circumcision, female The excision (removal) of part or all of the external female genitalia, including the clitoris, and sometimes extending to the labia. Female circumcision is practiced in some parts of the Middle East and Africa, particularly Sudan, and it is viewed with disfavor in other parts of the world. Also known as female genital…
circulatory system The system that moves blood through the body. The circulatory system is composed of the heart, arteries, capillaries, and veins. This remarkable system transports oxygenated blood from the lungs to the heart and throughout the body via the arteries. The blood goes from the arteries to the veins by passing through the capillaries….
circulatory Having to do with circulation, the movement of fluid in a regular or circuitous course.
circulation, fetal The blood circulation in the fetus (an unborn baby). Before birth, blood from the fetal heart that is destined for the lungs is shunted away from the lungs through a short vessel called the ductus arteriosus and returned to the aorta. When this shunt is open, it is said to be a patent…
circulation In medicine, the movement of fluid through the body in a regular or circuitous course. The circulatory system, composed of the heart and blood vessels, functions to produce circulation. Heart failure is an example of a problem with circulation.
circle of Willis A critical arterial circle at the base of the brain. The circle of Willis receives all the blood that is pumped up the two internal carotid arteries that come up the front of the neck. All the principal arteries that supply the two halves of the brain (hemispheres) branch off from the…
circinate balanitis See balanitis, circinate.
circadian clock An internal time-keeping system in all organisms. Changes in the external environment, particularly in the light–dark cycle, train this biologic clock. When environmental conditions are constant, rhythms driven by the circadian clock follow a nearly perfect 24-hour pattern. The human circadian clock regulates many daily activities, such as sleep and waking. When a…
circadian Refers to events occurring within the span of a full 24-hour day, as in a circadian clock.
ciliary neuralgia See cluster headache.
-cide Suffix indicating killing or killer, as in bactericide (a solution capable of killing bacteria).
Ci The abbreviation for a Curie, a unit of radioactivity. See also Curie.