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Ch 6 Conception, Pregnancy and Childbirth.docx

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Psychology 2075
Corey Isaacs

Conception, Pregnancy and Childbirth 10/30/2012 1:35:00 PM Chapter 6 Conception  Sperm meets the egg o On about day 14 of an average menstrual cycle the woman ovulates and enters the fallopian tubes, reaching the uterus about 5 days later if it is fertilized o Sperm is one of the tiniest cells in the human body composed of a head, midpiece and tail o Hyaluronidase – an enzyme secreted by the sperm that allows one sperm to penetrate the egg o Zygote – the developing organism from the time of the union of the sperm and the egg to about the second week of gestation o Embryo – the developing organism between the second and eighth week of gestation o Fetus – the developing organism from the eighth week to gestation through delivery Development of the Conceptus  The embryo and its support systems o During the embryonic period of development (first eight weeks) most of the major organ systems are formed very quickly o The cell divides itself into two layers at first, the endoderm and the ectoderm, and later the mesoderm forms between them  Ectoderm – forms the entire nervous system and skin  Endoderm – differentiates into the digestive and respiratory systems  Mesoderm – muscles, skeleton, connective tissues, reproductive and circulatory systems o The head develops before the rest of the body o Trophoblast – eventually becomes the placenta o Placenta – an organ formed on the wall of the uterus though which the fetus receives oxygen and nutrients and gets rid of waste products  Important feature is that is serves as a site for the exchange of substances between the woman’s blood and the fetus’s blood – the two circulatory systems are completely separated, only certain substances can pass through  Human chorionic gonadotropin (hCG) – a hormone secreted by the placenta, detected in pregnancy tests  Umbilical cord – tube that connects the fetus to the placenta  Formed during the fifth week of embryonic development  Amniotic fluid – the watery fluid surrounding a developing fetus in the uterus  Fetal development o Major milestones of fetal development First Trimester Weeks 3 and 4 Development of the head Nervous system begins to form Backbone is constructed Week 5 Formation of the umbilical cord Weeks 4 to 8 External body parts develop – eyes, ears, arms, hands, fingers, legs, feet and toes Second Trimester Week 14 Fetal movement or quickening Week 18 Fetal heartbeat detected by examiner Week 24 Fetus is sensitive to light and sound in utero Third trimester Week 28 Fat deposits form – gains chubby baby appearance Weeks 29 to birth Rapid growth Pregnancy  Stages of pregnancy o First trimester – first 12 weeks  Symptoms of pregnancy – missed period, increase in basal body temperature for a long period of time  Pregnancy tests – urine test is about 98% accurate, home pregnancy test  Signs of pregnancy  Presumptive signs – breast tenderness, nausea  Probable signs – tested by pregnancy tests  Positive signs – beating of fetal heart, active fetal movement and detection of a fetal skeleton by ultrasound o Second trimester – week 13 to 26  Physical changes – during the fourth month the woman can feel movement and notice an expanding belly  Edema – water retention and selling o Third trimester – week 27 to 38  Physical changes – the uterus is very large and hard  Braxton-Hicks contractions – contractions of the uterus during pregnancy that are not part of actual labour  Psychological changes – women who were found to have more stressful lives were more likely to experience pregnancy complications  Nutrition during pregnancy o Important for pregnant women to get enough protein, folic acid, calcium, magnesium and vitamin A  Deficiencies in calcium and magnesium are associated with premature birth  Substances that may result in birth defects o Teratogen – a substance the produces defects in a fetus
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