week 10. Early Human Development. Reproductive System

Prenatal Development Embryonic development fertilization - 8 weeks Fetal development 9 weeks - birth Postnatal Development gestation time period from fertilization to birth = gestation

Oocyte at Ovulation Oocyte (egg) released from ovary in Metaphase II. Oocyte (egg) released from ovary in Metaphase II. Occurs on Day 14 or 15 during menstrual cycle. Occurs on Day 14 or 15 during menstrual cycle. Spike in LH & FSH Spike in LH & FSH Travels down fallopian tube. Travels down fallopian tube. Fig 28-1

Fertilization Taking place in ?? Viability of gametes: –Oocyte –Oocyte h –Sperm –Sperm h During Menstrual Cycle, Uterus wall becomes thicker. Menses won’t occur when fertilized egg, successfully, attaches to thickened uterine wall.

The first Trimester weeks 1-12; fetus size ~ 3 in.; weight ~ 14 g Cleavage Cleavage Implantation Implantation Placenta Placenta Embryogenesis Embryogenesis Basic organ plan and tissues laid out – most susceptible to damage or disorganization at this time

Blastocyst with blastocoele cavity Morula solid ball of cellsCleavage Early division of zygote into multiple cells without increase in size, partitions contents Zygote

Day 10 Embryo completely embedded in uterus Blastula forms first. Pluripotent Stem cells present!! Placenta begins to form.

Gastrulation: 3 Germ Layers Formed Ectoderm Nervous system SkinEndoderm Digestive System Mesoderm Heart, Lungs, Muscles day 12:

Play-Doh Embryo Development Lab Mr. Gairani

Zygote Totipotent Totipotent Gives rise to every cell type in the body Gives rise to every cell type in the body Plancenta Plancenta

Morula Cells divide my mitosis Cells divide my mitosis Totipotent Totipotent Identical twins arise from this stage Identical twins arise from this stage

Blastula 3 rd day after conception 3 rd day after conception Hollow ball of cells Hollow ball of cells Outer layer becomes the placenta Outer layer becomes the placenta Inner cell mass are embryonic stem cells!! Inner cell mass are embryonic stem cells!! Stem cell lines Stem cell lines Pluripotent Pluripotent

Gastrula 14 days after fertilization 14 days after fertilization 3 germ layers 3 germ layers –Endoderm –Mesoderm –Ectoderm Multipotent Multipotent