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Anatomy: A branch of biology dealing with the structure of organisms.Anatomy, Comparative: The comparative study of animal structure with regard to homologous organs or parts. (Stedman, 25th ed)Red Cross: International collective of humanitarian organizations led by volunteers and guided by its Congressional Charter and the Fundamental Principles of the International Red Cross Movement, to provide relief to victims of disaster and help people prevent, prepare for, and respond to emergencies.Anatomy, Artistic: The study of the structures of organisms for applications in art: drawing, painting, sculpture, illustration, etc.Anatomy, Cross-Sectional: Descriptive anatomy based on three-dimensional imaging (IMAGING, THREE-DIMENSIONAL) of the body, organs, and structures using a series of computer multiplane sections, displayed by transverse, coronal, and sagittal analyses. It is essential to accurate interpretation by the radiologist of such techniques as ultrasonic diagnosis, MAGNETIC RESONANCE IMAGING, and computed tomography (TOMOGRAPHY, X-RAY COMPUTED). (From Lane & Sharfaei, Modern Sectional Anatomy, 1992, Preface)Dissection: The separation and isolation of tissues for surgical purposes, or for the analysis or study of their structures.Models, Anatomic: Three-dimensional representation to show anatomic structures. Models may be used in place of intact animals or organisms for teaching, practice, and study.Cadaver: A dead body, usually a human body.Cross-Sectional Studies: Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.Imaging, Three-Dimensional: The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.Blue Cross Blue Shield Insurance Plans: Prepaid health and hospital insurance plan.Cross Reactions: Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.Crosses, Genetic: Deliberate breeding of two different individuals that results in offspring that carry part of the genetic material of each parent. The parent organisms must be genetically compatible and may be from different varieties or closely related species.Medical Illustration: The field which deals with illustrative clarification of biomedical concepts, as in the use of diagrams and drawings. The illustration may be produced by hand, photography, computer, or other electronic or mechanical methods.Anatomy, Regional: The anatomical study of specific regions or parts of organisms, emphasizing the relationship between the various structures (e.g. muscles, nerves, skeletal, cardiovascular, etc.).Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Anatomy, Veterinary: The study of the anatomical structures of animals.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.History, 16th Century: Time period from 1501 through 1600 of the common era.History, 17th Century: Time period from 1601 through 1700 of the common era.Medicine in ArtReproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Quantitative Trait Loci: Genetic loci associated with a QUANTITATIVE TRAIT.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Skull: The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Receptor Cross-Talk: The simultaneous or sequential binding of multiple cell surface receptors to different ligands resulting in coordinated stimulation or suppression of signal transduction.Atlases as Topic: Collections of illustrative plates, charts, etc., usually with explanatory captions.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Phlebography: Radiographic visualization or recording of a vein after the injection of contrast medium.Computer-Assisted Instruction: A self-learning technique, usually online, involving interaction of the student with programmed instructional materials.Terminology as Topic: The terms, expressions, designations, or symbols used in a particular science, discipline, or specialized subject area.Dinosaurs: General name for two extinct orders of reptiles from the Mesozoic era: Saurischia and Ornithischia.Veins: The vessels carrying blood away from the capillary beds.Embryology: The study of the development of an organism during the embryonic and fetal stages of life.Hybridization, Genetic: The genetic process of crossbreeding between genetically dissimilar parents to produce a hybrid.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Ligaments, Articular: Fibrous cords of CONNECTIVE TISSUE that attach bones to each other and hold together the many types of joints in the body. Articular ligaments are strong, elastic, and allow movement in only specific directions, depending on the individual joint.Pelvis: The space or compartment surrounded by the pelvic girdle (bony pelvis). It is subdivided into the greater pelvis and LESSER PELVIS. The pelvic girdle is formed by the PELVIC BONES and SACRUM.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Physiology: The biological science concerned with the life-supporting properties, functions, and processes of living organisms or their parts.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Fascia: Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests MUSCLES, nerves, and other organs.Ligaments: Shiny, flexible bands of fibrous tissue connecting together articular extremities of bones. They are pliant, tough, and inextensile.Cerebral Veins: Veins draining the cerebrum.