Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates. Included in this definition are the living hagfish and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods; because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification; the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era.
Many fish of the Paleozoic developed external armor. The first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Most fish are ectothermic, allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish can communicate in their underwater environments through the use of acoustic communication. Acoustic communication in fish involves the transmission of acoustic signals from one individual of a species to another; the production of sounds as a means of communication among fish is most used in the context of feeding, aggression or courtship behaviour. The sounds emitted by fish can vary depending on the stimulus involved, they can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.
Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams to the abyssal and hadal depths of the deepest oceans, although no species has yet been documented in the deepest 25% of the ocean. With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates. Fish are an important resource for humans worldwide as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean, they are caught by recreational fishers, kept as pets, raised by fishkeepers, exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, as the subjects of art and movies. Fish do not represent a monophyletic group, therefore the "evolution of fish" is not studied as a single event. Early fish from the fossil record are represented by a group of small, armored fish known as ostracoderms. Jawless fish lineages are extinct.
An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils; the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. Fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways; the first ancestors of fish may have kept the larval form into adulthood, although the reverse is the case. Fish are a paraphyletic group: that is, any clade containing all fish contains the tetrapods, which are not fish. For this reason, groups such as the "Class Pisces" seen in older reference works are no longer used in formal classifications. Traditional classification divides fish into three extant classes, with extinct forms sometimes classified within the tree, sometimes as their own classes: Class Agnatha Subclass Cyclostomata Subclass Ostracodermi † Class Chondrichthyes Subclass Elasmobranchii Subclass Holocephali Class Placodermi † Class Acanthodii † Class Osteichthyes Subclass Actinopterygii Subclass Sarcopterygii The above scheme is the one most encountered in non-specialist and general works.
Many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise to Acanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the following major groups: Class Myxini Class Pteraspidomorphi † Class Thelodonti † Class Anaspida † Class Petromyzontida or Hyperoartia Petromyzontidae Class Conodonta † Class Cephalaspidomorphi † Galeaspida † Pituriaspida † Osteostraci † Infraphylum Gnathostomata Class Placodermi † Class Chondrichthyes Class Acanthodii † Superclass Osteichthy
The frontal bone is a bone in the human skull. The bone consists of two portions; these are the vertically oriented squamous part, the horizontally oriented orbital part, making up the bony part of the forehead, part of the bony orbital cavity holding the eye, part of the bony part of the nose respectively. The name comes from the Latin word frons; the frontal bone is made up of two main parts. These are the squamous part, the orbital part; the squamous part marks the vertical and the biggest part, the main region of the forehead. The orbital part is the second biggest region of the frontal bone, it enters into the formation of the roofs of the nasal cavities. Sometimes a third part is included as the nasal part of the frontal bone, sometimes this is included with the squamous part; the nasal part is between the brow ridges, ends in a serrated nasal notch that articulates with the nasal bones inferiorly, with the lacrimal and maxilla bones laterally. The border of the squamous part is thick serrated, bevelled at the expense of the inner table above, where it rests upon the parietal bones, at the expense of the outer table on either side, where it receives the lateral pressure of those bones.
The posterior borders of the orbital plates are thin and serrated, articulate with the small wings of the sphenoid. The frontal bone is presumed to be derived from neural crest cells; the frontal bone is ossified in membrane from two primary centers, one for each half, which appear toward the end of the second month of fetal life, one above each supraorbital margin. From each of these centers, ossification extends upward to form the corresponding half of the squama, backwards to form the orbital plate; the spine is ossified on either side of the middle line. At birth the bone consists of two pieces, separated by the frontal suture, obliterated, except at its lower part, by the eighth year, but persists throughout life, it is maintained that the development of the frontal sinuses begins at the end of the first or beginning of the second year, but may begin at birth. The sinuses are of considerable size by the seventh or eighth year, but do not attain their full proportions until after puberty.
