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Fetal Development

Fetal Development. Create a timeline outlining the stages of human development Label a diagram of the stages of human development. KEY WORDS Implantation Embryo Trimester Fetus . Haploid gametes contain 23 total chromosomes – 22 regular chromosomes and 1 sex chromosome .

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Fetal Development

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  1. Fetal Development

  2. Create a timeline outlining the stages of human development • Label a diagram of the stages of human development KEY WORDS Implantation Embryo Trimester Fetus

  3. Haploidgametes contain 23 total chromosomes – 22 regular chromosomes and 1 sex chromosome. • Two types of sex chromosomes- called X and Y • Sperm can have eitheroneX ORone Y. • Eggsalways have oneX chromosome. • Everymale body cell has one X and one Y. • Everyfemale body cell has two X.

  4. MEIOSIS– MALES DIPLOID 2n x x x x y y y y 46 Chromosomes x y HAPLOID 1n Female sperm Male sperm

  5. MEIOSIS– FEMALES DIPLOID 2n x x x x x x x x 46 Chromosomes x x HAPLOID 1n Female egg

  6. x x x x y x y x Female zygote Male zygote

  7. Egg and sperm meet in the oviduct - fertilization. • Sex is determined by the male at fertilization. • Nuclei are joined to produce a single diploid cellcalled a zygote. • 2 stages of development - fertilization to birth: • Embryostage: first eight weeks. • Fetusstage: from eight weeks to birth.

  8. Embryo Stage • Zygote implants in endometrial lining and begins to • grow (divide) by mitosis for first eight weeks. • Once implanted – called an embryo. Cleavage: mitotic divisions begin, changing zygote to a multicellularembryo.

  9. 2. Fetus Stage Developing embryo forms bone cells around the ninth week of pregnancy. Once bone forms - called a fetus until born. Placenta - exchanges waste and nutrients through umbilical cord. Amnion – protective sac filled with fluid.

  10. Pregnancy can also be divided in 3 trimesters: • 1st trimester – conception to 3rd month • development of all body systems and organs. • sex can be determined • embryo movements not perceptible to the woman. • she may not know that she is pregnant • At end - fetusweighs28 grams, 7.5 mm long. • fetus is particularly sensitive to alcohol, smoking and other drugs.

  11. 1st trimester

  12. 2nd trimester – 4th to 6th months • period of rapid and continuous growth. • Only brain and lungs still developing. • embryo movements can be felt. • At end - fetus weighs650 grams, 30 cm long. • If born prematurely: • Might survive with great • medical assistance. • Most do not survive.

  13. 2nd trimester

  14. 3rd trimester – 7th to 9th (birth) month • fetus kicks, stretches and moves freely. • Eyes sense light, fingerprints have formed. • At end – fetus weighs3300 grams, 35 cmlong. • Dangers include complications during delivery and lifestyle choices.

  15. 3rd trimester

  16. And then, before you know it...

  17. Zygote at fertilization. • Embryo at implantation to endometrium. • Fetus after bone development. • Baby at birth. • Fertilization to birth can be separated into 2 stages – embryo and fetus. • Pregnancy can be separated into 3 trimester.

  18. Homologous chromosomes are similar but NOT identical. Homologous means that the chromosomes contain the same types of genes. Gene - piece of DNA with instructions for a specific trait – hair colour, height, eye colour…

  19. A diploid cell will contain two variations of each gene. 1 – mom 1 – dad

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