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Human Growth & Development: The Beginning of Life

Human Growth & Development: The Beginning of Life. Chapter 21. The Beginning of Life. You began your life as a single microscopic cell. That cell divided over and over again until it formed the trillions of cells that now make up your body. . Prenatal Period .

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Human Growth & Development: The Beginning of Life

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  1. Human Growth & Development:The Beginning of Life Chapter 21

  2. The Beginning of Life • You began your life as a single microscopic cell. That cell divided over and over again until it formed the trillions of cells that now make up your body.

  3. Prenatal Period • begins at conception and continues until birth (about 39 weeks)

  4. Embryology • science of fetal growth and development

  5. Fertilization • A unique human body begins as a single cell that is the result of fertilization. • Fertilization is the joining together of two specials cells, one from each parent.

  6. Fertilization to Implantation requires about 10 days • fertilization usually occurs in the outer one third of the oviduct • zygote – a fertilized ovum (egg)

  7. Fertilization to Implantation requires about 10 days • after 3 days of cell division, the zygote is becomes a morula, which is a solid mass of cells • continued cell divisions of the morula produce a hollow ball of cells called a blastocyst.

  8. Fertilization to Implantation requires about 10 days • Blastocysts implants itself in the uterine wall about 10 days after fertilization • The blastocyst forms the amniotic cavity and chorion (fetal membrane) of the placenta

  9. Growth Inside the Uterus • The placenta is a thick, rich lining of tissue that builds up along the walls of the uterus and connects the mother to the fetus. • The umbilical cord is a tube that connects the fetus and the mother’s placenta. Food and oxygen in the mother’s blood are carried to the fetus through blood vessels in the umbilical cord. Waste products are carried away to the mother’s body, which then gets rid of them.

  10. Periods of Development • Length of pregnancy, or gestation, is about 39 weeks – divided into trimesters • The embryonic phase extends from the 3rd week after fertilization to the end of week 8. • Fetal phase extends from week 8 to week 39 of gestation • All organ systems are formed and functioning by month 4 (16 weeks) of gestation

  11. Formation of the Primary Germ Layers Three primary germ layers appear in the developing embryo after implantation of the blastocyst. Endoderm Mesoderm Ectoderm Pg 529

  12. Histogenesis and Organogenesis Histogenesis Organogenesis • the process of how the primary germ layers develop into many different kinds of tissues • the way in which those tissues arrange themselves

  13. Birth Defects • Any structural or functional abnormalities present at birth • may be caused by genetic factors – genes or # of chromosomes • may be caused by environmental factors

  14. Birth Otherwise known as the great escape!!

  15. Birth, or Parturition • Transition between pregnancy and postnatal periods of life • About 9 months after fertilization (39 weeks gestation), a fetus is fully developed and ready to be born. I’m ready for my close up!!

  16. BIRTH, OR PARTURITION • The uterus becomes irritable • Fetus takes head-down position against the cervix • Muscular contractions begin, and labor is initiated • Amniotic sac ruptures • Cervix dilates • Fetus moves through vagina to exterior

  17. Stages of Labor

  18. Stages of Birth • Stage One-period from onset of uterine contractions until dilation of the cervix is complete • Mild contractions signal the beginning of the first stage. • The cervix begins to open.

  19. Stages of Birth • Stage Two: the period of time of maximal cervical dilation until the baby exits through the vagina • The cervix is now open to a width of about 4 inches. • Very strong contractions, and are frequent • This stage ends with the baby being born

  20. Stages of Birth • Stage Three: process of expulsion of the placenta through the vagina • Contractions continue until the placenta is pushed out.

  21. Postnatal Period Birth to death

  22. POSTNATAL PERIOD • Infancy • birth until about 18 month • first 4 weeks are the neonatal period • First breath is stimulated due to increase of CO2 • “baby’s got back” : c-shaped spine • Rapid development of the nervous and muscular system

  23. POSTNATAL PERIOD • Childhood • end of infancy until puberty (12-14 yrs old) • Growth continues at a rapid pace • Start to loose the baby look and become more adolescent in appearance • Still have rapid development of the nervous and muscular system during the middle years • Start to get adult teeth

  24. POSTNATAL PERIOD Adolescence adulthood • Adolescence is usually 13 – 19 yrs old • Development of secondary sex characteristics • Full closure of growth plates • Maintenance of existing body tissue

  25. POSTNATAL PERIOD • Older adulthood • Degenerative changes • End in death

  26. EFFECTS OF AGING • Skeletal System • Integumentary System • Urinary System • Respiratory System • Cardiovascular System • Special Senses

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