Unit 8 Human Development and Sexuality .............................................. 732 Chapter 21 The Beginning of Life ................................................................... 734 Lesson 21.1 The Male Reproductive System ..................................... 736 Lesson 21.2 The Female Reproductive System .................................. 741 Lesson 21.3 Conception, Pregnancy, and Birth .................................. 750 Lesson 21.4 Teen Pregnancy and Parenthood .................................... 758 Chapter 22 Health Across the Life Span ........................................................... 770 Lesson 22.1 Understanding Development ......................................... 772 Lesson 22.2 Health During the Childhood Years ................................ 777 Lesson 22.3 Adolescence and Puberty .............................................. 782 Lesson 22.4 Adulthood and the Nature of Aging ................................ 788 Chapter 23 Understanding Sexuality ............................................................... 800 Lesson 23.1 Aspects of Sexuality ..................................................... 802 Lesson 23.2 Sexual Feelings and Behavior ........................................ 811 Chapter 24 Pregnancy Prevention ................................................................... 824 Lesson 24.1 What Is Contraception? ................................................. 826 Lesson 24.2 Barrier Methods ........................................................... 833 Lesson 24.3 Hormonal Methods ....................................................... 839 Lesson 24.4 Natural Methods and Sterilization .................................. 846 Background Lesson 1 The Body Systems ................................................. 856 Background Lesson 2 Personal Hygiene .................................................. 868 Background Lesson 3 Sleep .................................................................. 873 Glossary/Glosario .................................................................................. 875 Index ................................................................................................... 913 xii