weber (1795–1878). conductive hearing ability is mediated by the middle ear composed of the ossicles: the malleus, the incus, and the stapes. sensorineural hearing ability is mediated by the inner ear composed of the cochlea with its internal basilar membrane and attached cochlear nerve (cranial nerve viii). the outer ear consisting of the pinna, ear canal, and ear drum or tympanic membrane transmits sounds to the middle ear but does not contribute to the conduction or sensorineural hearing ability save for hearing transmissions limited by cerumen impaction (wax collection in the ear canal). the weber test has had its value as a screening test questioned in the literature. wernicke–korsakoff syndrome – (wks) is the combined presence of wernicke encephalopathy (we) and alcoholic korsakoff syndrome. due to the close relationship between these two disorders, people with either are usually diagnosed with wks as a single syndrome. it mainly causes vision changes, ataxia and impaired memory. wernicke's area – also called wernicke's speech area, is one of the two parts of the cerebral cortex that are linked to speech, the other being broca's area. it is involved in the comprehension of written and spoken language, in contrast to broca's area, which is involved in the production of language. it is traditionally thought to reside in brodmann area 22, which is located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of right-handed individuals and 60% of left-handed individuals. whiplash – is a non-medical term describing a range of injuries to the neck caused by or related to a sudden distortion of the neck associated with extension, although the exact injury mechanisms remain unknown. the term "whiplash" is a colloquialism. "cervical acceleration–deceleration" (cad) describes the mechanism of the injury, while the term "whiplash associated disorders" (wad) describes the injury sequelae and symptoms. white blood cell – white blood cells (wbcs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. all white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. leukocytes are found throughout the body, including the blood and lymphatic system. white matter – refers to areas of the central nervous system (cns) that are mainly made up of myelinated axons, also called tracts. long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials, acting as a relay and coordinating communication between different brain regions. working memory – is a cognitive system with a limited capacity that can hold information temporarily. working memory is important for reasoning and the guidance of decision-making and behavior. working memory is often used synonymously with short-term memory, but some theorists consider the two forms of memory distinct, assuming that working memory allows for the manipulation of stored information, whereas short-term memory only refers to the short-term storage of information. working memory is a theoretical concept central to cognitive psychology, neuropsychology, and neuroscience. wrist – in human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. this region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum. as a consequence of these various definitions, fractures to the carpal bones are referred to as carpal fractures, while fractures such as distal radius fracture are often considered fractures to the wrist. x xanthoma – a xanthoma (pl. xanthomas or xanthomata) (condition: xanthomatosis), from greek ξανθός (xanthós) 'yellow', is a deposition of yellowish cholesterol-rich material that can appear anywhere in the body in various disease states. they are cutaneous manifestations of lipidosis in which lipids accumulate in large foam cells within the skin. they are associated with hyperlipidemias, both primary and secondary types. y yaws – is a tropical infection of the skin, bones and joints caused by the spirochete bacterium treponema pallidum pertenue. the disease begins with a round, hard swelling of the skin, 2 to 5 centimeters in diameter. the center may break open and form an ulcer. this initial skin lesion typically heals after three to six months. after weeks to years, joints and bones may become painful, fatigue may develop, and new skin lesions may appear. the skin of the palms of the hands and the soles of the feet may become thick and break open. the bones (especially those of the nose) may become misshapen. after five years or more large areas of skin may die, leaving a scar. yellow fever – is a viral disease of typically short duration. in most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches. symptoms typically improve within five days. in about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. if this occurs, the risk of bleeding and kidney problems is increased. z zellweger spectrum disorders – are a group of rare disorders that create the same disease process. the subdivisions of this spectrum are hyperpipecolic acidemia, infantile refsum disease, neonatal adrenoleukodystrophy (nald), and zellweger syndrome. it can also be referred to as peroxisomal biogenesis disorders, zellweger syndrome spectrum, nald, cerebrohepatorenal syndrome, and zss. it can affect many body organs, including the kidneys, eyes, and hearing. it is named after hans zellweger. zika virus – (zikv) (pronounced /ˈziːkə/ or /ˈzɪkə/) is a member of the virus family flaviviridae. it is spread by daytime-active aedes mosquitoes, such as a. aegypti and a. albopictus. its name comes from the ziika forest of uganda, where the virus was first isolated in 1947. zika virus shares a genus with the dengue, yellow fever, japanese encephalitis, and west nile viruses. since the 1950s, it has been known to occur within a narrow equatorial belt from africa to asia. from 2007 to 2016, the virus spread eastward, across the pacific ocean to the americas, leading to the 2015–2016 zika virus epidemic. zoonosis – a zoonosis (plural zoonoses, or zoonotic diseases) is an infectious disease caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human animal (usually a vertebrate) to a human. typically, the first infected human transmits the infectious agent to at least one other human, who, in turn, infects others. zygomatic bone – in the human skull, the zygomatic bone (cheekbone or malar bone) is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. it is situated at the upper and lateral part of the face and forms the prominence of the cheek, part of the lateral wall and floor of the orbit, and parts of the temporal fossa and the infratemporal fossa. it presents a malar and a temporal surface; four processes (the frontosphenoidal, orbital, maxillary, and temporal), and four borders.