Template:Glossary
Glossary
Amniocentesis- A prenatal diagnostic test involving sampling of amniotic fluid by needle aspiration for genetic analysis.
Amnion- An extraembryonic membrane ectoderm and extraembryonic mesoderm in origin and forms the innermost fetal membrane, produces amniotic fluid. This fluid-filled sac initially lies above the trilaminar embryo disc and with embryoic disc folding this sac is drawn ventrally to enclose (cover) the entire embryo, then fetus.
Amniotic cavity- The fluid-filled (amniotic fluid) extraembryonic coelom (cavity) formed initially by epiblast and then ectoderm and surrounding extraembryonic mesoderm. In humans, it forms the innermost fetal membrane, produces amniotic fluid expanding to fuse with the chorionic membrane during week 8 of development.
Amniotic fluid- The fluid that fills amniotic cavity totally encloses and cushions the embryo.
Chorion- The extraembryonic membrane generated from trophoblast and extraembryonic mesoderm that forms placenta. chorion and amnion are made by the somatopleure. The chorion becomes incorporated into placental development. The avian and reptilian chorion lies beside the egg shell and allows gas exchange.
Chorionic villus sampling (CVS)- The taking a biopsy of the placenta, usually at the end of the second month of pregnancy, to test the fetus for genetic abnormalities.
Chromosome- double stranded DNA coiled around histones. Condenses during mitosis and meiosis.
Ectoderm- One of the initial 3 germ cell layers, which will form the nervous system from the neural tube and neural crest and also generates the entire epithelial layer of the skin covering the embryo.
Endoscope- a long slender medical instrument for examining the interior of a bodily organ or performing minor surgery
Endoderm- One of the initial 3 germ cell layers (ectoderm, mesoderm and endoderm) formed by the process of gastrulation. The endoderm forms as a cuboidal epithelium and contributes not only to the trilaminar embryo, but also lines the yolk sac. It will form the entire epithelial lining of the gastrointestinal tract (GIT), contribute to the accessory organs of GIT and also forms the epithelial lining of the respiratory tract.
Fetus- In mammals, term describes the period of development following the embryonic period. In humans, the development week 9 to 36 is the fetal stage (second and third trimester). (see fetal period above). This term is also used non-scientifically to describe the human conceptus at both embryonic and fetal stages of development.
Gene- A DNA sequence that is transcribed as a single unit and encodes a single polypeptide (protein) or a set of closely related polypeptides. There are approximately 20,000-25,000 protein encoding genes in the human genome. In each cell, DNA is found within the nucleus and also within mitochondria.
Gestation- The period of time from conception to birth. A pregnancy with multiple fetuses is referred to as a multiple gestation.
