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Questions and Answers
What is the primary function of phagocytes in the immune system?
What is the primary function of phagocytes in the immune system?
Which lymphocyte type is primarily responsible for the secretion of antibodies?
Which lymphocyte type is primarily responsible for the secretion of antibodies?
What role do secondary lymphoid organs such as lymph nodes play in the immune response?
What role do secondary lymphoid organs such as lymph nodes play in the immune response?
Which antibody class is primarily involved in allergic reactions?
Which antibody class is primarily involved in allergic reactions?
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Which of the following statements best describes macrophages?
Which of the following statements best describes macrophages?
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What does the process of phagocytosis involve?
What does the process of phagocytosis involve?
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What initiates the inflammatory response in tissues?
What initiates the inflammatory response in tissues?
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Natural killer cells are primarily involved in which type of immune response?
Natural killer cells are primarily involved in which type of immune response?
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What is the primary function of neutrophils in response to infection?
What is the primary function of neutrophils in response to infection?
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Which mechanism do natural killer (NK) cells use to trigger apoptosis?
Which mechanism do natural killer (NK) cells use to trigger apoptosis?
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What is one of the common signs of inflammation?
What is one of the common signs of inflammation?
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How do inflammatory mediators contribute to the inflammatory response?
How do inflammatory mediators contribute to the inflammatory response?
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Which type of cells can monocytes differentiate into upon reaching infected tissues?
Which type of cells can monocytes differentiate into upon reaching infected tissues?
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What role does vasodilation play in the inflammatory response?
What role does vasodilation play in the inflammatory response?
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Which statement is true regarding the difference between inflammation and infection?
Which statement is true regarding the difference between inflammation and infection?
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What substance do NK cells release to induce apoptosis in infected cells?
What substance do NK cells release to induce apoptosis in infected cells?
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What is the primary function of macrophages found in the spleen?
What is the primary function of macrophages found in the spleen?
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Which type of tonsils is located at the back of the throat?
Which type of tonsils is located at the back of the throat?
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Which cells are primarily involved in the inflammatory response?
Which cells are primarily involved in the inflammatory response?
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Natural Killer (NK) cells are best known for their ability to:
Natural Killer (NK) cells are best known for their ability to:
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Which of the following is NOT a type of phagocyte?
Which of the following is NOT a type of phagocyte?
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During tissue injury, which process is primarily responsible for healing?
During tissue injury, which process is primarily responsible for healing?
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Which of the following statements about antigens is correct?
Which of the following statements about antigens is correct?
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Where do lymphocytes of the adaptive immune system primarily mature?
Where do lymphocytes of the adaptive immune system primarily mature?
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Flashcards
Naive B Cells
Naive B Cells
B cells with antibodies on their surface that haven't encountered an antigen yet.
Plasma Cells
Plasma Cells
B cells that have been activated and are actively secreting antibodies.
Antibody Classes
Antibody Classes
The different types of antibodies found in humans, each with a distinct role in the immune system.
Primary Lymphoid Organs
Primary Lymphoid Organs
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Secondary Lymphoid Organs
Secondary Lymphoid Organs
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Naïve Lymphocytes
Naïve Lymphocytes
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Phagocytosis
Phagocytosis
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Macrophages
Macrophages
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Neutrophils
Neutrophils
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Natural Killer (NK) cells
Natural Killer (NK) cells
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Apoptosis
Apoptosis
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Inflammation
Inflammation
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Infection
Infection
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Inflammatory mediators
Inflammatory mediators
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Vasodilation
Vasodilation
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Spleen Structure
Spleen Structure
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Spleen Function (Filtering)
Spleen Function (Filtering)
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Tonsil Location
Tonsil Location
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Tonsil Function
Tonsil Function
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Antigen Composition
Antigen Composition
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Antigen Specificity
Antigen Specificity
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Immune Cell Origin
Immune Cell Origin
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Immune System vs. Lymphatic System
Immune System vs. Lymphatic System
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Study Notes
The Lymphatic System
- The lymphatic system is a network of vessels that collects lymph (fluid) from body tissues and returns it to the bloodstream.
- It also transports dietary fats and immune cells throughout the body.
- It prevents the accumulation of interstitial fluid, returning it to the bloodstream, and facilitating immune cell transport to tissues.
- Lymph is interstitial fluid that enters the lymphatic system.
Functions of the Lymphatic System
- Fluid Regulation: The lymphatic system prevents the buildup of interstitial fluid by draining excess fluid and returning it to the bloodstream.
- Lymph Formation: Approximately 3 liters of the 20 liters of plasma that leak into daily tissue spaces are managed by the lymphatic system.
- Lymphatic System and Health: Damage to lymphatic system results in lymphedema from the accumulation of protein-rich interstitial fluid.
