Importance of the smooth vascular cell

The tone of vascular smooth-muscle cells is governed by the autonomic nervous system and by the endothelium in tightly regulated
control networks. Autonomic neurons enter the blood vessel medial layer from the adventitia and modulate vascular smooth-muscle
cell tone in response to baroreceptors and chemoreceptors within the aortic arch and carotid bodies and in response to
thermoreceptors in the skin. These regulatory components include rapidly acting reflex arcs modulated by central inputs that

What is the vascular smooth muscle cell

The vascular smooth-muscle cell, the major cell type of the media layer of blood vessels, also contributes actively to vascular
pathobiology. Contraction and relaxation of smooth-muscle cells at the level of the muscular arteries controls blood pressure, and,
hence, regional blood flow and the afterload experienced by the left ventricle (see below). The vasomotor tone of veins, which is

The biology of aging

Thanks largely to the power of genetic analysis in model organisms such as Caenorhabditis
elegans (a nematode), Drosophila melanogaster (a fruit fly), and the laboratory mouse, major
advances have been made in the elucidation of what can be termed "public" modulations of
intrinsic biological aging—that is to say, commonalities of gene actions across widely diverse
phyla that explain, in part, the plasticity of processes of aging. There are hints that at least
one such conserved pathway may be operative in our own species. These observations,

THE EPIDEMIOLOGIC TRANSITION–CHANGES IN THE BURDEN OF DISEASE AND RISK FACTORS

The secular improvements in ages at death have been accompanied by changes in causes of death. In
the broadest terms, the proportion of deaths due to infectious disease and conditions associated with
pregnancy and delivery has fallen, and the proportion due to chronic, noncommunicable diseases, such
as heart and cerebrovascular diseases, diabetes, cancers, and age-related neurodegenerative
diseases such as Alzheimer's and Parkinson's diseases, has increased steadily and is expected to
continue to increase. Figure 70-5 shows results from an international comparative project that drew on

The effect of the financial conditions on the the health

There remains a great deal of diversity in health conditions both among and within national populations.
There is nothing inevitable about the mortality transition—in several African countries, the prevalence of
AIDS has been high enough to cause life expectancy to fall below the levels of 1980. Though none has
so far reached a scale to rival the AIDS epidemic, periodic outbreaks of new influenza viruses or

The future of life expectancy

The members of the population who could potentially become aged 80 and older in 2050 are those
aged 40+ who are alive today. The actual numbers who will be age 80 and older in 2050 will therefore
depend almost solely on adult and old age mortality rates over the next 40 years. The history of the
decline of mortality and increase in life expectancy suggests that improvements in the standard of living
including increased and improved education and improved nutrition coupled with improvements in

Demography of aging around the world

Current global life expectancy at birth is estimated to be 65.4 for men and 69.8 for women, with the
comparable figures for the more developed region being 73.6 and 80.5 years. Life expectancy in the
least developed countries averaged only 57.2 for women and 54.7 for men. Life expectancy at birth is
heavily influenced by infant and child mortality, which is considerably higher in poor countries. At older

REGIONAL AGING–NUMBERS AND PERCENTAGES OLDER THAN AGE 60 YEARS

REGIONAL AGING–NUMBERS AND PERCENTAGES OLDER THAN AGE 60 YEARS
Regions of the world are at very different stages of the demographic transition (Fig. 70-1). Of a world
population of 6.8 billion in 2009, approximately 11% were older than age 60 years, with Japan (30%)
and Europe (22%) being the oldest regions (Germany, Italy, and Sweden have the highest percentages,
25–26%), and the United States and Canada having 21% and 20%, respectively. The percentage of the
population older than age 60 years in the United States has remained lower than in Europe, due both tomodestly higher fertility rates and to higher rates of immigration. The Caribbean and some Latin
American countries average 10% older than age 60 years, with countries such as Uruguay, Cuba, and

Historical changes of population aging

Population aging around the world in recent decades has followed a broadly similar pattern, starting
with a decline in infant and childhood mortality that precedes a decline in fertility; at later stages,
mortality at older ages declines as well. Declining fertility began as early as the beginning of the
nineteenth century in the United States and France and extended to the rest of Europe and North
America and parts of East Asia by the middle of the twentieth century. Since World War II, fertility

Effect of population Aging on the community

Population aging is transforming the world in dramatic and fundamental ways. The age distributions of

populations have changed and will continue to change radically, due to long-term declines in fertility

rates and improvements in mortality rates (Table 70-1). This transformation, known as the

Demographic Transition, is also accompanied by an epidemiological transition, in which

noncommunicable chronic diseases are becoming the major causes of death and contributors to the

burden of disease and disability. A concomitant of population aging is the