Prenatal Development

1. Prenatal Development OBJECTIVES You will be able to…. Investigate the 3 periods of prenatal development Identify and describe the major components of the 3 periods of prenatal development

2. The Germinal Period: The First 14 Days • The zygote travels down the fallopian tube • The zygote duplicates and multiplies • When it grows to about 100 cells it is called a blastocyst • At about a week the 100 cells in the blastocystseparate into two distinct masses • The outer cells become the placenta • The inner cells form a nucleus that will be the embryo

3. The Germinal Period: The First 14 Days • When the blastocyst embeds itself into the endometrium of the uterus, implantation has occurred. • Pregnancy begins at conception (joining of sperm and egg) • The organism will not become an embryo until implantation is successful. • About ½ of all conceptions fail to grow or implant properly and this do not survive the germinal period

4. The Germinal Period: The First 14 Days

5. The Germinal Period: The First 14 Days

6. The Germinal Period: The First 14 Days

7. The Embryonic Period: From the 3rd through 8th week • The formless mass of cells becomes a distinct being • Embryo- the developing human from day 14 – day 56 • A thin line ( called the primitive streak) appears down the middle of the embryo • This will become the neural tube at day 22 and will eventually develop into the central nervous system, brain and spinal column

8. Think, Pair, Share • Why do you think the central nervous system, brain, and spinal column are the first things to form?

9. The Embryonic Period: From the 3rd through 8th week • The head appears the fourth week as eyes, ears, nose and mouth start to form • A tiny blood vessel that will become the heart beings to pulsate around the fourth week • Arm and leg buds emerge around the fifth week • Upper arms, then forearms, palms and webbed fingers grow • Legs, knees, feet and webbed toes can be seen a few days later • Each have the beginning of a skeletal structure • Day 52-54 the fingers and toes separate

10. The Embryonic Period: From the 3rd through 8th week • The head develops first in a cephalocaudalpattern- Head to Tail • The extremities (arms and legs) grow in a proximodistalpattern- Near to Far • At the end of 8 weeks, embryo weighs about 1 gram and is 1 inch long. • It has all basic organs and body parts (except sex organs) • It’s movements are frequent about 150 times per hour but such movement is random and imperceptible.

11. The Embryonic Period: From the 3rd through 8th week

12. The Embryonic Period: From the 3rd through 8th week

13. The Embryonic Period: From the 3rd through 8th week

14. The Embryonic Period: From the 3rd through 8th week

15. The Fetal Period: From the 9th Week Until Birth • The organism is called a Fetus from the ninth week after conception until birth • If the fetus is a male (XY) the SRY gene triggers the development of male sexual organs, otherwise female organs develop • The male fetus experiences a rush of the hormone testosterone • By the end of the third month, the sex organs are visible via ultrasound (sonogram) which uses sound waves to instead of radiation

16. Male genderWith the male fetus, the genital tubercle usually creates an angle of greater than 30° with the lower part of the spine.

17. Female genderIn the female fetuses, the genital tubercle protrudes in the same direction as the lower portion of the spine with an angle of less than 30° relative to the backbone.

18. The Fetal Period: From the 9th Week Until Birth • The head of the fetus comprises about half of the total body weight • Facial features appear human in placement and shape by the third month • In the fourth, fifth, and sixth months the heartbeat becomes stronger • Digestive and excretory systems develop • Fingernails, toenails and teeth buds form and hair starts to grow (even eyelashes!)

19. 14 week fetus Ultrasound • http://www.youtube.com/watch?v=WLXpXYo7arM&feature=related

20. The Fetal Period: From the 9th Week Until Birth • Age of Viability- When a pre-term newborn can survive outside the womb • 22 weeks is the current age of viability- with intensive medical treatment • Even with the most advanced technology, life cannot be maintained without some brain response. • As the brain matures and axons connect, the organs of the body begin to work in harmony

21. The Fetal Period: From the 9th Week Until Birth • The brain increases about six times in size • Half a million brain cells are created per minute • Might be the most important and crucial period for brain development • The entire central nervous system becomes responsive during mid-pregnancy (4-6 months) • Basic body functions like breathing, sucking, are regulated

22. The Fetal Period: From the 9th Week Until Birth Age of Viability – Only means life outside the womb is possible… Intensive newborn care is necessary to keep the neonate alive, healthy, and free of disabilities.

23. The Fetal Period: From the 9th Week Until Birth • The last three months of prenatal life, th e lungs begin to expand and contract • The fetus begins to exercise breathign muscles by swallowing amniotic fluid as a substitute for air • Heart valves mature • Arteries and veins throughout the body also mature

24. World’s Tiniest Babieshttp://www.cbsnews.com/2300-204_162-10010544.html

25. The Fetal Period: From the 9th Week Until Birth • The relationship between the mother and child intensifies during the final three months • The mother’s sounds, tastes for food, and behavior patterns become part of the fetal consciousness • Auditory communication from mother to child begins at the 28th week and improves each week as fetal hearing becomes more acute

26. The Fetal Period: From the 9th Week Until Birth • The fetus startles and kicks at loud noises • Listens to mother’s voice and heartbeat • Is comforted by rhythmic music and movement • If the mother is fearful or anxious, the fetal heart beats faster and body movements increase.