Final answer:
Chorionic villus sampling (CVS) is the procedure that tests placental tissue for prenatal diagnosis, distinguishing it from options like amniocentesis, pelvimetry, and Pap smear.
Step-by-step explanation:
The procedure that tests placental tissue for prenatal diagnosis is Chorionic villus sampling (CVS). This is a medical test where a sample of the placental tissue is taken to test for chromosomal abnormalities and certain other genetic problems. In contrast, Amniocentesis involves sampling the amniotic fluid, Pelvimetry assesses the size and shape of the mother's pelvis, and a Pap smear is a screening procedure for cervical cancer involving cells from the cervix.
The placenta is vital for fetal development, providing oxygen and nutrients to the growing fetus and removing waste products from the baby's blood. The umbilical cord is a tube that connects the fetus to the placenta and allows for the transfer of blood and nutrients. The placenta also acts as a barrier to protect the fetus from certain substances, although it is permeable to lipid-soluble fetotoxic substances like alcohol, nicotine, and certain drugs.
Answer: 2) Chorionic villus sampling