Pregnancy and Embryonic Development

Fertilization Oocyte is viable for 12 to 24 hours after it is cast out of the ovary Sperm generally retain their fertilizing power within the female reproductive tract for 12 to 48 hours It takes 1 to 2 hours for sperm to complete the journey up the female duct system

Fertilization After sperm entry, changes occur in the fertilized egg to prevent other sperm from gaining entry Fertilization occurs at the moment the genetic material of a sperm combines with that of an ovum to form a zygote The zygote represents the first cell of the new individual

Fertilization(conception) video h4v4

Cleavage provides large number of cells to serve as building blocks A solid ball of Blastomeres (a type of cell) Morula hollows out and fills with fluid

Human Development Video 9EmQ 9EmQ

Fetal Development Once the embryo is planted in the uterus, the blastocyst develops elaborate projections called chorionic villi, -Chorionic villi will operate with the tissues of the mother’s uterus to form the placenta Once the placenta is formed, the embryonic body is surrounded by a fluid-filled sac called the amnion -The amnion is attached to the placenta by umbilical cord

How a baby develops video _Yg&feature=youtu.be&src_vid=KXRbV33J5qk &feature=iv&annotation_id=annotation_

Childbirth Also called parturition It usually occurs within 15 days of the calculated due date The series of events that expel the infant from the uterus are referred to collectively as labor Cause of labor: high level of estrogen in the mother’s blood -Abundant oxytocin (hormone) receptors in the myometrium -Interfere with progesterone's quieting influence on the uterine muscle False labor: Braxton Hicks contraction, weak irregular uterine contractions

Stages of Labor Stage 1: Dilation Stage -Time from the appearance of true contractions until the cervix is fully dilated by the baby’s head ( about 10 cm in diameter) -Contractions gradually become stronger -As the infant’s head is forced against the cervix, the cervix begins to soften and becomes thinner and dilates -Eventually, the amnion rupture -Longest part of labor, usually last 6 to 12 hours

Stages of Labor Stage 2: Expulsion Stage -The period from full dilation to delivery of the infant -It last typically 50 min. in a first birth and around 20 min. in subsequent births -The head will be delivered first -After birth, the umbilical cord is clamped and cut Stage 3: Placental Stage -It is the delivery of the placenta -Usually within 15 min after birth of the infant