The Reproductive Syste2

The Reproductive Syste2 - Stretching of the uterus...

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The Reproductive System Formation of the General Body Structure o The limbs develop as outgrowths called limb buds. o The face develops by the fusion of five tissue masses. Development of the Organ Systems o The GI tract develops as the developing embryo closes off part of the yolk sac. o The heart develops as two tubes fuse into a single tube that develops septa to form four chambers. o The kidneys and reproductive system are closely related in their development. Growth of the Fetus o The fetus increases 15-fold in length and 1400-fold in weight. Parturition Uterine contractions force the baby out of the uterus during labor. Increased estrogens, decreasing progesterone levels, and secretions from the fetal adrenal cortex initiate parturition.
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Unformatted text preview: Stretching of the uterus stimulates oxytocin secretion, which stimulates uterine contractions. The Newborn Respiratory and Circulatory Changes o Inflation of the lungs at birth results in closure of the foramen ovale and the ductus arteriosus. o When the umbilical cord is cut, blood no longer flows through the umbilical vessels. Digestive Changes o The newborn digestive system only gradually develops the ability to digest a variety of foods. Lactation Estrogens and progesterone help stimulate the growth of the breasts during pregnancy. Suckling stimulates prolactin and oxytocin synthesis. Prolactin stimulates milk production, and oxytocin stimulates milk "letdown."...
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