Brill-Zinsser disease Reactivation of epidemic typhus years after an earlier attack of the disease. Rickettsia prowazekii, the agent that causes epidemic typhus, remains viable for many years. When the host’s defenses are down, it can be reactivated. See also rickettsial diseases; typhus, epidemic.
bridge 1 A set of one or more false teeth that is supported by a metal framework and used to replace one or more missing teeth. 2 A form of treatment that serves as a transition from a previous form of treatment and is followed with another form, such as in “bridge therapy.” 3 Tissue…
Brenner tumor A tumor of the surface of the ovary. Brenner tumors are usually benign, but in rare cases, they are cancerous.
breech birth Birth of a baby with the buttocks, rather than the head, emerging first. Breech birth is more likely to cause injury to the mother or the infant than head-first birth. In many cases a baby in the breech position can be turned before delivery by using repeated, gentle massage.
Breathing is the process of taking in oxygen (inhalation) and expelling carbon dioxide (exhalation) through the lungs. It is essential for the body to function, as oxygen is required for cellular respiration, which provides energy for various bodily functions. There are two primary phases of breathing: Breathing is typically regulated by the brainstem, which automatically…
breathing The process of respiration, during which air is inhaled into the lungs through the mouth or nose due to muscle contraction and then exhaled due to muscle relaxation.
breastfeeding The highly recommended practice of feeding an infant with the mother’s natural milk. Breast milk contains vitamins, minerals, and enzymes that aid the baby’s digestion, and immunity factors in breast milk can help infants fight off infections. Breast milk can be expressed, manually or with the assistance of a breast pump, for use while…
breastbone See sternum.
breast reduction Surgical reduction of breast size in order to reduce the weight of the breasts and relieve symptoms from unusually large, pendulous breasts. Breast reduction can relieve skin irritation of the chest, and pain in the back and shoulders. Also known as reduction mammaplasty.
breast milk Milk from the breast. Human milk contains a balance of nutrients that closely matches infant requirements for brain development, growth, and a healthy immune system. Human milk also contains immunologic agents and other compounds that act against viruses, bacteria, and parasites.
breast implant See breast augmentation.
breast cancer susceptibility gene An inherited factor that predisposes an individual to breast cancer. Two of these genes, BRCA1 and BRCA2, have been identified. Several other genes (those for LiFraumeni syndrome, Cowden disease, Muir-Torre syndrome, and ataxia-telangiectasia) are also known to predispose women to breast cancer. However, because all these known breast cancer susceptibility genes…