1. Chapter 16 Pregnancy & Development Notice: This presentation contains actual pictures of human reproductive anatomy

2. Menstrual (Uterine) Cycle  Cyclic changes of endometrium  Regulated by estrogens & progesterone  Stages 1. Menses – endometrium is sloughed 2. Proliferative stage – regeneration of functional layer 3. Secretory stage –increases in size & readies for implantation  Menarche – 1 st period

3. Menstrual phase Ovarian hormones are at their lowest levels Gonadotropins are beginning to rise Uterine wall is shed and the menstrual flow occurs Uterine Cycle

4. Proliferative phase Estrogen levels prompt generation of new functional layer. Glands enlarge and spiral arteries increase in number

5. Uterine Cycle Secretory phase Progesterone levels prompt Further development of endometrium Glandular secretion of glycogen

6. Hormonal Control of Ovarian & Uterine Cycles

8. Hormones of Ovaries 1. Estrogens  Produced by follicle cells  Cause secondary sex characteristics 1.Development of breasts 2.Appearance of pubic hair 3.Increase in fat beneath the skin 4.Widening and lightening of the pelvis 5.Onset of menses 2. Progesterone  Produced by the corpus luteum  Production continues until LH diminishes in the blood  Helps maintain pregnancy

9. Mammary Glands  Present in both sexes, but only function in females - Modified sweat glands  produce milk  Stimulated by sex hormones (mostly estrogens) to increase in size

10. Anatomy of Mammary Glands  Areola – central pigmented area  Nipple – protruding central area of areola  Lobes – internal structures that radiate around nipple  Lobules containing alveolar glands – clusters of milk producing glands within lobules  Lactiferous ducts – connect alveolar glands to nipple  Lactiferous sinus

11. Pregnancy Pregnancy: events that occur from fertilization until the infant is born Conceptus: the developing offspring Gestation period: time from the last menstrual period until birth (~280 days) Embryo: conceptus from fertilization through week 8 Fetus: conceptus from week 9 through birth

12. Figure 28.1 Fertilization 1-week conceptus 3-week embryo (3 mm) Embryo 12-week fetus (90 mm) 8-week embryo (22 mm) 5-week embryo (10 mm)

13. Stages of Pregnancy & Development  Fertilization  Embryonic development  Fetal development  Childbirth

14. Fertilization  Oocyte viable 12 - 24 hrs  Sperm viable 12 - 48 hrs  Sperm swim to fallopian tube for fertilization  At least 20 million sperm/ml needed

15. Mechanisms of Fertilization  Membrane receptors of oocyte pull in head of the first sperm cell to make contact  Membrane of oocyte stops other sperm  Oocyte undergoes 2nd meiotic division  Fertilization: sperm nucleus + oocyte nucleus = zygote.

16. The Zygote  First cell of new individual  Zygote begins rapid mitotis  Zygote stage is in the uterine tube, moving toward the uterus

17. The Embryo  Developmental stage: cleavage thru 9th week  Undergoes division w/o growth at first (morula)  Embryo enters uterus at 16-cell state (blastocyst)  Embryo floats in the uterus temporarily  Uterine secretions used for nourishment

18. Figure 28.4 (a) Zygote (fertilized egg) (b) 4-cell stage 2 days (c) Morula (a solid ball of blastomeres). 3 days (d) Early blastocyst (Morula hollows out, fills with fluid, and “hatches” from the zona pellucida). 4 days Blastocyst cavity Degenerating zona pellucida Zona pellucida Inner cell mass Blastocyst cavity Trophoblast (e) Implanting blastocyst (Consists of a sphere of tropho- blast cells and an eccentric cell clus- ter called the inner cell mass). 7 days Cavity of uterus Uterus Endometrium Ovulation Ovary Fertilization (sperm meets and enters egg) Uterine tube Oocyte (egg) Sperm

19. The Blastocyst  Hollowed out ball-like circle of cells  Begins at ~ 100 cells  Secretes human chorionic gonadotropin (hCG) to produce the corpus luteum to continue producing hormones (test)  Functional areas of the blastocyst -Trophoblast – large fluid-filled sphere -Inner cell mass

20.  The late blastocyst floats for 2-3 days then begins to implant in the wall of the uterus (6-7days after ovulation)  Gastrulation -Blastocyst folds in on itself -Primary germ layers formed

21. Figure 28.5a (a) Uterine endometrial epithelium Inner cell mass Trophoblast Endometrium Blastocyst cavity Lumen of uterus

22. Implantation The implanted blastocyst is covered over by endometrial cells Implantation is completed by the twelfth day after ovulation

23. Figure 28.6 Gestation (weeks) Ovulation and fertilization Birth Human chorionic gonadotropin Progesterone Estrogens

24. Derivatives of Germ Layers 1. Ectoderm  Nervous system  Epidermis 2. Endoderm  Mucosae  Glands 3. Mesoderm  Everything else

25. Development ( Ovulation to Implantation )

26. Development After Implantation  Chorionic villi (projections of the blastocyst) develop - Cooperate with cells of the uterus to form the placenta  Embryo surrounded by amnion (fluid filled sac)  Umbilical cord forms

27. Development After Implantation

28. Functions of Placenta  Barrier between mother & embryo (blood not exchanged)  Delivers nutrients & O 2  Removes waste  Becomes endocrine organ (produces hormones) and takes over for the corpus luteum  Estrogen  Progesterone  Other hormones that maintain pregnancy

29. The Fetus ( Beginning of the Ninth Week )  All organ systems formed by the end of the 8th week  Time for organ specialization  Stage of tremendous growth and change in appearance

30. Effects of Pregnancy on the Mother  Pregnancy – conception until birth  Anatomical changes - Enlargement of uterus - Accentuated lumbar curvature - Relaxation of pelvic ligaments and pubic symphysis due to production of relaxin

31. Effects of Pregnancy on the Mother  Physiological changes A. Gastrointestinal system  Morning sickness - elevated progesterone  Heartburn - organ crowding by the fetus  Constipation - digestive tract slows B. Urinary System  Kidneys – work more/more urine  Uterus compresses bladder

32. Effects of Pregnancy on the Mother C. Respiratory System  Nasal mucosa congested and swollen  Vital capacity & respiratory rate increase D. Cardiovascular system  Body water rises  Blood volume increases 25 to 40%  Blood pressure & pulse increase  Varicose veins common

33. Childbirth (Parturition) 1. Labor – events that expel infant from uterus 2. Initiation of labor  Estrogen levels rise  Uterine contractions begin  Placenta releases prostaglandins  Oxytocin is released by the pituitary  Contractions

34. Labor Contractions - + Feedback

35. Stages of Labor

36. Developmental Aspects  Gender determined at fertilization - Males = XY; Females = XX - Gonads form starting week 8  Testes in abdominal cavity; descend to scrotum 1 month before birth  Testosterone determines ovaries or testes.  Reproductive organs not functional until puberty  Puberty - begins ages 10 - 15  1st menses occurs ~ 2 yrs after puberty starts  Peak reproductive ability - late 20s

37. Developmental Aspects  Menopause - ovulation & menses stop - Ovaries stop functioning as endocrine organs  No equivalent of menopause in males, but there is a steady decline in testosterone