How do we produce offspring?

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

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.cellsaliv

e.com/meiosis.htm

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.ta

rleton.edu/~anatomy/oogenesis.html

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.htmlhttp://en.wikibooks.org/wiki/Human_Physiology/The_male_reproductive_system

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

Male

Continuously once puberty reached

400 billion + in lifetime

Under control of hormones, particularly LH and testosterone

Female Monthly cycle http://www.sumana

sinc.com/webcontent/animations/content/ovarianuterine.html

http://www.embryology.ch/anglais/cgametogen/oogenese04.html

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)

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.html http://embryology.med.unsw.edu.au/