Chapter 16 Pregnancy & Development

1. Chapter 16Pregnancy & 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 – 1st period

3. Hormonal Control of Ovarian & Uterine Cycles

4. Hormonal Control of Ovarian & Uterine Cycles

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

6. 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

7. Anatomy of Mammary Glands • Areola – central pigmented area • Nipple – protruding central area of areola • Lobes – internal structures that radiate around nipple • Alveolar glands – clusters of milk producing glands within lobules • Lactiferous ducts – connect alveolar glands to nipple

8. Stages of Pregnancy & Development • Fertilization • Embryonic development • Fetal development • Childbirth

9. 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

10. 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.

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

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

13. The Blastocyst • 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

14. The late blastocyst implants in the wall of the uterus (by day 14) • Gastrulation • Blastocyst folds in on itself • Primary germ layers formed

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

16. Development (Ovulation to Implantation)

17. 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

18. Development After Implantation

19. Functions of Placenta • Barrier between mother & embryo (blood not exchanged) • Delivers nutrients & O2 • Removes waste • Becomes endocrine organ (produces hormones) and takes over for the corpus luteum • Estrogen • Progesterone • Other hormones that maintain pregnancy

20. 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

21. 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

22. 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

23. 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

24. Childbirth (Partition) 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

25. Labor Contractions - + Feedback

26. Stages of Labor

27. 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

28. 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