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Textbook notes chap 6.docx

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Psychology 2075

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Textbook notes Chapter 6Conception Pregnancy and ChildbirthConceptionSperm meets egg The incredible journeyOn about day 14 of an average menstrual cycle the woman ovulates The egg is released from the ovary into the body cavity Typically it is then picked up by the fimbriae and enters the fallopian tube It then begins a leisurely trop down the tube toward the uterus reaching it in about five days if it has been fertilized Otherwise it disintegrates in about 48 hours The conception occurs in the outer third of the fallopian tube As they approach a chemical secreted by the egg attracts the sperm to the egg A thin gelatinous layer called zona pellucida surrounds the egg Sperm swarm around the egg and secrete an enzyme called hyaluronidase produced by the acrosome located in the head of the sperm This enzyme dissolves the zona pellucida permitting one sperm to penetrate the egg The fertilized egg called the zygote continues to travel down the fallopian tube About 36 hours after conception it begins the process of cell division For the first 2 weeks of gestation the conceptus is called a zygote between weeks 2 and 8 an embryo and from then until birth a fetusImproving the chances of conception Making a baby Have intercourse every 2448 hours to allow time to manufacture the sperm Position during woman on her back and after intercourse remain on her back with legs pulled up is important Lubricants and suppositories should not be usedDevelopment of the ConceptusPregnancy lasts for about nine months Typically divided into three equal period of three month called trimestersThe embryo and its support systemsDuring the embryonic period the inner part of the ball cells implanted in the uterus now differentiates into two layers the endoderm and the ectoderm Later a third layer the mesoderm forms between them The ectoderm will form the entire nervous system and the skin The endoderm differentiates into the digestive system and the respiratory system Skeleton and connective tissues and reproductive and circulatory systems derive from mesoderm Development generally proceeds in a cephalocaudal order That is the head develops first The placenta develops out of the mass of tissues that surrounds the conceptus early in development and nurtures its growth by producing tendrils that penetrate the blood vessels in the wall of the uterus The placenta is a site for the exchange of substances between the womans blood and the fetuss blood There is a membrane barrier between the two blood systems Some substances are capable of passing through this barrier whereas others are not The placenta also produces large quantities of estrogen and progesterone Human chorionic gonadotropin hCG is also produced and is the hormone detected in pregnancy tests The umbilical cord is formed during the fifth week of embryonic development Normally it contains three blood vessels two arteries and one vein Two membranes surround the fetus the chorion and the amnion The amnion is filled with a watery liquid called amniotic fluid that maintains the fetus at a constant temperature and most importantly cushion the fetus against possible injuryFetal Development
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