Dictionary

chromatography, gas An automated technique for separating mixtures of substances in which the mixture to be analyzed is vaporized and carried by an inert gas through a special column and thence to a detection device.

chromatid One of the two daughter strands created by the lengthwise division of the chromosome. The two chromatids are at first joined together by a centromere, and then they separate, with each chromatid becoming a chromosome.

Christmas disease See hemophilia B.

choroiditis An inflammation of the layer of the eye behind the retina, either in its entirety (multifocal choroiditis) or in patches (focal choroiditis). The only symptom is usually blurred vision. Choroiditis is treated with medications that reduce inflammation. See also uveitis.

chorionic villus sampling A procedure for first-trimester prenatal diagnosis. Abbreviated CVS. CVS may be done between the eighth and tenth weeks of pregnancy. The aim is to diagnose severe abnormalities that are present in the fetus. Tissue is withdrawn from the villi of the chorion, a part of the placenta, and then prepared for diagnostic…

chorionic gonadotropin, human See human chorionic gonadotropin.

chorion The outermost of the two fetal membranes (the amnion is the innermost) that surround the embryo. The chorion develops villi (vascular finger-like projections) and develops into the placenta.

choriocarcinoma A highly malignant tumor that arises from trophoblastic cells within the uterus. Choriocarcinoma may follow any type of pregnancy but is especially likely to occur with a hydatidiform mole. The prognosis for women with metastatic choriocarcinoma has improved with the advent of multidrug chemotherapy. See also hydatidiform mole.

chorioangioma, placental A benign tumor of a blood vessel in the placenta. Large chorioangiomas can cause complications, including excess amniotic fluid (polyhydramnios), maternal and fetal clotting problems (coagulopathies), premature delivery, toxemia, fetal heart failure, and hydrops (excess fluid) affecting the fetus. Chorioangiomas probably act as shunts between arteries and veins (arteriovenous shunts), leading to progressive…

chorioamnionitis Inflammation of the chorion and the amnion, the membranes that surround the fetus. Chorioamnionitis usually is associated with a bacterial infection. This may be due to bacteria ascending from the mother’s genital tract into the uterus to infect the membranes and the amniotic fluid. Chorioamnionitis is dangerous to the mother and child.

chorea, Sydenham’s See Sydenham’s chorea.

chorea, Huntington’s See Huntington’s disease.