Intercellular Fluid and Lymph

  Arterioles branching from the arteries, divide further to form capillaries with one cell thick walls. The blood in the capillaries at the arteriole end is at high pressure. This high pressure causes plasma, most dissolved substances and some white blood cells to filter out between the cells in the capillary walls into the intercellular spaces. Only plasma proteins and erythrocytes cannot filter through the capillaries walls. The capillaries that filter out and occupies the spaces between the cells is known as intercellular or tissue fluid. It contains water, dissolved oxygen, dissolved food and hormones. Materials needed by the cells via the intercellular fluid. Waste materials must also be transported from the cells to the blood via the intercellular fluid. Thus, the intercellular fluid act as a middleman in the transport and exchange of materials between the blood and the cells.

       Intercellular fluid is returned to the blood in two ways:

 • The blood in the capillaries at the volume end contains mainly plasma proteins and little water, hence, it is highly concentrated. In the other hand, the intercellular fluid that flows around the capillaries near the venules is a weak solution since it has given up most of its dissolved materials to the body cells. As a result, some if the intercellular fluid is absorbed into the blood in the capillaries.

 • Unabsorbed intercellular fluid passes into blindly ending lymphatic vessels near the capillaries. the Luis in the lymphatic vessels is known as lymph. the fine lymphatic vessels join to form large vessels. These eventually join to form two large lymphatic vessels which empty their contents into veins in the neck region.

    From this, we see that the intercellular fluid, lymph and blood are in continuous circulation in the body.

    Lymph is made to flow along the lymphatic vessels by movements of the body muscles. These movement squeeze the lymphatic vessels. Back flow of lymph is prevented by valves present in the vessels.

    At certain points along the lymphatic vessels, there are bean shaped structures called lymph nodes. These produce white blood cells. Disease causing micro organisms, foreign particles and cell fragments found in the lymph are filtered out in the lymph nodes and engulfed by phagocytes.