthalmic division of trigeminal Enters the orbit through the sup orbital fissure (outside the common tendinous ring) Runs forwards and lateral, above the lateral rectus Receives a communication from the zygomatico-temporal nerve (which carries secretory fibers to the lacrimal gland) Supplies the lacrimal gland Gives palpebral branches to the lateral part of upper eyelid Lacrimal nerve Lacrimal nerve Frontal nerve Lacrimal gland Lev Palp Sup Lateral rectus Frontal nerve Zygomatico- temporal nerve Maxillary nerve Ophthalmic nerve Zygomatic nerve

Communication between lacrimal and zygomatico-temporal Lacrimal nerve Common tendinous ring Trochlea Zygomatico- temporal nerve Communication between lacrimal and zygomatico-temporal Zygomatico- temporal nerve

Frontal Nerve The largest branch of ophthalmic nerve The highest structure in the orbit Enters the orbit through the superior orbital fissure (outside the common tendinous ring) Runs forwards beneath the roof, above the levator palpabrae superioris Terminates by dividing into supratrochlear nerve, passes above the trochlea to the forehead supraorbital nerve, passes through the supra-orbital foramen to the forehead Supra-orbital nerve Lacrimal nerve Lev Palp Sup Frontal nerve Supraorbital nerve Supra-trochlear nerve Frontal nerve Trochlea

Nasociliary Nerve Branches: A branch of the ophthalmic nerve Enters the orbit through the sup orbital fissure (inside the common tendinous ring) Crosses above the optic nerve from lateral to medial Runs along the medial wall of the orbit, between the superior oblique and medial rectus muscles Terminates by dividing into 1. anterior ethmoidal nerve 2. infratrochlear nerve Infratrochlear nerve Lacrimal gland & nerve Anterior ethmoidal nerve Long ciliary nerves Branches: Sensory root to the ciliary ganglion Long ciliary nerves (carry sympathetic fibers from the plexus around ICA to supply dilator pupillae muscle) Posterior ethmoidal nerve Anterior ethmoidal nerve Infratrochlear nerve Ciliary ganglion Posterior ethmoidal nerve Sensory root to ciliary ganglion Nasociliary nerve

Posterior ethmoidal nerve Passes into the posterior ethmoidal canal Supplies the mucosa of the posterior ethmoidal sinus Infratrochlear nerve Lacrimal gland & nerve Anterior ethmoidal nerve Passes into the anterior ethmoidal canal Supplies the mucosa of the anterior and middle ethmoidal sinuses Reaches the anterior cranial fossa Passes through the cribriform plate of ethmoid to reach the nose, where it divides into: -Two internal nasal nerves (medial and lateral) for the septum and lateral wall of the nose -External nasal nerve, supplies the skin on the lower part of the nose Anterior ethmoidal nerve Long ciliary nerves Ciliary ganglion Posterior ethmoidal nerve Sensory root to ciliary ganglion Nasociliary nerve Infratrochlear nerve Passes below the trochlea to reach the face Supplies skin of upper part of the nose and medial parts of the eyelids

Zygomatic Nerve Branch of the maxillary nerve Enters the orbit through the inferior orbital fissure Divides into zygomatico-temporal and zygomatico-facial nerves The zygomatico-temporal nerve carries parasympathetic secretory fibers from the sphenopalatine ganglion to the lacrimal gland (via the communication between it and the lacrimal nerve) Nasociliary nerve Lacrimal nerve Frontal nerve Ophthalmic nerve Maxillary nerve Mandibular nerve Zygomatic nerve Zygomatico- temporal nerve

Motor Nerves in the Orbit Oculomotor nerve CN III: Divides into superior and inferior divisions Both divisions enter the orbit through the superior orbital fissure (inside the common tendinous ring) The superior division supplies: superior rectus levator palpebrae superioris The inferior division supplies: Medial rectus Inferior rectus Inferior oblique Superior rectus Superior division Superior oblique Oculomotor nerve Lev palp superioris Medial rectus Inferior division NB. The nerve to inferior oblique carries the parasympathetic root to the ciliary ganglion These parasympathetic fibers arise from the Edinger Westphal nucleus in the midbrain The postganglionic fibers supply the constrictor pupillae and the ciliary muscle Inferior rectus Ciliary ganglion Inferior oblique

Trochlear nerve CN IV Enters the orbit through the sup orbital fissure (outside the common tend ring) Supplies the superior oblique muscle Trochlear nerve Superior oblique

Abducent nerve CN VI Enters the orbit through the sup orbital fissure (inside the common tend ring) Passes between the two heads of the lat rectus m and supplies it from its deep surface.