In most vertebrates, the frontal bone is paired, rather than presenting the single, fused structure found in humans. It lies on the upper part of the head, between the eyes, but in many non-mammalian animals it does not form part of the orbital cavity. Instead, in reptiles, bony fish and amphibians it is separated from the orbits by one or two additional bones not found in mammals; these bones, the prefrontals and postfrontals, together form the upper margin of the eye sockets, lie to either side of the frontal bones. The frontal bone is one of the principal paired mid-line bones in dinosaur skulls; this bone is part of the skull roof, a set of bones that cover the brain and nostrils. The frontal makes contact with several other bones in the skull; the anterior part of the bone articulates with the prefrontal bone. The posterior part of the bone articulates with the parietal bone; this bone defines all of part of the upper margin of the orbit. Frontal eminence Frontal lobe This article incorporates text in the public domain from page 135 of the 20th edition of Gray's Anatomy Anatomy photo:23:os-0101 at the SUNY Downstate Medical Center "Anatomy diagram: 34256.000-1".
Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01
The endocranium in comparative anatomy is a part of the skull base in vertebrates and it represents the basal, inner part of the cranium. The term is applied to the outer layer of the dura mater in human anatomy. Structurally, the endocranium consists of a boxlike shape, open at the top; the posterior margin exhibit the foramen magnum, an opening for the spinal cord. The floor of the endocranium has several paired openings for the cranial nerves, the anterior margin holds a spongy construction, allowing for the external nasal nerves to pass through. All bones of the structure derive from the cranial neural crest during fetal development. In humans and other mammals, the endocranium forms during fetal development as a cartilaginous neurocranium, that ossifies from several centers. Several of these bones merge, in the adult primates, the endocranium is composed of only five bony elements: The Ethmoid bone, lying behind the nose; the Sphenoid bone, underlying the forward portion of the brain Paired petrous part of the temporal bones, containing the inner ear structures The Occipital bone, surrounding the foramen magnum The endocranium in mammals is much reduced in relative size and number of bones compared to the condition in the ancestral land vertebrates, though the occipital bone occur as several bony elements in several mammal groups.
The occipital bone is found as several bony elements in birds and reptiles, while the skull of modern amphibians is reduced with a simplified endocranium. The skull of early labyrinthodonts were rather complex, contained in addition to the bones mentioned above several small cartilaginous components that are fused to temporal and occipital bones in mammals: Paired prootic and opisthotic bones above each fenestra ovalis, fused to the petrous part of the temporal bones in mammals. Paired exoccipital bones medially and a single basioccipital bone below the foramen magnum, part of the occipital bone in mammals. While the endocranium is an integral part of the skull in mammals and reptiles, its connection to the roofing parts of the skull is more loose in the lower vertebrates. In Agnathans and Chondrichthyes, the skull lacks the skull roof dermal elements, their whole cranium being composed of the endocranium, properly called a chondrocranium. In most Osteichthyes, the skull is only loosely joined, the endocranial elements do not form a unit with the skull roof.
An endocast or endocranial cast is a cast made of the mold formed by the impression the brain makes on the inside of the neurocranium, providing a replica of the brain with most of the details of its outer surface. Endocasts can form when sediments fill the empty skull, after which the skull is destroyed and the cast fossilized. Scientists are utilizing computerized tomography scanning technology to create digital endocasts without damaging valuable specimens; this gives a 3D representation of the brain. Brain size and complexity can be determined. Endocasts were used for looking at the brains of Homo sapiens to find hemispheric specialization. Dermatocranium Splanchnocranium
The ethmoid bone is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof between the two orbits; the cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones; the ethmoid bone is an anterior cranial bone located between the eyes. It contributes to the medial wall of the orbit, the nasal cavity, the nasal septum; the ethmoid has three parts: cribriform plate, ethmoidal labyrinth, perpendicular plate. The cribriform plate forms the roof of the nasal cavity and contributes to formation of the anterior cranial fossa, the ethmoidal labyrinth consists of a large mass on either side of the perpendicular plate, the perpendicular plate forms the superior two-thirds of the nasal septum. Between the orbital plate and the nasal conchae are the ethmoidal sinuses or ethmoidal air cells, which are a variable number of small cavities in the lateral mass of the ethmoid; the ethmoid articulates with thirteen bones: two bones of the neurocranium—the frontal, the sphenoid.
