Lesson 1 The Beginning of the Life Cycle

Lesson 1 The Beginning of the Life Cycle Did you know that your body is made of trillions of cells? Your heart, lungs, skin, bones, and other body organs all began as a single cell that is smaller than the period at the end of this sentence.

Lesson 1 Lesson Objectives In this lesson, you will learn to: • Identify the stages of fetal development from conception through pregnancy and birth • Explain how a pregnant female transfers nutrients and other substances to her fetus

Lesson 1 Conception and Implantation Fertilization • The entire complex human body begins as one microscopic cell that is formed by fertilization. • The resulting cell is called a zygote. • Within a day after the zygote forms, it begins dividing as it travels down the fallopian tube.

Lesson 1 Conception and Implantation • By the time it reaches the uterus, the zygote has divided many times to form a cluster of cells. • After implantation of the zygote, the cluster of cells is known as an embryo. Click image to view movie.

Lesson 1 Conception and Implantation Embryo Click image to view movie.

Lesson 1 Embryonic Growth Structures Formed During Embryonic Growth • As the embryo grows, its cells continue to divide, forming three tissue layers that later become various body systems. • During this time, two important structures form outside the embryo: 1. Amniotic sac 2. Umbilical cord

Lesson 1 Embryonic Growth Substances Passed to the Embryo • Although the blood supply of the mother and the developing embryo are kept separate, materials diffuse from one blood supply to the other through the umbilical cord. • Nutrients and oxygen pass from the mother’s blood to the embryo, and wastes from the embryo diffuse into the mother’s blood. • If a pregnant female uses harmful substances, they can cross the placenta and harm the developing embryo.

Lesson 1 Fetal Development Trimesters • The time from conception to birth is usually about nine full months. • These nine months are divided into three 3 -month periods called trimesters. • During the period of growth in the uterus, the fetus develops in preparation for living outside the mother’s body.

Lesson 1 Fetal Development First Trimester – 0 -14 Weeks In the first trimester, the fetus develops a human profile. By week 12 the fetus makes crying motions but no sound and may suck its thumb.

Lesson 1 Fetal Development Second Trimester – 15 -28 Weeks In the second trimester, the fetus can hear conversations and has a regular cycle of waking and sleeping. Weight increases rapidly.

Lesson 1 Fetal Development Third Trimester – 29 Weeks to Birth In the third trimester, the fetus uses all five senses and begins to pass water from the bladder.

Lesson 1 Stages of Birth Changes Experienced During Labor • Many females experience weak, irregular muscular contractions of the uterus for weeks or even months before the baby is born. • As the time approaches for the baby to be born, however, these contractions become regular, stronger, and closer together. • The stronger contractions induce labor.

Lesson 1 Stages of Labor Stage 1: Dilation Stage 2: Passage through birth canal Stage 3: Afterbirth Stages of Birth

Lesson 1 Quick Review Choose the appropriate option. Q. The union of a male sperm cell and a female egg cell is called _____. 1. zygote 2. implantation 3. fertilization 4. labor

Lesson 1 Quick Review - Answer A. 3. fertilization The union of a male sperm cell and a female egg cell is called fertilization. Click Next to attempt another question.

Lesson Quick Review 1 Choose the appropriate option. Q. The zygote attaches to the uterine wall in the process called _____. 1. labor 2. implantation 3. fertilization 4. cell division

Lesson 1 Quick Review - Answer A. 2. implantation The zygote attaches to the uterine wall in the process called implantation. Click Next to attempt another question.

Lesson 1 Quick Review Choose the appropriate option. Q. In a developing fetus, nutrients from the mother pass to the fetus through the blood in the umbilical cord. True False

Lesson 1 Quick Review - Answer A. True. In a developing fetus, nutrients from the mother pass to the fetus through the blood in the umbilical cord. Click Next to attempt another question.

Lesson 1 Quick Review Choose the appropriate option. Q. Harmful substances taken in by a pregnant female can be transferred to a developing fetus, but the fetus is too small to be affected negatively. True False

Lesson 1 Quick Review - Answer A. False. Harmful substances taken in by a pregnant female can be transferred to a developing fetus, and the fetus can be affected negatively. Click Next to attempt another question.

