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Lymphatic system Anatomy Physiology Lymphatic vessels Thin walled tubes Throughout the body, but numerous in the dermis Progress is size from small capillaries to large vessels such as the thoracic duct Have numerous valves Allows for diffusion Drains excess fluids from all over the body Allow them to transport various size particles (microorganisms to proteins) Allows lymph to move in a single direction

Fun fact: Florence Rena Sabin (born in 1871), studied pig embryos to determine how the lymphatic system develops. Sabin discovered that lymphatic vessels arose from veins. She found that the outer layer of cells on veins sprouted buds, much like stems growing out of the branches of trees. As these stems grew outward, they connected with each other forming the lymphatic vessels.

Why do lymph vessels have valves? Lymph vessel valves Why do lymph vessels have valves?

Lymphatic capillaries converge to form lymph vessels that ultimately return lymph fluid back to the circulatory system via the subclavian vein. The presence of one-way valves in the lymph vessels ensures unidirectional flow of lymph fluid toward the subclavian vein.

Anatomy Physiology Lymph Nodes masses of tissue enclosed in a capsule located throughout the body, prevalent in the neck, groin, bends of elbows and knees, armpits and in the mediastinum contain T-lymphocytes and B-lymphocytes Filter lymph before it reenters the bloodstream Guard the body Foundation of the immune system

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Anatomy Physiology Lymph the excess tissue fluid pumped through the lymphatic vessels consists of organic materials such as proteins and fats, some lymphocytes, maybe some red blood cells, and any microorganisms present Maintains homeostasis by balancing fluid distribution in the body Gets filtered in nodes and functional materials are recycled into the bloodstream. What do you think would be recycled?

Edema If excess fluid cannot be returned to the blood stream then interstitial fluid builds up, leading to swelling of the tissues with fluid, this is called edema. Link

Anatomy Physiology Thymus a gland that is larger in children than in adults produces thymosin, a hormone  that stimulates the differentiation and maturation of T cells

Anatomy Physiology Spleen a large lymph node that serves as a home for cells of the immune system  filters blood stores excess blood

Summary Video Link What 3 structures make up the lymphatic system? Vessels, nodes, and lymph The lymphatic system does not have a pump. How is lymph moved? Muscle action What structure keeps lymph flowing in one direction? Valves Why are proteins often transported in the lymphatic system? Proteins can more easily diffuse into lymph capillaries which carry the proteins to the veins What infection fighting cells are found in the lymph nodes? Lymphocytes