Über die Autorin bzw. den Autor

Mark Liponis, M.D., is the medical director of the Canyon Ranch Spa in all its locations. He is the coauthor of New York Times bestseller Ultraprevention, which won the 2003 Books for a Better Life Award in the health category.

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UltraLongevity

Little Brown and Company

Chapter One

Inside you are more than thirty different organs, which include more than two hundred different cell types and about 100 trillion cells. Each organ is patrolled by your immune system, which is constantly performing surveillance for possible threats. Following are some of the major players.

BONE MARROW

Bone marrow, the reddish-looking material inside nearly every bone in the human body, is where all of the blood cells are produced.

Inside the marrow, on an inner framework, lie the bone marrow stem cells. These cells are constantly dividing, producing huge numbers of cells that turn into red and white blood cells.

The bone marrow stem cells continue to divide, even as they keep making red and white blood cells. And just as a couple of million are being produced every second, the same number are being gobbled up and destroyed in the spleen, which is, in effect, the cells' decommissioning center. The spleen is where blood cells are taken out of circulation once they've completed their useful life cycle (see below).

This process-birth in the bone marrow, death in the spleen- should be evenly balanced. If it isn't, you will be prone to a blood disorder. For example, if your system is destroying more red blood cells than it's making, you'll become anemic, which will make you feel tired and appear pale. If you're making more than you are destroying, you'll become polycythemic, or suffer from blood that is overcrowded with red blood cells.

Once the cells form in the bone marrow, they remain there and mature, at which time they exit and enter the bloodstream. There they circulate, the red cells carrying oxygen and carbon dioxide, and the white cells patrolling for invaders.

THE THYMUS

The thymus, located in front of your windpipe in the upper chest region, is the most mysterious organ in your homeland.

In infants, the thymus is, relatively speaking, huge. It grows until about puberty and then starts to shrink. By old age, the thymus has almost completely disappeared.

The thymus serves the role of a kind of boot camp for the white blood cells called T cells-it's where these cells go to mature. The thymus is especially active early in life because, during youth, T cells are constantly being exposed to new things, from new proteins in your diet to new germs. These T cells need to have a place to congregate, share information, and learn about threats and attacks.

For example, let's say one of the cells in your immune system comes in contact with a foreign invader. It now has to communicate that information to other cells so they can become aware of the invader too. The thymus is where this information is shared and training occurs.

Why does the thymus later atrophy? Science doesn't know for certain, but as you grow older, your immune system has less to learn. So the current thinking is that there may be less need for a large thymus as we age. But although the thymus is not as big or as active as it was when we were young, the smaller thymus is still able to help train T cells well into our eighties, nineties, and beyond.

THE SPLEEN

Another important training center and meeting ground for the immune system is the spleen. This large organ, about the size of your fist, is located on the left side of your belly, tucked under your ribs.

The spleen is a common meeting place for all the immune system's cells. Blood routes to the spleen, where the cells circulate and mingle, allowing them to tell each other what they've learned, what they've seen, what they've killed, and what antibodies they've made.

The heart pumps the blood around the body about once every minute, which means each blood cell might find itself in the spleen about 1,400 times a day. That's a great many trips.

The spleen is also important because it's where the body decides if a red or a white blood cell has gotten too old. Once the decision is made, the cell is decommissioned and disassembled and its building blocks are recycled.

You can live without a spleen; if it ruptures, the liver can take over its functions. Still, if your spleen is removed or no longer works, your immunity becomes impaired; people without a spleen are more susceptible to infections.

LYMPHATIC SYSTEM

Nearly everyone knows about the bloodstream: it's a road map of blood vessels that allow our blood to circulate through our body. But few people realize that another important, and completely different, circulatory system exists in the body-the lymphatic system, which circulates our lymph.

Lymph is a clear fluid that travels through your body, cleaning your tissues and keeping them nourished. Just as blood circulates back to the heart through our veins, lymph must also be recycled and return to the heart, which it does through the lymphatic system.

The lymphatic system is something of a secondary transportation system for your homeland troops. Like the circulatory system, it is composed of a series of vessels and tubes. The major difference between the circulatory and the lymphatic systems is that the latter lacks a pump to move the fluid it carries. For the blood, that pump is the heart. For lymph, the flow back to the heart is achieved through a more passive process involving muscle contractions and gravity.

You may have noticed that your feet swell during a long journey on an airplane or in a car. This is due to lack of movement; your muscles haven't been able to circulate lymph, so because of gravity, it collects at the lowest part of your body-your feet.

You also may be aware of a condition known as edema, which is swelling that results from a collection of lymph. Edema occurs when excess lymph fluid cannot be returned back into circulation.

The bloodstream is extensive, branching out from its main trunk, the aorta, as well as smaller arteries, arterioles, capillaries, veins, and venules, but there is still a large portion of our tissues the capillaries can't reach.

Here is where the lymph comes into play. Nutrients such as glucose (blood sugar) must be helped so they can reach and nourish each and every cell, including those the bloodstream can't reach. That happens via the lymph fluid, which bathes and nourishes all of the body's tissues. And once those nutrients have been used, the fluid must be recycled or your body would swell up like the Michelin tire man.

Along the course of the lymphatic system are way stations known as lymph nodes. These are outposts whose sentries make sure nothing passes through the lymphatic channels that shouldn't. The lymphatic system could provide easy and direct access for a germ or microbe to our heart and bloodstream, so to prevent that from happening, lymphocytes (T cells and B cells) aggregate in lymph nodes, waiting for something bad to pass by. When they spot that something, the node cells attack before it can venture into the heart and bloodstream.

When a problem is stirring in your body, the lymph nodes become enlarged. For example, if you have swollen glands in the neck, your nodes may have found some virus that landed in the back of the throat and is trying to gain access to the lungs or bloodstream. Lymph nodes responding to some infection can become swollen almost anywhere: in the...