Medical and Healthy Living Glossary - R
This page of our online glossary of medical and healthy living is for medical and healthy living terms beginning with the letter 'R'.
- Radiolytic Products - Substances that are produced when food is irradiated.
- Receptors - Nerve endings or cells that detect stimuli such as cold or heat and trigger signals that produce a particular response in a body part.
- Recommended Daily Amount (RDA) - Also known as the recommended daily allowance. Figures issued by the health authorities in many countries indicate the average quantities of key nutrients people need to obtain from their food. In the European Union, 'labelling RDAs' are often shown on food labels, where, for example, the amount of iron in a typical serving is shown as a percentage of the RDA for iron. These RDAs' are said to apply to 'average adults', and are therefore really only a very rough guide to healthy eating.
- Red Blood Cells (Erythrocyte) - Cells circulating in the bloodstream that contain haemoglobin and carries oxygen to the tissues and takes carbon dioxide from them.
- Refined Foods - White sugar, white flour and polished white rice are all examples of refined food products, in which the main ingredient has been processed. This usually results in some of its nutrients being lost. For example, refined flour and rice lose most of their dietary fibre and rice also loses most of its vitamin B1. However, refining foods can prolong their shelf life, and make the product more appetising.
- Resistant Starch - A type of starch that cannot be broken down in the normal way by enzymes in the small intestine. Resistant starch is found in raw potatoes, unripe fruit and some processed foods. It passes undigested into the large intestine, where it can act like insoluble fibre and help to prevent constipation. However, resistant starch can also ferment, which causes wind and discomfort.
- Retina - The light-sensitive lining at the rear of the eye. Light enters the eye through the pupil and strikes the retina. Light-sensitive cells in the retina (cones and rods) convert the light to nervous impulses. The optic nerve then sends these impulses to the brain which interprets them as images.
- Rheumatoid Arthritis - The second most common form of joint disease, after osteoarthritis, that usually affects the feet, ankles, fingers and wrists. The condition is diagnosed using X-rays. The X-rays show a typical pattern of changes around the inflamed joints, known as rheumatoid erosions. At first there is swelling of the joint and inflammation of the synovial membrane, followed by erosion and loss of cartilage and bone. The condition varies greatly in its degree of severity, but at its worst can be progressive and seriously disabling. However, in other people, after an initial active phase, there may be a long period of remission. A number of different drugs are used to treat rheumatoid arthritis, including analgesics and anti-inflammatory agents.
- RNA (Ribonuleic Acid) - The substance, occurring in every living cell, that enables the body to develop according to the genetic code contained in its DNA. There are several forms of RNA. Messenger RNA carries information from the DNA in the cell's nucleus to its ribosomes, the sites where proteins are made. By following the code, transfer RNA ensures that amino acids (the building blocks for protein) are assembled correctly.
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