End Show Slide 1 of 47 Warm-Up #19 Answer questions #1-6 on Text 1024 Section Assessment. Answer in complete sentences. Copyright Pearson Prentice Hall

End Show Slide 2 of 47 Copyright Pearson Prentice Hall 39–4 Fertilization and Development

End Show Slide 3 of 47 Objectives 1.Describe fertilization 2.Identify the stages of early development 3.Describe the function of the placenta Copyright Pearson Prentice Hall

End Show Slide 4 of 47 Fertilization The process of a sperm joining an egg is called fertilization. It occurs in the oviduct. If an egg is fertilized, a zygote forms and begins to undergo cleavage, also known as cell division (mitosis), as it travels to the uterus. As each cell divides, the number of cells doubles. Four days after fertilization, the embryo is a solid ball of about 64 cells called a morula. As the morula grows, a cavity forms in the center—this hollow structure is called a blasotcyst. Copyright Pearson Prentice Hall

End Show Slide 5 of 47 39–4 Fertilization and Development Copyright Pearson Prentice Hall Fertilization ??

End Show 39–4 Fertilization and Development Slide 6 of 47 Copyright Pearson Prentice Hall Early Development The stages of early development include implantation, gastrulation, and neurulation.

End Show Slide 7 of 47 Implantation About six or seven days after fertilization, the blastocyst attaches itself to the wall of the uterus. The embryo secretes enzymes that digest a path into the soft tissue. A cluster of cells, known as the inner cell mass, develops within the inner cavity of the blastocyst. The embryo will develop from these cells, while the other cells will differentiate into tissues that surround the embryo. Differentiation is the specialization of cells to develop into specific tissues and structures. Copyright Pearson Prentice Hall

End Show Slide 8 of 47 39–4 Fertilization and Development Copyright Pearson Prentice Hall Blastocyst Formation The First Two Weeks

End Show Slide 9 of 47 Copyright Pearson Prentice Hall Development is.. Cell division Growth Differentiation From embryonic tissues to Specialized tissues & organs

End Show 39–4 Fertilization and Development Slide 10 of 47 Copyright Pearson Prentice Hall Early Development Implantation & Differentiation Implantation

End Show 39–4 Fertilization and Development Slide 11 of 47 Copyright Pearson Prentice Hall Early Development Gastrulation The inner cell mass of the blastocyst gradually sorts itself into two layers, which then give rise to a third layer. Early Gastrulation Amniotic cavity Primitive streak Ectoderm Endoderm Mesoderm

End Show 39–4 Fertilization and Development Slide 12 of 47 Copyright Pearson Prentice Hall Early Development 3 Germ Layers The ectoderm develops into the skin and nervous system. The endoderm forms the digestive lining and organs. Mesoderm cells differentiate into internal tissues and organs.

End Show 39–4 Fertilization and Development Slide 13 of 47 Copyright Pearson Prentice Hall Early Development Neurulation the development of the nervous system.

End Show Slide 14 of 47 39–4 Fertilization and Development Copyright Pearson Prentice Hall Neural crest Neural fold Notochord Early Development

End Show Slide 15 of 47 39–4 Fertilization and Development Copyright Pearson Prentice Hall Neural crest Neural tube Ectoderm Notochord Early Development Gradually, these folds move together to create a neural tube from which the spinal cord and the nervous system develop. Nova - Gastrulation

End Show Slide 16 of 47 39–4 Fertilization and Development Copyright Pearson Prentice Hall Morphing Embryos

End Show 39–4 Fertilization and Development Slide 17 of 47 Copyright Pearson Prentice Hall Early Development Extraembryonic Membranes As the embryo develops, membranes form to protect and nourish the embryo. Two of these membranes are the amnion and the chorion.

