Ch 49 Early Embryonic Stages Key terms

diamniotic

multiple pregnancies with two amniotic sacs

dichorionic

multiple pregnancy with two chorionic sacs

embryologic age

age calculated from when conception occurs

menstrual age

length of time calculated from the first day of the last normal menstrual period to the point at which the pregnancy is being assessed

monoamniotic

multiple pregnancy with one amniotic sac

monochorionic

multiple pregnancy with one chorionic sac

primary yolk sac

first site of formation of red blood cells that will nourish the embryo

secondary yolk sac

formed at 23 days when the primary yolk sac is pinched off by the extraembryonic coelom

zygote

conceptus resulting from union of male and female gametes

amniotic cavity

-cavity in which the fetus exists

-forms early in gestation

-fills with amniotic fluid to protect the fetus

chorionic cavity

surrounds the amniotic cavity and contains the yolk sac

chorionic villi sampling

invasive diagnostic genetic testing that involves sampling zygotic cells from developing placental tissue

crown-rump length

most accurate measurement of the embryo in the first trimester

decidua basalis

uterine decidual surface on the maternal side of the placenta

decidua capsularis

uterine decidua on the surface of the implantation site

double decidual sac sign

inner surface between the decidua capsular and the echogenic, highly vascular endometrium

embryonic period

time between 4 and 10 weeks

hematopoiesis

production and development of blood cells

human chorionic gonadotropin

-hormone secreted by the trophoblastic cells of the blastocyst

-laboratory test indicates pregnancy when values are elevated

IUP

intrauterine pregnancy

MSD

mean sac diameter

transvaginal transducer

high frequency transducer that is inserted into the vaginal canal to obtain better definition of first trimester pregnancy

yolk stalk

the umbilical duct connecting the sac with the embryo