These alveoli join to form groups known as lobules. Each lobule has a lactiferous duct that drains into openings in the nipple . 86 What are the roles of hormones prolactin and oxytocin in lactation? Prolactin stimulates the production of breast milk and is necessary for normal milk production during breastfeeding. Oxytocin is responsible for stimulation of milk ejection (milk letdown) and for stimulation of uterine smooth muscle contraction at birth. 87 What are the functions of the following anatomical structures: placenta, amnion, amniotic fluid, allantois, yolk sac, chorion, umbilical cord, chorionic villi? Placenta: Amnion : a membranous sac which surrounds and protects the embryo.
Amniotic fluid : offers protection from any blows that may come to the uterus area. It may cushion the blow if the mother falls. When the fetus swallows the amniotic fluid, it is practicing using and developing the digestive system. Allantois : collects liquid waste from the embryo, as well as to exchange gases used by the embryo. Yolk sac: also responsible for the initial circulation and is in charge of delivering nutrients, via a primitive aorta, to the developing embryo through a process called vitelline circulation. Chorion: one of the four extraembryonic membranes that make up the amniotic egg that provide for the nutrients and protection needed for the embryo's survival. Umbilical cord : c onnects your baby to the placenta, contains three vessels: two arteries, which carry blood from the baby to the placenta, and one vein, which carries blood back to the baby. The blood in the arteries contains waste products, such as carbon dioxide, from the baby's metabolism. Chorionic villi : essential element in pregnancy from a histomorphologic perspective, and are, by definition, a product of conception. Branches of the umbilical arteries carry embryonic blood to the villi. 88 List the stages of embryonic development (zygote, morula, blastula, gastrula) and describe each stage. During this first week the egg, then zygote, morula then the blastula is moving along the uterine horn into the uterus for implantation in the uterine wall. Implantation also begins in this first week, as the implantation process is completed by the end of the second week. 89 What is “decidua” and what role does it play? The thick layer of modified mucous membrane that lines the uterus during pregnancy and is shed with the afterbirth. It participates in the exchanges of nutrition, gas, and waste with the gestation. It also protects the pregnancy from the maternal immune system. 90. How is sex determined by our chromosomes?