Anatomy of the Lymphatic System
- The lymphatic system comprises various components, such as lymph nodes, tonsils, thymus, thoracic duct, spleen, and Peyer's patches in the small intestine.
- Bone marrow is the site of immune cell production and maturation of B-cells.
- Hematopoiesis is the process of blood cell formation.
- The thymus is where T-cells mature.
Primary Lymphoid Organs
- Bone Marrow: Site of immune cell production
- Thymus: Site of maturation of T-cells
Secondary Lymphoid Organs
- Lymph nodes
- Lymphatic vessels
- Spleen
- Tonsils
Lymph Nodes
- Located in various regions like groin, armpits, neck, chest, and abdomen.
- Approximately 500-600 lymph nodes throughout the human body.
- Act as crucial sites for immune cells to develop and coordinate responses.
- Act as filters for lymph, removing debris and pathogens, and transporting pathogens for destruction by dendritic cells and macrophages.
Lymph Node Pathways
- Afferent Lymphatic Vessels: Brings lymph into the node.
- Efferent Lymphatic Vessels: Takes lymph out of the node.
- Internal Structure of Lymph Node: -Subcapsular Sinus: Entry point of lymph, macrophages, and reticular fibers. -Cortex: Contains lymphoid follicles, germinal centers of rapidly dividing B cells, surrounded by T cells. -Medulla: Contains medullary cords (B cells and plasma cells) and medullary sinuses (lymph gathers before exiting).
Lymphatic System vs. Cardiovascular System
- Lymph is not actively pumped by the heart as blood is in the circulatory system.
- Lymph is propelled through vessels by body movement (skeletal muscle contractions and breathing).
- One-way valves (semi-lunar valves) in lymphatic vessels maintain flow towards the heart.
- The path of lymph flow: lymphatic capillaries --> lymphatic vessels --> lymphatic ducts --> circulatory system.
Lymphatic Vessels
- Structure: Begins as open-ended capillaries and progresses into larger lymphatic vessels connected to the bloodstream via ducts.
Lymph Capillaries (Terminal Lymphatics)
- Function: Serve as the entry points for interstitial fluid.
- Distribution: Found throughout body tissues, interwoven with arterioles and venules in soft connective tissues.
- Exceptions: Absent in the CNS, bone marrow, bone, teeth, and the cornea of the eye.
Lymphatic Capillaries in the Small Intestine (Lacteals)
- Lacteals: specialized lymphatic capillaries crucial for transporting dietary lipids and soluble vitamins to the blood.
- Formation of Chyle: Dietary triglycerides and other lipids combine with proteins.
- Role: Carry chyle through the lymphatic system into the liver and bloodstream.
What is the role of Peyer's Patches?
- Keeping intestinal flora at appropriate levels and pathogens at bay to prevent infections.
Lymphatic Vessels and Valves
- Three-tunic structure similar to veins.
- One-way valves are closely spaced, causing bulges, giving the vessels a beaded appearance.
- Formation of Lymphatic Trunks: Superficial and deep lymphatics merge into larger vessels called lymphatic trunks.
- Drainage Pathways:
- Right side (head, thorax, right upper limb) drains into the right lymphatic duct, then right subclavian vein.
- Remaining body areas drain into the thoracic duct on the left side, emptying into the left subclavian vein.
- Origin: Thoracic duct beings beneath the diaphragm in the cisterna chyli, receiving lymph from the lower abdomen, pelvis, and lower limbs.
The Spleen
- Size and Position: Approximately 12 cm (5 in) long attached to the stomach.
- Fragile Structure: Lacks a strong capsule, contains extensive vascularization (dark red appearance).
- Functions:
- "Filter of the Blood": Removes microbes and waste, including dying red blood cells.
- Immune Responses: Acts as a site for immune responses against pathogens.
Tonsils
- Locations and Importance: Located along the inner surface of the throat
- Types: Pharyngeal and palatine tonsils.
- Histological Features: Lack a complete capsule and contain deep crypts, allowing pathogens to penetrate deeper and be eliminated by lymphoid structures.
- Functions: Recognized, fight, and produce immunity against common pathogens. Indicated for removal in recurring throat infections (especially swelling in children).
Lymphatic System vs. Immune System
- The immune system fights harmful pathogens.
- The lymphatic system works closely with the immune system to filter pathogens and manage excess fluids.
Antigens
- Large, complex components on pathogens with multiple antigenic determinants.
- Determinants are small regions where receptors bind.
- Composition: Protein (6 or less amino acids), Carbohydrate (1 or 2 sugars).
- Importance:
- Carbohydrates on bacterial cell walls and ABO blood group antigens (on red blood cells).
- Proteins are crucial for immune responses to viruses and parasites (in relation to shape and complimentary antigen binding).
Immune Cell Origins
- Cells of the immune system originate from the bone marrow in the hematopoietic system.
