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Chapter 16 Pregnancy & Development Notice: This presentation contains actual pictures of human reproductive anatomy
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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
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Hormonal Control of Ovarian & Uterine Cycles
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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
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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
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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
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Stages of Pregnancy & Development Fertilization Embryonic development Fetal development Childbirth
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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
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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.
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The Zygote First cell of new individual Zygote begins rapid mitotis Zygote stage is in the uterine tube, moving toward the uterus
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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
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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
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The late blastocyst implants in the wall of the uterus (by day 14) Gastrulation -Blastocyst folds in on itself -Primary germ layers formed
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Derivatives of Germ Layers 1. Ectoderm Nervous system Epidermis 2. Endoderm Mucosae Glands 3. Mesoderm Everything else
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Development ( Ovulation to Implantation )
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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
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Development After Implantation
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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
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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
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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
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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
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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
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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
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Labor Contractions - + Feedback
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Stages of Labor
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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
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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
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