adulthood. For example, heart disease, cancer, and diabetes become more common during
this time. This is the stage of life when people are most likely to achieve career goals. Their
children also grow up and may leave home during this stage.
Late Adulthood
Late adulthood begins in the mid-60s. It continues until death. This is the stage of life
when most people retire from work. They are also likely to reflect on their life. They may
focus on their grandchildren. During late adulthood, people decline in physical abilities. For
example, they usually have less muscle tone and slower reflexes. Their immune system also
doesn’t work as well as it did. As a result, they have a harder time fighting diseases like flu.
The risk of developing diseases such as heart disease and cancer continues to rise. Another
health problem that is common in late adulthood is osteoporosis. Arthritis is also common.
In arthritis, joints wear out and become stiff and painful. As many as one in four late adults
may develop Alzheimer’s disease. In this disease, brain changes cause mental abilities to
decline steadily. Exercising the body and brain, and maintaining social connections can
alleviate some of these effects. The various stages of adulthood discussed are pictured in
Figure22.11.
Despite problems such as these, many people remain healthy and active into their 80s or
even 90s. Do you want to be one of them? Then adopt a healthy lifestyle now and follow it
for life. Doing so will increase your chances of staying healthy and active to an old age.
Lesson Summary
- Fertilization occurs when an egg unites with a sperm to form a zygote.
- Azygotedevelopsintoanembryoandthenafetus. Thisoccursascellsdivide, different
types of cells develop, and organs form. - An individual grows rapidly and develops new abilities during infancy and childhood.
- A child becomes sexually mature and changes in many other ways during adolescence.
- Adulthood is divided into the stages of early, middle, and late adulthood. Each stage
is associated with different traits and concerns.
Review Questions
- What is fertilization?
- Define embryo and fetus.
- At about how many weeks after fertilization is a fetus usually ready to be born?
- Describe an embryo at the end of the 8thweek after fertilization.
- How does a fetus change during the last two months before birth?
- Explain the role of the amniotic sac and placenta during fetal development.