Ch. 7.9 Key Terms
A dilated sac at the inferior end of the thoracic duct, serving as a large collecting area for lymph from the lower body and the intestines. It plays a crucial role in the initial transport of lymph and chyle (lymph containing fats) back toward the circulation.
Cisterna
the body's ability to resist or protect itself against harmful foreign substances, such as pathogens (bacteria, viruses, fungi) and toxins. It involves a complex network of cells, tissues, and organs, primarily the lymphatic system, which recognizes and neutralizes these foreign invaders.
Immunity
specialized lymphatic capillaries located within the villi of the small intestine. Their primary function is to absorb dietary fats (in the form of chylomicrons) and fat-soluble vitamins, transporting them into the lymphatic circulation before they are transferred to the bloodstream. The fluid they carry is called chyle
Lacteals
the fluid that circulates throughout the lymphatic system. It is formed from interstitial fluid (tissue fluid) that collects in the lymphatic capillaries. is similar to blood plasma but contains fewer proteins and carries white blood cells (lymphocytes), which are essential for immune defense, along with fats, waste products, and cellular debris.
Lymph
small, bean-shaped organs distributed along the lymphatic vessels. They function as filters, containing dense masses of immune cells (lymphocytes and macrophages) that cleanse the lymph by trapping and destroying foreign substances, cancer cells, and pathogens before the lymph is returned to the blood.
Lymph Nodes
a vital part of the circulatory and immune systems. It consists of a network of vessels, ducts, nodes, and organs (like the spleen and thymus) that performs three main functions: draining excess interstitial fluid (to prevent edema), transporting absorbed dietary fats, and carrying out immune responses against disease.
Lymphatic System
a network of thin-walled tubes that transport lymph throughout the body. They start as microscopic lymphatic capillaries in the tissues, merge into larger vessels, and ultimately deliver the lymph to the two large collecting ducts (thoracic duct and right lymphatic duct) for return to the bloodstream.
Lymphatic Vessels
one of the two main lymph-collecting ducts. It is responsible for draining lymph from the upper right quadrant of the body: the right side of the head and neck, the right arm, and the right side of the thorax. It empties this lymph into the right subclavian vein
Right Lymphatic Duct
the largest lymphatic organ, located in the upper left abdomen. It has several functions: it filters blood, removes old or damaged red blood cells, stores platelets, and houses a significant number of lymphocytes and macrophages, making it a key site for immune surveillance and response against blood-borne pathogens.
Spleen
the major lymph-collecting vessel in the body, originating at the cisterna chyli. It collects lymph from the rest of the body (the entire lower body, left side of the upper body, and left side of the head and neck) and empties it into the left subclavian vein.
Thoracic Duct
primary lymphoid organ located in the mediastinum, behind the sternum. It is the site where T-lymphocytes (a type of white blood cell) mature and are "educated" to recognize and combat specific pathogens, a process crucial for adaptive immunity. It is most active during childhood and gradually atrophies in adults.
Thymus
masses of lymphoid tissue strategically positioned in the pharynx (throat). They form a ring (Waldeyer's ring) around the entrance to the digestive and respiratory tracts, where they trap inhaled and ingested pathogens. They initiate early immune responses by producing lymphocytes in reaction to these foreign substances.
Tonsils