Lymphatic System and Immunity

• The immune system consists of cells, tissues, and molecules mediating resistance to infections.
• Immunology is the study of the immune system's structure and function.
• Immunity is the host's resistance to pathogens, and their toxic effects.
• The immune response is a collective, coordinated response to foreign substances, mediated by cells and molecules.
• The lymphatic system includes cells, tissues, and organs defending the body against environmental hazards and internal threats like cancer.
• Lymphocytes are the primary cells of the lymphatic system.
• Lymphocytes respond to pathogens, abnormal cells, and foreign proteins, eliminating or neutralizing them physically and chemically.
• Pathogens include viruses, bacteria, fungi, and parasites.
• The lymphatic system is vital for resisting or overcoming infection and disease.

The Lymphatic System Components

• Network of Lymphatic Vessels
• Lymph fluid
• Lymph nodes

Lymphoid Organs and Tissues

• Spleen
• Thymus
• Tonsils
• Lymph nodes
• The body employs innate (nonspecific) defenses and adaptive (specific) defenses.
• The immune system is a functional system involving integumentary, skeletal, lymphatic, cardiovascular, respiratory, and digestive systems.
• Organs such as Tonsils and adenoids, Thymus, Lymph nodes and Spleen employ Cells like Lymphocytes, T-Lymphocytes, B-Lymphocytes, plasma cells and Natural Killers lymphocytes and Molecules like Antibodies, Complement, cytokines and interleukines
• Peyer's patches, Appendix, Lymphatic vessels and Bone marrow employ cells like Monocytes, macrophage, Granulacytes, neutrophils, eosinophils and basophils and Molecules like Interforns

Functions of the Lymphatic System

• The main role of the lymphatic system is to produce, maintain, and distribute lymphocytes and lymphoid cells for defense against infections and foreign substances.
• Lymphocytes detect problems and reach injury or infection sites for effective defense.
• The system maintains normal blood volume.
• It eliminates interstitial fluid variations by distributing hormones, nutrients, and waste.

Lymph Composition

• Water
• Sugars, proteins, and fats
• Vitamins, minerals, and salts
• Waste products from cells
• Germs or toxins
• Damaged or abnormal cells, including cancer cells

Lymph Functions

• Lymph collects excess tissue fluid and returns it to the bloodstream, aiding fluid balance.
• Lymph removes harmful substances and filters out abnormal cells and waste.
• Lymph transports nutrients and proteins to cells and tissues.
• Lymph collects fluid from the intestines with fats and molecules too large for capillaries, called chyle, and transports it to the bloodstream.
• Lymph has an immune defense role by producing lymphocytes that destroy invaders like bacteria, viruses, parasites, and fungi.
• Lymph enables intercellular communication between cells.

Lymph Flow

• Lymph is a watery, milky, or pale yellow fluid.
• Color comes from protein waste products and immune cells.
• Interstitial fluid, a plasma, passes through capillary walls.
• Lymph capillaries pick up interstitial fluid into the lymphatic system.
• Lymph travels through lymph vessels to lymph nodes, which filter it.
• Filtered lymph returns to the bloodstream.
• Obstruction of lymphatic vessels causes lymphedema, resulting in large lymph accumulation in the affected region, leading to swelling, especially in subcutaneous tissues.
• Persistent lymphedema causes connective tissues to lose elasticity, making the swelling permanent.
• Lymphedema itself is not life-threatening; the risk of uncontrolled infection in the affected area poses a danger.
• Stagnant interstitial fluids allow toxins and pathogens to overwhelm local defenses, hindering full activation of the immune system.

Tonsils

• Tonsils' Functions:
• They trap germs in the back of the throat, preventing bacteria and viruses from entering the body through the mouth or nose.
• Tonsils contains white blood cells that kill germs and produce help prevent and fight infections.
• Lymphocytes trigger the body's immune system when they bind to pathogens.

Spleen

• Spleen contains the largest mass of lymphoid tissue in the body.
• Spleen performs same function for blood as lymph nodes do for lymph (filter)
• Removes abnormal red blood cells and other blood components by phagocytosis
• Stores iron recycled from red blood cells
• Initiates immune response by B cells and T cells in response to antigens in circulating blood.
• The removal of the spleen causes increased risk for bacterial infection

Thymus

• Unique Role: produces and trains T-cells to help the immune system fight infection and disease.
• T-cell Production: Most T-cells are produced before birth, and the remainder in childhood. by puberty that will cells for life.
• T-cell education teaches to distinguish between self and non-self antigens. this involves positive and negative selection where only T-cells that do not react with self-antigens survive.
• T-cell Maturation: T-cells mature in the thymus passing throught eh cortex and medulla regions.
• T-cell expert only 5-10% of t cells leave thymus to fully mature in secondary organs

