Also known as fertility awareness, natural family planning, and periodic abstinence, this approach to contraception entails not having sexual intercourse on the days of a woman’s menstrual cycle when she could become pregnant or using a barrier method (such as a condom, the diaphragm or a cervical cap) for birth control on those days.
Because a sperm may live in the female’s reproductive tract for up to 7 days and the egg remains fertile for about 24 hours, a woman can get pregnant within a substantial window of time — from 7 days before ovulation to 3 days after. Methods to approximate when a woman is fertile are usually based on the menstrual cycle, changes in cervical mucus, or changes in body temperature.
- Rhythm, sinus
The normal regular rhythm of the heart set by the natural pacemaker of the heart called the sinoatrial (or sinus) node. It is located in the wall of the right atrium (the right upper chamber of the heart). Normal cardiac impulses start there and are transmitted to the atria and down to the ventricles (the […]
One of the 12 paired arches of bone that form the skeletal structure of the chest wall (the rib cage). The ribs attach to the vertebrae of the spine in the back. The 12 pairs of ribs consist of 7 pairs of ribs that attach to the sternum in the front and are known as […]
- Rib cage
The structure formed by the thoracic vertebrae and ribs, the sternum (breastbone), and the costal cartilages (that attach the ribs to the sternum). A cage is an enclosure made of “open work” that usually houses animals. The rib cage was thought to resemble an animal cage (although the largest “animals” it holds are the heart […]
- Rib, cervical
An extra rib that arises from the seventh cervical vertebra. It is located above the normal first rib. A cervical rib is present in only about 1 in 200 people. It may cause pinching of nearby nerves or arteries, in which case it sometimes is removed surgically.
- Rib, floating
The lower five ribs do not directly connect to the sternum and are known as false ribs. The upper three false ribs connect to the costal cartilages of the ribs just above them. The last two false ribs, however, usually have no ventral attachment (no anchor at all in front) and are called floating, fluctuating […]