Ch 34 – Section 3 & 4 Development Conception  embryonic development  fetal development  birth Oocyte in suspended meiosis II at ovulation (in tube) until Oocyte activation 1.Occurs when a single sperm penetrates the corona radiata 2.Causes sperm contact with oocyte membrane 3.Causes Na+ into cell 4.Causes Ca+ to increase 5.Sperm receptors deactivated and zona pellucida hardens 6.Oocyte completes meiosis II (forming 2 nd polar body) 7.Enzymes activated to increase metabolic activity 8.Contents of male nucleus and oocyte fuse to form zygote

Development Conception has occurred (in uterine tube) Prenatal development/gestation occurs in 3 phases or trimesters 1 st trimester = conception  embryogenesis Cleavage  implantation  placentation  embryogenesis

1 st trimester: Cleavage Post fertilization with increased cell division Zygote becomes pre embryo ~ 3 days = morula (solid ball) ~ 6 days = blastocyst (hollow ball)

Germ layers form = gastrulation Endoderm = respiratory, digestive, urinary, some endocrine and reproductive Mesoderm = skeletal, muscular, circulatory, lumphatic, some endocrine, reproductive and urinary Ectoderm = integumentary, nervous, some skeletal, endocrine, respiratory and digestive

1 st trimester: Implantation Formation of extra-embryonic membranes Yolk sac Amnion Allontois Chorion Later blood cell formation Later protective ‘sac’ Later urinary bladder Later chorionic villi for nutrient exchange (and placenta)

1 st trimester: Placentation Development of placenta on uterine wall Placental allows for gas, nutrient, waste exchange between fetus and mother Placenta/fetus connected via umbilical cord

1 st trimester: Embryogenesis Formation of viable embryo ( 1 st 2 months of development) Definitive cell orientation Beginning of organogenesis 2 nd trimester 3 rd trimesters Organ development Significant fetal weight gain Rapid fetal growth

Maternal systems in gestation Increased respiratory rate Increased blood volume (> X 50%) Increased nutrient need (X 10 – 30%) Glomerular filtration rate increased by > X 50% Uterus enlarges Mammary glands enlarge and begin secretion

Parturition (birth) Oxytocin is the hormone that triggers Labor 3 stages of labor = dialation expulsion placental Cervix dilates to allow fetus to pass into birth canal Fetus is pushed out through birth canal into outside world (birth) Placenta (afterbirth) detaches from endometrium and is delivered

after birth…. Significant changes take place in baby’s body Lungs fill with air for respiration Circulatory changes = lower heart rate blood cell production Digestion begins Urinary system active Temperature control Neonate dependant on milk secretions for nutrients, fluids, immunity Neonate Infancy Childhood Adolescence Birth  1 month1 month  2 years 2 years  12 years (physical/sexual maturity) Sexual Maturity