Pregnancy and Embryonic Development Fertilization Oocyte is viable

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 • https: //www. youtube. com/watch? v=BFr. Vm. D gh 4 v 4

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 • https: //www. youtube. com/watch? v=Ug. T 5 r. U Q 9 Em. Q

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 • https: //www. youtube. com/watch? v=h 82 ltr 84 _Yg&feature=youtu. be&src_vid=KXRb. V 33 J 5 qk &feature=iv&annotation_id=annotation_2692 649789

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