Dictionary

ultraviolet B See ultraviolet radiation.

ultraviolet C See ultraviolet radiation.

ultraviolet radiation Invisible rays that are part of the energy that comes from the sun. Abbreviated UV. UV radiation is made up of three types of rays: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). UVC is the most dangerous type of UV light in its potential to harm life on earth, but…

umbilical cord The cord that connects the developing fetus with the placenta while the fetus is in the uterus. The umbilical arteries and vein run within this cord. The umbilical cord is clamped and cut at birth, and its residual tip forms the bellybutton.

unconscious 1 Interruption of awareness of oneself and one’s surroundings; the lack of the ability to notice or respond to stimuli in the environment. A person may become unconscious due to oxygen deprivation, shock, injury, or use of central nervous system depressants such as alcohol and drugs. 2 In psychology, the part of thought and…

unconsciousness, temporary A partial or complete loss of consciousness; interruption of awareness of oneself and one’s surroundings. When the loss of consciousness is temporary and recovery is spontaneous, it is referred to as syncope or, more commonly, fainting. Temporary unconsciousness may also occur with some types of seizures, from a head injury, or as part…

undulant fever See Brucellosis.

unicornuate Having one horn, or being horn shaped. For example, the uterus is normally unicornuate.

unilateral Having, or relating to, one side. For example, a unilateral rash is one that is only on one side of the body.

typhus, scrub A mite-borne infectious disease that is caused by the microorganism Orientia (formerly Rickettsia) tsutsugamushi. Characteristic symptoms include fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy), and a dark crusted ulcer, called an eschar or tache noire, at the site of the chigger (mite larva) bite. Scrub typhus occurs in the area bounded…

typhus, tick See Rocky Mountain spotted fever.

typhus, tropical See typhus, scrub.