orbit(redirected from Planetary orbit)
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1. the bony cavity containing the eyeball and its associated muscles, vessels, and nerves; the ethmoid, frontal, lacrimal, nasal, palatine, sphenoid, and zygomatic bones and the maxilla contribute to its formation.
2. the path of an electron around the nucleus of an atom. adj., adj or´bital.
The bony cavity containing the eyeball and its adnexa; it is formed of parts of seven bones: the frontal, maxillary, sphenoid, lacrimal, zygomatic, ethmoid, and palatine.
See orbital cavity.
ORBITCardiology A clinical trial Oral Glycoprotein IIb/IIIa receptor Blockade to Inhibit Thrombosis
orbitThe bony cavern in the skull that contains the eyeball and OPTIC NERVE, the muscles that move the eye, the LACRIMAL GLAND, a quantity of fat and various arteries, veins and nerves.
orbitthe body cavity or socket in the vertebrate skull containing the eyeball.
The cavity in the skull containing the eye-ball; formed from seven bones: frontal, maxillary, sphenoid, lacrimal, zygomatic, ethmoid, and palatine.
A rigid bony cavity in the skull which contains an eyeball, orbital fat, the extraocular muscles, the optic nerve, nerves and blood vessels, lacrimal system and fibrous tissue of various kinds. This packing serves to keep the eyeball reasonably well fixed in place as it rotates. The orbital cavity has the approximate form of a pyramid. The walls of the orbital cavity are formed by seven bones. The medial wall of the orbit consists of: (1) the frontal process of the maxilla (maxillary); (2) the lacrimal bone; (3) the lamina papyracea of the ethmoid; and (4) a small part of the body of the sphenoid. The floor of the orbit consists of: (1) the orbital plate of the maxilla; (2) the orbital surface of the zygomatic (malar) bone and (3) the orbital process of the palatine bone. The lateral wall of the orbit consists of (1) the orbital surface of the greater wing of the sphenoid, and (2) the orbital surface of the zygomatic. The roof of the orbit is made up mainly by the frontal bone and behind this by the lesser wing of the sphenoid. The orbit is lined with a membrane of tissue called the periorbita (or orbital periosteum) which extends to the orbital margin (anterior rim of the orbit) where it becomes continuous with the periosteum covering the facial bones. The periorbita is loosely attached to the bones except at sutures, foramina and the orbital margin where it is firmly attached. The bones are much thicker at the margin (rim) than they are along the walls of the orbital cavity. There are many apertures and gaps in the orbit through which blood vessels and nerves pass (see Table O4). See orbital axis; optic canal; inferior orbital fissure; superior orbital fissure; orbital fracture; cavernous haemangioma; lamina papyracea.
|Table O3 Bones forming the walls of the orbit|
|1. frontal||1. maxilla|
|2. lesser wing of sphenoid||2. lacrimal|
|1. maxilla||1. greater wing of sphenoid|
|3. palatine||2. zygomatic|
|Table O4 Orbital apertures|
|optic canal||at the apex (in lesser sphenoid)||optic nerve|
sympathetic nerve fibres
|superior orbital fissure||at the apex (gap between greater and lesser sphenoid)||III, IV, V, VI nerves|
sympathetic nerve fibres
recurrent lacrimal artery
|inferior orbital fissure||between lateral wall and posterior part of the floor||infraorbital nerve|
branch of inferior ophthalmic vein
nerve fibres from the
ganglion to orbital periosteum
|ethmoidal foramina (anterior and post.)||medial wall (frontal/ethmoidal suture)||ethmoidal vessels|
ethmoidal nerve/external nasal nerve
|zygomatic foramen||lateral wall||zygomatic nerve and vessels|
|nasolacrimal canal||medial wall (maxilla/lacrimal)||nasolacrimal duct|
Bony cavity containing eyeball and its adnexa.