**3.2 GI-tract lymphatic system anatomy**

The anatomy of the lymphatic system include the thymus, GI-tract, lymph nodes, spleen, and tonsils, and is very similar to the circulatory system expansion. In many organs of the body (e.g., neck, chest, pelvis, etc.), this system is seen in the form of lymph vessels in cooperation with these organs. The lymphatic vascular system consists of a network of vessels that extends to every part of the body except the brain and spinal cord. Of course, lymphatic vessels are found only in the hard palate [67, 68].

Even though the body fluids can move between blood vessels and tissues through very small pores. So in this system, lymphoid organs and lymph nodes monitor and control the composition of body fluids (ie. blood and hemolymph), which includes the following activities [67, 68]:


Also, many endocrine functions require the lymphatic system and even the absorption and transfer of fats and fat-soluble vitamins from the digestive system to the lymph. From there, most organs with the lymphatic system drain their byproducts into the lymphatic system and enter the circulatory system from there. That is why this system has a one-way function [67]. There is an extensive network of

lymph nodes and lymph vessels in the pelvis that are connected to the tissues and organs of the pelvis, especially the intestines. The gut-associated lymphoid tissues (GALT) perform many functions including monitoring the proliferation and regeneration of gut epithelial cells, Peyer's patches in the small intestine, controlling water absorption from the intestine, and intestinal health conditions [69].
