1) lungs – through them carbon dioxide, water vapor are removed from the human body;
2) sweat glands of the skin – water, salts and a small amount of urea are removed through them;
3) kidneys – through them, the final products of protein metabolism (urea), excess water and mineral salts are removed;
4) the gastrointestinal tract – through it, excess water and substances disinfected in the liver are removed.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.