Immunity Types

• Immunity Role:
• Defends agains microbes and pathogens
• Defends against the growth of Tumor cells
• Homeostasis destruction or abnormal or dead cells

Innate Immunity

• Innate Immunity:
• Does not distinguish one type of threat from one another
• Response to treat it to same regardless of invading agent
• Present at birth
• Provides nonspecific resistance
• Prevents approach, denies entry
• Rapid response, within minutes of infection
• Has no memory

First Line of Defense

• Intact skin epidermis: mechanical barrier preventing entry of harmful substances.
• Acid mantle of skin: Skin secretions make epidermal surface acidic, inhibiting bacterial growth and containing various bactericidal chemicals.
• Keratin: Keratin provides resistance against acids, alkalis, and bacterial enzymes.
• Intact mucous membranes: physical barrier to stop the entry of pathogens.
• Mucus: Traps microorganisms in respiratory and digestive tracts.
• Nasal hairs: Filter and trap microorganisms in nasal passages.
• Cilia: Propel debris-laden mucus away from nasal cavity and lower respiratory passages.
• Gastric juice: Concentrated hydrochloric acid and protein-digesting enzymes destroy pathogens in the stomach.
• Acid mantle of vagina: Inhibits growth of bacteria and fungi in the female reproductive tract.
• Lacrimal secretion (tears); saliva: Lubricates and cleanses eyes and oral cavity, containing lysozyme to destroy microorganisms.
• Urine: Acid pH inhibits bacterial growth, cleansing the urinary tract as it flushes from the body.
• Phagocytes: Engulf and destroy pathogens that breach barriers; macrophages contribute to adaptive immune responses.
• Natural killer (NK) cells: Induce apoptosis by attacking infected or cancerous cells; recognize abnormalities; do not form memory cells.
• Inflammatory response: Prevents spread of injurious agents, disposes of pathogens/dead cells, promotes repair; inflammatory chemicals attract phagocytes.
• Interferons proteins released by virus-infected/lymphocytes that protect uninfected cells, mobilize immune system.
• Complement: A group of bloodborne proteins activated that lyse microorganisms, enhance phagocytosis, and intensify inflammatory/immune responses.
• Fever: High body temperature inhibits microbe multiplication and enhances repair processes triggered by pyrogens.
• Adaptive immunity: utilizes defenders and protects against threats depending on the activities of (lymphocytes, B cells, T Cells)
• Specific Properties:
• Can identify and destroy specific pathogens
• To detect a wide range of pathogens including viruses and protozoa
• Can remember released in response to a pathogen Can differentiate between the body's cells and foregin cells

Immune Response

• Cellular Immunity: T-Lymphocytes: eliminate intracellular microbes that survive within phagocytes or other infected cells
• Humoral Immunity: B-Lyphocytes: mediated by antibodies

Functions in Immune Response

• B cell: A lymphocyte that matures in the bone marrow and creates plasma and memory cells.
• Plasma cell: Produces huge numbers of antibodies and is an effector B cell.
• Helper T (TH) cell: An effector CD4 T cell central to humoral and cellular immunity. It stimulates production of killer cells and the reproduction of plasma cells
• Cytotoxic T (Tc) cell: Effector CD8 T cells kill virus-invaded body cells and cancer cells.
• Regulatory T (Treg) cell: Stops activity of the immune system.
• Memory cell: A cell that is able to enable quicker response.

Difference between blood and lymphatic capaliries.

• Branch through peripheral tissues
• They are closed at one end rather than forming constant tubes.
• Larger luminal Diameters
• Thinner Walls
• Have a flattened/ irregular pattern

Differences between Active vs Passive

• Active: naturally acquired after and exposure to Antigens of enviornment and induced by an admin of antigen(vaccines)
• Passive: naturally by a tranfer of maternal antibodies with milk and artificially induced by admin of antibodies to paitents
• Antigens trigger and antibodys fight its response
• Antigen (Ag): intruder triggers

Major Histocompatibility Complex

The major histocompatibility complex (MHC) is a group of genes that code for proteins that help the immune system identify and respond to foreign substances.

• MHC Class I- the surface of ( T cells that kille infected cells)
• MHC Class II (B cells)

Explore lymphatic system functions including waste removal, fat transport, and immune response. Understand lymph flow, lymphedema causes, and the role of tonsils and lymphocytes. Learn about the consequences of a compromised lymphatic system.