• Many different organs and systems work together in an effort to keep us alive and healthy.

• In this ongoing struggle, the lymphatic system plays a central role.

• The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance, defends the body against infections, and assists in tissue repairs.

• The production, maintenance and distribution of lymphocytes.

– to defend the body against disease by producing lymphocytes

– The lymphocytes, protect the body against antigens (viruses, bacteria, etc.) that invade the body.

– Lymphocytes are produced and stored within lymphoid organs, such as the spleen, thymus and bone marrow.

• The return of fluid and solutes from the peripheral tissues of the blood.– to collect and return interstitial fluid, including

plasma protein to the blood, and thus help maintain fluid balance.

– The return of fluids through the lymphatic system maintains normal blood volume.

– The flow is ~3.6 liters per day and a break in a major lymphatic vessel can cause a rapid and potentially fatal decline in blood volume.

• The distribution of hormones, nutrients and waste products from their tissues to the general circulation.

– to absorb lipids from the intestine and transport them to the blood.

– Substances that are unable to enter the blood stream directly can do so via the lymphatic vessels.

• 3 components• 1. Vessels-

– A network of lymphatic vessels that begins in the peripheral tissues and connects to the venous system.

• 2. Fluid– Called Lymph (clear and watery), flows through the lymphatic

vessels. – Lymph Fluid contains:

• Fluid from the intestines (chyme), which contains proteins and fats. • Red blood cells • White blood cells, especially lymphocytes, the cells that attack

bacteria in the blood

• 3. Lymphoid organs-– Lymphoid organs are connected to the lymphatic vessels and

contain large numbers of lymphocytes. (Ex. Lymph nodes, spleen and thymus).

• Carry lymph from the peripheral tissues to the venous system in all parts of the body except the CNS (central nervous system).

• The smallest vessels are called lymphatic capillaries. These capillaries carry lymph to the larger lymphatic vessels.

• The lymphatic vessels ultimately empty into two large collecting ducts: thoracic duct and right lymphatic duct.

– Lymph organs include the bone marrow, lymph nodes, spleen, and thymus.

– Human lymph nodes, called lymph glands and “swollen glands,” are bean-shaped and range in size from a few millimeters to about 1-2 cm in their normal state.

– They may become enlarged due to a tumor or infection.

– White blood cells are located within honeycomb structures of the lymph nodes.

– Spleen- The spleen, which is located in the upper left part of the abdomen under the ribcage, works as part of the lymphatic system to protect the body.

– It clears worn out red blood cells and other foreign bodies from the bloodstream to help fight off infection.

• Tonsil—The tonsils are areas of lymphoid tissue on either side of the throat.

• An infection of the tonsils is called tonsillitis.

• Thymus- an organ located in the upper anterior portion of the chest cavity just behind the sternum.

• Hormones produced by this organ stimulate the production of certain infection-fighting cells.

• Through the hormones it produces, the thyroid gland influences almost all of the metabolic processes in your body. 

• Thyroid disorders can range from a small, harmless goiter (enlarged gland) that needs no treatment to life-threatening cancer. 

• The most common thyroid problems involve abnormal production of thyroid hormones. 

• Too much of these vital body chemicals results in a condition known as hyperthyroidism.  

• Insufficient hormone production leads to hypothyroidism.

• Hyperthyroidism-• All types of hyperthyroidism are due to an

overproduction of thyroid hormones, but the condition can occur in several different ways.

• Hypothyroidism-• By contrast, stems from an underproduction of

thyroid hormones.  • For your body to have the energy it needs, it

requires certain amounts of thyroid hormones, a drop in hormone production leads to lower energy levels.