If someone next Thanksgiving asks you what you are thankful for, I have a suggestion. Why not describe all the things your body does to keep you healthy and alive, the automatic processes you have no control over.

You could start with the immune system, which consists of two responses to anything that enters the body that doesn't belong, innate and adaptive.

The innate immune system is responsible for the first wave of defense when confronted with an invader, whether it is bacteria, virus or venom. The adaptive system remembers previous attackers and allows the body to mount a better response the next time those invaders attempt to re-enter the body.

As soon as invaders are detected the innate system takes action. Mast cells, packed with histamine and heparin and macrophages, engulf anything that does not belong there. Inflammation is triggered — it is a carefully regulated response to kill some types of bacteria and viruses without damaging the body.

Macrophages eat bacteria, viruses and other foreign particles. If the macrophages do not destroy all of the invaders, they release compounds that attract neutrophils, a type of white blood cell.

As the battle continues between the innate system and the unwelcome visitors, the adaptive system kicks in. It includes dendritic cells and T cells. All T cells have specialized receptors, and only those whose receptors match what the dendritic cells are presented will be activated. Some will remain as memory T cells, while others become killer T cells to help macrophages and neutrophils. A third subset activate B cells, which are the body's antibody factories.

With the combined attack of the antibodies, T cells, macrophages and neutrophils, the invaders should be defeated. Just imagine trying to orchestrate that cascade under your direction. Moreover, you should recall that before the birth of modern medicine, it was the patient's immune system that cured him or her, or that didn't.

When you finish profusely thanking the immune system, you can extol the virtues of your liver. According to Natalie Angier from the New York Times, its to-do list is second only to the brain and numbers well over 300 items. This includes systematically reworking the food we eat into usable building blocks for our cells; neutralizing potentially harmful substances we incidentally ingest; generating a vast storehouse of hormones, enzymes, clotting factors and immune molecules; controlling blood chemistry; and so on. There is no machine available to replace all of the liver's diverse functions.

The liver is our largest internal organ, weighing 3½ pounds and measuring 6 inches long. It is always flush with blood, holding about 13 percent of the body's supply at any given time.

Finally, it is the liver's responsibility to keep track of the body's moment- to-moment energy demands, releasing glucose as needed from its stash of stored glycogen, along with any vitamins, minerals, lipids, amino acids or other micronutrients that might be required.

If you still have an audience at the dinner table you can then praise your pancreas. It, indeed, is a miraculous organ and performs a number of vital functions without our instructions or knowledge.

The pancreas is composed of two main elements: exocrine and endocrine tissues. The exocrine tissue is organized into a large number of sac-like structures lined with cells that secrete various enzymes important to the digestive process. As these pancreatic juices are made, they flow into the main pancreatic duct connecting the pancreas to the liver and gall bladder.

Scattered throughout the exocrine tissue are small, isolated pockets of endocrine tissue known as the islets of Langerhans. Islets may be composed of several types of cells, predominantly alpha and beta cells. Granules in the beta cells produce insulin, while those in the alpha cells provide glucagon. Insulin helps control carbohydrate metabolism, while glucagon counters the action of insulin.

Strangely, the pancreas can churn out huge quantities of enzymes to rapidly reduce our fast food diets into particles of amino acids, carbohydrates and fats, miraculously without digesting its own tissue in the process.

Any unlikely remaining individual could then be lectured about the central nervous system, blood, hormones, respiration and circulation. With regard to the former, one author summarized the central nervous system as essentially a number of masses of nerve cells connected to each other by a complex set of fibers. The function of a nerve cell is to interpret the impulse brought by the nerve fiber, and to initiate new impulses to be sent out over other nerve fibers. He indicated that his summary contains everything that matters; none of which are under our immediate supervision. We indeed have a lot to be thankful for.

Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, will touch on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at maxsherman339@gmail.com.