加拿大生物_妊娠课件.ppt

Pregnancy and Birth ;After fertilization, Blastocyst (fertilized egg) takes 3-5 days to reach the uterus 2-4 days after it reaches the uterus, blastocyst implants in endometrium: this marks the beginning of pregnancy if pregnancy is established, menstruation does not occur ;During implantation, outer layer of blastocyst produces, HCG ( human chorionic gonadotropin) HCG: prevents degeneration of the corpus luteum (up to 9 months) stimulates it to secrete larger quantities of progesterone, which maintains the uterine lining and prevents contractions Pregnancy tests identify the presence of HCG in the urine of women ;;Placenta : disc-shaped organ which contains maternal and fetal blood vessels it grows to about the size of a dinner plate weighs less than 1 kg there is no direct mixing of maternal and fetal blood! ;;; the umbilical cord contains two fetal arteries which carry deoxygenated blood to the placenta from the fetus, and one fetal vein which carries oxygenated blood to the fetus from the placenta ;怀殖棘桐今随掠的寂额处群谴羊缉咖曾治瑚箱大廉叁那檀蛾裸岸倾泉或戏加拿大生物_妊娠课件加拿大生物_妊娠课件;Paturition;Childbirth;relaxin produced by the placenta causes the ligaments of the pelvis to loosen, enlarging the passageway for the baby during birth progesterone secretion decreases, which allows the uterus to contract ;2. Delivery ;3. Afterbirth ;Lactation;;Mammary Glands