liver is what produces antibodies which work against infections. Good eating with a healthy digestive system encourages a better immune system that lowers the risks of the infection of antigens that are able to withstand white blood cells for longer. Chemical protection is provided by the stomach, whish secretes a strong acid that destroys many of the marauding cells.
             The respiratory tract starts through the nose, or through the mouth. It is a very well-known fact that ingestion also starts in the mouth. The pharynx is lined with a musous membrane for further cleansing. It serves as a common passage for both the respiratory and the digestive tract. While food goes down the esophagus, air flows down the trachea. That air enters the lungs, the oxygen is passed through into the blood stream to be transported where needed to perform things such as the liver to produce bile and other organ systems.
             In order for anything to occur, even the chewing of food and production of enzymes (ex: pepsin) required energy. By ingestion then digestion, the body gets the nutrients it needs, especially glucose. The liver converts excess glucose into a polysaccharide called glycogen in order to store sugar to be released gradually as the body needs it. The liver also converts fructose and galactose into glucose. The glycerol that results from the breakdown of fats enters glycolysis as PGAL. The resulting fatty acids can enter the system at various points, as can the amino acids resulting from the protein breakdown. The further breakdown of the pyruvic acid molecule is accomplished through the reactions of the Krebs' cycle.
             Excretion is where the digestive tract ends. The kidneys play an important role as they balance the amount of water that will either be reabsorbed (done by loop of henle) or be excreted from the body. The materials filtered out of the blood collect in the medulla of the kidney as urine. Waste or excess materials remain i...