How do the cardiovascular and lymphatic systems work together

Topic Resources

Like the venous system, the lymphatic system transports fluids throughout the body. The lymphatic system consists of

• Thin-walled lymphatic vessels

• Lymph nodes

• Two collecting ducts

Lymphatic vessels, located throughout the body, are larger than capillaries (the smallest blood vessels, which connect arteries and veins), and most are smaller than the smallest veins. Most of the lymphatic vessels have valves like those in veins to keep the lymph, which can clot, flowing in the one direction (toward the heart). Lymphatic vessels drain fluid called lymph from tissues throughout the body and return the fluid to the venous system through two collecting ducts.

Lymph begins as fluid that has diffused through the very thin walls of capillaries into the space between cells. Most of the fluid is reabsorbed into the capillaries and the rest is drained into the lymphatic vessels, which eventually return it to the veins. Lymph also contains many other substances including

• Proteins, minerals, nutrients, and other substances, which provide nourishment to tissues

• Damaged cells, cancer cells, and foreign particles (such as bacteria and viruses) that may have entered the tissue fluids

Lymph nodes are tiny bean-shaped organs that serve as collection centers for lymph. All lymph passes through strategically placed lymph nodes, which filter damaged cells, cancer cells, and foreign particles out of the lymph. Lymph nodes also contain specialized white blood cells (for example, lymphocytes Lymphocytes One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more

The lymphatic vessels drain into collecting ducts, which empty their contents into the two subclavian veins, located under the collarbones. These veins join to form the superior vena cava, the large vein that drains blood from the upper body into the heart.

Lymphatic System: Helping Defend Against Infection

The lymphatic system may not carry out its function adequately due to

• Blockage (obstruction): Obstruction in the lymphatic system leads to an accumulation of fluid (lymphedema Lymphedema Lymphedema is the accumulation of lymph in tissues, resulting in swelling. When lymphatic vessels are injured or obstructed, lymph fluid cannot drain and accumulates in tissues, causing swelling... read more

  
  ). Obstruction may result from scar tissue that develops when the lymph vessels or nodes are damaged or removed during surgery, by radiation therapy, by injury, or in tropical countries, by infection with a threadworm (filariasis Lymphatic Filariasis Lymphatic filariasis is infection of the lymphatic system caused by one of three species of roundworms. People have a fever, swollen lymph nodes, pain in the limbs and groin, and, if the infection... read more
  
  ) that blocks the lymphatic ducts.

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