The cells of the whole body are connected to each other, between them there is an exchange of substances and energy. Cells form tissues, and tissues form organs. Groups of organs similar in function are included in organ systems. Organ systems form the body. The normal functioning of organ systems is supported by humoral and nervous regulation.
Example: the circulatory system is associated with the respiratory system, the heart provides blood flow, blood saturates organs and tissues with oxygen after inhalation, etc.
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.