Human Development

27.9 Relate the structure of sperm to its role in fertilization. Describe the mechanisms that prevent more than one sperm from fertilizing an egg and that prevent hybridization between different species.

Describe this picture…

27. 10. Describe the process and results of cleavage 27.10 Describe the process and results of cleavage. Explain how identical and nonidentical twins form.

Describe this picture…

27.11 Describe the process of gastrulation and the resulting arrangement of the embryo.

Gastrulation Establish 3 cell layers ectoderm mesoderm endoderm gastrulation in primitive chordates Establish 3 cell layers ectoderm outer body tissues skin, nails, teeth nerves, eyes, lining of mouth mesoderm middle tissues blood & lymph, bone & notochord, muscle excretory & reproductive systems endoderm inner lining digestive system lining of respiratory, excretory & reproductive systems ectoderm mesoderm endoderm protostome vs. deuterostome

27.12 Explain how organs form after the development of a gastrula.

Explain how changes in cell shape, induction, cell migration, and apoptosis contribute to development

Pattern formation during embryonic development is controlled by ancient genes

27.15 Describe the initial embryonic stages and the formation and functions of the extraembryonic membranes in humans.

Human fetal development 4 weeks 5 weeks

Human fetal development 10 weeks

Human fetal development 14 weeks 20 weeks

Human fetal development The fetus just spends much of the 2nd & 3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid Week 20

Human fetal development 24 weeks (6 months; 2nd trimester) fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

Human fetal development 30 weeks (7.5 months) umbilical cord

Getting crowded in there!! 32 weeks (8 months) The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming