prenatal stage of development
DESCRIPTION
TRANSCRIPT
Chapter 4: Prenatal Development and BirthImportance:1. Hereditary endowment is fixed2. Favorable conditions in the
mother’s body3. Proportionally greater growth and
development takes place4. Influence of significant people
Major Phases of Prenatal DevelopmentScientific term used to describe baby-to-be
Major developments in each period
I. Germinal Period
Period of the Zygote
8-14 days or Weeks 1-2
Conception until implantation
Germinal Period
Germinal Period
Germinal Phase
Germinal Phase
Germinal Phase
Germinal Period
Germinal Period
Germinal Period
Germinal Period
Germinal Period
Implantation
Implantation
II. Period of the Embryo When zygote is completely embedded in the uterine wall
Body structures and internal organs develop
3 layers begin to form in the embryo:1. Ectoderm: hair, skin, nervous system2. Mesoderm: muscles, bones, circulatory
system3. Endoderm: digestive system and lungs
Period of the Embryo
Embryo rests in a sac called amnion amniotic fluid shock-absorbing protection; constant
temperatureChorion: 2nd membrane after about a month of development; helps form the placenta
Weeks 3-8
Period of the Embryo
3-week old: salamander8-week old: most of the organs found in a mature human are in place; visible eyes, jaw, arms and legs
About 1 inch long and weighs only a fraction of an ounce
Period of the Embryo
Period of the Embryo
Period of the Embryo
Period of the Embryo
Period of the Embryo
III. Period of the Fetus
Weeks 9-38 Much larger and bodily systems begin to work (respiration, digestion, vision)
By 22-28 weeks, most systems function well enough that a fetus has a chance to survive
age of viability
Period of the Fetus
Distinct baby-like lookMay still have trouble breathing and cannot regulate body temperature yet
Fetus starts to behave as movements become obvious
Begins to hear sounds, taste different flavors
Period of the Fetus: 3rd Month
Period of the Fetus: 4th Month
Period of the Fetus:5th Month
Period of the Fetus:6th Month
Period of the Fetus:7th Month
Period of the Fetus:8th Month
Period of the Fetus:9th Month
Changes in a pregnant woman’s body