End Show 39–4 Fertilization and Development Slide 18 of 47 Copyright Pearson Prentice Hall Early Development The amnion develops into a fluid-filled amniotic sac, which cushions and protects the developing embryo. Uterus Amnion Fetus Amniotic sac Placenta Umbilical cord

End Show 39–4 Fertilization and Development Slide 19 of 47 Copyright Pearson Prentice Hall Fingerlike projections called chorionic villi form on the outer surface of the chorion and extend into the uterine lining. Early Development Fetal portion of placenta Maternal portion of placenta Maternal artery Maternal vein Umbilical vein Umbilical arteries Umbilical cord Amnion Chorionic villus

End Show 39–4 Fertilization and Development Slide 20 of 47 The Placenta The placenta is the connection between the mother and the developing embryo or fetus. It is through the placenta that the embryo gets its oxygen and nutrients and excretes its waste products. Copyright Pearson Prentice Hall

End Show 39–4 Fertilization and Development Slide 21 of 47 The Placental Barrier The placenta acts as a barrier to some harmful or disease-causing agents. Other disease-causing agents can penetrate the placenta and affect development—AIDS and German measles, for example. Drugs, including alcohol, medications and other addictive substances cause also cross the placenta and cause damage to the developing fetus. Copyright Pearson Prentice Hall

End Show 39–4 Fertilization and Development Slide 22 of 47 Copyright Pearson Prentice Hall

End Show 39–4 Fertilization and Development Slide 23 of 47 Copyright Pearson Prentice Hall Early Development Fetal Development (after 8+ weeks). After three months (the first trimester), most major organs and tissues are formed. During this time, the umbilical cord also forms. The umbilical cord connects the fetus to the placenta. Placenta & Fetal DevelopmentFetal Development

End Show 39–4 Fertilization and Development Slide 24 of 47 Copyright Pearson Prentice Hall Later Development 4–6 months after fertilization (the second trimester): The heart can be heard with a stethoscope. Bone replaces cartilage that forms the early skeleton. A layer of soft hair grows over the fetus’s skin. The fetus grows and the mother can feel it moving.

End Show 39–4 Fertilization and Development Slide 25 of 47 Copyright Pearson Prentice Hall Later Development During the last three months (the third trimester), the organ systems mature. The fetus doubles in mass. It can now regulate its body temperature. The central nervous system and lungs completely develop.

End Show 39–4 Fertilization and Development Slide 26 of 47 Copyright Pearson Prentice Hall Childbirth About nine months after fertilization, the fetus is ready for birth. A complex set of factors affects the onset of childbirth.

End Show 39–4 Fertilization and Development Slide 27 of 47 Copyright Pearson Prentice Hall Childbirth The mother’s posterior pituitary gland releases the hormone oxytocin, which affects involuntary muscles in the uterine wall. These muscles begin rhythmic contractions known as labor. The contractions become more frequent and more powerful.

End Show 39–4 Fertilization and Development Slide 28 of 47 Copyright Pearson Prentice Hall Childbirth The opening of the cervix expands until it is large enough for the head of the baby to pass through it. At some point, the amniotic sac breaks, and the fluid it contains rushes out of the vagina. Contractions force the baby out through the vagina.

End Show 39–4 Fertilization and Development Slide 29 of 47 Copyright Pearson Prentice Hall Childbirth The baby now begins an independent existence. Its systems quickly adapt to life outside the uterus, supplying its own oxygen, excreting waste on its own, and maintaining its own body temperature.

End Show 39–4 Fertilization and Development Slide 30 of 47 SUMMARY What is fertilization? What is a morula? What is a blastocyst? What are the early stages of development? What are the three germ layers? What are the extraembryonic tissues? What is the function of the placenta? Copyright Pearson Prentice Hall

End Show 39–4 Fertilization and Development Slide 31 of 47 Study Guide page 60. Copyright Pearson Prentice Hall

End Show 39–4 Fertilization and Development Slide 32 of 47 Homework STUDY FOR TEST Homework Packets Warm-Ups #18-20 Study Guide Extra Credit Article Copyright Pearson Prentice Hall