Conception and Fetal Development

1. Conception and Fetal Development Revised Fall 2012

2. How does the Female Body Prepare for Conception? Describe the process of maturation of an ovum

3. Menstrual Cycle • Varies every 28 - 35 days • The time between ovulation and menstruation is relatively constant (14 days). Lutealphase. • The variable is from menses to ovulation. It can not be predicted, the Follicular phase. • Affected by various physical and emotional factors

4. Maturation of the OvumOvarian Cycle • Follicular Phase- Development of the graafianfollicle (ovum) • Ovulatory Phase- about 2 days before ovulation • Luteal Phase- Formation of corpus luteum

5. How will the patient know that she is ovulating?

6. Signs and Symptoms of Ovulation • 1. Body temperature increase • 2. Mittelshmerz • 3. Cervical mucus changes • Increase in amount • Becomes thin, watery, and clear • Ferning • Stretchable: spinnbarkheit • Alkaline

7. What happens to the corpus leteum of I do not get pregnant?

8. What happens to the corpus luteum if I become pregnant?

9. Endometrial Cycle • The uterine endometriumrepsonds to ovarian hormones and goes through the phases in building up the lining of the uterus in preparation for implantation • Proliferative • Secretory • Menstural

10. Hormonal Cycle • FSH- Follicle stimulating hormone • Begins growth and maturation of the graafian follicle • LH- Luteinizing hormone • Assists in continued growth of the graafian follicle • Estrogen • Responsible for proliferation of endometrium • Progesterone • “Pro gestation”. The corpus luteum produces progesterone so the endometrium won’t slough off

11. Conception • Maturation of ovum and sperm cells • Pregnancy comes about from the union of a female germ cell, ovum with a male germ cell, the spermatozoon • Conception

12. One ovum per month is discharged from the ovary. It is transported into the fallopian tube where it begins its journey through the tube in search of the sperm. Viable for 12-24 hours

13. Fertalization When intercourse occurs, millions of sperm travel in search of an ova. During travel through the female reproductive system, capacitation occurs

14. Fertilization • As the sperm swarm around the ova, the Acromosome caps of sperm release zona digesting enzymes

15. Why is the number of sperm so important if only one sperm enters the egg?

16. Fertilization • Distal portion of the fallopian tube • Only one sperm penetrates ova • Each contributes 23 chromosomes • Sex of baby determined at this time

17. Pre-embryonic Development

18. Fertilized ovum begins its travel to the uterus

19. Cellular Multiplication • Morula eventually forms a fluid filled cavity within the cell mass. • Inner solid cell mass is called the blastocyst • Outer cell mass that surrounds the cavity is called the trophobast

20. Trophoblast Outer layer of cells Placenta Chorion Blastocyst Inner cell mass Fetus Amnion

21. Implantation

22. Germ Layers • Ectoderm • Mesoderm • Endoderm

23. Development Periods • Stage 1 – pre-embryonic • weeks 1 - 2 • Stage 2 -- embryonic • weeks 3 - 8 • period of ORGANOGENESIS • Stage 3 -- fetal • weeks 9 - 40

24. Embryonic PeriodWeeks 4-8 Week 4 • anterior end of neural tube closes to form the brain and the posterior end closes to form the spinal cord • Heart begins to beat • Eyes appear • Limb Buds for arms • and legs • CR = 4 mm

25. Week 5 • Head grows larger • Hand and feet plates develop • Facial features begin to develop • CR = 8 mm.

26. Week 6 • Fetal circulation is established • Chambers form in the heart • Upper lip and palate start fusing • Eyes move to front of face • Fingers are webbed • External ear develops

27. Week 7 • Eyelids start to form • Fingers develop; elbows visible • Diaphragm separates abdomen from chest • Bronchi develop • Arms and legs move

28. Week 8 • Fingers and toes distinct • Skeletal ossification begins • Testes and ovaries are distinguishable • Heart has four chambers • Circulation through umbilical cord occurs *** ALL essential external and internal structures are present and now will continue to grow

29. The patient tells the nurse that she is worried that the baby may have some defect because she was on antibiotics and other cold medication during the first week after intercourse/conception • What is happening during the first week after conception that would assist the nurse in answering her question?

30. Fetal PeriodWeeks 9-40

31. Weeks 9-12 • Head size increases • Face is well formed • Nails appear • Eyelids appear and close and fuse shut • Kidneys excrete urine • Intestines are forming; peristalsis begins • Heartbeat can be heard via ultrasound • Tooth buds appear for the baby teeth

32. Weeks 13-16 • Lips form, facial contour develops • Ossification of bone begins • Meconium begins to form in the intestines • Hair present on scalp • Sex can be determined visually

33. Weeks 17-20 • Hair abundant on head • Lanugo covers the body • Vernix begins to form • Myelination of spinal cord begins • Suck and swallow begin • Quickening occurs ~ 18 weeks

34. Weeks 21-24 • Respiratory movement with air sacs formed • Surfactant production begins ~ 24 weeks • Brain appears mature • Eyebrows and eyelashes can be seen • Reacts to sudden noise with active movement

35. Weeks 25-28 • Eyelids open and close • Capillaries proliferate around the lungs’ alveoli making gas exchange possible • Skin has wrinkled red appearance • Rapid brain development

36. Weeks 29-32 • Subcutaneous fat forms • Testes start descending • Fingernails and toenails are complete • Bones are fully developed, but still soft and pliable

37. Weeks 33-40 • Limbs start to flex • Muscle tone is developed • Lanugo disappears • Body begins to store fat • Maternal antibodies transfer to the fetus • Exhibits sleep and awake patterns

38. Answer this…… • The fetal nervous system is formed by the germ layer known as the: a. ectoderm b. mesoderm c. entoderm d. endoderm

39. Auxillary Structures Placenta Fetal Membranes

40. Functions of the Placenta • Fetal Respirations • Fetal Nutrition • Endocrine Functions • Elimination of Wastes • Barrier against certain substances

41. Amnion • Smooth, glistening membrane known as the Amnion is the lining of a fluid filled space that develops around the embryo

42. Functions of Amniotic Fluid • Keeps the fetus at an even temperature • Cushions the fetus against possible injury • Provides place for the fetus to move easily and grow symmetrically • Fetus drinks the fluid

43. Chorion • Thick membrane with finger-like projections called chorionic villi. • Chorionic villi contain blood vessels that are main connection with mother. • Chorionic villi produce human chorionic gonadotropin (HCG) • Merges with the deciduabasalis to form the PLACENTA.

44. Umbilical Cord • Body stalk that attaches the embryo to the yolk sac • Contains blood vessels that extend into the chorionic villi • Protected by wharton’s jelly

45. Teratogens • Risk factors such as environmental substances • Smoking • Alcohol • Drugs • Viruses • Occupational hazards

46. During what period of time is the baby most susceptible to damage from teratogens?

47. Review • Describe the components of the process of fertilization.

48. Ovum released into fallopian tube—viable for 24 hr. • Sperm deposited into vagina—viable for 48 to 72 hr (highly fertile for 24 hr). • Sperm must undergo capacitation and acrosomal reaction. • Sperm penetration causes a chemical reaction that blocks more sperm penetration. • Fertilization occurs in the distal end of the fallopian tube. • Sperm enters ovum. The nuclei of the ovum and sperm unite and become a diploid zygote.

49. Review How can knowledge of the normal fertilization process assist in helping couples conceive?

50. Review • How can knowing the gestational age of the fetus help in assessment for the potential effects of a teratogen?