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Human Reproduction

Human Reproduction. How do we produce offspring?. What has to happen…. Each parent-to-be must produce gametes The gametes have to be able to get together The fertilized egg has to have a place to develop The baby must be provided nourishment during fetal development period

mackenzie-gibbs
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Human Reproduction

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  1. Human Reproduction How do we produce offspring?

  2. What has to happen… • Each parent-to-be must produce gametes • The gametes have to be able to get together • The fertilized egg has to have a place to develop • The baby must be provided nourishment during fetal development period • The baby has to have a way to be delivered • The baby must be provided nourishment following birth

  3. How do we produce gametes? • Gametes: haploid sexual reproductive cells—eggs, sperm • Produced through meiosis cell divisions • 2 consecutive cell divisions which take chromosomal count from diploid (2n = 46) to haploid (n =23) • Meiosis • http://www.cellsalive.com/meiosis.htm

  4. Gametogenesis • Spermatogenesis http://www.soc.ucsb.edu/sexinfo/images/12-06-spermatogenesis.gif http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookREPROD.html • Oogenesis • http://www.tarleton.edu/~anatomy/oogenesis.html

  5. Where does gamete formation occur? Male • In testes in scrotal sacs (lowers T) • Meiosis occurs continuously in seminiferous tubules • Sperm stored in epididymis • 100,000,000 sperm per day! http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookREPROD.html http://en.wikibooks.org/wiki/Human_Physiology/The_male_reproductive_system

  6. Where does gamete formation occur? Female • In ovaries • Born with ~500,000 eggs • One egg matured per month, once puberty has been reached • Continues until menopause • http://en.wikipedia.org/wiki/Ovary

  7. When are gametes produced? Male • Continuously once puberty reached • 400 billion + in lifetime • Under control of hormones, particularly LH and testosterone Female • Monthly cycle • http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html • http://www.embryology.ch/anglais/cgametogen/oogenese04.html

  8. Getting gametes together:fertilization Where • Outer third of fallopian tubes (oviducts) http://http://catalog.nucleusinc.com/enlargeexhibit.php?ID=4631 • http://health.howstuffworks.com/adam-200112.htm When • Within 12-18 hours of release of mature egg • If not fertilized, it degenerates and is discarded • Sperm can wait up to 5-6 days for egg (either side of ovulation) • 200-300million sperm per ejaculation (20% defective, 25% die immediately)

  9. Success! (if planned)! Egg fertilized …now what? • Undergoes repeated mitotic divisions to form blastocyst • Must reach this stage when entering uterus to be able to implant in uterine wall • http://www.biology.iupui.edu/biocourses/n100/2k4ch39repronotes.html • http://embryo.soad.umich.edu/carnStages/carnStages.htmlhttp://embryology.med.unsw.edu.au/

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