Pregnancy and Development Flashcards
- Name the site of human fertilization. Define fertilization.
1.Oviduct; joining of egg & sperm. Fertilization is the point where the sex of the baby is determined. If the sperm was carrying a Y chromosome it is a boy and if the sperm was carrying an X chromosome it is a girl.
- Define capacitation.
2.Change in head of sperm weakening the acrosomal cap so that it may release its enzymes upon the layers around the egg.
- Define zygote.
3.Fertilized egg diploid
- Contrast dizygotic and monozygotic twins.
- Dizygotic are fraternal and are 2 different eggs fertilized by 2 different sperm. Monozygotic are identical with one egg plus one sperm forming one zygote that then splits into two.
- Describe the events immediately following fertilization.
5.Egg wall changes so that no other sperm may enter. Nucleus of egg and sperm unite then cleavage begins
- Define cleavage morula and blastocyst.
6.Cleavage is mitosis as zygote travels down oviduct. A ball of identical cells formed from cleavage is a morula. Once in the uterus the cells rearrange to become a blastocyst.
- Define implantation and where and when it occurs.
7.When the blastocyst burrows its way into the mom’s endometrium on day 7 or 8 this is implantation.
- Describe the events of gastrulation neurulation and organogenesis.
8.Gastrulation is the stage where the germ layers form. Depending which layer a cell ends up in determines which organ it will become. Neurulation is the formation of the neural tube which will become brain cranially and spinal cord organogenesis is the beginning of the formation of all major organs in the body and is occurring at about week 4.
- Describe the 3 germ layers and the organs that arise from each layer.
9.Ectoderm becomes skin & nervous system Mesoderm becomes cardiovascular system muscles bone connective tissues Endoderm becomes digestive structures and lungs
- Define embryo and fetus.
10.At the end of the second month of gestation the embryo distinctly has human characteristics and at that point is called a fetus.
- Describe the function of HCG and where and when it is produced.
11.HCG is made by the embryo from about week 2-12. It is the hormone that is tested for in do-it-yourself pregnancy tests. It keeps the corpus luteum alive so that the endometrium won’t be sloughed as with a non-pregnant menstrual cycle. By keeping the corpus luteum alive estrogen & progesterone continue to be produced.
- Describe the functions of the placenta.
12.By week 12 the placenta takes over the role of making estrogen & progesterone and continues to do so throughout the rest of pregnancy. The placenta is where mom’s blood meets baby’s blood without the blood actually mixing. However diffusion allows nutrients and oxygen to travel from mom’s blood to baby’s and diffusion allows waste and carbon dioxide to travel from baby’s blood to mom’s.
- Name the tissues that comprise the placenta.
13.Mom’s endometrium (=decidua basalis) plus baby’s chorion
- Describe the decidua basalis trophoblast cells chorion chorionic villi umbilical artery and vein umbilicus amnion and amniotic fluid.
14.Decidua basalis is mom’s endometrium trophoblast cells are the outer cells of the blastocyst stage of the embryo that develop into an outer membrane called the chorion. The chorion is vascular and has finger-like extensions digging into mom’s endometrium called villi. Here is the location of diffusion. The Umbilical arteries & vein comprise the umbilical cord and connect baby to the placenta. The fetal membrane immediately surrounding the fetus is the amnion and it is filled with the fetus plus fluid called amniotic fluid. The fluid allows movement is a protective cushion and keeps a constant temperature for the fetus.
- What is the average length of human gestation?
15.40 full weeks = 280 days.
