1096708
| Question | Answer |
| morulla | 16 cell stage of zygote with an inner cell mass and outer cell mass |
| blastomeres | the dividing zygote from 30 hours until 4 days (morula 16-cell) of development |
| blastocyst | stage of embryogenesis at the time of implantation where outer trophoblast cells form a fluid-filled sphere with a small group of embryoblast cells, the inner cell mass, at one pole |
| embryoblast | cells of the inner cell mass |
| trophoblast | cells of the outer cell mass which flatten to form the epithelial wall of the blastocyst |
| embryonic stem cells (ES cells) | pluripotent cells, can form any cell or tissue type, derived from the inner cell mass of the embryo and have the potential for curing a variety of diseases |
| cytotrophoblast | the inner layer of mononucleated cells in the trophoblast |
| syncytiotrophoblast | the outer multinucleated zone without distinct cell boundaries in the trophoblast |
| hypoblast layer | a layer of small cuboidal cells adjacent to the blastocyst cavity derived from cells of the inner cell mass or embryoblast |
| epiblast | a layer of high columnar cells adjacent to the amniotic cavity derived from the cells of the inner cells mass or embryoblast |
| extraembryonic mesoderm | cells derived from yolk sac cells form a fine loose connective tissue which eventually fills all of the space between the trophoblast externally and the amnion and exocoelomic membrane internally |
| chorionic cavity | a new space formed when large cavities develop in the extraembryonic mesoderm and become confluent |
| primary villi | cellular columns with syncytial covering protruding from the cytotrophoblast to the syncytiotrophoblast |
| connecting stalk | mesodermal connection that connects the embryo to the placenta. It contains the allantois and umbilical vessels and will be incorporated into the umbilical cord with the yolk sac (vitelline) stalk (duct) |
| ectopic pregnancy | implantation that occurs outside the uterus. Ex: In the rectouterine pouch, on the mesentery, in the uterine tube, or in the ovary |
| hydatidiform mole | the trophoblast develops and forms placental membranes, although little or no embryonic tissue is present. They secrete high levels of hCG (human chorionic gonadotropin) and may produce benign or malignant tumors |
| gastrulation | 3rd week of gestation, the process that establishes all 3 germ layers (ectoderm, mesoderm, and endoderm) in the embryo |
| primitive streak | formation of this marks the beginning of gastrulation. appears on the surface of the epiblast |
| primitive node | cephalic end of the streak and consists of a slightly elevated area surrounding the small primitive pit |
| primitive pit | depression in the primitive node |
| notochord | extended column of midline cells lying immediately ventral to the floor plate of the central nervous system and extending from the hypophysis to the end of the spinal cord. |
| prechordal plate | collection of mesoderm cells lying between the oropharyngeal membrane and the cranial end of the notochord. These cells represent some of the first to pass through the primitive streak and are important for forebrain induction using SHH as a signal molecule |
| cloacal membrane | formed at the caudal end of the embryo from adhesion between epiblast and hypoblast cells. Later, it covers the cloaca and eventually breaks down to form openings into the urogenital sinus and anus |
| endoderm | one of the three basic germ layers that form the gut and its derivitaves |
| ectoderm | one of the three basic germ layers that forms skin, the central nervous system, hair, and many other structures |
| mesoderm | one of three basic germ layers that form blood vessels, bone, connective tissue, and other structures |
| anterior visceral endoderm (AVE) | collection of endoderm cells at the cranial end of the bilaminar disc responsible for inducing the head region through secretion of transcription factors including, OTX2, LIM1, and HESX1. |
| situs inversus | complete reversal of left- and right- sidedness of the organs in the thorax and abdomen |
| laterality sequences | right and left sides are established during gastrulation in the third week of development. Patients with defects in sidedness, such that they are primarily bilaterally right or left sided, have this. |
| primary villi | present in trophoblast that consis of a cytotrophoblastic core covered by a cyncytial layer |
| secondary villi | mesodermal cells penetrate the core of primary villi and grow toward the decidua. |
| tertiary villi (definitive placental villus) | mesodermal cells in the core of the villus differentiate into blood cells and small blood vessels, forming the villous capillary system |
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