lacrimal bone
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lac·ri·mal bone
[TA]an irregularly rectangular thin plate, forming part of the medial wall of the orbit posterior to the frontal process of the maxilla; it articulates with the inferior nasal concha, ethmoid, frontal, and maxillary bones.
Synonym(s): os lacrimale [TA], os unguis
Farlex Partner Medical Dictionary © Farlex 2012
lacrimal bone
n.
A thin irregularly rectangular plate forming part of the medial wall of the eye socket behind the frontal process of the maxilla.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
lac·ri·mal bone
(lak'ri-măl bōn) [TA]An irregularly rectangular thin plate, forming part of the medial wall of the orbit behind the frontal process of the maxilla; it articulates with the inferior nasal concha, ethmoid, frontal, and maxillary bones.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
lacrimal bone
A small plate of bone, situated just inside the inner wall of the eye socket (orbit), with a shallow hollow to accommodate the LACRIMAL SAC.Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
orbit
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 | |
roof | medial wall |
1. frontal | 1. maxilla |
2. lesser wing of sphenoid | 2. lacrimal |
3. ethmoid | |
4. sphenoid | |
floor | lateral wall |
1. maxilla | 1. greater wing of sphenoid |
2. zygomatic | |
3. palatine | 2. zygomatic |
Table O4 Orbital apertures | ||
aperture | location | contents |
optic canal | at the apex (in lesser sphenoid) | optic nerve ophthalmic artery sympathetic nerve fibres |
superior orbital fissure | at the apex (gap between greater and lesser sphenoid) | III, IV, V, VI nerves sympathetic nerve fibres ophthalmic vein recurrent lacrimal artery |
inferior orbital fissure | between lateral wall and posterior part of the floor | infraorbital nerve zygomatic nerve branch of inferior ophthalmic vein nerve fibres from the pterygopalatine (sphenopalatine) 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 |
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
lac·ri·mal bone
(lak'ri-măl bōn) [TA]An irregularly rectangular thin plate, forming part of the medial wall of the orbit behind the frontal process of the maxilla; it articulates with the inferior nasal concha, ethmoid, frontal, and maxillary bones.
Medical Dictionary for the Dental Professions © Farlex 2012