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Last reviewed: 19.11.2021
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The orbita (orbita) is a pair of cavities resembling a four-sided pyramid with rounded edges. The base of the pyramid is turned forward and forms the entrance to the eye socket (aditus orbitae). The tip of the orbit is directed back and medially. Here passes the visual canal (canalis opticus). In the cavity of the orbit are the eyeball, its muscles, tear gland and other formations. The cavity of the orbit has four walls: the upper, medial, lower and lateral.
The upper wall is formed by the orbital part of the frontal bone and only behind is supplemented by a small wing of the sphenoid bone. At the border of the upper wall with the lateral wall of the orbit, there is a shallow fossa of the lacrimal gland. At the medial edge of the upper wall, near the frontal notch, there is a subtle indentation - the block fossa, near which the block awn is located.
The medial wall is formed by the frontal process of the upper jaw, the tear bone, the orbital plate of the latticed bone, the body of the sphenoid bone (posterior) and the medial part of the orbital part of the frontal bone (above). In the anterior part of the medial wall is a pit of the lacrimal sac. The fossa passes into the nasolacrimal canal (canalis nasolacrimal), which opens into the lower nasal passage of the nasal cavity. Behind and up from the pit of the lacrimal sac, in the seam between the frontal bone and the orbital plate of the latticed bone, two holes are visible: a foramen ethmoidale anterius and a posterior trellis foramen ethmoidale posterius for the nerves and vessels of the same name.
The lower wall of the orbit is formed by the orbital surfaces of the upper jaw and zygomatic bone. The posterior wall is supplemented by the ophthalmic procession of the palatine bone. In the lower wall of the orbit there is an infraorbital furrow, which in front passes into the same channel, which opens on the front surface of the body of the upper jaw by the infraorbital opening.
The lateral wall is formed by the orbital surfaces of the large wing of the sphenoid bone and the frontal process of the malar bone, and also by a small portion of the malar bone of the frontal bone. Between the lateral and upper walls in the depth of the orbit is the upper orbital fissure, leading from the orbit into the middle cranial fossa. Between the lateral and lower walls there is an extensive lower glandular fissure (fissura orbitalis inferior); it is formed by the posterior edge of the orbital surface of the body of the upper jaw, the orbital process of the palatine bone below and the lower edge of the orbital surface of the large wing of the sphenoid bone at the top. This gap communicates the orbit with the pterygoid-palatal and transverse fossa. On the lateral wall of the orbit there is a cheek-eyed orifice (for the zygomatic nerve) leading to the canal, which is divided into two canalicules in the depth of the bone. One of them opens on the lateral surface of the zygomatic bone with a bilobed aperture, the other on the temporal surface with a cheek-shaped aperture.
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