tubule
DEFINITION:
A small tube.
arcuate renal tubule - A short, curved part of the distal end of the renal tubule (See below), extending from the distal convoluted tubule (See below) to the straight collecting tubule (See below). Called also junctional (connecting) tubule .
collecting tubule - A channel through which fluids pass from the secreting cells.
connecting tubule - Arcuate renal tubule (See above).
distal convoluted tubule - A distal, rolled-together or coiled part of the ascending limb of the renal tubule (See below), extending from the distal straight tubule (See below) to the junctional (connecting) tubule (See below).
distal straight tubule - Part of the renal tubule (See below) primarily on the ascending limb, extending from the thin tubule (See below) to the distal convoluted tubule (See above).
junctional (connecting) tubule - See arcuate renal tubule (above).
proximal convoluted tubule - The most proximal part of the renal tubule (See below), extending from the glomerular capsule to the proximal straight tubule (See below).
proximal straight tubule - Part of the descending limb of the renal tubule (See below), extending from the thin tubule (See below) to the distal convoluted tubule (See above).
renal collecting tubule - The arcuate renal tubule (See above), straight collecting tubule (See below), and papillary duct considered together. Called also collecting duct .
renal tubule - One of the minute, reabsorptive, secretory, and collecting canals, made up of basement membrane lined with epithelium, that form the substance of the kidneys. See also nephron .
straight collecting tubule - The lower straight part of the renal collecting tubule (See above), extending from the arcuate renal tubule (See above) to the papillary duct.
thin tubule - Part of the renal tubule (See above) at the lower end where the walls are especially thin; it extends from the proximal straight tubule (See above) to the distal straight tubule (See above). In juxtamedullary and deep cortical nephrons it makes up most of the length of Henle's loop.
proteins
DEFINITION:
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.
binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).
carrier proteins - A binding protein (See above).
plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.
transport protein - binding protein (See above).
breast cancer
DEFINITION:
The most common cancer in women. Causes of breast cancer are believed to be due to either hormonal influences or diet. The incidence of breast cancer is known to be raised in women whose menstrual periods began when they were young and those whose menopause was late; in those who had no children or had their first child in their late 20s or 30s; and in those with mothers or sisters who had breast cancer. The dietary link is indicated also, however, for the disease is rare in Japan, which has a low fat diet, but Japanese women living in the US and eating an American diet have the same rate of breast cancer as Americans. Tall, heavy women have more breast cancer than short, thin ones. Breast cancer may also be more common among women who have previously had nonmalignant cysts and tumors removed from their breasts.
There is no agreement on the part played by the oral birth-control pill in the cause of breast cancer. Some groups believe that women who take the pill in their teens have a slightly increased risk; others claim that it is protective. At present the evidence suggests that any increase in breast cancer from the pill, if at all, is small---and that it is outweighed by the effect of the pill in lowering the incidence of cancers of the ovary and uterus.
The most common site of a malignant breast tumor is the upper, outer part of the breast. The lump is usually felt rather than seen, and in most cases is not painful. Other symptoms include a dark discharge from the nipple, retraction (indentation) of the nipple, and an area of dimpled, creased skin over the lump. In 90 percent of the cases only one breast is affected.
Monthly examination of the breasts should enable a woman to detect at an early stage any new or changed breast lump or any change in her nipples. The breast examination is important and should routinely be done by internists and gynecologists. In addition, X rays of the breasts, called mammograms, are recommended for high-risk women at age 40 and for all women after age 50.
A physician may determine that a lump is merely a cyst, in which case the lump (or sac) may be aspirated. If the physician suspects possible cancer, a biopsy will be performed and the suspect tissue examined under the microscope. If cancer is discovered, blood tests, X rays, and scanning will determine whether the disease has spread to other parts of the body.
Treatment usually includes surgical removal of the tumor, combined with radiation therapy or anticancer drug therapy, or both. The outlook is optimistic if detection is made early and cancer has not spread.
