Human Development

• Prenatal


  before birth, divided into three trimesters (3 months each)
• Stage One

  zygote begins cleavage which is rapid cell division without enlargment, then turns into a morula, the 16 cell stage
• Stage 2

  blastocyst made out of 2 layers, trophoblast (outer) and embyroblast (inner), when implantation occurs
• Trophoblast


  becomes the chorion, secretes enzymes that digest the endometrium for implantation and secretes hCG
• hCG


  maintains corpus luteum (no menstruation)
• Embryoblast

  inner cell mass, develops into embryo
• Stage 3

  gastrulation, the start of morphogenesis and differentiation that form 3 layers
• Ectoderm


  nervous system and skin (epidermis)
• Mesoderm


  skeleton, muscles and reproductive structures
• Endoderm


  lining of digestive and respiratory systems and endocrine glands
• Chorion


  formed from trophoblast cells, outer membrane that forms fetal part of placenta
• Chorionic Villi


  projections of the chorion that go into endometrium (implantation)
• Placenta


  temporary organ that allows for exchange between mom and baby, provides passive immunity, produces progesterone, estrogen and hCG
• Mom to Baby

  O2 and nutrients
• Baby to Mom

  CO2 and waste
• Amnion


  sack filled with amniotic fluid that cushions embryo and regulates temperature
• Allantois


  forms umbilical cord that connects fetus to placenta
• Yolk Sac


  produces first blood cells and becomes apart of digestive tract
• First Trimester


  neurulation, neural tube becomes CNS, organs are formed, cartilage skeleton formed
• Second Trimester


  heart beat detected, bones form, brain begins to form limbs grow
• Third Trimester


  brain grows rapidly, testes descend, fat layer grows, digestive and respiratory system mature
• Teratogen


  substance disrupts normal fetus, most harmful in the first 9 weeks
• Thalidomide


  helped with morning sickness but caused deformed babies with flipper like arms
• Estrogen and Progesterone during Pregnancy


  first produced by the corpus luteum then the placenta, breast grow and morning sickness
• Relaxin


  produced by placenta, hips widen
• Pregnancy Changes


  increased urination, difficulty breathing, blood volume and pressure increase
• Do estrogen levels increase or decrease during onset?

  increase
• What other hormone is produced during onset?

  oxytocin
• Oxytocin


  causes contractions, drops after birth
• Dilation


  amnion breaks (water breaks) cervix opens, can take between 2-20 hours
• Expulsion


  pushing phase, can take around 0.5-2 hours
• Placental


  placenta and umbilical cord are pushed out, 10-15 minutes after
• Lactation


  formation and secretion of breastmilk
• What is released and from where during lactation?

  prolactin from the anterior pituitary