Human Anatomy and Physiology - N. I. Fedyukovich 2003

Cells and Tissues
Organs and Organ Systems. The Organism as a Whole

p>By combining with one another, different tissues form Organs. An organ is a part of the body that has a specific shape and Structure, occupies a particular position, and performs a specific function. Various tissues participate in The formation of any organ, but only one of them is primary, while the others perform an auxiliary function. For example, Connective Tissue forms the framework of an organ, Epithelial Tissue forms the mucous membranes of the respiratory and digestive tracts, Muscle tissue forms the walls of hollow organs (Esophagus, intestines, Urinary Bladder, etc.), and Nervous Tissue is represented by nerves innervating the organ and nerve ganglia located within the organ walls. Organs vary in shape, size, and position. In addition to individual variations, There are also sex- and age-related differences.

Organs that are similar in structure and origin and perform a common function are called a system. The following Organ Systems are distinguished in The Human Body:

1) digestive — integrates the organs through which food is digested and absorbed by the body;

2) respiratory — includes the respiratory organs in which gas exchange occurs between the Blood and the environment;

3) cardiovascular — unites The Heart and Blood Vessels that provide Blood Circulation;

4) urinary — excretes Metabolic waste products (salts, urea, creatinine, etc.) formed in the body;

5) nervous — connects all organs and systems into a single whole, regulating their activity;

6) sensory system — perceives stimuli from the external and internal environments;

7) endocrine — regulates all processes in the body using special substances (Hormones).

Some organs are grouped functionally into apparatuses (for example, the musculoskeletal or endocrine apparatus). Sometimes these organs differ in their Functions but are developmentally related (for example, the Urogenital apparatus).

The combination of organ systems and apparatuses forms the integral human Organism, in which all its component parts are interconnected. The primary role in integrating the body belongs to the cardiovascular, nervous, and endocrine systems. These systems act in concert, providing Neurohumoral regulation of bodily functions. The Nervous system transmits signals in the form of nerve impulses, while the Endocrine System releases hormones that are carried by the blood to target organs.

Interaction between the Cells of the nervous and endocrine systems is mediated by various cellular messengers derived from Amino Acids (releasing hormones, endorphins, etc.). Produced in the nervous system in low concentrations, they exert an exceptionally strong influence on the endocrine apparatus.

In addition to the joint Regulation of the body's vital functions, the nervous and endocrine systems can act independently.

Self-regulation of physiological functions is the primary mechanism for maintaining the body's vital activity at a relatively constant level. The relative constancy of the internal environment in humans is maintained by neurohumoral physiological mechanisms that regulate The activity of the cardiovascular, respiratory, and digestive systems, as well as the Kidneys and Sweat Glands, which ensure the removal of metabolic waste products from the body.

Thus, the nervous and endocrine systems ensure the dynamic Development of the organism and the stability of its primary physiological functions.



Last update: 08/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.