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.History, 18th Century: Time period from 1701 through 1800 of the common era.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Corrosion Casting: A tissue preparation technique that involves the injecting of plastic (acrylates) into blood vessels or other hollow viscera and treating the tissue with a caustic substance. This results in a negative copy or a solid replica of the enclosed space of the tissue that is ready for viewing under a scanning electron microscope.Image Enhancement: Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural MICROSCOPY, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Petrous Bone: The dense rock-like part of temporal bone that contains the INNER EAR. Petrous bone is located at the base of the skull. Sometimes it is combined with the MASTOID PROCESS and called petromastoid part of temporal bone.Education, Medical, Undergraduate: The period of medical education in a medical school. In the United States it follows the baccalaureate degree and precedes the granting of the M.D.Biomechanical Phenomena: The properties, processes, and behavior of biological systems under the action of mechanical forces.Heart Defects, Congenital: Developmental abnormalities involving structures of the heart. These defects are present at birth but may be discovered later in life.Image Interpretation, Computer-Assisted: Methods developed to aid in the interpretation of ultrasound, radiographic images, etc., for diagnosis of disease.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.History, 15th Century: Time period from 1401 through 1500 of the common era.Mesophyll Cells: Large and highly vacuolated cells possessing many chloroplasts occuring in the interior cross-section of leaves, juxtaposed between the epidermal layers.Visible Human Projects: Digital image data sets, consisting of complete, anatomically detailed, three-dimensional representations of the normal male and female human bodies.Prevalence: The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.Vocabulary, Controlled: A specified list of terms with a fixed and unalterable meaning, and from which a selection is made when CATALOGING; ABSTRACTING AND INDEXING; or searching BOOKS; JOURNALS AS TOPIC; and other documents. The control is intended to avoid the scattering of related subjects under different headings (SUBJECT HEADINGS). The list may be altered or extended only by the publisher or issuing agency. (From Harrod's Librarians' Glossary, 7th ed, p163)History, 19th Century: Time period from 1801 through 1900 of the common era.Radiographic Image Interpretation, Computer-Assisted: Computer systems or networks designed to provide radiographic interpretive information.Surgery, Computer-Assisted: Surgical procedures conducted with the aid of computers. This is most frequently used in orthopedic and laparoscopic surgery for implant placement and instrument guidance. Image-guided surgery interactively combines prior CT scans or MRI images with real-time video.SculptureCross Protection: Protection conferred on a host by inoculation with one strain or component of a microorganism that prevents infection when later challenged with a similar strain. Most commonly the microorganism is a virus.Teaching: The educational process of instructing.Head: The upper part of the human body, or the front or upper part of the body of an animal, typically separated from the rest of the body by a neck, and containing the brain, mouth, and sense organs.Famous PersonsPaintingsProspective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Angiography: Radiography of blood vessels after injection of a contrast medium.Skull Base: The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface.Cystic Duct: The duct that is connected to the GALLBLADDER and allows the emptying of bile into the COMMON BILE DUCT.Otologic Surgical Procedures: Surgery performed on the external, middle, or internal ear.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Temporal Bone: Either of a pair of compound bones forming the lateral (left and right) surfaces and base of the skull which contains the organs of hearing. It is a large bone formed by the fusion of parts: the squamous (the flattened anterior-superior part), the tympanic (the curved anterior-inferior part), the mastoid (the irregular posterior portion), and the petrous (the part at the base of the skull).Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Coronary Sinus: A short vein that collects about two thirds of the venous blood from the MYOCARDIUM and drains into the RIGHT ATRIUM. Coronary sinus, normally located between the LEFT ATRIUM and LEFT VENTRICLE on the posterior surface of the heart, can serve as an anatomical reference for cardiac procedures.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Occipital Bone: Part of the back and base of the CRANIUM that encloses the FORAMEN MAGNUM.