Lymphatic System and its Functions

Lymphatic System Functions

• The lymphatic system includes structures and organs with lymphatic tissue, bone marrow, and the fluid lymph, all flowing within lymphatic vessels.
• Lymphatic system functions include transporting escaped fluids from the cardiovascular back into the blood, playing roles in body defense and resistance to disease, and transporting fats from the digestive system through lacteals to the bloodstream.
• Lymph passing through lacteals appears white and is known as chyle due to the presence of fat.

Lymphatic System Component

• The lymphatic system includes lymphatic capillaries, vessels, organs, and tissues, especially those that house T and B cells
• Vessels transport fluids that have escaped from the blood vascular system back to the blood.
• Lymphoid tissues and organs house phagocytic cells and lymphocytes and facilitate body defense and resistance to disease.
• Lymphatic vessels include lymphatic capillaries, small lymphatic vessels, lymphatic trunks, and lymphatic ducts.
• Lymphatic organs include the thymus, lymph nodes, and spleen.
• Lymphatic tissue includes tonsils and Peyer's patches.

Lymphatic Vessels and Capillaries

• Vessels start as lymphatic capillaries and are closed on one end; they're located between cells of many tissues.
• Vessels merge to form lymphatic vessels resembling veins and connect to lymph nodes at intervals; they have thin walls, many valves, and operate in a one-way system.

Lymphatic Capillaries

• Lymphatic capillaries weave between tissue cells and blood capillaries
• Capillaries walls overlap to form flaplike mini valves that allow fluid to leak into them, they are also anchored to tissues via filaments
• Higher pressure on the inside of the capillary closes the minivalves, preventing backflow; fluid gets forced along the vessel.

Formation and Flow of Lymph

• The flow of lymph is as follows: blood capillaries (blood) -> interstitial spaces (interstitial fluid) -> lymphatic capillaries (lymph)-> lymphatic vessels (lymph) -> lymphatic ducts (lymph) -> junction of the internal jugular and subclavian veins (blood)
• Plasma is first filtered by the blood capillaries, and then passes into interstitial tissue spaces, where it is called interstitial fluid.
• When the interstitial fluid passes into lymph capillaries, that fluid now becomes lymph, which then moves into lymphatic vessels.

Lymph

• Lymph characteristics include similar to blood plasma but with less protein, usually clear and colorless, may be milky if draining lipids from the small intestine.
• Components: lymphocytes, macrophages, bacteria, viruses, debris, and sometimes cancer cells

Lymphatic Vessels

• Lymphatic vessels are similar to veins of the cardiovascular system with thin walls, large valves, and low pressure; they function as a pumpless system.
• Lymph transport is aided by skeletal muscle action, pressure changes in the thorax during breathing, and smooth muscle in the walls of lymphatics.

Lymphatic Trunks and Ducts

• Lymph passes from the vessels through lymph nodes, and then into lymph trunks.
• Lymph trunks comprise the lumbar, intestinal, bronchomediastinal, subclavian, and jugular trunks.
• Lymph trunks merge to form either the thoracic duct or the right lymphatic duct.
• These ducts then return the lymph to the blood stream, near the heart

General Distribution of Lymphatic Collecting Vessels/Lymph Nodes

• The right lymphatic duct drains the right head, chest, and upper limb; and empties into the right subclavian vein.
• The thoracic duct is larger and longer than the right lymphatic duct.
• Thoracic duct drains the body below the diaphragm, the left head, neck, chest, and upper limb; and empties into the left subclavian vein.

Lymphoid Organs and Tissues

• Primary lymphatic organs include the bone marrow and thymus; sites where stem cells divide and become immunocompetent.
• Secondary lymphatic organs are sites where most immune responses occur, including the spleen and other lymphoid tissues like the tonsils.
• Primary lymphoid organs are organs where immune cells become immunocompetent – which are the red bone marrow and thymus.
• Secondary lymphoid organs and tissues include the lymph nodes, spleen and lymphatic nodules.
• The importance of the lymphoid organs and tissues is that they house and provide a proliferation site for lymphocytes, in addition to providing sureveillance points for lymphocytes and macrophages

Thymus

• The thymus is located at the inferior neck and extends into the superior thorax.
• This gland secretess thymoproietin and thymosins that cause T lymphocytes to mature.
• It is important at an early age, recesses in size at puberty, and loses structure at old age.

