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[01:830:331] - Final Exam Guide - Comprehensive Notes for the exam (55 pages long!)

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Linnea Dickinson
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Prenatal Development: 3 Stages
Guidepost 1: What are the three stages of prenatal development, and what happens during
each stage?
Early signs and symptoms of pregnancy
Tender/swollen breasts or nipples, fatigue; need to take extra naps, slight
bleeding or cramping, nausea with/out vomiting, food cravings, frequent
urination, frequent, mild headaches, constipation, mood swings, faintness and
dizziness, raised basal body temperature
Gestation: period between conception and birth
37-41 weeks
Gestational age: usually dated from the first day of an expectant mother’s last menstrual
Prenatal development takes place in 3 stages: germinal, embryonic, and fetal
Fertilized ovum grows into an embryo and then a fetus
Cephalocaudal principle: dictates that development proceeds from the head to the lower
part of the trunk
Latin meaning “head to tail”
Embryo’s head, brain, and eyes develop earliest and are disproportionately large
until the other parts catch up
Proximodistal principle: development proceeds from parts near the center of the body to
outer ones
Latin meaning “near to far”
Embryo’s head and trunk develop before limps, and the arms and legs before the
fingers & toes
Germinal Stage (fertilization 2 weeks)
Germinal stage: first 2 weeks after fertilization
Zygote divides, becomes more complex, implanted in uterus wall
Within 36 hours of fertilization, the zygote enters mitosis
During ^ travels down the fallopian tube and changes into a blastocyst:
fluid-filled sphere which floats freely in the uterus until implantation: it
implants itself in the uterine wall @/around day 6
Embryonic disk: thickened cell mass from with the embryo begins to develop
Already differentiating into two layers
Ectoderm: outer layer skin, nails, hair, teeth, sensory organs, nervous
system (brain and spinal cord)
Endoderm: inner layer becomes digestive system, liver, pancreas,
salivary glands, and respiratory system
Middle layer (mesoderm): develops into inner layer of skin, muscles,
skeleton, and excretory and circulatory systems
Embryonic Stage (2-8 weeks)
Embryonic stage: 2nd stage of prenatal development
organs and major body systems (respiratory, digestive, and nervous)
develop rapidly
■ Organogenesis
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