Lesson 1 End of Lesson 1 Click Home to view the Main menu.

Lesson Quick Review - Answer 1 A. Correct! The union of a male sperm cell and a female egg cell is called fertilization. Click Next to attempt another question.

Lesson 1 Quick Review - Answer You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

Lesson Quick Review - Answer 1 A. Correct! The zygote attaches to the uterine wall in the process called implantation. Click Next to attempt another question.

Lesson 1 Quick Review - Answer You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

Lesson 1 Stages of Labor Stage 1: Dilation Stage 2: Passage through birth canal Stage 3: Afterbirth Stages of Birth

Lesson 1 Stages of Labor Stage 1: Dilation Stage 2: Passage through birth canal Stage 3: Afterbirth Stages of Birth

Lesson 1 Conception and Implantation Fertilization • The entire complex human body begins as one microscopic cell that is formed by fertilization. • The resulting cell is called a zygote. Fertilization is the unionitof a • Within a day after the zygote forms, begins dividing as it travels down the fallopian male tube. sperm cell and a female egg cell.

Lesson 1 Conception and Implantation • By the time it reaches the uterus, the zygote has divided many times to form a cluster of cells. • After implantation of the zygote, the cluster of cells is known as an Implantation embryo. is the attachment Click image to view movie. of zygote to the uterine wall.

Lesson 1 Conception and Implantation • By the time it reaches the uterus, the zygote has divided many times to form a cluster of cells. • After implantation of the zygote, the cluster of cells is known as an embryo. Embryo is the Click image to view movie. developing child from the time of implantation until about the eight week of development.

Lesson 1 Embryonic Growth Structures Formed During Embryonic Growth The • As the embryo grows, itsamniotic cells continue to divide, forming sac that is a thin, three tissue layers later fluidbecome various body systems. filled membrane that surrounds and structures form outside the • During this time, two important protects the embryo: developing embryo. 1. Amniotic sac 2. Umbilical cord

Lesson 1 Embryonic Growth Structures Formed During Embryonic Growth • As the embryo grows, its cells continue to divide, forming three tissue layers that later become various body systems. The umbilical cord is a ropelike • During this time, structure two important that structures form outside the embryo: connects the embryo and the mother’s 1. Amniotic sac placenta. 2. Umbilical cord

Lesson 1 Embryonic Growth Substances Passed to the Embryo • Although the blood supply of the mother and the placenta developing. The embryo are kept separate, materials diffuse is a blood thick, supply blood-rich from one to the other through the umbilical cord. tissue that lines the walls of the uterus • Nutrients andpregnancy oxygen pass during andfrom the mother’s blood to the embryo, and wastes from the embryo diffuse into the nourishes the embryo. mother’s blood. • If a pregnant female uses harmful substances, they can cross the placenta and harm the developing embryo.

Lesson 1 Fetal Development Trimesters • The time from conception to birth is usually about nine full Fetus is the months. developing embryo in the uterus. • These nine months are divided into three 3 -month periods called trimesters. • During the period of growth in the uterus, the fetus develops in preparation for living outside the mother’s body.

Lesson 1 Stages of Birth Changes Experienced During Labor • Many females experience weak, irregular muscular Labor is the final contractions of the uterus for of weeks or eveninmonths before stage pregnancy the baby is born. which the uterus contracts and pushes • As the time approaches the for baby the baby to the be born, however, out of these contractions become regular, stronger, and closer mother’s body. together. • The stronger contractions induce labor.

Lesson 1 Quick Review - Answer A. Correct! In a developing fetus, nutrients from the mother pass to the fetus through the blood in the umbilical cord. Click Next to attempt another question.

Lesson 1 Quick Review - Answer You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

Lesson 1 Quick Review - Answer A. Correct! Harmful substances taken in by a pregnant female can be transferred to a developing fetus, and the fetus can be affected negatively. Click Next to attempt another question.

Lesson 1 Quick Review - Answer You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.