Lymphoid Tissues & Organs and Lymph Nodes

• Secondary lymphatic organs and tissues include lymph nodes, the spleen, and lymphatic nodules.
• Lymph nodes filter lymph before it is returned to the blood; clustering along lymph vessels.
• Lymph nodes filter harmful materials including bacteria, viruses, cancer cells, and cell debris.
• Defense cells within lymph nodes include macrophages, which engulf and destroy bacteria, viruses, and foreign substances; and lymphocytes, which respond to foreign substances in lymph.

Lymphatic Nodes

• Lymphatic nodes are typically kidney-shaped, less than 1 inch long, and buried throughout connective tissue; they are surrounded by a capsule and divided into compartments by trabeculae.
• The cortex (outer part) contains follicles which contain collections of lymphocytes and germinal centers that enlarge when antibodies are released by plasma cells.
• The medulla (inner part) contains phagocytic macrophages.

Lymph Flow

• Lymph enters the convex side of the lymph node through afferent lymphatic vessels.
• It then flows through a number of sinuses inside the node before exiting through efferent lymphatic vessels.
• Because there are fewer efferent than afferent vessels, the flow of fluid is slowed.

Spleen

• Located on the left side of the abdomen.
• Filters and cleans blood of bacteria, viruses, and debris.
• Is a major site for lymphocyte proliferation and immune surveillance.
• Destroys worn-out blood cells and forms blood cells in the fetus.

Lymphatic Nodules

• Lymphatic nodules are masses of lymphatic tissue, not surrounded by a capsule.
• They are scattered throughout the lamina propria of mucous membranes lining the gastrointestinal, urinary, and reproductive tracts, as well as respiratory airways.
• They are often referred to as mucosa-associated lymphatic tissue (MALT).

Tonsils and Peyer's Patches

• Tonsils are small masses of lymphoid tissue deep to the mucosa surrounding the pharynx.
• They function to trap and remove bacteria and other foreign pathogens.
• Peyer's patches are found in the wall of the small intestine, where Macrophages capture and destroy bacteria in this part of the digestive system

Immune System

• Immunity: the body's ability to protect itself by resisting or eliminating harmful foreign invaders or abnormal cells.
• Immune system functions include defending against invading pathogens, removing worn-out cells and damaged tissue, and immune surveillance to identify and destroy abnormal cancer cells.
• Major targets of the immune system are pathogenic bacteria and viruses, as well as any virulenence.
• Leukocytes are effector cells of the immune system - that include neutrophils, eosinophils, basophils, monocytes, and lymphocytes.
• Innate responses are a nonselective defense against foreign material, while adaptive responses selectively target particular invaders.

Innate (non-specific) Defense System

• It includes first and second line of defense meant to barricade the body against invaders.
• The adaptive (specific) defense system is the body's third line of defense.
• Innate immunity is also called as non-specific immunity, natural immunity, and native immunity and is the first and second line of defense.
• Most components exist prior meet with infection and the response is fast (takes few hours) to prevent entry of pathogens or foreign substance.

Components of Innate Immunity

• Physical barriers: 1st line of defence such as as skin covering, mucous membranes with its secretions
• Normal flora: 2nd line of defence harmless bacteria that live on our bodies
• Cellular barriers: E.g Leukocytes, Phagocytes, Cytotoxic leukocytes, Inflammatory leukocytes – Chemical barriers: the last defense where the body will begin to create proteins
• Chemical barriers: E.g Lysozyme, acids, digestive enzymes, lactoferrin
  • Acute inflammatory reaction and fever: E.g inflammation due to infection in tissues

Physical Barriers: Skin

• Skin is composed of layers of epithelial cells with outer layers of dead cells with waterproof keratin that that are to stop foreign substance from entering the body.
• Keratin is not affected by weak acids and bases and is resistant to bacterial enzymes and toxins.
• The pH, 3-5, discourages growth of many microbes and the dermis produces sweat containing high salt concentration.

Physical Barriers: Mucous membrane

• Mucous membrane: lining of the digestive, respiratory, urogenital tact and eyes.
• Mucous traps foreign substances in the body, and also contains :lysozyme that break the cell wall of any foreign bacteria, Digestive Enzymes that help kill many microorganisms and Lactoferrin that helps create antibacterial substances.
• Also sites of secretion of other substances that contribute to body defenses:
  • Lysozyme breaks down the cell wall of many bacteria
  • Acids, secreted in the stomach (pH2), kills most microorganisms that enter the body
  • Digestive enzymes and bile salts kills microorganisms
  • Lactoferrin in saliva, milk, seminal fluid
  • Spermine: - antibacterial found in semen

Mechanisms of Fluids

• Fluid:
  • Flow: wash wash away foreign subsyance
  • -Some membrane have cilia Cilia sweep the substance out

Normal Flora (2nd line of defence)

• Microbes that live on our body but do not cause any diseases nor any complications
• compete with pathogenic microbes and prevents invasion
• can inhibit growth of bacteria and fungi which are potential pathogen by competing, secreting toxic substances and forming bacterial layer.

