Role of the digestive system in removal of waste:
Forming the last part of the digestive tract, the main role of the colon is the elimination of waste, the absorption of water, the maintenance of fluid balance and the absorption of certain vitamins by the body. Food residues (composed mainly of organic compounds from plant or muscle fibers, nitrogen, potassium, phosphorus, stercobillogene (metabolite of bilirubin), and germs of the intestinal flora) pass through the colon and progress to the rectum. Stool passes through the rectum, where it is stored before defecation, induced by a reflex mechanism.
Role of the respiratory system in removal of waste:
Eliminate an equal volume of carbon dioxide delivered to the lungs by the alveolar capillaries.
Eliminate excess surface fluids and debris such as inhaled particles and senescent phagocytic and epithelial cells.
Eliminate volatile particles such as alcohol, ammonia, ketone bodies ...
Role of the urinary system in removal of waste:
The urinary system includes organs (kidneys), different structures (the bladder, the urethra, the ureter) and many blood vessels to eliminate nitrogenous waste produced by cellular metabolism (urea, creatinin and uric acid).
It eliminates the surpluses of certain minerals, named electrolytes, and returns in the blood the substances useful to the good functioning of the organism.
The relation between wastes and the three ressouces core:
The three core resources are carbohydrates, amino acids (proteins) and lipids.
The elimination of CO2 by the lungs is due to the consumption of carbohydrates and lipids. and the elimination of ketone bodies by the lungs is due to the consumption of lipids (fatty acids).
The elimination of urea and creatinine by the urine is due to the consumption of amino acids. The elimination of uric acid is due to the consumption of nucleic acids.
Stool contains indigestible particles, minerals and water, as well as stercobillogen from metabolism of hemoglobin (proteins).