(Orbit).khyber medical college peshawar..

(Orbit).khyber medical college peshawar..

• 1.
  The Bony Orbit AIZAZ DemonstratorSurgical IPMS-Khyber Medical University Peshawar
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  Orbit The bony orbits(or eye sockets) are bilateral and symmetrical cavities in the head. They enclose the eyeball and its associated structures.
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  Anatomical Relations The orbitcan be thought of as a pyramidal structure, with the apex pointing posteriorly and the base situated anteriorly. The boundaries of the orbit are formed by seven bones. lacrimal, ethmoid , sphenoid , frontal , and zygomatic, maxilla and palatine It is also important to consider the anatomical relations of the orbital cavity – this is clinically relevant in the spread of infection, and in cases of trauma.
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  Anatomical Relations The bordersand anatomical relations of the bony orbit are as follows: Roof (superior wall): Formed by the frontal bone and the lesser wing of the sphenoid. The frontal bone separates the orbit from the anterior cranial fossa. Floor (inferior wall): Formed by the maxilla, palatine and zygomatic bones. The maxilla separates the orbit from the underlying maxillary sinus. Medial wall – Formed by the ethmoid, maxilla, lacrimal and sphenoid bones. The ethmoid bone separates the orbit from the ethmoid sinus. Lateral wall – Formed by the zygomatic bone and greater wing of the sphenoid. Apex – Located at the opening to the optic canal, the optic foramen. Base – Opens out into the face, and is bounded by the eyelids. It is also known as the orbital rim.
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  Openings into theOrbital Cavity Orbital opening: Lies anteriorly. About one sixth of the eye is exposed; the remainder is protected by the walls of the orbit.
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  Openings into theOrbital Cavity Supraorbital notch (Foramen): The supraorbital notch is situated on the superior orbital margin. It transmits the supraorbital nerve and blood vessels.
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  Openings into theOrbital Cavity Infraorbital groove and canal: Situated on the floor of the orbit in the orbital plate of the maxilla they transmit the infraorbital nerve (a continuation of the maxillary nerve) and blood vessels.
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  Openings into theOrbital Cavity Nasolacrimal canal: Located anteriorly on the medial wall; it communicates with the inferior meatus of the nose . It transmits the nasolacrimal duct.
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  Openings into theOrbital Cavity Inferior orbital fissure: Located posteriorly between the maxilla and the greater wing of the sphenoid ; it communicates with the pterygopalatine fossa. It transmits the maxillary nerve and its zygomatic branch, the inferior ophthalmic vein, and sympathetic nerves.
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  Openings into theOrbital Cavity Superior orbital fissure: Located posteriorly between the greater and lesser wings of the sphenoid. it communicates with the middle cranial fossa. It transmits the lacrimal nerve, the frontal nerve, the trochlear nerve, the oculomotor nerve (upper and lower divisions), the abducent nerve, the nasociliary nerve, and the superior ophthalmic vein.
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  Contents The bony orbitcontains the eyeballs and their associated structures: Extra-ocular muscles – These muscles are separate from the eye. They are responsible for the movement of the eyeball and superior eyelid. Eyelids – These cover the orbits anteriorly. Nerves: Several cranial nerves supply the eye and its structures; optic, oculomotor, trochlear, trigeminal and abducens nerves. Blood vessels: The eye receives blood primarily from the ophthalmic artery. Venous drainage is via the superior and inferior ophthalmic veins Any space within the orbit that is not occupied is filled with orbital fat. This tissue cushions the eye, and stabilizes the extraocular muscles.
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  Orbital Fascia The orbitalfascia is the periosteum of the bones that form the walls of the orbit. It is loosely attached to the bones and is continuous through the foramina and fissures with the periosteum covering the outer surfaces of the bones. The muscle of Müller, or orbitalis muscle, is a thin layer of smooth muscle that bridges the inferior orbital fissure.
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  Nerves of theOrbit
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  Optic Nerve • Theoptic nerve enters the orbit from the middle cranial fossa by passing through the optic canal. • It is accompanied by the ophthalmic artery, which lies on its lower lateral side. • The nerve is surrounded by sheaths of pia mater, arachnoid mater, and dura mater
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  Lacrimal Nerve • Thelacrimal nerve arises from the ophthalmic division of the trigeminal nerve. • It enters the orbit through the upper part of the superior orbital fissure and passes forward along the upper border of the lateral rectus muscle
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  Frontal Nerve • Thefrontal nerve arises from the ophthalmic division of the trigeminal nerve. • It enters the orbit through the upper part of the superior orbital fissure and passes forward on the upper surface of the levator palpebrae superioris beneath the roof of the orbit. • It divides into the supratrochlear and supraorbital nerves that wind around the upper margin of the orbital cavity to supply the skin of the forehead; the supraorbital nerve also supplies the mucous membrane of the frontal air sinus.
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  Trochlear Nerve • Thetrochlear nerve enters the orbit through the upper part of the superior orbital fissure. • It runs forward and supplies the superior oblique muscle
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  Oculomotor Nerve • Thesuperior ramus of the oculomotor nerve enters the orbit through the lower part of the superior orbital fissure. supplies the superior rectus muscle, then pierces it, and supplies the levator palpebrae superioris muscle • The inferior ramus of the oculomotor nerve enters the orbit in a similar manner and supplies the inferior rectus, the medial rectus, and the inferior oblique muscle
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  Nasociliary Nerve • arisesfrom the ophthalmic division of the trigeminal nerve. • It enters the orbit through the lower part of the superior orbital fissure. • It crosses above the optic nerve, runs forward along the upper margin of the medial rectus muscle, and ends by dividing into the anterior ethmoidal and infratrochlear nerves • The posterior ethmoidal nerve supplies the ethmoidal and sphenoidal air sinuses
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  Abducent Nerve • Theabducent nerve enters the orbit through the lower part of the superior orbital fissure and supplies the lateral rectus muscle