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Chapter 3: Prenatal Development and Birth. Prenatal Development. By Kati Tumaneng (for Drs. Cook & Cook). Prenatal Development. Development of an organism that occurs before (“pre”) its birth (“natal”). Conception. Ovulation – Release of an egg (ovum) from the female ovary; every 28 days.
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Chapter 3: Prenatal Development and Birth Prenatal Development By Kati Tumaneng (for Drs. Cook & Cook)
Prenatal Development • Development of an organism that occurs before (“pre”) its birth (“natal”)
Conception • Ovulation – Release of an egg (ovum) from the female ovary; every 28 days. • Fertilization – sperm cell combines with ovum yielding one fertilized cell with a unique combination of genes along 46 chromosomes. • Differentiation – Process that occurs during cell division in which each new cell, as it divides, is committed to becoming a particular structure and serving a particular function.
Stages of Prenatal Development • Germinal Stage – conception to week 2 • Embryonic Stage – weeks 3-8 • Fetal Stage – week 8 to birth (38-40 weeks)
Germinal Stage • Begins with conception in fallopian tube. • First cell division at 12 hours. • 3-4 days – Zygote enters uterus; first cell differentiation leads to trophoblast and blastocyst. • 8-12 days – Implantation of zygote in uterine lining. • Failure to implant ends in pregnancy loss.
Embryonic Stage • Cephalocaudal pattern – Areas in head and upper body tend to form and grow before the areas in the lower body. • Proximodistal Pattern – Areas closer to center of the body tend to form and grow before the areas toward the extremities. • Critical Periods – Segments of time when structures are first forming and most vulnerable to damage. • 14 days – Blastocyst differentiates to form ectoderm, mesoderm, and endoderm. • 3 weeks – Spinal cord and brain begin to form. • 3-4 weeks – Placenta and umbilical cord form.
Embryonic Stage • 4 weeks – Eyes begin to form, heart flutters, arm buds appear. • 5 weeks – Arms developed, leg buds appear. • 8 weeks – Organogenesis (organ formation) complete; all major organs and structures have begun. Embryo weighs 1/30th of one once. • Failure to differentiate may lead to miscarriage. Embryo: www.visembryo.com/
Fetal Stage • 8-12 weeks – First arm and leg movements, not detected by mother; first reflexes appear; sex can be detected with ultrasound. • 17-20 weeks – Mother feels fetal movements; heartbeat can be heard with stethoscope. • 24 weeks – Fat begins to form; rapid weight gain begins. • 26-28 weeks – Lungs mature enough to support breathing; fetus weighs approx. 2 lbs. • 38-40 weeks – Normal gestational age for birth; newborn weighs 7.5 lbs. on average.
Fetal Stage 3 months 5 months
Image on Slide 2: from Cook, J. L., & Cook, G. (2005). Child development: Principles and perspectives (1st ed.) (p. 88). Boston: Allyn and Bacon. • Female Reproductive System on Slide 4: from Cook, J. L., & Cook, G. (2005). Child development: Principles and perspectives (1st ed.) (p. 89). Boston: Allyn and Bacon. • Embryo on Slide 9: from Cook, J. L., & Cook, G. (2005). Child development: Principles and perspectives (1st ed.) (p. 92). Boston: Allyn and Bacon. • Fetus on Slide 11: from Cook, J. L., & Cook, G. (2005). Child development: Principles and perspectives (1st ed.) (p. 93). Boston: Allyn and Bacon. • All other images retrieved from Microsoft PowerPoint Clip Art.
