Lymphatic System of Dogs

The lymphatic system is responsible for the movement of lymph and for regulating and participating in many basic immune functions in the bodies of all mammals. The system is present throughout the entire body and is composed of small glands known as lymph nodes, which are attached to one another by tiny vessels called lymphatics. The lymphatic system also includes essential organs like the spleen, thymus, bone marrow, and gut-associated lymphoid tissue (GALT). We will be discussing each of these organs in the following article.


Lymph itself is a milky white fluid that courses throughout the entire system. It is composed of fats, proteins and a kind of white blood cell called lymphocytes. Lymph is taken from the fluids of tissues and is later deposited in the blood. It also transports specific proteins from tissues that cannot enter the blood circulatory system.

In fact, the lymphatic system is a lot like the blood circulatory system in that it is made up of thousands of intricate ducts and channels that run along with the blood vessels. At the end of their journey, these lymphatic vessels merge with a far larger channel known as the thoracic duct. From there the lymph is transported to larger vessels until they all meet up and empty the lymph into the cranial vena cave, which leads directly to the heart.

The lymph is then pumped through vessels directly to the lymph nodes.
Another important part of the lymphatic system is bone marrow. Marrow is composed of connective tissue and cells that form intricate arabesques within the marrow cavity. This cavity is sustained by many tiny blood vessels. The primary function of bone marrow is to produce red and white blood cells.

The spleen is easily the largest organ in the lymphatic system. It stores red blood cells and collects proteins used in the immune system that are called antigens. The spleen also stores white blood cells that are also know as lymphocytes. Lastly, the spleen removes unwanted cells from the blood and is essential in the production and storage of blood cells.

The thymus is an age-specific organ that is extremely important for young mammals because it is where the earliest immune cells are produced and without it the animal would be not last long.

Galt runs through the gastrointestinal tract. Its job is to protect and defend the lining of the intestinal tract since it is often exposed to foreign agents and is particularly susceptible to infection.

Functions of the Lymphatic System

To begin with, the lymphatic system is responsible for removing waste from the tissues of the body. Because as cells do their jobs, they produce waste products and proteins, and it is the duty of the lymph to collect these by products and move them away from the tissue since they cannot be safely released into the bloodstream.

The lymphatic system also: absorbs excess fluid from tissues and releases into the blood, takes fat from the gastrointestinal tract, carries white blood cells, helps to regulate the immune system, and produced essential antibodies without which the body could not fight off attacks or infections.


A common lymphatic disorder that affects dogs is called lymphoma. The disease is a malignant kind of cancer that attacks the white blood cells and can wreak havoc in many parts of the lymphatic system. Lymphoma often takes the form of a solid tumor in the lymph nodes, kidneys, liver, or spleen. It is can only be treated with chemotherapy and the odds of your animal surviving it are not good.