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Lymph ducts are part of the body’s lymphatic system. They work in conjunction with lymph nodes and other vessels to circulate disease-fighting lymph throughout the body. A lymph duct specifically moves lymph from various bodily tissues into blood vessels. The human body contains two main types of lymph ducts: the thoracic duct and the right lymph duct.
The lymphatic system is vital to human immune responses, as it helps fight invasive bacteria. Lymph is the primary substance of this system. It consists of a clear to yellowish liquid containing white blood cells, and it is transferred from tissues in the body to the blood via the lymphatic system. While lymph nodes filter the liquid, lymph ducts assist in the transportation of lymph from smaller lymph vessels to blood vessels.
The first primary lymph duct, the thoracic duct, runs along the abdomen to the neck. The chief function of this duct is to collect lymph from the digestive tract, the body’s left side, and the lower right side of the body. As the largest lymphatic vessel in the body, this lymph collector moves about 2 to 4 liters (about 0.5 to 1.1 gallons) of lymph through an individual every day. Lymph movement is aided by the duct's smooth muscle composition, and an individual's breathing facilitates the transport. Once lymph has exited the thoracic duct, it moves to the left subclavian vein, which is a large blood vessel located around the ribs.
Located near the base of the neck, the right lymph duct operates in the same manner as the thoracic duct. Both utilize a low-pressure system to create slow lymph movement. Also like its companion duct, this vessel contains valves that prevent the backflow of lymph and blocks blood from entering the duct. A right duct, as its name implies, is responsible for collecting lymph on the right upper side of the body. As such, tissue vessels in the head, neck, and chest lymph drain into the right duct. Following this process, lymph deposits into the right subclavian vein.
On occasion, these ducts or other lymphatic vessels can become blocked. When a blockage occurs, lymphedema can result. This condition is characterized by a buildup of lymph fluid in body tissues, causing swelling, tightness, and occasional burning or itching in areas like the arms or legs. A test of the lymphatic system called a lymphoscintigraphy can detect such a condition. Ducts may also become dilated, which can cause discomfort as well. Any suspect systems should be examined by a medical professional.