Find I and the power absorbed by each element in the network of Fig. 1.30.
Clemson University Spring 2016 Lymphatic System PowerPoint Slide 1: Lymphatic System (Overview) • Relation to the circulatory system: -‐ All exchanges that occur between the circulatory system (Blood stream) and tissues have to pass through the interstitial space -‐ Fluids move out into the interstitial space from the arteriole side of the capillary bed -‐ Most fluids return to the blood stream through the venous side of the capillary bed -‐ The rest of the fluids that did not come back through the venous side are picked up by the lymphatic system • Ultimately, the lymphatic system returns the leftover fluids into circulation • Osmotic pressure is generated with the capillaries due to the proteins (Ex: Albumin) found in the circulatory system • These proteins are not able to diffuse across capillaries so the lymphatic system functions in bringing the proteins into the lymphatic vessels so that they can be put into the circulatory system • Overall: Lymphatic system functions to— a) Return fluid to the circulatory system to maintain blood volume b) Allows large molecules to pass into the circulatory system c) Filters blood fluids d) Involved with some immune function • Lymphatic system acts as a transition between the circulatory system and immune system Slide 2: Components • Lymphatic vessels: -‐ Collect interstitial fluid and ultimately return it back into the circulatory system • Lymphoid tissues and organs: -‐ Most of the lymphoid tissues are made up of reticular connective tissue -‐ Specialized organs: Lymph nodes, spleen, tonsils, thymus -‐ Lymph: o Excess fluid formed from plasma that accumulates in tissues as interstitial fluid o Fluid inside the lymphatic vessels that enters into circulation to become a part of the plasma (Again) o Fluid includes proteins that are ultimately transported to the blood -‐ Within the lymphoid tissues and organs, there are many active cells (B and T lymphocytes and phagocytic cells) that provide the immune functions for the lymphatic system • Overall: Lymphatic system has immune, blood filtration, and blood volume functions Slide 3: Lymphatic Vessels • Lymph flows in the lymphatic vessels one way towards the heart à Close-‐ ended circuit • Lymphatic capillaries are the smallest of the lymphatic vessels and are dead-‐ ended structures • Fluid in the interstitial space makes its way into lymphatic capillaries that travels into other lymphatic vessels until it’s dumped back into the jugular veins near the heart Slide 4: Lymphatic Capillaries • Smallest of the lymphatic vessels • Only have one layer of tissue = endothelium • Endothelial cells are anchored by connective tissue (Collagen filaments) • Lymphatic capillaries are formed by loosely overlapping endothelial cells à Allows them to be able to open and close as cells get distended because of pressure difference inside and outside the capillary -‐ Spaces are created as a result = minivalve system -‐ Minivalves: Overlapping endothelial cells that allows fluid into lymphatic capillaries but not out • Minivalve system: -‐ Higher pressure of the fluid outside of the lymphatic capillary (Flud in the interstitial space) causes it to bed à Opens the overlapping flaps (AKA minivalve flaps) so that fluid can move in -‐ Higher pressure of fluid inside the lymphatic capillary than outside in the interstitial space pushes the minivalves shut so that the cells overlap à Exit for fluid is shut off so that the fluid stays inside the lymphatic capillary and flows in one direction towards the heart • Found throughout the entire body except in bones, teeth, and nervous system Slide 5: Lacteals • Lymphatic capillaries of the intestines • The villi of the small intestine contains tiny capillaries that will collect stuff (lacteals) • Small intestine is the site of digestion and absorption of nutrients à Some molecules are too large to go through the regular capillaries of the blood so they enter through the lacteals • Lipids especially go through lacteals à circulatory system • Chyle: Lymph in the small intestine lacteals à Chyle is rich in fats Slide 6: Lymphatic Vasculature: Lymphatic Capillaries • Start with tiny, dead-‐ended, very permeable lymphatic capillaries that are branched everywhere Slide 7: Lymphatic Vasculature: Lymphatic Collecting Vessels • Some lymphatic capillaries merge into the lymphatic collecting vessel • Contain tunica interna, tunica media, and tunica externa • Unlike veins, lymphatic collecting vessels’ tunics are much thinner • Lymphatic vessels also have valves to prevent back flow of blood (Uni directional flow) + have more valves than veins -‐ Valves are important especially because there isn’t a pump to provide pressure to push the lymph towards the heart Slide 8: Lymphatic Vasculature: Lymphatic Trunks • Lymphatic collecting vessels à lymphatic trunks • Lymphatic trunks: Collect and drain large regions of the body Slide 9: Major Lymphatic Trunks • 5 named based on areas they drain: a) Bronchomediastinal: -‐ Located where the heart is -‐ Drain the lungs—Middle of the thorax b) Subclavian: -‐ Located under the clavicle -‐ Drain upper limbs c) Jugular: -‐ Drain from the head d) Lumbar: -‐ Drain lower extremities or lower abdominal cavity e) Intestinal: -‐ Drains abdominal cavity Slide 10: Lymphatic Vasculature: Lymphatic Ducts • Right Lymphatic Duct: -‐ Drains the head, upper arm, and thorax -‐ Upper right portion of the body in general • Thoracic Lymphatic Duct: -‐ Drains the rest of the