The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of the lacrimal bone function in the process of lacrimation or crying. Specifically, the lacrimal bone helps form the nasolacrimal canal necessary for tear translocation. A depression on the anterior inferior portion of the bone, the lacrimal fossa, houses the membranous lacrimal sac. Tears or lacrimal fluid, from the lacrimal glands, collect in this sac during excessive lacrimation. The fluid then flows through the nasolacrimal duct and into the nasopharynx. This drainage results in what is commonly referred to a runny nose during excessive crying or tear production. Injury or fracture of the lacrimal bone can result in posttraumatic obstruction of the lacrimal pathways.
Position of the lacrimal bone (shown in green).
Medial wall of the orbit. Lacrimal bone is in yellow.
|Anatomical terms of bone|
The lateral or orbital surface is divided by a vertical ridge, the posterior lacrimal crest, into two parts.
In front of this crest is a longitudinal groove, the lacrimal sulcus (sulcus lacrimalis), the inner margin of which unites with the frontal process of the maxilla, and the lacrimal fossa is thus completed. The upper part of this fossa lodges the lacrimal sac, the lower part, the nasolacrimal duct.
The portion behind the crest is smooth, and forms part of the medial wall of the orbit.
The crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the orbicularis oculi and ends below in a small, hook-like projection, the lacrimal hamulus, which articulates with the lacrimal tubercle of the maxilla, and completes the upper orifice of the nasolacrimal canal; the hamulus sometimes exists as a separate piece, and is then called the lesser lacrimal bone.
The medial or nasal surface presents a longitudinal furrow, corresponding to the crest on the lateral surface.
Of the four borders:
The lacrimal is ossified from a single center, which appears about the twelfth week in the membrane covering the cartilaginous nasal capsule.
In early lobe-finned fishes and ancestral tetrapods, the lacrimal bone is a relatively large and robust bone, running from the orbit to the nostrils. It forms part of the side of the face, between the nasal bones and the maxilla. In primitive forms, it is often accompanied by a much smaller septomaxilla bone, lying immediately behind the nasal opening, but this is lost in most modern species. The lacrimal bone is often smaller in living vertebrates, and is no longer always directly associated with the nasal opening, although it retains its connection with the orbit. The bone is entirely absent in living amphibians, as well as some reptilian species.
In dinosaurs, the lacrimal bone usually defines the anterior rim of the orbit (eye socket), and the posterior rim of the antorbital fenestra. In some theropods (e.g. Allosaurus, Ceratosaurus, Albertosaurus) the upper part of the lacrimal bone grew in such a manner as to form a horn on the top of the dinosaur's head, usually situated above, and anterior to the eye. In many dinosaurs, the lacrimal bone comes into contact with the nasal bone, the jugal bone, the prefrontal bone, and the maxillary and premaxillary bones. The boundaries where some of these bones meet with the others are called sutures. Rarely, the lacrimal bones fused with the nasal bones to form a pair of "nasolacrimal" crests, which are present in dinosaurs such as Dilophosaurus, Megapnosaurus and Sinosaurus.
The agger nasi (from Latin: agger meaning "mound or heap") is a small ridge on the lateral side of the nasal cavity. It is located midway at the anterior edge of the middle nasal concha, directly above the atrium of the middle meatus. It is formed by a mucous membrane that is covering the ethmoidal crest of the maxilla.
It is also called the nasoturbinal concha and the nasal ridge. In 90% of patients an anterior ethmoidal cell (called the "agger nasi cell") can be found in the lacrimal bone below the agger nasi ridge. An enlarged agger nasi cell may encroach the frontal recess area, constricting it and causing mechanical obstruction to frontal sinus drainage.Carusia
Carusia is an extinct genus of lizards from the Late Cretaceous of Mongolia. It is a close relative of the family Xenosauridae, which includes living knob-scaled lizards. Fossils of the type and only species Carusia intermedia come from the late-Campanian age Barun Goyot Formation and have been found in the Flaming Cliffs, Ukhaa Tolgod, and Kheerman Tsav fossil localities. Carusia was first described in 1985 under the name Carolina intermedia, but since the name Carolina was preoccupied by a genus of scarab beetles that had been named in 1880, it was renamed Carusia intermedia. Carusia had initially been known from fragmentary skull material, complicating efforts to determine its evolutionary relationships with other lizards; it had variously been described as an indeterminate scincomorph, a xenosaurid, or some other type of autarchoglossan lizard convergent with xenosaurids. However, the discovery of 35 complete skulls in the 1990s, three of which were described in a detailed 1998 monograph, revealed that Carusia was the sister taxon (closest relative) of Xenosauridae, compelling the authors of the monograph to create a new clade called Carusioidea to include both taxa.Like xenosaurids, Carusia has a skull roof covered in large rounded osteoderms (bony plates embedded in the skin). It also shares with xenosaurids closely spaced orbits (eye sockets) with fused frontal bones between them, and a connection between the jugal and squamosal bones. However, many other features of its skull set it apart from xenosaurids, including the lack of a lacrimal bone, the wideness of the palatine bone, and the small size and high number of teeth in its jaws.Cherminotus
Cherminotus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, Cherminotus longifrons, was named in 1984.Crichtonpelta