Ciliary Ganglion Long ciliary nerves A minute parasympathetic ganglion lateral to the optic nerve Roots: Sensory: from the nasociliary n. Parasymp: from the nerve to inferior oblique Symp: from the plexus around the ICA Branches: 15-20 short ciliary nerves which pierce the sclera aound the optic nerve They carry: Sensory fibers: to the cornea and iris Parasympathetic fibers: to the sphincter pupillae and ciliary muscles Sympathetic fibers: to the ciliary vessels Short ciliary nerves Ciliary ganglion

(from plexus around ICA) Sympathetic root (from plexus around ICA) Parasympathetic root carried by nerve to inferior oblique Ciliary ganglion Short ciliary nerves Sensory root from nasociliary nerve Ophthalmic nerve

Blood Vessels of the Orbit Arteries Ophthalmic artery Veins Superior ophthalmic vein Inferior ophthalmic vein Central vein of the retina

Ophthalmic Artery A branch of the ICA Enters the orbit through the optic canal below and lateral to the optic nerve and within its meningeal sheath Crosses above the optic nerve from lateral to medial (accompanied by the nasociliary nerve) Runs along the med wall of the orbit below the superior oblique muscle Terminates near the medial end of the upper eyelid by dividing into: Supratrochlear artery Dorsal nasal artery Optic nerve Ophthalmic artery Nasociliary nerve Ciliary ganglion Oculomotor nerve Ophthalmic nerve Maxillary nerve

Medial palpebral a. Supratrochlear a. Supraorbital a. Latearl palpebral a. (from lacrimal a.) Dorsal nasal a. Anterior ethmoidal a. Zygomatic branches (from lacrimal a.) Posterior ethmoidal a. Posterior ciliary a. Central retinal a. Lacrimal a. Ophthalmic a. ICA

Branches of the Ophthalmic Artery Central artery of the retina: pierces the optic nerve 12mm behind eyeball and runs through the center of the nerve Lacrimal artery: supplies the lacrimal gland and gives: -Zygomatico-temporal and zygomatico-facial arteries -Lateral palpebral artery -Recurrent meningeal branch Ciliary arteries -Posterior ciliary arteries -Anterior ciliary arteries Supraorbital artery, passes out through the supraorbital foramen Post ethmoidal artery, passes through the post ethmoidal canal to the anterior cranial fossa and gives meningeal branches and nasal branches, which reach the nose through cribriform plate of ethmoid Ant ethmoidal artery, passes through the anterior ethmoidal canal to the ant cranial fossa and gives meningeal branches and nasal branches, which reach the nose through cribriform plate of ethmoid Recurrent meningeal branch, passes backwards through the sup orbital fissure to the middle cranial fossa Medial palpebral artery, superior and inferior to medial parts of eyelids Supratrochlear artery, passes above the trochlea to the forehead Dorsal nasal artery, passes below the trochlea and anastomoses with the termination of facial (angular) a.

Ophthalmic Veins Superior ophthalmic vein: Inferior ophthalmic vein: Begins behind the medial part of the upper eyelid Runs posteriorly with the ophthalmic artery Receives tributaries corresponding to branches of the ophthalmic artery. Passes through the superior orbital fissure outside the common tend ring to end in the cavernous sinus Superior ophthalmic vein Facial vein Inferior ophthalmic vein: Begins at the ant part of the floor of the orbit and runs backwards Communicates with the pterygoid plexus of veins throught the inferior orbital fissure Passes through the sup orbital fissure (outside the common tend ring) and terminates in the cavernous sinus Cavernous sinus Central vein of the retina: Runs with the artery in the center of the optic nerve Pierces the optic nerve 12 mm behind the eyeball Ends in the cavernous sinus Inferior ophthalmic vein Pterygoid plexus of veins

Structures passing through the superior orbital fissure (from lateral to medial) Lacrimal n. Frontal n. Trochlear n. Superior div of oculomotor n. Nasociliary n. Inferior div of oculomotor n. Abducent n. Ophthalmic vein. Outside the common tendenous ring Inside the common tend ring Structures passing through the inferior orbital fissure Maxillary nerve (to continue as the infraorbital nerve) Zygomatic nerve (branch from the maxillary nerve) Infraorbital vessels Communication between inferior ophthalmic vein and pterygoid plexus of veins