Examples of orbit in the following topics:
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- The orbital cavity is formed from seven bones.
- The frontal bone forms the superior border of the orbital rim and also the
superior wall (roof) of the orbital surface.
- The zygomatic bone forms the
lateral (and half of the basal) border of the orbital rim, and also the lateral
wall of the orbital surface—this is the thickest region of the orbit as it is
most exposed to external trauma.
- Completing the basal and medial border of the
orbital rim is the maxillary bone, which also forms the inferior wall (floor) of
the orbital surface.
- The lacrimal and ethmoid bones contribute
to the medial wall of the orbit and also to the medial wall of the orbital canal.
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- It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the levator palpebrae superiors muscle.
- It runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic nervous system, and a communicating branch from the ophthalmic division of the trigeminal nerve.
- It then divides into two branches that enter the orbit through the superior orbital fissure, between the two heads of the lateral rectus
(a muscle on the
lateral side of the eyeball in the orbit).
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- The two zygomatic bones form the cheeks and
contribute to the orbits.
- The two lacrimal bones form the medial wall of the orbit
and articulate with the frontal, ethmoid, maxilla, and inferior nasal conchae.
- They provide the bed for the upper teeth, the floor
of the nose, and the base of the orbits.
- The palatine bones fuse in the
midline to form the palatine, located at the back of the nasal cavity that
forms the roof of the mouth and the floor of the orbit.
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- The maxillary sinuses (also called the maxillary antrechea, the largest of the paranasal sinuses) are located under the orbits in the maxillary bones.
- The frontal sinuses are superior to the orbits and are in the frontal bone.
- The ethmoid sinuses are formed from several discrete air cells within the ethmoid bone between the nose and the orbits.
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- Supraorbital foramen: Located in the
frontal bone, it allows passage of the supraorbital vein, artery, and nerve into the
orbit.
- Optic foramen: Located in the sphenoid, it
allows the passage of the ophthalmic artery and nerve from the optic canal into
the orbit.
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- The sphenoid bone is situated in the middle
of the skull towards the front and forms the rear of the orbit.
- The greater wings form
the floor of the middle cranial fossa that houses the frontal lobes and pituitary
gland, and also the posterior wall of the orbit.
- The lesser wings project laterally
and form the floor of the anterior cranial fossa and the superior orbital
fissure through which several key optical nerves pass.
- It is
lightweight due to its spongy, air-filled construction and is located at the roof
of the nose and between the two orbits.
- Orbital: This part lies inferiorly and forms the superior border of the orbit.
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- It then enters the orbit through the superior orbital fissure and innervates the lateral rectus muscle of the eye.
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- Spreading to the orbit may result in periorbital cellulitis, subperiosteal abscess, orbital cellulitis, and abscess.
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- The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running postero-medially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.
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- In this position, the orbitales (eye sockets), lower margins of the orbits, and the poria (ear canal upper margins) all lie in the same horizontal plane.