body – Lymph comes from the entire body below the diaphragm • The body is divided into these two regions that are not considered to be halves—Up high = right region and down low = thoracic region • Both ducts connect at the junction between the jugular and subclavian veins (The jugular connection is where the lymph goes back into the blood stream in the circulatory system) Slide 11: Factors Assisting Lymphatic Flow • Valves: -‐ Support unidirectional flow of lymph towards heart • Muscular pump: -‐ Activity of skeletal muscle helps push fluid in one direction along with working with the valves -‐ In terms of lymph filtration: o Ex: If there is a puncture wound in the skin, it is possible for bacteria to have entered the fluid in the interstitial space à It is necessary to filter this through the lymph organs (Such as spleen) o Being physically active allows the body to filter the lymph and blood even more to remove disease causing agents—muscular pump helps prevent illness as a result and speeds up recovery in • Respiratory pump: -‐ During low pressure status in the chest, the lymph is allowed to move more easily • Arterial pumping: -‐ Lymph vessels are located next to arteries so when blood has a wave pushing it through the blood vessels, the wave also helps the lymph vessel to have the same sort of effect • Smooth muscle contraction: -‐ Even though the tunica media is very small in the lymphatic arteries, the smooth muscle contraction will still help move the lymph towards the heart -‐ Smooth muscle contraction is especially important with the lymphatic trunks and thoracic duct • Gravity can also play a role in helping lymph from the top part of the body to move towards the heart Slide 12: Lymphoid Cells: Lymphocytes • Lymphocytes: -‐ White blood cells that are mostly composed of nucleus -‐ All made in the red bone marrow -‐ B lymphocytes: o Immune function o Lymphoid follicles of the cortex of a lymph node contain germinal centers that are dominated by B lymphocytes, which produce antibodies against antigenic agents o When encounters a pathogen such as a bacterium in a blood stream: Triggered to produce plasma which starts to produce antibodies that can attach to foreign cells with specific markers à Marks the foreign cell to be destroyed by something like a macrophage o AKA B lymphocytes do not destroy pathogens themselves (Mark them for destruction by other cells) -‐ T lymphocytes: o Immune function o Directly attacks and destroys foreign cells that have already invaded our body cells (NOT a free floating pathogen at this point) o Attaches to pathogen and through secretion of chemicals, it causes the pathogen to lyse and break apart -‐ Able to produce memory cell after interacting with a foreign substance for the first time Slide 13: Lymphoid Cells: Macrophages • When monocytes diapedese and leave the circulatory system à Interstitial space to become a macrophage • Phagocytic cell • Activate T cells • Take in foreign cells and starts to break it up à T lymphocyte comes and kills it • Function in the stroma in lymph organs Slide 14: Lymphoid Cells: Dendritic Cells • Phagocytic • Activate T cells • Take in foreign cells and then T cell comes to kill pathogen • Function in the stroma in lymph organs • *Macrophages and dendritic cells difference in their mechanism by which they attach to foreign cells Slide 15: Lymphoid Cells: Reticular Cells • Reticular cells have reticulocyte fibers that make the mesh/network to produce stroma that can house/hold other cells temporarily such as macrophages • Filter the lymph à Lymph is able to pass by active cells that can detect foreign cells and get rid of them Slide 16: Lymphoid Tissue • Lymphoid tissue—Mainly made up of reticular cells • In the lymph node, it has a nodular component that contains the stroma = germinal centers • Germinal centers: -‐ Have the reticular cells holding cells such as macrophages, lymphocytes, etc. à Everything is held in place temporarily (Some move in and out) -‐ Proliferation for lymphocytes (Location where the other types of cells in the lymphoid organs proliferate/accumulate in the centers) -‐ Allows detection of infection or damage: o As lymph passes through lymphoid tissue, impurities can be attacked and removed before the lymph goes back into the circulatory system • Thymus does NOT contain reticular tissue -‐ All embryonic tissue is derived from the mesoderm but the thymus isn’t -‐ Thymus develops first though and controls the development of lymph organs Slide 17: Lymph Nodes • Principal lymphatic organs of the body • Accumulations of lymph nodes are found along the larger lymph vessels so that as the lymph passes through the vessels towards the heart, the lymph nodes filter it • Lymph nodes possess germinal centers with accumulations of lymphocytes à Detect foreign substances and initiate immune responses Slide 18: Spleen • Largest lymph organ • Located behind the stomach • Allows lymphocyte proliferation + detection of foreign substances = immune function • Site of blood cleansing too (Site of breakdown)à Removes aged and defective cells + gets rid of platelets and recycles these components • The spleen contains many macrophages à phagocytosis of foreign cells • Plays an important role with infants: -‐ Blood cells are produced in red bone marrow -‐ Infants are generally born without an intact skeletal system so the bone marrow isn’t fully functional -‐ Babies/embryos then obtain blood cells from the spleen • Overall in adults the function of the spleen is to filter lymph, recycling