Module 1 Flashcards
pre-embryonic period
first 2 weeks after conception
Morula
A solid ball of cells that makes up an embryo; in humans, this stage occurs within four days of fertilization. 16 cells.
Zygote
the fertilized egg; it enters a 2-week period of rapid cell division and develops into an embryo
monozygotic twins
identical twins formed when one zygote splits into two separate masses of cells, each of which develops into a separate embryo
dizygotic twins
twins who are produced when two separate ova are fertilized by two separate sperm at roughly the same time
High Multifetal Gestation
More than 2 babies in one pregnancy
embryonic period
the period from 2 to 8 weeks after fertilization, during which the major organs and structures of the organism develop
Teratogen
agents, such as chemicals and viruses, that can reach the embryo or fetus during prenatal development and cause harm
Week 8 of development
-embryo has distinct human appearance
Ectoderm
outermost germ layer; produces Central Nervous System and epidermis
Mesoderm
middle germ layer; develops into muscles, and much of the circulatory, reproductive, and excretory systems
Endoderm
innermost germ layer; develops into the linings of the digestive tract and much of the respiratory system
fetal period
The third and longest period of prenatal development, extending from the ninth week until birth.
Placenta: main function
Gas exchange
foramen ovale
Hole between the right and left atria that bypasses the non-functioning lungs before birth. Closes when the baby takes their first breaths.
Ductus ateriosus
A structure that connects the pulmonary artery and descending aorta during fetal life. Sends oxygen poor blood to the lower half of the fetal body. Closes when the umbilical cord is cut.
ductus venosus
A structure that connects the umbilical vein to the inferior vena cava, bypassing the liver. Closes when the umbilical cord is cut.
Weeks 9-12
Fetal head 1/2 size of body
Weeks 13-16
Placenta is formed.
Weeks 17-20
Quickening (fetal movement can be felt)
Weeks 21-24
Fetus has a startle reflex
Weeks 25-28
Rapid skin growth.
Weeks 29-32
Rounder body.
Weeks 33-38
Steady weight gain.
Uterus is at belly button
Fundal height at 20 weeks gestation