|Flowing slowly along the primary lymphatics, the lymph empties
into progressively larger lymphatic vessels which ultimately converge as the Thoracic Duct and drain their contents into
the right and left subclavian veins in the thorax. In summary the lymphatic system serves
as a slow flowing, low pressure drainage system that collects a small portion of the interstitial fluid
from throughout the body and returns it to the bloodstream. The Thoracic Duct arises anterior to the
second lumbar vertebra as enlarged sac, beginning as the cisterna chyli. This sac like lymphatic mass collects lymph
from lower limbs of the body as well as the digestive system.
Unlike the circulatory systems, the lymphatic system lacks any central "heart" like organ to pump lymph throughotu the lymph vessels. Instead, the lymphatic system depends on muscular movement, breathing, and simple gravity to move lymph fluid throughout the body. However, the Thoracic Duct does contain smooth muscle (the same muscle type that exists in the lower digestive system and the arterial system) in order aid lymph flow. Thus, frequent movement is critical for humans to properly move lymph and prevent lymph fluid build-up in certain areas of the body.