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Fetal Development

Fetal Development. Prenatal Growth from Conception to Birth. Outline of Topics. Conception •Sperm •Ovum Zygotic Period •Conception - 1st week Embryonic Period •2nd week - 2nd month Early Fetal Period •3rd - 6th month Later Fetal Period •7th - 9th month/birth. Conception Sperm Ovum

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Fetal Development

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  1. Fetal Development Prenatal Growth from Conception to Birth Fetal Development

  2. Outline of Topics Conception•Sperm•Ovum Zygotic Period•Conception - 1st week Embryonic Period•2nd week - 2nd month Early Fetal Period•3rd - 6th month Later Fetal Period•7th - 9th month/birth Fetal Development

  3. Conception Sperm Ovum Zygote Mitosis Embryo Ectoderm Mesoderm Endoderm Congenital Malformations Fetus Key Terms Fetal Development

  4. Conception • Conception occurs when the sperm meets and penetrates the ovum, or egg Fetal Development

  5. Sperm • Sperm is the male reproductive cell Chief Characteristics: • Tightly packed tip (acrosome) that contains 23 chromosomes that carry genetic information • Short neck region • Trail to propel it in its search for the ovum • Microscopic Fetal Development

  6. Sperm Facts • Remains capable of fertilizing egg for 24-48 hours after ejaculation • Of 200 million sperm that enter the vagina, only about 200 survive the journey to the fallopian tubes, where fertilization occurs • Males, at birth, have in their testes those cells that will eventually produce sperm Fetal Development

  7. Ovum (Egg) • The ovum is the female reproductive cell Chief Characteristics: • Round • .01 mm in diameter • Consistency of stiff jelly • Contributes 23 chromosomes Fetal Development

  8. Ovum (Egg) Facts • Females already have 1-2 million primal eggs at birth • Eggs usually fertilized about 12 hours after discharged from the ovary or they die within 12-24 hours Fetal Development

  9. Zygotic Period(Conception - 1st Week) • A zygote is a fertilized egg with 46 chromosomes • Genetic potential determined at this time • Egg is 2.5 mm in diameter at end of 1st week • Mitosis, a process of cell division, occurs during this period Fetal Development

  10. A variety of reasons cause about 50% of fertilized eggs to spontaneously abort during this period Reasons include: • Rejection from the body • Continuance of ingestion of drugs or alcohol by mother (usually unaware of pregnancy at this time) Fetal Development

  11. Embryonic Period(2nd Week - 2nd Month) • The differentiation of embryonic cells into layers marks the beginning of the embryo, or embryonic period • Period when all body systems form • Highly sensitive for susceptibility of congenital malformations, or abnormal conditions with which an infant is born Fetal Development

  12. 3 Layers of Cells in the Embryonic Period: • Ectoderm--sense organs and nervous system develop from this layer • Mesoderm--accounts for formation of muscular, skeletal, circulatory systems • Endoderm--eventually accounts for formation of digestive and glandular systems Fetal Development

  13. Embryonic Period: End of the 1st Month • 1/4 inch (6 mm) long • 1 oz. Weight • Crescent-shaped with small limb buds on sides • Tail with tiny ridges • Rudimentary circulatory system is forming • Heart begins to beat • Growth acceleration Fetal Development

  14. Embryonic Period:End of 2nd Month • 1.5 inches long • Beginning of face, neck, fingers, toes develop • Limb buds lengthen • Muscles enlarge • Sex organs begin to form • Rapid brain development • Embryo is firmly planted on uterine wall and is receiving nourishment from placenta and umbilical cord Fetal Development

  15. Early Fetal Period(3rd - 6th Month) • Period of the fetus begins around the 3rd month and continues until delivery • Movement first becomes apparent to mother at this time • No new anatomical features appear during this period, yet still critical time Fetal Development

  16. Early Fetal Period:3rd Month • Rapid growth, 3 inches long at end of 3rd month • Sexual differentiation continues • Teeth buds emerge • Stomach and kidneys begin to function • Vocal cords appear • Reflex actions felt: opens/closes mouth, clenches fist, sucks thumb Fetal Development

  17. Early Fetal Period:4th Month • Most rapid growth rate (doubles in length to 6-8 inches) • 6 oz. Weight • Hands fully shaped • Bony tissue begins to form Fetal Development

  18. Early Fetal Period:5th Month • Reaches 1/2 of birth length (8-10 inches) • Only 10% of birth weight (1/2 lb.) • Skin, hair, nails appear • Internal organs grow and assume proper anatomical positions • Pigmented hair on head and eyebrows appears Fetal Development

  19. Early Fetal Period:6th Month • 13 inches long • 1 lb. Weight • Eyelids reopen and are completed • Structurally complete but functionally immature Fetal Development

  20. Later Fetal Period(7th - 9th Month/Birth) • From the 7th month to birth, the fetus triples in weight • This is a period of filling out • Preparation for birth Fetal Development

  21. Later Fetal Period:7th Month • A layer of adipose tissue begins to form under skin (serves as both insulator and food supplier) • Rapid 2-4 lb. Weight gain • 14-16 inches long • Fetus is quiet for long periods of time • Brain more active and is increasing control over body systems Fetal Development

  22. Later Fetal Period:8th Month • Fetus is more active (frequent changes in position) • Fatty deposits distributed • 16-18 inches long • 4-6 lbs. Fetal Development

  23. Later Fetal Period:9th Month (Birth) • 19-21 inches long • 6-8 lbs. • Birth process is initiated by placenta and contraction of uterine muscles • Birth generally occurs after week 40 of gestation (normal is 38-42 wks.) Find out more about birth at: Childbirth.org Fetal Development

  24. Review Activity • Now it is time to test your new knowledge on Fetal Development! • Click the arrow above to view and print a “Review Activity” worksheet. • The next five slides will show only pictures and brief descriptions of each of the five periods of development in random order. • Your job is to write down the letter of the slide next to the corresponding stage on the worksheet. • We will go over the answers at the end of the lesson. Good luck! Fetal Development

  25. A. • Movement first becomes apparent to the mother • Fetus begins to suck it’s thumb • Skin, hair, and nails appear • No new anatomical features during this period, yet still a critical time Fetal Development

  26. B. • The sperm meets and penetrates the ovum, or egg Fetal Development

  27. C. • The differentiation of embryonic cells into layers marks the beginning of this period • Highly susceptible period for congenital malformations • Heart begins to beat • Beginnings of face, neck, fingers, toes develop Fetal Development

  28. D. • Genetic potential determined during this period • Mitosis occurs • 50% of fertilized eggs spontaneously abort at this time Fetal Development

  29. E. • Fetus triples in weight • Period of filling out and preparation • Rapid weight gain • More active Fetal Development

  30. Answers: How did you do? Good Job! Fetal Development

  31. References • Dacey, J.S. & Travers, J.F. (2002) Human Development Across the Lifespan. McGraw Hill. New York • Gallahue, D.L. & Ozmun, J.C. (2002) Understanding Motor Development. McGraw Hill. New York • Fetal Development Overview: http://www.w-cpc.org/fetal.html • Conception Icon: http://warmcat.com/milksop/conception.jpg • Ovum Icon: http://www.advancedfertilityservices.com/ • Sperm Icon:http://www.hc.cc.tx.us/san_angelo/departments/general_studies/Biology/Images/sperm.jpg Fetal Development

  32. Review Activity Fetal Development

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