During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called
implantation
.
What happens at the end of the germinal period?
The germinal stage ends
when the blastocyst implants in the endometrium of the uterus
(days 8-9). After implantation occurs, the blastocyst is called an embryo, and it will soon obtain nutrients from the mother’s blood via a temporary organ called the placenta.
How does the blastocyst attempt to feed itself?
During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called
implantation
.
What is the most important factor in determining what crosses the placenta barrier?
The primary determining factors of what type of drugs will cross the placental barrier are
molecular weight, lipid (fat or fat-like) solubility
, polarity (molecular charge), protein binding, and receptor mediation.
What percentage of natural conceptions fail to grow or implant properly?
It is estimated that about
60 percent
of natural conceptions fail to implant in the uterus. The rate is higher for in vitro conceptions. During this time, the organism begins cell division through mitosis. After five days of mitosis, there are 100 cells, which is now called a blastocyst.
What are the signs of unsuccessful implantation?
- Chronic pelvic pain.
- Bowel obstruction.
- Painful menses.
- Pain during intercourse.
- Infertility.
- Increased incidence of ectopic pregnancy.
When does a zygote become a blastocyst?
The zygote’s single cell contains all of the 46 necessary chromosomes, getting 23 from the sperm and 23 from the egg. The zygote phase is brief, lasting only about four days.
Around the fifth day
, the mass of cells becomes known as a blastocyst.
What can go wrong during embryonic stage?
Your developing baby is most vulnerable to injury during the embryo stage when organs are developing. Indeed,
infections and drugs
can cause the greatest damage when exposure occurs two to 10 weeks after conception. Diabetes and obesity can possibly increase your child’s risk of birth defects.
What develops during the germinal stage?
During the germinal stage, the cells necessary for the placenta, umbilical cord, and amniotic fluid will differentiate to form
the embryo
. The mass of cells has yet to attach itself to the lining of the uterus; once this attachment occurs, the next stage begins.
How long does the germinal stage last?
The germinal period (
about 14 days in length
) lasts from conception to implantation of the zygote (fertilized egg) in the lining of the uterus.
Do all drugs pass through the placenta?
Almost every drug passes from the mother’s bloodstream through the placenta to the fetus
. Illicit substances that cause drug dependence and addiction in the mother also cause the fetus to become addicted.
Can alcohol pass through the placental barrier?
During pregnancy,
alcohol and its toxic metabolites
can cross the placental barrier into the foetal bloodstream and amnionic fluid.
Which drug does not cross blood placental barrier?
Most drugs with MW < 500 Da cross the placenta, and most drugs with MW > 1000 Da do not cross the placenta (ex.
heparin, protamine, insulin
). Neither succinylcholine (highly ionized) or non-depolarizing NMBDs (high molecular weights) cross the placenta.
What percentage of blastocysts do not implant successfully?
Two-thirds of all human embryos
fail to develop successfully. Now, in a new study, researchers at the Stanford University School of Medicine have shown that they can predict with 93 percent certainty which fertilized eggs will make it to a critical developmental milestone and which will stall and die.
Why do eggs not implant?
The lining of the uterus is receptive to the embryo for only a brief time, called the Window of Implantation. It is possible that a perfectly normal embryo might not implant
because the lining was not ready for it
.
What happens to fertilized eggs that don’t implant?
If the egg is not fertilized or does not implant,
the woman’s body sheds the egg and the endometrium
. This shedding causes the bleeding in a woman’s menstrual period. When a fertilized egg does implant, a hormone called human chorionic gonadotropin (hCG) begins to be produced in the uterus.
