Question

Ch 21The Lymphatic and Immune Systems

  4. Describe how lymph nodes function as lymphatic organs.

  5. Describe the function, recirculation, and activation of lymphocytes.

  6. Relate the structure of lymphoid tissue to its infection-fighting function.

  7. Describe the locations, histological structure, and immune functions of the following lymphoid organs: thymus, lymph nodes, spleen, tonsils, aggregated lymphoid nodules in the intestine and appendix.

  8. Describe the basic characteristics of two disorders of the lymphatic vessels: chylothorax, lymphangitis; and three disorders of lymphocytes and lymphoid organs; mononucleosis, and Hodgkin’s lymphoma.

Answer 1

4.The lymphatic system is a network of tissues and organs that help rid the body of toxins, waste and other unwanted materials. The primary function of the lymphatic system is to transport lymph, a fluid containing infection-fighting white blood cells, throughout the body.Lymph nodes filter and transmit nutrients, lymph fluid, and waste between the body's tissues and the bloodstream. Lymphatic tissues such as the spleen, tonsils, and thymus contain high concentrations of white blood cells and are able to identify and destroy toxins in lymph fluid.

5.Lymphocytes are primarily involved in the body's immune response mechanism. This involves complex phenomena which end in the development of humoral and cellular immunity. Humoral immunity involves the production of antibodies (immunoglobulins), and is brought about by lymphocytes, which are called B-cells.Lymphocyte recirculation refers to the continuous transport of large numbers of naïve lymphocytes between the blood and lymphatic systems. ... Subsequently, they leave these tissues and migrate continuously between the lymphoid and nonlymphoid organs, using the blood vessels and lymphatic system as trafficking routes.Lymphocyte activation occurs when lymphocytes (B cells or T cells) are triggered through antigen-specific receptors on their cell surface. This causes the cells to proliferate and differentiate into specialized effector lymphocytes.

6.The lymphatic system's travels in a relatively similar was as the circulatory system. It's circulatory structure allows for the liquid that transports throughout the body to easily drain fluid from our cells, and also makes it easier for lymph vessels to distribute our immune cells around the body.

7.

• Thymus - The thymus is located in the upper anterior (front) part of your chest directly behind your sternum and between your lungs.The thymus is an encapsulated primary lymphoid organ. Histologically, it is divided into subcapsular cortical, cortical and medullary regions within each lobule, created by the intervening connective tissue septae extending from the capsule. ... These are the thymic epithelial cells and thymocytes.The thymus produces progenitor cells, which mature into T-cells (thymus-derived cells). The body uses T-cells help destroy infected or cancerous cells. T-cells created by the thymus also help other organs in the immune system grow properly.
• Lymph nodes are small, bean-shaped glands that are located along the lymphatic system (a system of vessels similar to arteries and veins through which lymph fluid travels).The lymph nodes are organized lymphoid organs that contain lymphocytes within a fine reticular stroma. ... The range of normal histological findings within groups of lymph nodes due to normal immune functions should also be considered.Dendritic cells and macrophages within this organ internalize and kill many of the pathogens that pass through, thereby removing them from the body. The lymph node is also the site of adaptive immune responses mediated by T cells, B cells, and accessory cells of the adaptive immune system.
• Spleen: Function, Location & Problems. The spleen is located on the left side of the abdomen, under the ribs. The spleen is the largest organ in the lymphatic system. It is an important organ for keeping bodily fluids balanced, but it is possible to live without it. Your spleen's main function is to act as a filter for your blood. It recognizes and removes old, malformed, or damaged red blood cells.Your spleen also plays an important part in your immune system, which helps your body fight infection. Just as it detects faulty red blood cells, your spleen can pick out any unwelcome micro-organisms (like bacteria or viruses) in your blood.
• The tonsils (palatine tonsils) are a pair of soft tissue masses located at the rear of the throat (pharynx). Each tonsil is composed of tissue similar to lymph nodes, covered by pink mucosa (like on the adjacent mouth lining).Tonsils are large non-encapsulated (or partially encapsulated) masses of lymphoid tissue, that lie in the walls of the pharynx and nasopharynx and at the base of the tongue. The luminal surface of the tonsils are covered with a stratified squamous epithelium (in common with the oral epithelia).The tonsils are part of the body's immune system. Because of their location at the throat and palate, they can stop germs entering the body through the mouth or the nose. The tonsils also contain a lot of white blood cells, which are responsible for killing germs.
• Peyer's patches (or aggregated lymphoid nodules) are located in your small intestine, usually in the ileum area. The ileum is the last portion of your small intestine. In addition to further digesting the food you eat, the ileum also absorbs water and nutrients from food.Peyer's patches are observable as elongated thickenings of the intestinal epithelium measuring a few centimeters in length. About 100 are found in humans. Microscopically, Peyer's patches appear as oval or round lymphoid follicles (similar to lymph nodes) located in the mucosa layer of the ileum and extend into the submucosa layer. Peyer's patches are small masses of lymphatic tissue found throughout the ileum region of the small intestine. Also known as aggregated lymphoid nodules, they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines.

8.

• A chylothorax is an accumulation of lymphatic fluid in the space surrounding the lung (pleural space). Lymph formed in the digestive system is called chyle and accumulates in the pleural space due to either disruption or obstruction of the thoracic duct. In people on a normal diet, this fluid collection can sometimes be identified by its turbid, milky white appearance, since chyle contains triglycerides. It is important to distinguish a chylothorax from a pseudochylothorax (a fluid collection in the pleural space that is high in cholesterol), which has a similar appearance, but is caused by more chronic inflammatory processes, and requires a different treatment.Chylothorax is a rare but serious condition. It results from leakage of lymph fluid from the thoracic duct or one of its tributaries. There are many treatments, both surgical and conservative. About 2-3% of all fluid collections surrounding the lungs (pleural effusions) are chylothoraces.

• Lymphangitis is an inflammation or an infection of the lymphatic channels that occurs as a result of infection at a site distal to the channel. The most common cause of lymphangitis in humans is Streptococcus pyogenes (Group A strep), although it can also be caused by the fungus Sporothrix schenckii.Lymphangitis is sometimes mistakenly called "blood poisoning". In reality, "blood poisoning" is synonymous with sepsis.Signs and symptoms include a deep reddening of the skin, warmth, lymphadenitis (inflammation of a lymphatic gland), and a raised border around the affected area. The person may also have chills and a high fever along with moderate pain and swelling. A person with lymphangitis should be hospitalized and closely monitored by medical professionals.Lymphangitis is the inflammation of the lymphatic vessels and channels. This is characterized by certain inflammatory conditions of the skin caused by bacterial infections. Thin red lines may be observed running along the course of the lymphatic vessels in the affected area, accompanied by painful enlargement of the nearby lymph nodes.When the inferior limbs are affected, the redness of the skin runs over the great saphenous vein location and confusion can be made with a thrombophlebitis.Chronic lymphangitis is a cutaneous condition that is the result of recurrent bouts of acute bacterial lymphangitis.

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