Anemia, pernicious: Low red blood cell count caused by inadequate vitamin B12. Abbreviated PA. Patients with PA do not produce intrinsic factor (IF), a substance that allows the body to absorb vitamin B12 from foods. The resulting inadequacy of vitamin B12 hampers the production of red blood cells. PA can be treated by injection of vitamin B12: oral administration will not work because people with PA cannot absorb orally administered vitamin B12. Also known as Addison’s anemia.
Relating to anemia, the condition of having less than the normal number of red blood cells or less than the normal quantity of hemoglobin in the blood. The oxygen-carrying capacity of the blood is, therefore, decreased. Persons with anemia may feel tired and fatigue easily, appear pale, develop palpitations (feelings of rapid heart beating) and […]
- Anemia, sickle cell
A genetic blood disorder caused by the presence of an abnormal form of hemoglobin. These hemoglobin molecules tend to aggregate after unloading oxygen forming long, rod-like strictures that force the red cells to assume a sickle shape. Unlike normal red cells, which are usually smooth and malleable, the sickle red cells cannot squeeze through small […]
Anencephaly: A neural tube defect (NTD) that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th days of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp. Infants with this disorder are born without a forebrain, the largest part […]
Anergy: A state of immune unresponsiveness. Induced when the T cell’s antigen receptor is stimulated, effectively freezing T cell responses pending a “second signal” from the antigen-presenting cell. The delivery of the second signal by the antigen-presenting cell rescues the activated T cell from anergy, allowing it to produce the lymphokines necessary for the growth […]
Anesthesia: Loss of feeling or awareness, as when an anesthetic is administered before surgery.