Crichtonpelta is a genus of extinct herbivorous ankylosaurid dinosaur from the Cretaceous of China.In 2007, Lü Junchang, Ji Qiang, Gao Yubo and Li Zhixin named and described a second species of Crichtonsaurus: Crichtonsaurus benxiensis. The specific name refers to the Benxi Geological Museum.The holotype, BXGMV0012, is a skull found near Beipiao in a layer of the Sunjiawan Formation probably dating from the Albian. Specimen BXGMV0012-1, a skeleton lacking the skull, discovered in the same quarry as the holotype, was referred to the species. Furthermore, a skeleton with skull, displayed by the Sihetun Fossil Museum as a Crichtonsaurus bohlini specimen, was in 2014 referred to Crichtonpelta. In 2017, a fourth specimen was described, from the same quarry as the holotype, G20090034, consisting of a skull lacking the front snout.In 2014, Victoria Arbour concluded that Crichtonsaurus were a nomen dubium. Therefore, she named a separate genus for its second species: Crichtonpelta. The generic name combines a reference to Michael Crichton, the author of Jurassic Park, with a Greek πέλτη, peltè, "small shield". At the time this was an invalid nomen ex dissertatione. However, in 2015, Crichtonpelta was validly named by Arbour and Philip John Currie. The type species is Crichtonsaurus benxiensis; the combinatio nova is Crichtonpelta benxiensis. There was a possibility that, though Crichtonsaurus bohlini was a nomen dubium, its fossil material in fact belonged to Crichtonpelta. Arbour however, noted clear differences in the scapula and humerus between BXGMV0012-1 and LPM 101, a specimen previously referred to Crichtonsaurus bohlini: the scapula of the former has a tab-like acromion and its humerus a much longer deltopectoral crest.Arbour established several distinguishing traits. One of these was an autapomorphy, unique derived trait: the apex of the (quadrato)jugal, or cheek, horn, is pointing upwards. Also a unique combination of in themselves not unique traits is present. The upper snout armour forms an amorphous mass, not clearly separated into distinctive tiles. The jugal bone is deeper than that of Pinacosaurus. The skull roof is not notched at the lacrimal bone as in Pinacosaurus grangeri. The squamosal horns are shorter than those of Pinacosaurus mephistocephalus. However, these horns are longer and more pointed than those of Gobisaurus or Shamosaurus. The point of the cheek horn is located on the rear edge. The transverse crest on the top of the rear skull has two points.The holotype of Crichtonpelta is somewhat larger than Crichtonsaurus, itself about three to four metres long. It is uncertain whether Crichtonpelta already possessed a tail club.Crichtonpelta was, within the Ankylosauridae, placed in the Ankylosaurinae, in a basal position. If correct, this makes it the oldest known ankylosaurine.Dacryon
The point of junction of the maxillary bone, lacrimal bone, and frontal bone is named the dacryon.Daemonosaurus
Daemonosaurus (pron.:"DAY-mow-no-SORE-us") is an extinct genus of theropod dinosaur from the Late Triassic of New Mexico. Fossils have been found from deposits in the Chinle Formation, which is latest Triassic in age. While theropods had diversified into several specialized groups by this time, Daemonosaurus is a basal theropod that lies outside the clade Neotheropoda. Daemonosaurus is unusual among early theropods in that it had a short skull and long protruding teeth.Fossa for lacrimal sac
A smooth, more deeply concave depression on the lacrimal bone, which forms the medial wall of the orbital cavity, in which the lacrimal sac that drains into the nasolacrimal duct is located, is referred to as the lacrimal fossa (or fossa for the lacrimal sac).Kogia pusilla
Kogia pusilla is an extinct species of sperm whale from the Middle Pliocene of Italy related to the modern day dwarf sperm whale (K. sima) and pygmy sperm whale (K. breviceps). It is known from a single skull discovered in 1877, and was considered a species of beaked whale until 1997. The skull shares many characteristics with other sperm whales, and is comparable in size to that of the dwarf sperm whale. Like the modern Kogia, it probably hunted squid in the midnight zone, and frequented continental slopes. The environment it inhabited was likely a calm, nearshore area with a combination sandy and hard-rock seafloor. K. pusilla likely died out due to the ice ages at the end of the Pliocene.Lacrimal
The term Lacrimal (), also spelled lachrymal, can refer to:
A type of Stroke ending (typography)
Lacrimal canaliculi (singular: canaliculus), also known as Lacrimal ducts
Lacrimal fossa (disambiguation)
Lacrimal fluid, see Tears
Lacrimal groove, also known as Lacrimal sulcus
Lacrimal secretion, see Tears
Nasolacrimal ductLacrimal groove
On the nasal surface of the body of the maxilla, in front of the opening of the sinus is a deep groove, the lacrimal groove (or lacrimal sulcus), which is converted into the nasolacrimal canal, by the lacrimal bone and inferior nasal concha; this canal opens into the inferior meatus of the nose and transmits the nasolacrimal duct.Lacrimal hamulus
The posterior lacrimal crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the orbicularis oculi and ends below in a small, hook-like projection, the lacrimal hamulus, which articulates with the lacrimal tubercle of the maxilla, and completes the upper orifice of the lacrimal canal; it sometimes exists as a separate piece, and is then called the lesser lacrimal bone.Lacrimal sac
The lacrimal sac or lachrymal sac is the upper dilated end of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla. It connects the lacrimal canaliculi, which drain tears from the eye's surface, and the nasolacrimal duct, which conveys this fluid into the nasal cavity.Medial palpebral ligament
The medial palpebral ligament (medial canthal tendon) is about 4 mm in length and 2 mm in breadth. Its anterior attachment is to the frontal process of the maxilla in front of the lacrimal groove, and its posterior attachment is the lacrimal bone. Laterally, it is attached to the tarsus of the upper and lower eyelids.
Crossing the lacrimal sac, it divides into two parts, upper and lower, each attached to the medial end of the corresponding tarsus.
As the ligament crosses the lacrimal sac, a strong aponeurotic lamina is given off from its posterior surface; this expands over the sac, and is attached to the posterior lacrimal crest.Nasolacrimal canal
The canal containing the nasolacrimal duct is called the nasolacrimal canal.
It is formed by indentations in the inferior nasal conchae, maxilla and lacrimal bone. The canal drains into the nasal cavity through the anterior portion of the inferior meatus, which is between the inferior concha and the floor of the nasal cavity.Nephelomys moerex
Nephelomys moerex is a species of rodent in the genus Nephelomys of family Cricetidae. The type locality is at Mindo in western Ecuador, where it has been recorded together with three other rodents of the oryzomyine group, Sigmodontomys aphrastus, Mindomys hammondi, and Handleyomys alfaroi, as well as three opossums, Chironectes minimus and unidentified species of Didelphis and Marmosa. Mindo is a "tiny agricultural community" located at 0°02'S, 78°48'W and 1,264 metres (4,150 ft) above sea level. It was originally described by Oldfield Thomas as a subspecies of Oryzomys albigularis. It remained synonymized under this species until it was recognized as a separate species when the genus Nephelomys was established for Oryzomys albigularis and related species in 2006.Unlike in the type species of the genus, N. albigularis, the lacrimal bone of the skull is connected primarily to the maxillary bone, not equally to the maxillary and frontal bones. The incisive foramina, perforations in the palate between the incisors and the molars, are shorter than in some other Nephelomys species, not extending between the molars, and closer to the molars they are wider than further to the front, also unlike in some other species of the genus. These foramina are similar in shape to those in N. nimbosus. The alisphenoid strut, an extension of the alisphenoid bone of the skull which separates two openings in the skull, the buccinator–masticatory foramen and the accessory oval foramen, is usually present, although it is more commonly absent in other Nephelomys.Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. Anatomical term created by Gerard of Cremona. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is 30 millilitres (1.06 imp fl oz; 1.01 US fl oz), of which the eye occupies 6.5 ml (0.23 imp fl oz; 0.22 US fl oz). The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and nasolacrimal duct, the eyelids, medial and lateral palpebral ligaments, check ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves.Perryella
Perryella is an extinct genus of dvinosaurian temnospondyl. The type and only species, P. olsoni, was named in 1987 from the Wellington Formation of Oklahoma, which is Early Permian in age. It is known from several skulls and partial remains of vertebrae and limbs. It has large orbits, or eye sockets, and large otic notches (rounded indentations at the back of the skull). A bone called the palatine, which is usually found on the underside of the skull, is partially exposed on the top of the skull. Present on the margin of the orbit, the palatine takes the place of the lacrimal bone, which usually touches the orbit in temnospondyls. Another distinguishing feature of Perryella is the presence of two small projections on the quadratojugal bone at the back of the skull. The lowermost projection forms a cup-like shape that attaches to the lower jaw.The classification of Perryella was at first uncertain because it shared features with two groups, Trimerorhachidae and Dissorophoidea, which were thought to be distantly related. In 2006, a phylogenetic analysis involving Perryella placed it within Dvinosauria as an intermediate form between trimerorhachids and other dvinosaurs.Posterior lacrimal crest
The lateral or orbital surface of the lacrimal bone is divided by a vertical ridge, the posterior lacrimal crest, into two parts.
In front of this crest is a longitudinal groove, the lacrimal sulcus (sulcus lacrimalis), the inner margin of which unites with the frontal process of the maxilla, and the lacrimal fossa is thus completed.
The upper part of this fossa lodges the lacrimal sac, the lower part, the nasolacrimal duct.
The portion behind the crest is smooth, and forms part of the medial wall of the orbit.
The crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the orbicularis oculi and ends below in a small, hook-like projection, the lacrimal hamulus, which articulates with the lacrimal tubercle of the maxilla, and completes the upper orifice of the lacrimal canal; the hamulus sometimes exists as a separate piece, and is then called the lesser lacrimal bone.Prefrontal bone
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles. The prefrontal is lost in early mammaliaforms and so is not present in modern mammals either.