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Prenatal Development. Conception. Stages (NOT Trimesters). Germinal/Blastocyst/Zygote Stage Begins with Conception and ends with implantation 0-(8-14) days-first two weeks Egg and sperm meet (Zygote) travel down the fallopian tube to the uterus and implants ~ 3-4 days after conception
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Stages (NOT Trimesters) • Germinal/Blastocyst/Zygote Stage • Begins with Conception and ends with implantation • 0-(8-14) days-first two weeks • Egg and sperm meet (Zygote) • travel down the fallopian tube to the uterus and implants • ~ 3-4 days after conception • Differentiation of cells begins • eventually becoming the blastocyst: embryonic disk and trophoblast • Amnion, Chorion, & Placenta • 30-50% of all conceptions end • Death?? • 12-17 conceptions are male to 1 female-WHY?
Stages (NOT Trimesters) • Embryonic Period • Begins with implantation and ends with ossification (calcification) of the bones. • 2-8th week • First two (or so) weeks: Embryonic disk forms 3 layers: • Ectoderm-Nervous system & skin • Mesoderm-Muscles, skeleton, circulatory system • Endoderm-digestive system, lungs, urinary tract, glands • Second month: systems become more complex & defined
Stages (NOT Trimesters) • Embryonic Period (cont) • Organogenesis complete (heart beat) • Skeleton complete • Sexual differentiation between 7-10 weeks • Female unless presence of presence of Gene, SRY, is present on the short arm of the Y chromosome • Differentiation of gonads into testes • 25-50% of all pregnancies terminate spontaneously • Death?
Stages (NOT Trimesters) • Fetal Period • Begins with ossification of the bones and ends with birth • Purpose is for growth (in size and complexity) and connections • 9-38 weeks +/- 2 weeks • 5% born on due date • Less than ¼ conceptions make it to delivery • From last menstrual period→40 weeks • At Birth 106 males to 100 females • But, at 1 year 96 males to 100 females • Page 88-92 of your text- pics BUT DON’T FOCUS ON TRIMESTERS. FOCUS ON PERIODS
Critical Period • What is it? • Embryonic Period??
Critical Period • Embryonic Period • Cell differentiation is occurring, organogenesis, skeleton forming, timing is all genetically programmed.
Development and Growth • Cephalocaudal- Head to toe • Proximal-Distal- Inside to out • At birth approximately 19-21 inches • At birth approximately 6-8 ½ lbs • 7 ½ white> Af Am>Native Americans & Latino Americans
Group Exercise • The mother can feel movement • Implantation occurs • The groundwork for all body structures is laid. • The placenta is connected to the developing organism by the umbilical chord • The baby has reached the age of viability • A mass of cells drifts down and out of the fallopian tubes and attaches itself to the wall of the uterus • The ectoderm, mesoderm, and endoderm are formed • Organs, muscles, and nervous system start to become organized and connected • The embryonic disk (blastocyst) is formed • The developing organism is sensitive to sound and light
Group Exercise • The mother can feel movement (fetal) • Implantation occurs (germinal) • The groundwork for all body structures is laid (embryonic). • The placenta is connected to the developing organism by the umbilical chord (germinal) • The baby has reached the age of viability (fetal) • A mass of cells drifts down and out of the fallopian tubes and attaches itself to the wall of the uterus (germinal) • The ectoderm, mesoderm, and endoderm are formed (embryonic) • Organs, muscles, and nervous system start to become organized and connected (fetal) • The embryonic disk (blastocyst) is formed (germinal) • The developing organism is sensitive to sound and light (fetal)