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CHAPTER 22
Human Development and Aging
22-1 Fertilization
Fertilization occurs in the upper third of the oviduct.
Very few sperm make it to the site of fertilization.
Sperm travel by swimming and muscular contraction of the female reproductive
tract.
Sperm contain enzymes that help them penetrate the protective layers surrounding
the egg.
Only one sperm can fertilize an egg.
Sperm and egg nuclei join to create a zygote with 46 chromosomes.
22-2 Pre-embryonic Development
Pre-embryonic development begins at fertilization and ends at implantation.
The embryo embeds in the wall of the uterus.
Implantation occasionally occurs outside of the uterus.
Placental hormones are essential to reproduction.
The amnion forms from the inner cell mass.
22-3 Embryonic Development
Embryonic development ends when the organs are more or less formed.
22-4 Fetal Development
During fetal development organs continue to develop and grow.
The fetal circulatory system contains three bypasses around the lungs and liver.
22-5 Birth Defects
Birth defects include structural and functional defects that appear in a newborn.
22-6 Childbirth and Lactation
Uterine muscle contractions are stimulated by a change in hormonal levels.
Childbirth occurs in three stages.
The dilation
The expulsion
The placental
Milk production, or lactation, is controlled by the hormone prolactin.
22-7 Aging and Death
Aging is the progressive deterioration of the body.
Aging occurs as a result of a decline in cell numbers and their function.
Although declines in body function occur with age, we can age in a healthy
fashion, living out our later years in good health, free of disease.
The likelihood of contracting diseases of old age largely depends on lifestyle.
Death may be defined by the loss of brain or heart and pulmonary function.
© 2012 Jones and Bartlett Learning, LLC
22-8 Health and Homeostasis
Radiation from VDTs might help cause miscarriages, but further research is
needed to verify the connection.
© 2012 Jones and Bartlett Learning, LLC