red blood cells, and cleanse the blood Slide 19: Lymphoid Organs: Thymus • Thymus is very active in new born babies à decreases in size as get older • Promotes immunocompetency in T cells à Gives the cell the ability to interact with something foreign • Each class of T lymphocytes bind to specific receptors on foreign cells • B lymphocytes become immunocompetent in the bone marrow Slide 20: Lymphoid Organs: Tonsils • Gather and remove pathogens entering the body through the food that is being consumed or air breathed • Located in oral and nasal cavities Slide 21: Lymphoid Organs: Peyer’s Patches • Located in the distal part of the small intestine • Able to destroy bacteria Slide 22: Lymph Node Action • A cortex and capsule surround the whole lymph node • At the center is the medulla • Hilum: Depression/indention of a lymph node • Contains 2 different draining lines • Lymph that is flowing through the lymphatic vessels enters the lymph node via afferent lymphatic vessels and passes through the cortex through the sinuses to the germinal centers where there is reticular tissue with macrophages and macrocytes that filter the lymph • Next, the lymph goes to the medulla and exits at the hilum where it is then pushed out through efferent lymphatic vessels • There are fewer efferent than afferent lymphatic vessels à Means that the flow of lymph is slowed down so that there is lymph filtration efficiency • Efferent lymphatic vessels can lead to other lymph nodes where the lymph can be filtered again • Mastering HA&P Description: Afferent vessels deliver lymph to the lymph node. The lymph then filters through the subcapsular sinus of the node and then into a number of smaller sinuses that cut through the node's cortex and lead into the medulla. Eventually, lymph exits the node via the hilum and is carried away by efferent vessels Slide 23: Spleen Action • Blood vessel supply goes directly to the spleen through the splenic artery • White pulp: Surrounds the blood vessel • Fluid in the blood is pushed through the white pulp so that it is filtered and then it gets pushed out through red pulp à splenic vein à back to circulation • Red pulp: Makes up most of the spleen that surrounds the white pulp • Again: Spleen gets rid of old cells, recycles, and checks fluid for impurities Slide 24: Thymus Action • Secretes 2 chemicals: Thymosin and thymopoietin à Can trigger white blood cell production in the red bone marrow • Chemicals cause immunocompetency to occur in T lymphocytes • No reticular tissue is in the thymus so no filtration of lymph occurs (Nothing is there to hold the other cells in place that function in the filtration) Slide 25: Palatine Tonsils • Multiple sets of tonsils are in the body • Filter food and air that is breathed à Pass the pharynx where the tonsils are there to stop pathogens • Tonsil names are based on where they’re located • Largest tonsil: Palatine à Located in the back of the throat on each side of the oral cavity where they meet the pharynx and is the one more lastly to become infected and removed via tonsillectomy Slide 26: Lingual Tonsils • Two are located on each side under the base of the tongue Slide 27: Pharyngeal Tonsil (Adenoids) • Single one located on the posterior wall of the nasal cavity • Often times when the palatine tonsils are removed, the adenoids are also removed since they’re easy to get to Slide 28: Tubal Tonsils • In order for hearing to work, the middle ear has to be equal to the atmospheric pressure • There is the pharyngeal tube that runs down the middle pharynx and it is where the tonsils surround the tube Slide 29: Tonsil Histology • Follicles with germinal centers • Crypts: Dead end ally ways à As swallowing or breathing the liquid or air gets into the crypts à Diffuses into lymphatic tissue à Passes through germinal centers with reticular tissue to get filtered Slide 30: Tonsil Action • Crypts trap bacteria and other particulates à Bacteria cross membrane and get into tonsil tissue ultimately passing through reticulocytes where all the lymphoid cells accumulated in the germinal centers that destroy pathogens – In this process, memory cells can be formed Slide 31: Peyer’s Patches • Isolated clusters of lymphoid follicles in the distal portion of the small intestine that destroy bacteria • Contain lymphoid tissue that filters chyle • Produce memory cells especially since food that is being digested and the absorbed is likely to be there again Slide 32: Lymphatic Development • 5 week post-‐conception is when the production of lymphatic vessels begins • Lymph sacs bud off developing veins and are first to form on the jugular veins à Where the connection is going to be for the lymphatic and circulatory systems • Some lymph sacs form on the vena cava and iliac veins (Low at bottom thoracic trunk) • Lymph sacs then begin to branch: Start with the big vessels and branch down to the small ones (Different than how arteries and veins develop) • Jugular lymph sac attaches to the jugular vein to become the right lymphatic duct and thoracic duct • All organs except the thymus come from the mesodermal mesenchyme that becomes reticular tissue • Lymphoid organs develop and migrate to different parts of the body • Thymus: -‐ Endoderm derivation -‐ Outgrowth of pharynx that detaches and migrates to the thoracic cavity -‐ First lymphatic organ to form -‐ Starts to accumulate lymphocytes until after birth -‐ Secretions of thymocytes (Thymopoietin and thymosin) are important in the regulation of development of other lymphatic organs