Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «U»:
Unresolved grief: Grief characterized by the extended duration of the symptoms, by interference of the grief symptoms with the normal functioning of the mourner, and/or by the intensity of the symptoms (for example, intense suicidal thoughts or acts). See: Complicated grief....
Unsaturated fat: A fat that is liquid at room temperature and comes from a plant such as olive, peanut, corn, cottonseed, sunflower, safflower, or soybean. Unsaturated fats tend to lower the level of cholesterol in the blood....
Unstable diabetes: A type of diabetes when a person's blood glucose (sugar) level often swings quickly from high to low and from low to high. Also called "brittle diabetes" or "labile diabetes."...
Unsteadiness: Loss of one's equilibrium in regard to
the environment, often with a feeling of almost falling, or the
result of bumping into things. There are many causes for
unsteadiness, including problems in the cerebral or cerebellar
portions of the brain, the spinal cord, vestibular system, ...
Unwell: Not well or in good health, ailing, sick, indisposed. For example, "I am well-nigh choked with the sulfurous heat of the weather -- or I am unwell." (1826, Journal of Sir Walter Scott)
"Unwell" is also a euphemism for experiencing menstruation. It medicalizes women with the implication that...
Up-regulation: See: Upregulation....
Upper GI series
Upper GI series: A series of x-rays of the esophagus, stomach,
and small intestine (upper gastrointestinal, or GI, tract) that are taken after the
patient drinks a barium solution. (Barium is a white, chalky substance that outlines the
organs on the x-ray.)...
Upper leg: The upper leg is the superior (top) segment of the leg: the part above the knee.
As compared to the lower leg which boasts two bones (the tibia and the fibula), the upper leg has only one bone: the femur but a very large bone it is, the largest in the human body, extending by necessity ...
Upper motor neuron
Upper motor neuron: A neuron that starts in the motor cortex of the brain and terminates within the medulla (another part of the brain) or within the spinal cord. Damage to upper motor neurons can result in spasticity and exaggerated reflexes. There is no standard laboratory test for upper motor neu...
Upper respiratory infection
Upper respiratory infection: An infection of the upper part of the respiratory system which is above the lungs. An upper respiratory infection can be due to any number of viral or bacterial infections. These infections may affect the throat (pharyngitis), nasopharynx (nasopharyngitis), sinuses (sinu...
Upregulation: An increase in the number of receptors on the surface of target cells, making the cells more sensitive to a hormone or another agent. For example, there is an increase in uterine oxytocin receptors in the third trimester of pregnancy, promoting the contraction of the smooth muscle of t...
Urachus: A canal connecting the bladder of the fetus with the allantois, a
structure that contributes to the formation of the umbilical cord. The lumen
(inside) of the urachus is normally obliterated during embryonic development,
transforming the urachus into a solid cord, a functionless remnant....
Uracil (U): A nucleotide base and one member of the A-U (adenine-uracil) base pair in RNA. The other base pair in RNA is G-C (guanine-cytosine).
Uracil takes the place in RNA that thymine (T) occupies in DNA....
Uranium: A metallic element that is used as nuclear fuel and is highly toxic and radioactive. Exposure to radiation from uranium can occur in various ways. The breakdown of uranium products creates radon daughters. These can attach to dust particles and, if workers inhale the dust, the particles lod...
Urate: A salt derived from uric acid. When the
body cannot metabolize uric acid properly, urates can build
up in body tissues or crystallize within the joints. See
also gout, uric acid....