Eleven bones of the viscerocranium—, two nasal bones, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, the vomer. The ethmoid is ossified in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, one for each labyrinth; the labyrinths are first developed, ossific granules making their appearance in the region of the lamina papyracea between the fourth and fifth months of fetal life, extending into the conchæ. At birth, the bone consists of the two labyrinths, which are ill-developed. During the first year after birth, the perpendicular plate and crista galli begin to ossify from a single center, are joined to the labyrinths about the beginning of the second year; the cribriform plate is ossified from the perpendicular plate and from the labyrinths. The development of the ethmoidal cells begins during fetal life; some birds and other migratory animals have deposits of biological magnetite in their ethmoid bones which allow them to sense the direction of the Earth's magnetic field.
Humans have a similar magnetite deposit. Fracture of the lamina papyracea, the lateral plate of the ethmoid labyrinth bone, permits communication between the nasal cavity and the orbit on the same side of the body through the inferomedial orbital wall, resulting in orbital emphysema. Increased pressure within the nasal cavity, as seen during sneezing, for example, leads to temporary exophthalmos; the porous fragile nature of the ethmoid bone makes it susceptible to fractures. The ethmoid is fractured from an upward force to the nose; this could occur by landing on the ground after a fall. The ethmoid fracture can produce bone fragments; this trauma can lead to a leak of cerebrospinal fluid into the nasal cavity. These openings let opportunistic bacteria in the nasal cavity enter the sterile environment of the central nervous system; the CNS is protected by the blood-brain barrier, but holes in the cribriform plate let bacteria get through the barrier. The blood-brain barrier makes it difficult to treat such infections, because only certain drugs can cross into the CNS.
An ethmoid fracture can sever the olfactory nerve. This injury results in anosmia. A reduction in the ability to taste is a side effect because it is based so on smell; this injury is not fatal, but can be dangerous, as when a person fails to smell smoke, gas, or spoiled food. In fact, people with anosmia were more than four times as to die in five years compared to those with a healthy sense of smell; this article incorporates text in the public domain from page 153 of the 20th edition of Gray's Anatomy Saladin, Kenneth S.. Anatomy and Physiology: the Unity of Form and Function. New York: McGraw Hill. ISBN 978-0-07-128341-0. Banks, Peter. Fractures of the facial skeleton. Oxford: Wright. ISBN 0-7236-1034-7. Http://www.theregister.com/2006/11/17/the_odd_body_nose_compass/ "Anatomy diagram: 34256.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01
Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets and from the Phoenician alphabet. Latin was spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the dominant language in Italy and subsequently throughout the western Roman Empire. Vulgar Latin developed into the Romance languages, such as Italian, Portuguese and Spanish. Latin and French have contributed many words to the English language. In particular, Latin roots are used in English descriptions of theology, science and law. By the late Roman Republic, Old Latin had been standardised into Classical Latin. Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the written language from the 3rd century and Medieval Latin was used from the 9th century to the Renaissance which used Renaissance Latin.
Early Modern Latin and New Latin evolved. Latin was used as the language of international communication and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the official language of the Holy See and the Roman Rite of the Catholic Church. Latin is taught in primary and postsecondary educational institutions around the world. Latin is a inflected language, with three distinct genders, up to seven noun cases, five declensions, four verb conjugations, three tenses, three persons, three moods, two voices, two or three aspects and two numbers. A number of historical phases of the language have been recognized, each distinguished by subtle differences in vocabulary, spelling and syntax. There are no fast rules of classification; as a result, the list has variants, as well as alternative names. In addition to the historical phases, Ecclesiastical Latin refers to the styles used by the writers of the Roman Catholic Church as well as by Protestant scholars from Late Antiquity onward.
After the Western Roman Empire fell in 476, Germanic kingdoms took its place, the Germanic people adopted Latin as a language more suitable for legal and other, more formal uses. The earliest known form of Latin is Old Latin, spoken from the Roman Kingdom to the part of the Roman Republic period, it is attested both in inscriptions and in some of the earliest extant Latin literary works, such as the comedies of Plautus and Terence. The Latin alphabet was devised from the Etruscan alphabet; the writing changed from what was either a right-to-left or a boustrophedon script to what became a left-to-right script. During the late republic and into the first years of the empire, a new Classical Latin arose, a conscious creation of the orators, poets and other literate men, who wrote the great works of classical literature, which were taught in grammar and rhetoric schools. Today's instructional grammars trace their roots to such schools, which served as a sort of informal language academy dedicated to maintaining and perpetuating educated speech.
