Gestation (pregnancy) is the period of time between conception and the birth of\u00a0the child.<\/p>\n
The normal duration of human pregnancy is about 40 weeks or 10 lunar\u00a0months (28 days each) or 280 days. The time period is calculated by counting from the\u00a0date of the beginning of the mother’s last menstrual period. Even though the child was\u00a0not conceived until two weeks after this date, the date of the beginning of the last\u00a0menstrual period is used to calculate the expected date of delivery. Usually, the exact\u00a0date of fertilization cannot be determined.<\/p>\n
a. Embryonic Growth<\/strong>. From the time it has embedded itself in the uterine wall\u00a0until the end of the eighth week after fertilization, the new, developing organism has a\u00a0new name–embryo. During this period, the process of organogenesis is taking place.\u00a0Organogenesis is the differentiation of cells into specific organs and parts.<\/p>\n b. Fetal Growth<\/strong>. At the beginning of the ninth week, the growing organism is\u00a0referred to by another name–fetus. This term is used for the period of growth and\u00a0development until delivery. At about the twentieth week, the fetal heart sounds can be\u00a0heard by placing a stethoscope on the mother’s abdomen. The mother can also begin\u00a0to feel the fetus move.<\/p>\n (1) Placenta<\/span>. The placenta is a disc-like organ which is formed by tissue\u00a0from the mother and also from the fetus. The placenta brings nourishment to the fetus\u00a0and carries away fetal excretions. Hormones such as estrogen and progesterone are\u00a0secreted by the placenta.<\/p>\n (2) Umbilical cord<\/span>. The fetus and the placenta are connected by the\u00a0umbilical cord. The cord has two arteries that carry blood to the placenta and one vein\u00a0which carries blood to the fetus. The exchange of oxygen and other substances\u00a0between maternal blood and fetal blood takes place in the placenta. The exchange of\u00a0substances occurs without any actual mixing of maternal blood and fetal blood since\u00a0each flows in its own capillaries.<\/p>\n (3) Membranes<\/span>. Two thin, opaque membranes cover the embryo through\u00a0its development as a fetus. The amnion, which forms on the eighth day after\u00a0fertilization, is a fluid-filled sac which surrounds the fetus and then embryo protectively.\u00a0This sac is more commonly known as the bag of waters. The amniotic fluid serves as a\u00a0shock absorber for the developing fetus. The chorion, the outermost membrane, is first\u00a0an outer covering for the embryo and then the fetus. Eventually, the amnion membrane\u00a0fuses to the inner layer of the chorion membrane.<\/p>\n","protected":false},"excerpt":{"rendered":" Gestation (pregnancy) is the period of time between conception and the birth of\u00a0the child. The normal duration of human pregnancy is about 40 weeks or 10 lunar\u00a0months (28 days each) or 280 days. The time period is calculated by counting from the\u00a0date of the beginning of the mother’s last menstrual period. Even though the child … Continue reading 1-13. GESTATION<\/span>