How to distinguish tissues, organs and systems?

It is composed of a group of cells and interstitial cells with similar morphology and same function, which is called tissue; Several tissues combine with each other to form a structure with certain shape and function, which is called an organ; Some closely related organs can be combined to complete certain physiological functions and become a system.

(2) Different functions: tissues do not necessarily have specific functions, organs have specific functions, and systems can perform specific physiological functions.

Take the physiological function of digestion as an example:

First of all, four tissues of human body (epithelial tissue, connective tissue, nerve tissue and muscle tissue) are combined in turn to form digestive organs such as mouth, pharynx, esophagus, stomach, duodenum, jejunum, ileum, large intestine and anus, and these digestive organs are organically and closely combined to form the digestive system. The digestive organs in the digestive system all participate in the functional activities of digestion and absorption, but each has its own function. Any organ dysfunction will affect digestion and absorption.

The human body is composed of eight systems: motor system, nervous system, endocrine system, circulatory system, respiratory system, digestive system, urinary system and reproductive system. These systems are interrelated and mutually restricted, and play their different physiological functions.

Extended data

Functions of human tissues:

(1) Epithelial tissue: plays a protective and secretory role.

(2) Connective tissue: It has the functions of support, connection, protection, nutrition and even contraction and relaxation.

(3) Nerve tissue: able to receive stimulation and generate and conduct excitement.

(4) Muscle tissue: It has the functions of contraction and relaxation.

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