biopsy, sentinel-lymph-node Examination of the first lymph node that receives lymphatic drainage from a tumor to learn whether that node has tumor cells in it. The sentinel node’s identity is determined by injecting around the tumor a tracer substance that travels through the lymphatic system to the first draining node, thereby identifying it. If the…
biopsy, stereotactic needle A procedure in which the spot to be biopsied is located threedimensionally, the information is entered into a computer, and then the computer calculates the information and positions a needle to remove the biopsy sample. Stereotactic needle biopsy can be done in a properly equipped physician’s office, and it carries a minimal…
biotechnology The fusion of biology and technology, the application of biological techniques to product research and development. In particular, biotechnology involves the use by industry of recombinant DNA, cell fusion, and new bioprocessing techniques to produce large molecules useful in treating and preventing disease. Slang biotech.
bioterrorism Terrorism using biologic agents that are harmful to humans. Biological diseases and the agents that might be used for terrorism have been listed by the US Centers for Disease Control and Prevention (CDC). These agents include viruses, bacteria, rickettsiae (microorganisms that have traits common to both bacterial and viruses), fungi, and biological toxins. The…
bipolar disorder A disorder, formerly called manic-depressive illness, in which the patient cycles through uncontrollable mood states. Less prevalent than simple clinical depression, bipolar disorders involve cycles of depression, hypomania (elevated mood), mania (extremely elevated mood), and in some cases psychosis. Sometimes the mood switches are dramatic and rapid, but most often they are gradual….
birth The process of delivering a fetus from the uterus. Normally, the fetus is expelled through the cervix and birth canal with the assistance of rhythmic muscle contractions. Birth may instead be a surgical procedure: a Caesarean section. See also caesarean section.
birth control The practice of exercising some level of control over contraception. Birth control methods are many, and they vary in effectiveness. The most effective method is abstinence from sex, followed by oral, injectible, or implanted contraceptives; barrier methods used consistently and with spermicidal gel; and the basal temperature method, if used carefully and consistently….
birth control pill See oral contraceptive.
birth defect Any defect present in a baby at birth. Birth defects involve many different tissues, including the brain, heart, lungs, liver, bones, and intestinal tract. These defects can occur for many reasons, including genetic conditions and toxic exposures of the fetus (for example, to alcohol). All parents are at risk of having a baby…
birthmark A discoloration of the skin that may or may not be raised and is present at birth. Most birthmarks are harmless. Occasionally a specific type of birthmark can be a visible marker for a more serious health problem. See also café au lait; port-wine stain.
birthrate The number of live births divided by the average population, or by the population at midyear. Also known as crude birthrate.
bisexual 1 An individual who engages in both heterosexual and homosexual sexual relations. Bisexual can also refer to the corresponding lifestyle. 2 In physical biology, bisexual refers to an individual who was born with gonadal tissue of both sexes (that is, both testicular and ovarian tissue). Also known as true hermaphrodite.