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Magnetic Resonance Angiography: Non-invasive method of vascular imaging and determination of internal anatomy without injection of contrast media or radiation exposure. The technique is used especially in CEREBRAL ANGIOGRAPHY as well as for studies of other vascular structures.Alligators and Crocodiles: Large, long-tailed reptiles, including caimans, of the order Loricata.Blood-Brain Barrier: Specialized non-fenestrated tightly-joined ENDOTHELIAL CELLS with TIGHT JUNCTIONS that form a transport barrier for certain substances between the cerebral capillaries and the BRAIN tissue.Diagnostic Imaging: Any visual display of structural or functional patterns of organs or tissues for diagnostic evaluation. It includes measuring physiologic and metabolic responses to physical and chemical stimuli, as well as ultramicroscopy.Education, Medical: Use for general articles concerning medical education.Vascular Malformations: A spectrum of congenital, inherited, or acquired abnormalities in BLOOD VESSELS that can adversely affect the normal blood flow in ARTERIES or VEINS. Most are congenital defects such as abnormal communications between blood vessels (fistula), shunting of arterial blood directly into veins bypassing the CAPILLARIES (arteriovenous malformations), formation of large dilated blood blood-filled vessels (cavernous angioma), and swollen capillaries (capillary telangiectases). In rare cases, vascular malformations can result from trauma or diseases.Histology: The study of the structure of various TISSUES of organisms on a microscopic level.Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.Equipment Design: Methods of creating machines and devices.Infant, Newborn: An infant during the first month after birth.Heart Septum: This structure includes the thin muscular atrial septum between the two HEART ATRIA, and the thick muscular ventricular septum between the two HEART VENTRICLES.Software: Sequential operating programs and data which instruct the functioning of a digital computer.Masticatory Muscles: Muscles arising in the zygomatic arch that close the jaw. Their nerve supply is masseteric from the mandibular division of the trigeminal nerve. (From Stedman, 25th ed)Heart Septal Defects, Ventricular: Developmental abnormalities in any portion of the VENTRICULAR SEPTUM resulting in abnormal communications between the two lower chambers of the heart. Classification of ventricular septal defects is based on location of the communication, such as perimembranous, inlet, outlet (infundibular), central muscular, marginal muscular, or apical muscular defect.Hyoid Bone: A mobile U-shaped bone that lies in the anterior part of the neck at the level of the third CERVICAL VERTEBRAE. The hyoid bone is suspended from the processes of the TEMPORAL BONES by ligaments, and is firmly bound to the THYROID CARTILAGE by muscles.Questionnaires: Predetermined sets of questions used to collect data - clinical data, social status, occupational group, etc. The term is often applied to a self-completed survey instrument.Tendons: Fibrous bands or cords of CONNECTIVE TISSUE at the ends of SKELETAL MUSCLE FIBERS that serve to attach the MUSCLES to bones and other structures.Prosthesis Design: The plan and delineation of prostheses in general or a specific prosthesis.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Coronary Vessel Anomalies: Malformations of CORONARY VESSELS, either arteries or veins. Included are anomalous origins of coronary arteries; ARTERIOVENOUS FISTULA; CORONARY ANEURYSM; MYOCARDIAL BRIDGING; and others.Contrast Media: Substances used to allow enhanced visualization of tissues.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Back: The rear surface of an upright primate from the shoulders to the hip, or the dorsal surface of tetrapods.Cross Circulation: The circulation in a portion of the body of one individual of blood supplied from another individual.Neck: The part of a human or animal body connecting the HEAD to the rest of the body.Hybrid Vigor: The adaptive superiority of the heterozygous GENOTYPE with respect to one or more characters in comparison with the corresponding HOMOZYGOTE.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Chenopodiaceae: The goosefoot plant family of the order Caryophyllales, subclass Caryophyllidae, class Magnoliopsida. It includes beets and chard (BETA VULGARIS), as well as SPINACH, and salt tolerant plants.Circle of Willis: A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.Brachial Plexus: The large network of nerve fibers which distributes the innervation of the upper extremity. The brachial plexus extends from the neck into the axilla. In humans, the nerves of the plexus usually originate from the lower cervical and the first thoracic spinal cord segments (C5-C8 and T1), but variations are not uncommon.Students, Medical: Individuals enrolled in a school of medicine or a formal educational program in medicine.Forelimb: A front limb of a quadruped. (The Random House College Dictionary, 1980)Databases, Factual: Extensive collections, reputedly complete, of facts and data garnered from material of a specialized subject area and made available for analysis and application. The collection can be automated by various contemporary methods for retrieval. The concept should be differentiated from DATABASES, BIBLIOGRAPHIC which is restricted to collections of bibliographic references.Feasibility Studies: Studies to determine the advantages or disadvantages, practicability, or capability of accomplishing a projected plan, study, or project.Larynx: A tubular organ of VOICE production. It is located in the anterior neck, superior to the TRACHEA and inferior to the tongue and HYOID BONE.Hepatic