The Lymphatic System

1. The Lymphatic System

2. The Function of the Lymphatic System • The lymphatic system is designed to fend off pathogenic organisms. It also removes excess fluids in between cells and brings it back to the blood stream. • Lymph is also responsible for the absorption of fats in the small intestines.

3. Lymphatic pathways • Patterns of vessels that transport lymph. This allows the transport and relocation of various components like T-cells and lymph.

4. Lymphatic capillaries • Microscopic tubes that extend interstitially (between cells) and parallel to the circulatory system. • The fluids inside these vessels is called lymph.

5. Lymphatic vessels • Lymph from the lymphatic capillaries is carried into the lymphatic vessels. These vessels have flaps on them just like in the veins of the circulatory system to prevent lymph from flowing backwards.

6. Lymph nodes and Lymphatic trunks • The larger bundles of lymphatic tissue are referred to as lymph nodes. • Lymph nodes then dump their lymph into even larger bundles called lymphatic trunks.

7. Lymphatic trunks • Lymphatic trunks are aptly named for the regions in which they serve. All trunks dump into one of two specialized collecting ducts. • Collecting ducts • Thoracic duct • Right lymphatic duct

8. Thoracic and right lymphatic duct • Thoracic duct- Larger and longer of the two ducts. Gathers lymph from the lower limbs, abdominal region, left side of the thorax, head and neck. Empties into the left subclavian vein.

9. Right lymphatic duct- smaller of the two, gathers lymph from the right side of the head neck and thorax. Empties into the right subclavian vein, near the right jugular vein.

10. Lymphatic tissue fluid formation • Tissue fluid originates as blood plasma. • That plasma contains water and dissolved proteins in it. Parts of this fluid can be removed by diffusion and filtration. • Some of the smaller proteins free floating in the plasma are not reabsorbed through venular ends of the capillaries. • This causes a change the level of osmotic pressure in the fluid.

11. The higher osmotic pressure in turn causes a large increase in the hydrostatic pressure (pressure that water has when at equilibrium) forcing some liquid into the lymph capillaries where it becomes lymph. • The lymph returns most of the proteins lost back when it enters the bloodstream. • At the same time, lymph transports foreign particles like bacteria and viruses to the lymph nodes.

12. Lymph Nodes • It is in the lymph nodes that the most lymphocytes and macrophages do battle with the microorganisms that enter the body everyday. • There is an indented region in the lymph node where blood vessels and nerves run to the node. This region is called the hilium.

13. Locations of major lymph nodes • Thoracic cavity nodes- chest • Cervical nodes- throat • Axillary nodes- armpit • Supratrochlear nodes- distal end of the humerous • Abdominal cavity nodes- abdomen • Pelvic cavity nodes- pelvic region • Inguinal nodes- upper thigh and groin region.

14. Major organs in the lymphatic system • Thymus- located anterior to the heart and posterior to the sternum. Soft and bilobed (two lobed). Large in children, small and reduced in adults. • Some T-cells can be found here.

15. Spleen • Largest lymphatic organ, located in the upper left portion of abdominal cavity. Inferior to the diaphragm. Posterior and lateral to stomach.

16. D -

17. The body fighting against infection • Pathogen-disease causing agent • Two types of defense: • Nonspecific • Specific (immunity)

18. Nonspecific defenses • Nonspecific defenses are designed to deal with a variety of different pathogens. Different nonspecific defenses are: • Species resistance • Skin and mucus membranes • Interferons- proteins secreted by immune system to fight infection • Inflammation • Phagocytosis

19. Species defense • When a disease only affects one species of organism, all other species are immune to getting that disease. • Oak blight kills oak trees. Humans are not oak trees, thus cannot get oak blight.

20. Mechanical barriers • Body’s first line of defense. When not damaged, they prevent most diseases from entering the body. • Skin • Mucus membranes

21. Chemical barriers • Chemical barriers are chemicals secreted by the body that due to their very nature can make it impossible for a bacteria to survive. • Pepsin and HCl in the stomach. • Interferons eliminating viral coats and tumor cells.

22. Fever • The body begins to raise its overall temperature. • Liver and spleen begin to hold on to extra iron as a result. • Bacteria need more iron as the temperature rises, this causes a composition change in the blood and kills the bacteria in the blood. • (bad news) maintaining a high fever (105O F or greater) over an extended period can cause organ and brain damage if not brought down.

23. Pus- when lymphocytes and bacteria are all collected in one place, pus may form.

24. Phagocytosis • When monocytes and neutrophils devour foreign invaders, they attack indiscriminately, regardless of the make up of the bacteria or virus.

25. Specific Immunity • Specific immunity is designed to target one specific problem. When you get a flu shot each year, you receive a vaccine, you receive immunity to a specific strand of the flu virus. That strand has a unique protein coat that only it has. When your body runs into that protein coat again (after vaccination) you will immediately produce the antibodies to remove the threat without getting sick again.

26. Antigens • Cell surface markers. Helps body recognize other cells as “self” or “foreign.”

27. lymphocytes • Provide immunity by creating antibodies. Can differentiate into B-cells and T-cells. Upon reaching the thymus, lymphocytes can be given the biochemical cocktail they need to specialize into t-cells. B-cells will specialize in the bone marrow.

28. T-cells and B-cells • B-cell- 20-30% of lymphocytes in the blood. B-cells tend to settle in lymphatic organs. Produce antibodies that destroy antigens and antigen bearing agents. Using antibodies (immunoglobulins) to destroy a pathogen is called antibody-regulated immunity. • T-cell- 70-80% of lymphocytes in the blood. Interact directly with antigen source with agents to destroy that source. Binding to the pathogen directly is called cell-mediated immunity.

29. When to attack • T-cell activation- When a pathogen is phagocytized by a monocyte, some of the antigens from the pathogen stick out of the monocyte near a major histocompatibility complex (MHC). If the T-cell recognizes the antigen as a foreign antigen, then the T-cell will activate. This type of T-cell is called a helper T-cell because it assists another lymphocyte in non-self cell removal.

30. Another way this occurs is when T-cells subdifferentiate into cytotoxic T-cells. They recognize a non-self antigen as being cancerous or viral and binds to the antigen and activates and releases a protein that shreds the antigen bearing agent.

31. B-cell activation • B-cells will come in contact with an antigen bearing source. As a result, the B-cell will bind to it and begin to divide and create more copies of itself. When an activated T-cell finds a B-cell that is now bound to an antigen, the helper cell will release cytokines that cause the B-cell to grow and increase antibody producing cells. • Later outbreaks of that pathogen will be easily quelled due to some B-cells becoming memory-cells and “remembering” that pathogen. When that pathogen appears again, it will be quelled near instantly.

32. Immune Response • Primary Immune Response- First response to an antigen. Ends with creation of memory cells. • Secondary Immune Response- subsequent response to encountering antigen. Memory cells know what to do and eliminate threat to the body.

33. Active Immunity • Two ways to acquire active immunity: • First way- Get sick, produce memory cells that now recognize antigen. • Second way- Vaccination. Vaccinations introduce a dead (inactivated) or weakened (attenuated) virus into the body. The body easily fights off this virus, gains the memory cells it needs, and now is ready to encounter the full strength virus.

34. Passive immunity • When immunity is given by receiving antibodies from an outside source. Often given when we fail to produce immunity fast enough or if we are not able to at all. • i.e. Rabies vaccine.

35. Allergies • Hypersensitive response to a stimulus. • Eating tree nuts- not normally harmful but the body perceives it as a threat and attacks the threat in full force.