A B C D E F G H

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How a single fertilized egg develops into a new organism

 How long does human gestation take? (a baby to develop from fertilized egg to birth)  Which cell process occurs to allow a fertilized egg to grow?  What are the differences between a zygote, an embryo and a fetus?  What is the importance of implantation in a woman’s pregnancy?

 Human Gestation requires about 9 months from conception  Or 40 weeks from the first day of the woman’s last menstruation date  Stages of development are divided into three trimesters  The first trimester is often the most crucial:  The fundamental structures are formed during the first three months

1. Fertilization 2. Implantation 3. Gastrulation 4. Neurulation

 The union of a sperm cell and egg cell  Forms a zygote

The zona pellucida is a thick barrier of glycoproteins that surround and protect the egg. Sperm must penetrate this barrier and bind to receptor sites on the egg’s surface before its nucleus can enter the egg. The acrosome of the sperm cell contains enzymes that will help digest through the protective layers of the egg. The membrane of the sperm will then fuse with the membrane of the egg—if the membrane receptors match up! The zona reaction prevents multiple sperm from entering the egg. Once a sperm cell binds with the egg, the zona pellucida hardens like concrete freezing loser sperm in their tracks! Watch it!

A scanning electron micrograph of a human embryo at the eight-cell stage (day three). After fert., before implantation... a. The zygote begins to divide -First few mitotic cell divisions are called cleavage b. Soon a solid ball of cells is formed, called a.... Image from:

2. After fert., before implantation... a. The zygote begins to divide i. First few mitotic cell divisions are called cleavage b. Soon a solid ball of cells is formed, called a.... morula c. Next, the morula will change into a fluid filled ball of cells, called a... Image and video from:

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Implantation Embryo

e. c. f. b. d. a. Label the stages of the development after ovulation.

 When the cells of the blastocyst roll inward to form three layers of cells  Embryo is now a…

 Endoderm  Endoderm: Innermost layer (digestive system)  Mesoderm  Mesoderm: Middle layer (internal organs and muscle)  Ectoderm  Ectoderm: Outer-most layer (skin and nervous system)

a. Endoderm Inner-most layer (digestive tract) b. Mesoderm Middle layer (internal organs) c. Ectoderm Outer-most layer (skin and nervous system) The formation of 3 germ layers Images from: steps-for-beautiful-glowing-skin-cleanse.html;

 Stem Cells: unspecialized cells that have the potential to differentiate into any tissue.  Cell Differentiation: When stem cells are given specific functions—growth factors and hormones tell them when and how to change.

 Once gastrulation is complete, the nervous system begins to develop  Cells of the ectoderm gather and form a tube =qisrNX3QjUg

ZygoteMorulaBlastulaGastrula

Homework: NONE DO NOW:

 Tissues formed outside the baby to protect and nourish the developing embryo

1. Amnion : forms the amniotic sac— fluid filled to cushion embryo  The “water” 2. Chorion : forms the placenta— combines with the uterus tissues.

AA maternal-fetal organ BBegins developing at implantation EExchanges nutrients, gases, and waste products DDrugs and alcohol have been known to cross the placenta.

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Also include: Zygotelocations in body Cleavage3 germ layers Differentiationplacenta development 1.FERTILIZATION Morula Blastocyst 2.IMPLANTATION3.GASTRULATION4.NEURULATION

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 Labor : Hormone levels of Estrogen and Oxytocin increase—cause contractions of uterus  Positive Feedback: presence of hormones cause even more hormones to be released  Yay! Delivery of baby!  Afterbirth: Delivery of placenta  Hormones adjust, Oxytocin allows production of breastmilk

1. What does “differentiation” mean? 2. From which germ layers do the brain, the heart and the small intestines form? 3. Which tissues (membranes) become the amniotic sac and the placenta? 4. When is an embryo considered a fetus? 5. How many weeks is considered “Full Term?”

 ns/lifecycle/index.asp ns/lifecycle/index.asp  Site for possible student research  htm htm

 Poem, story, or song  Track the life of a cell from fertilization to birth.  Be sure to include vocabulary covered in class!!  Must include ONE PICTURE/DIAGRAM  Can be hand-drawn or printed out on assignment