Human Development


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…


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  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

gastrulation in primitive chordates ectoderm endoderm mesoderm 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 2 nd trimesters just growing & 3 rd …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