Philological analysis of Archaic Latin works, such as those of Plautus, which contain snippets of everyday speech, indicates that a spoken language, Vulgar Latin, existed concurrently with literate Classical Latin. The informal language was written, so philologists have been left with only individual words and phrases cited by classical authors and those found as graffiti. However, philologists have found traces of this written language in the earlier works and drafts of William Shakespeare's many plays. One of the examples most prominent is in one of Shakespeare's first drafts of Titus Andronicus, where Shakespeare referred to the villain of the play as a "adipem pullum"; as it was free to develop on its own, there is no reason to suppose that the speech was uniform either diachronically or geographically. On the contrary, romanised European populations developed their own dialects of the language, which led to the differentiation of Romance languages; the decline of the Roman Empire meant a deterioration in educational standards that brought about Late Latin, a postclassical stage of the language seen in Christian writings of the time.
It was more in line with everyday speech, not only because of a decline in education but because of a desire to spread the word to the masses. Despite dialectal variation, found in any widespread language, the languages of Spain, France and Italy retained a remarkable unity in phonological forms and developments, bolstered by the stabilising influence of their common Christian culture, it was not until the Moorish conquest of Spain in 711 cut off communications between the major Romance regions that the languages began to diverge seriously. The Vulgar Latin dialect that would become Romanian diverged somewhat more from the other varieties, as it was cut off from the unifying influences in the western part of the Empire. One key marker of whether a given Romance feature was found in Vulgar Latin is to compare it with its parallel in Classical Latin. If it was not preferred in Classical Latin it most came from the undocumented contemporaneous Vulgar Latin. For example, the Romance for "horse" came from Latin caballus.
However, Classical Latin used equus. Therefore, caballus was most like
Tympanic part of the temporal bone
The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, surrounding the external part of the ear canal. It originates as a separate bone. Evolutionarily, a portion of it is derived from the angular bone of the reptilian lower jaw, its postero-superior surface is concave, forms the anterior wall, the floor, part of the posterior wall of the bony ear canal. Medially, it presents a narrow furrow, the tympanic sulcus, for the attachment of the tympanic membrane, its antero-inferior surface is quadrilateral and concave. Its lateral border is free and rough, gives attachment to the cartilaginous part of the ear canal. Internally, the tympanic part is fused with the petrous portion, appears in the retreating angle between it and the squama, where it lies below and lateral to the orifice of the auditory tube. Posteriorly, it blends with the squama and mastoid part, forms the anterior boundary of the tympanomastoid fissure.
Its upper border fuses laterally with the back of the postglenoid process, while medially it bounds the petrotympanic fissure. The medial part of the lower border is sharp; the central portion of the tympanic part is thin, as it gives rise to the bony inner two-thirds of the ear canal, in 5 - 20% of skulls the lower surface is perforated by a hole, the foramen of Huschke that opens onto the temporomandibular joint due to incomplete fusion of the anterior and posterior prominences during development. The bony portion of the ear canal is nearly 2 cm long and is directed inward and forward: at the same time it forms a slight curve, so that the floor of the canal is convex upward. In sagittal section it presents an oval or elliptical shape with the long axis directed downward and backward, its anterior wall and floor and the lower part of its posterior wall are formed by the tympanic part. Its inner end is closed, by the tympanic membrane; the auditory bulla is a hollow bony structure on the ventral, posterior portion of the skull that encloses parts of the middle and inner ear.
In most species, it is formed by the tympanic part of the temporal bone. In all extant and extinct primates, including humans, the auditory bulla is formed by the petrosal bone; this is a diagnostic trait that can be used to distinguish primates, including anthropoids, tarsiers and lorises, from all other mammals. This article incorporates text in the public domain from page 145 of the 20th edition of Gray's Anatomy Anatomy photo:22:os-0402 at the SUNY Downstate Medical Center - "Osteology of the Skull: Lateral Surface of Skull"