Veins: Veins which drain the liver.Age Factors: Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Persia: An ancient civilization, known as early as 2000 B.C. The Persian Empire was founded by Cyrus the Great (550-529 B.C.) and for 200 years, from 550 to 331 B.C., the Persians ruled the ancient world from India to Egypt. The territory west of India was called Persis by the Greeks who later called the entire empire Persia. In 331 B.C. the Persian wars against the Greeks ended disastrously under the counterattacks by Alexander the Great. The name Persia in modern times for the modern country was changed to Iran in 1935. (From Webster's New Geographical Dictionary, 1988, p546 & Asimov, Words on the Map, 1962, p176)Aortography: Radiographic visualization of the aorta and its branches by injection of contrast media, using percutaneous puncture or catheterization procedures.History, 20th Century: Time period from 1901 through 2000 of the common era.Educational Measurement: The assessing of academic or educational achievement. It includes all aspects of testing and test construction.Gestational Age: The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Ultrasonography: The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Genetic Markers: A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.Phantoms, Imaging: Devices or objects in various imaging techniques used to visualize or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with x-ray or ultrasonic machines. (From Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990)Curriculum: A course of study offered by an educational institution.Thorax: The upper part of the trunk between the NECK and the ABDOMEN. It contains the chief organs of the circulatory and respiratory systems. (From Stedman, 25th ed)Orbit: Bony cavity that holds the eyeball and its associated tissues and appendages.Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Nasal Cavity: The proximal portion of the respiratory passages on either side of the NASAL SEPTUM. Nasal cavities, extending from the nares to the NASOPHARYNX, are lined with ciliated NASAL MUCOSA.Situs Inversus: A congenital abnormality in which organs in the THORAX and the ABDOMEN are opposite to their normal positions (situs solitus) due to lateral transposition. Normally the STOMACH and SPLEEN are on the left, LIVER on the right, the three-lobed right lung is on the right, and the two-lobed left lung on the left. Situs inversus has a familial pattern and has been associated with a number of genes related to microtubule-associated proteins.Tomography, Spiral Computed: Computed tomography where there is continuous X-ray exposure to the patient while being transported in a spiral or helical pattern through the beam of irradiation. This provides improved three-dimensional contrast and spatial resolution compared to conventional computed tomography, where data is obtained and computed from individual sequential exposures.Lumbosacral Plexus: The lumbar and sacral plexuses taken together. The fibers of the lumbosacral plexus originate in the lumbar and upper sacral spinal cord (L1 to S3) and innervate the lower extremities.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Transposition of Great Vessels: A congenital cardiovascular malformation in which the AORTA arises entirely from the RIGHT VENTRICLE, and the PULMONARY ARTERY arises from the LEFT VENTRICLE. Consequently, the pulmonary and the systemic circulations are parallel and not sequential, so that the venous return from the peripheral circulation is re-circulated by the right ventricle via aorta to the systemic circulation without being oxygenated in the lungs. This is a potentially lethal form of heart disease in newborns and infants.User-Computer Interface: The portion of an interactive computer program that issues messages to and receives commands from a user.Coronary Vessels: The veins and arteries of the HEART.History, Medieval: The period of history from the year 500 through 1450 of the common era.Endoscopy: Procedures of applying ENDOSCOPES for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. transluminal, to examine or perform surgery on the interior parts of the body.Blood Vessel Prosthesis: Device constructed of either synthetic or biological material that is used for the repair of injured or diseased blood vessels.Jaw: Bony structure of the mouth that holds the teeth. It consists of the MANDIBLE and the MAXILLA.Observer Variation: The failure by the observer to measure or identify a phenomenon accurately, which results in an error. Sources for this may be due to the observer's missing an abnormality, or to faulty technique resulting in incorrect test measurement, or to misinterpretation of the data. Two varieties are inter-observer variation (the amount observers vary from one another when reporting on the same material) and intra-observer variation (the amount one observer varies between observations when reporting more than once on the same material).Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Pelvic Floor: Soft tissue formed mainly by the pelvic diaphragm, which is composed of the two levator ani and two coccygeus muscles. The pelvic diaphragm lies just below the pelvic aperture (outlet) and separates the pelvic cavity from the PERINEUM. It extends between the PUBIC BONE anteriorly and the COCCYX posteriorly.Heart Ventricles: The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.Blood Vessel Prosthesis Implantation: Surgical insertion of BLOOD VESSEL PROSTHESES to repair injured or diseased blood vessels.Cardiac Catheters: Catheters inserted into various locations within the heart for diagnostic or therapeutic purposes.X-Ray Microtomography: X-RAY COMPUTERIZED TOMOGRAPHY with resolution in the micrometer range.Breeding: The production of offspring by selective mating or HYBRIDIZATION, GENETIC in animals or plants.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Artificial Intelligence: Theory and development of COMPUTER SYSTEMS which perform tasks that normally require human intelligence. Such tasks may include speech recognition, LEARNING; VISUAL PERCEPTION; MATHEMATICAL COMPUTING; reasoning, PROBLEM SOLVING, DECISION-MAKING, and translation of language.Genetic Linkage: The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.Arteries: The vessels carrying blood away from the heart.Cervical Atlas: The first cervical vertebra.Hominidae: Family of the suborder HAPLORHINI (Anthropoidea) comprising bipedal primate MAMMALS. It includes modern man (HOMO SAPIENS) and the great apes: gorillas (GORILLA GORILLA), chimpanzees (PAN PANISCUS and PAN TROGLODYTES), and orangutans (PONGO PYGMAEUS).Epiglottis: A thin leaf-shaped cartilage that is covered with LARYNGEAL MUCOSA and situated posterior to the root of the tongue and HYOID BONE. During swallowing, the epiglottis folds back over the larynx inlet thus prevents foods from entering the airway.Cyperaceae: The sedge plant family of the order Cyperales, subclass Commelinidae, class Liliopsida (monocotyledons)Regression Analysis: Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.Classification: The systematic arrangement of entities in any field into categories classes based on common characteristics such as properties, morphology, subject matter, etc.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Models, Cardiovascular: Theoretical representations that simulate the behavior or activity of the cardiovascular system, processes, or phenomena; includes the use of mathematical equations, computers and other electronic equipment.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Sex Factors: Maleness or femaleness as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or effect of a circumstance. It is used with human or animal concepts but should be differentiated from SEX CHARACTERISTICS, anatomical or physiological manifestations of sex, and from SEX DISTRIBUTION, the number of males and females in given circumstances.Microsurgery: The performance of surgical procedures with the aid of a microscope.Coronary Angiography: Radiography of the vascular system of the heart muscle after injection of a contrast medium.Fetal Heart: The heart of the fetus of any viviparous animal. It refers to the heart in the postembryonic period and is differentiated from the embryonic heart (HEART/embryology) only on the basis of time.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Foot: The distal extremity of the leg in vertebrates, consisting of the tarsus (ANKLE); METATARSUS; phalanges; and the soft tissues surrounding these bones.Hepatic Artery: A branch of the celiac artery that distributes to the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum.Mice, Inbred C57BLSchools, Medical: Educational institutions for individuals specializing in the field of medicine.Paleontology: The study of early forms of life through fossil remains.Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.History, Ancient: The period of history before 500 of the common era.Seeds: The encapsulated embryos of flowering plants. They are used as is or for animal feed because of the high content of concentrated nutrients like starches, proteins, and fats. Rapeseed, cottonseed, and sunflower seed are also produced for the oils (fats) they yield.Tooth: One of a set of bone-like structures in the mouth used for biting and chewing.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Histology, Comparative: The study of the similarities and differences in the structures of homologous tissues across various species.Inbreeding: The mating of plants or non-human animals which are closely related genetically.Quantitative Trait, Heritable: A characteristic showing quantitative inheritance such as SKIN PIGMENTATION in humans. (From A Dictionary of Genetics, 4th ed)Anatomic Variation: Peculiarities associated with the internal structure, form, topology, or architecture of organisms that distinguishes them from others of the same species or group.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Chromosomes, Plant: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of PLANTS.Neurosurgical Procedures: Surgery performed on the nervous system or its parts.Stents: Devices that provide support for tubular structures that are being anastomosed or for body cavities during skin grafting.Xylem: Plant tissue that carries water up the root and stem. Xylem cell walls derive most of their strength from LIGNIN. The vessels are similar to PHLOEM sieve tubes but lack companion cells and do not have perforated sides and pores.Mandible: The largest and strongest bone of the FACE constituting the lower jaw. It supports the lower teeth.