The composition of the internal environment of the body and its functions.

The internal environment is the fluids (blood, lymph and tissue fluid) that surround living cells and provide the necessary conditions for their life.

The structure of the internal environment of the body

The main part of the internal environment of the body is the intercellular substance, which is most of all in the connective tissues. In the blood, this substance is liquid (plasma).

Blood in the human body moves only through the blood vessels. But part of the plasma under pressure is filtered through the thin walls of the capillaries. Water comes out into the intercellular space with mineral and organic substances dissolved in it. This is how tissue fluid is formed.

Some of the substances from the interstitial fluid pass into the blind-closed lymphatic capillaries and form lymph. Lymphatic capillaries collect in larger lymphatic vessels. At the confluence of the lymphatic vessels, there are lymph nodes. Lymphatic capillaries, vessels and nodes form the lymphatic system.

The internal environment of the body is formed by blood, tissue fluid and lymph.

The three fluids that make up the internal environment of the body provide all its cells with the necessary substances, remove metabolic products and maintain the constancy of its physiological functions.

Internal environment functions

Each structure of the internal environment performs a number of specific functions.

Functions of the internal environment of the body:

• blood mainly performs a transport function (carries oxygen and carbon dioxide, nutrients, and takes metabolic products from tissues).
• Tissue fluid binds blood and cells. From the tissue fluid, nutrients and oxygen enter the cells, which the blood delivers to the tissues.
• Lymph performs the function of drainage (returns tissue fluid to the bloodstream), as well as a protective function.