Know Your Body and it Functions
The human body is often likened to a machine, but no machine in the world operates as effectively and effeciently. Although medical scientists have been studying the body for hundreds of years, there is still much we don’t fully understand about its normal functioning and about diseas processes. Nonetheless, we do know that the various organ systems work in amazing harmony most of the time, thanks to a highly complex internal communications network. Although we tend to describe a single organ system or disease, ususlly the entire body is affected by an activity or disorder. We focus considerable attention on disease and organ systems and the common disorders that affect them will be described in detail. this section presents a brief overview of how these organ systems work in harmony to sustain life, day-to-day activities, and general good health.
the actual digestive process begins with chewing, a consious effort involoving the skeletal muscles of the jaw, mouth, food is broken into small pieces and mixed with saliva and other digestive juices. Saliva contains an enzyme, ptyalin, that begins to break down starches or complex carbohydrates into simple sugars that can be absorbed easily farther along the digestive tract.
from the back of the mouth, food is squeezed through the pharynx, a funnel-shaped structure, into the esophagus, a food-long tube that leads to the stomach. In 4 to 8 seconds, the bolus of chewed food passes through the esophagus and in to the upper part of the stomach.
the muscles in the lower esophagus, unlike those in the jaw, are involuntary and respond automatically to the stimulus of swallowing. An involuntary series of coordianted muscle waves, a process called peristalsis, moves the food through the esophagus, as well as through the rest of the digestive tract. Rings of muscle that function as a valve between the esophagus and stomach relax to admit the food. These muscular valves then close to prevent to backflow (regurgitation) into the esophagus.
much of the digestive process occurs in the stomach. Four or five times every minute, rippling waves controlled by the autonomicnervous system pass through the muscles of the stomach walls, mixing food with gastric acid and digestive enzymes and further breaking it down. Food is reduced to a thin liquid mass and the digestive juices break down some of the nutrients into forms that can be utilised by the body. Carbohydrates continue to be broken down in the stomach; gastric juices and enzymes also begin breaking down protein and fat into forms that can be absorbed.
this partially digested liquid food mass moves next thorugh the muscular pylaric valve to duodenum, the initial portion of the small intestine. The emptying of the stomach is a complx act, requiring an integration of feedback messages to and from the brain carried by the vagus nerve, as well as by intestinal hormones released by changes in volume and acid levels. As food entres the upper part of the small intestine, hormones stimulated by its arrival coordinate the flow of digestive enzymes from the pancreas and of the bile from liver and gallbladder. The pancreatic juices and bile give the duodenum its alkaline environment, in contrasr to the acidic environment of the stomach. These digestive secretions complete the breakdown of protiens and fats, processes that take longer than the digestion of carbohydrate and its conversion to glucose. The small intestine is about 22 feet long, and as the now liquified and well-mixed food continues its journey, a steady flow of basic nutrients is available to the body.
the small intesitne is lined with villi, fingerlike projections that greatly increase the total surface area of the intestines. The villi also permit each cell to come in contact with a blood capillary. These microscopic blood vessels are only one cell thick, and permit the direct exchange of biological chemicals between the intestine and the blood. (A similar physiological mechnism to increase the surface area for blood-organ interchange occures in the lungs and kidneys.) digested nutrients pass though the villi. Sugars (from carbohydrates and some protien) and amino acids (from protien) pass directly into the bloodstream and are carried to the liver or muscles to be further metabolised or used as fuel. The digested fats pass from the villi to blood or the lymphatic system and enter the bloodstream through a vein. Blood rich in digested nutrients flows from the small intestine into the liver, which, acting in concert with the endocrine and distributiuin to individual body tissues. Liver and other body systems, regulates the amount of the nutrients, particularly glucose, that enter the bloodstream for the distribution to individual body tissues.
the liver, the largest of the internal organs, carries on a number of highly complicated chemical processes. It produces bile from old blood cells, which are being reprocessed. One of the breakdown products of hemoglobin gives bile and hence the stool its brown colour. Bile is essential to the digestion of fats. The liver manufactures a number of other substances as well, including cholestrol, enzymes, vitamin A, blood cogulation factors, and complex proteins. The liver also acts as a storehouse for blood, certain vitamins and minerals, and fuel, in the form of glycogen, which is readily converted to glucose as the body needs it. It deoxifies alchohal and many other potentially harmful chemicals.
finally, food that is not digested moves from the small intestine into the colon or large intestine. In the colon, water is extracted from the waste material and what remains moves via peristalsis through the 3 feet of the large intestine to the rectum for eventual elimination in the form of a bowel movement. Just as the begining of the digestive process – the chewing of food in the mouth – is controlled by our conscious actions, voluntary control returns at this end of the digestive processes are going on, other body systems are carrying on their respective functions in a finely tuned, coordianted manner.
with each breath, the lungs take in oxygen and eliminate carbon dioxide and other gaseous wastes.
the circulatory system carries oxygenated blood and other nutrients to cells throught the body and collects their wastes. Each cell comes in direct contact with a blood capiliary, which brings it oxygen and other nutrients and takes away cellular waste, kidneys. The kidneys filter out the waste and help regulate blood pressure and internal chemical fluid balance.
Muscles and Bones
the muscles & bones give us shape, movement, and stregth and protect the internal organs. The marrow of the bones is essential for the manufacture o0f blood components.
the endocrine system produces chemical messengers that coordinate many of these processes and control such vital functions as reproduction and growth.
Central Nervous System
the central nervous system provides the seat of our intelligence and emotions. It also coordiantes & controls other vital functions, often in concert with the endocrine system.
The immune system helps protect the body from invading micro-organisms and other forign substances.
The skin also protects the body, help regulate tempreture, and carries on a number of important metabolic functions. This is highly oversimplified summary, in reality, most organ systems have multiple functions and none acts independently, the smooth functioniong of one is highly dependent upon other. A breakdown of one process or system is likely to have an impact throuout the body. Thus, it is important to remeber that symptoms affectng one part of the body may have their origin in a quite distant and seemingly unrelated organ. Few of us truly appreciate just how precise and fine-tuned the body is until something goes awry. Even then, the body often can remedy the situation on its own. This does not mean that maintaining good health requires no effort. For most people, a life style thatprovides the basics of god nutrition, adequate rest, physical activity, and a commonsense approach to life in general will go a long way toward meeting most health needs. When something does go wrong, being able to recognoze warning signs and then seeking proper medical attention will further ensure that you maintain good health.
A HEALTHY LIFESTYLE
Good health is a good toward which many of us strive. After all, we know that, in great measure, our physical well being determines the quality of our life. But deciding which approach to a healthy life-style will best improve or maintain personal heal this no easy task. It is virtually impossible to read a newspaper, watch television, listen to the radio, or browse in a book-store without being bombarded by information from experts and so-called experts on the art of staying healthy. It is no wonder that confusion abounds. Are vitamins the elixir of the fountain of Youth? Will regularattendance at a spa, running more sensible? Should we worry most about our weight, our cholestrol intake, the food we eat, or the air we breathe? If we give up that cocktail before dinner, eat organic foods, get regular medical checkups and follow the advice in a best selling exercise manual, are we guaranteed to live a longer, healthier life? Unfortunately, the answers we hear to these questions too often come from enterpreneurs, advertisers, or well meaning, but ill-informed advisors rather than medical experts. The truth is that there is no secrets or complex trick to optimizing your chances of living a long and healthy life. All it takes is following such simple health habits as avoiding smoking, drinking in moderation, eating a well-balanced diet, controlling weight, reducing stress, and exercising regularly.