Part 1
1. Briefly explain the formation of the germ layers. Germ layer formation is also known as gastrulation. The Ectoderm forms as the first layer. It eventually becomes what is known as the skin, brain, spinal cord, and pituitary gland. The Mesoderm germ layer forms next and is the middle layer. This will eventually become muscle, bone and gonads. The third and internal layer is the Endoderm layer. It will form into the GI tract, liver, pancreas, bladder, thyroid etc. After the blastocyst forms into the endometrial layer
2. Briefly explain the primitive streak. The primitive streak is created when the epiblast cells from the two ends of the epiblast layer migrate to the midline. The streak itself forms the axis of the developing baby.
3. Briefly explain the formation of the neural tube. The neural tube forms from the neural folds as they begin to thicken and move together and fuse forming the neural tube. This forms the spinal cord, spine and brain.
4. What malformations can occur during this stage of development? At this stage of development neural tube defects are some of the most common anomalies. Malformations of the spinal cord, spine and brains can be caused before a woman is even aware she is pregnant. One of the most common being spina bifida, which is caused by a spinal cord that doesn’t close completely. Another common defect is anencephaly causing a baby’s brain to be underdeveloped due to a defect in the spinal cord development.
5. During which week does cardiovascular activity begin? And on approximately which day? At the end of the 3rd week, around day 21-22.
6. When can the heartbeat be detected via ultrasound? Around 5 weeks, 7 weeks from the last period date.
7. When does nourishment transition from the yolk sac to maternal blood supply? By the end of the 3rd week.
8. What are the products of conception? Any tissues developed in pregnancy, including the placenta and the fertilized egg.
9. What is the difference between embryonic and gestational age? Embryonic age is counted from the moment of conception (fertilization) without adding or subtracting any weeks. So 9 week old embryonic age means that it has been 9 weeks since conception. Gestational age is counted from the first day of the woman's last menstrual period, which can be anywhere from 12-14 days before fertilization. So 9 week old gestational age means that it has been 7 weeks from conception but 9 weeks from the last menstrual period.
10. When implantation occurs outside the uterus what is this called? An ectopic pregnancy.
11. Why does it occur? Often an ectopic pregnancy occurs in the fallopian tubes and that usually is because of scarring or tube damage.
12. How is it most often detected? By ultrasound.
13. When does the fetal period begin? The fetal period begins 8 weeks after fertilization which is 10 weeks of gestation.
14. What is defined as viability? The ability for the fetus to survive outside of the uterus.
15. Define quickening. Fetal movements.
16. When does quickening take place? Between weeks 17-20.
17. What are influencing factors on fetal growth? Maternal and fetal environment, drugs, smoking, alcohol, or infection.
18. Discuss the various diagnostic techniques and the benefits and risk of each. Diagnostic Amniocentesis is performed between weeks 15-18 gestation and is done by inserting a needle through the mothers abdomen into the amniotic sac and extracting amniotic fluid to then be tested. The benefits are that it can aid in diagnosing abnormalities in a fetus early on. Risks are low although present, and it is best to have an expert perform the procedure. Chorionic Villus sampling is also done by inserting a needle through the mothers abdomen and into the amniotic cavity and taking a biopsy to then be tested. The benefits obviously are that tests are done that can determine any abnormalities. The risks are slightly higher for miscarriage than the amniocentisis diagnostic.
19. What are significant developmental milestones during the fetal period. (List 5) ● Rapid body growth ● Developmental compilation of organs and tissues ● Brain and nervous system fully developed ● Ossification of the fetal skeleton ● Muscle tone
Part 2
Practical application of information learned is an excellent way to ensure that concepts become real and understood to each of us. In this section we will look at several “case studies” of situations that may actually occur. These stories are based on the information in this section and will give you the opportunity to look at how it relates to real world cases. For each case study there will be a list of questions. You will answer these questions and give your best understanding as to what is happening in each and why.
Case #1 A woman with a history of early spontaneous abortions had an ultrasound examination to determine whether her embryo was still implanted.
1. Is the use of an ultrasound during the third week of pregnancy of any help in this situation? Why or why not? No it will not because it is too early into the pregnancy to tell. 3 weeks gestation means the egg has barely been fertilized and most likely still traveling through the fallopian tube and not implanted yet.
2. If a pregnancy test was performed for this woman and it came back negative, would it be safe to assume she is not pregnant? Why or why not? Again, too early into pregnancy. HCG hormones are released after implantation and those are what trigger positive pregnancy tests.
3. Would there be the possibility of an extrauterine gestation present in this case? Why or why not? At this point and time it is too early to tell. The egg is fertilized and divides cellularly very fast on its way to the uterus. It is too early to tell if it will implant into the fallopian tube instead.
Case #2
A 30-year-old woman was unsure when her LNMP was. She stated that her periods were irregular.
1. Why may information about the starting date of a pregnancy provided by a patient be unreliable? Give examples. Some women may not have gotten their period back since a previous pregnancy and get pregnant on the first ovulation without ever getting a period. Or a woman may have a much lighter “period” which really turns out to be implantation bleeding.
2. What clinical techniques are now available for evaluating embryonic age? Give two or more and describe each. And ultrasound can determine the size of the baby and assess age off of that by measurements and developmental milestones. Fundal measurement. The length from the top of the pubic bone to the top of the uterus closely follows the fetal age.
Case #3
An ultrasound examination of a pregnant woman revealed IUGR of the fetus.
1. What factors may cause IUGR? Discuss them. Be specific and thorough. Maternal, fetal environment, maternal age, placenta vaso-constriction, smoking, drugs or alcohol, nutrition. 2. Which factors can the mother eliminate? Smoking, nutrition, drugs or alcohol.