Cellular Barriers (3rd line of defence)

• Phagocytic Leukocytes: ingestion of any foreign bacteria- Greek word cell – Phagocytic & Non-phagocytic Leukoytes
• • E.g Monocytes Macrophages Neutrophilis Eosinophiles

Complement System

• Complement proteins are synthesized mainly by the liver and then widely distribute in blood, lymph and extracellular fluid.
• Proteins helps or complements the ability of antibodies and phagocytic cells to clear pathogens by coating pathogens and facilitating destruction.
• Function of complement system in the body
  • Opsonization: The microbe cells are coated so macrophages can internalize and destroy
  • -Chemotaxis: Attracting macrophages and neutrophils
  • Cell lysis: disrupting membranes of foreign cells
• -Clumping of antigen: bearing agents

Acute inflammatory reaction & Fever

• Inflammatory reaction occurs when tissue is damaged whether its physical, chemical agent and pathogens
• Characterized by swelling, redness, heat and pain Functions: i. To deliver leukocytes ii. to localize the mico organism Iii To repair and replace tissue damaged by the harmful products

Major events in acute inflammation

• Vasodilation: diameter of blood vessels,
  • Following: tissue damage and vasoactive agents and histamine, -Increase bloow to damaged area causing redness, erthymea and increase in tissue permeability

Leukoytes Function

• Repair: To restore damage to tissue back to original from

Fever

• is a systemic response to attacking microorganism accompanying systemic inflammation, above 37°C.
• The are triggered by a chemical substance pyroogen: Endotoxins bacteria • Helps reduce the rate of bacterial growth by reducing rates of F and Zn
• and Increases the activity of phagocyte, T-leukocytes and repair process

Adaptive Immunity: Self Nonself Recognition

• Identifies self and non self
• A self marker lables bodies cells as friends that are not able to harm any of the other cells
• Identidyong non-self markers such as antigens are recognizes as forieign substances to cells, therefore the cells can attack.

Adaptive Immunity: Antigen Specificity

• Inates are able to recognize the markers on a variety of non self invades, where as aptive are able to recognize very specific markers.

Adaptive Immunity: Immunological Memory

• Is the abiltiy to recall what the cell have in their memory to see if their has been any contact with any forieng molecules.
• respond with more rapid and larger response

Types of adaptive immunity

• Adaptive immunity is the immune, humoral and mediated cells that have extracellular and intracellular microbes
• Involves: Antibodies, B,T and cytoxin cells

Development of B and T cells

Lymphoyctes are to develop from precursor cells that that originate form the bone marrow and themus.

B Lymphocytes

• A lymphocye is produced and matured in the bone marrow
• They become anditboys and plasma cells
• They will become antibdodies

A naïve B cell

• When it interctacts with an antigen, it will create plasma and memory cells.

Antibody

• Naive B cells matches woth an antibody -It will divide by becommign memory and cell
• Plasma cells helps to bind the antegens so it eliminate the origonal antegens from the body.

Adaptive Immunity :

• -Innate
• -Self Non self recognition -Antigen Specific,
• Immuno logical Memory

Helper + cytotic T cecl

• T cells must match the major histocompatibility complex.
• If all matches it will activate the cytotoxic t cell so it destrys it and creates a response with a helper to cell

Activation of Naïve T cells

• Naïve T cells express the antigen receptor CD4+ and it turns into a helper

Three ( mature of type of active and helper T)

• -Recognize and bind
• • secrete chemical that help simualte that helps poduce B and ab

naieve t cells who posses ag+ CD=8 it ill become cytotoxic t cells.

Comparison of Adaptive Immunity:

• adaptive immunitu includes, "Humoral Immunity"which will help identify bacteria such as, ext cell, virus and bacteria
• Adaptive cells
• Cell mediared cell also helps indentidfy all protens that are presented to the apcc, to see if it has a moleculre compund.

Explore the primary functions of the lymphatic system, focusing on its vital role in immunity, fluid balance, and lipid absorption. Understand the interconnections between lymph, lymphatic vessels, and lymphoid tissues, and the consequences of lymphatic system impairment.