- Lymphocytes of the adaptive immune system mature in primary lymphoid organs (bone marrow and thymus).
Primary and Secondary Organs
- Primary: Bone marrow and thymus, where lymphocytes mature.
- Secondary: Sites of mature immune cells gathering to respond to pathogens.
Phases of Immune Function
- Barrier Defenses: Immediate protection against pathogen invasion by the skin and mucous membranes.
- Innate Immune Response: Rapid, non-specific defense mechanism by specialized cells and soluble factors.
- Adaptive Immune Response: Slower, specific and powerful defense by lymphocytes.
- Blood Cell Origins: All immune cells originate from hematopoietic stem cells in the bone marrow, which continuously differentiate to replace aging cells.
Barrier Defenses (1st line)
- Physical Barriers: First line of defense against pathogens.
- Continuous Protection: Work constantly.
- External Surfaces: Outside the body susceptible to pathogen entry.
- Skin: Main barrier with dead outer layers unsuitable to germ growth. Sweat and secretions help maintain unfavorable pH and wash away microbes.
Barrier Defenses (continued)
- Saliva: Contains lysozyme, an enzyme that breaks down bacteria.
- Stomach Acids: Deadly environment for many germs.
- Mucus: Traps germs and dirt in different areas like gastrointestinal, respiratory, and reproductive tracts. Respiratory tract mucus has cilia to move trapped foreign substances away.
Cells of the Immune Response (Diagram)
Immune Response - Two Mechanisms
- Innate immune response:
- Speed: Quick but not very specific.
- Effectiveness: Sometimes not fully effective.
- How it works: Acts quickly against a range of pathogens without specific targeting, slows pathogen growth, buys time for the adaptive immune system. -Cells: neutrophils, monocytes, macrophages, dendritic cells, NK cells, basophils, eosinophils
- Adaptive immune response:
-Speed: Slower to develop during the first encounter with a pathogen
- Effectiveness: Highly specific and effective against pathogens
- How it works: Tailors its responses to specific pathogens, learning and adapting in time -Cells: B-lymphocytes, T-lymphocytes
Lymphocytes in Adaptive Immune Responses
- B Cells: Originate in bone marrow, produce antibodies that bind to antigens on pathogens (and differentiate into plasma cells).
- T Cells: Originate in bone marrow, mature in the thymus, diverse functions (signal molecules, cells infected with pathogens).
- Plasma Cells: Specialized B cells that secrete antibodies.
- Natural Killer Cells (NK): Participants in the innate immune response, circulating blood cells, cytotoxic granules (destroy infected cells), key role in defending against viruses and cancers.
Antibodies
- Antibody Basics: Molecules crucial in the immune system's defense (immunoglobulins); secreted versions of B cell receptors for recognizing and neutralizing pathogens.
- Genetic Similarity: The genes coding for secreted antibodies and surface immunoglobulins (B cell receptors) are the same, with a minor difference in their production.
- Antibody Classes: Humans have five main classes (IgM, IgD, IgG, IgA, IgE) with distinct roles in the immune response.
Types of Lymphocytes
- B lymphocyte: Generates diverse antibodies.
- T lymphocyte: Secretes chemical messengers (cytokines).
- Plasma cell: Secretes antibodies.
- NK cell: Destroys virally infected cells.
B and T Cell Development
- Critical for Adaptive Immune Response: Crucial for understanding adaptive immune responses (developing ability to fight pathogens without harm to own cells).
- Primary Lymphoid Organs: Bone marrow and thymus gland (for lymphocyte growth, increase in number, and training to recognize and attack harmful invaders).
Secondary Lymphoid Organs and Active Immune Responses
- Role of Secondary Organs: Lymphocytes mature in primary organs but respond to antigens in secondary organs.
- Lymph Nodes, Spleen, and Others: Lymphocytes gather in these areas.
- Naïve Lymphocytes: Functional but have not encountered antigens yet.
- Common Features: Lymphoid follicles, reticular fiber internal structure, germinal centers, high endothelial venules.
Two Processes in Immunity
- Phagocytosis
- Cell lysis
Phagocytes and Phagocytosis
- Phagocyte: 'To eat', 'cell'.
- Job: Engulf and eat up particles or cells.
- What they do: Clean up waste, old cells, or fight bad germs (bacteria).
- First line of defense: Quick and strong defenders against germs that evade the body's defenses.
Phagocytosis (Diagram)
Types of Phagocytes
-
Macrophages: Versatile defenders, adaptable cells, found in high numbers in lymph nodes, perform phagocytic functions, crucial for stronger defenses and cooperation with other cells.
-
Neutrophils: Infection reinforcements, spherical cells (granulocytes) attracted to infection, rush from blood to infected areas, contain substances like histamine, reinforcements in the battle against germs.
-
Monocytes: Precursor cells, circulating cells that can become macrophages or dendritic cells, quickly drawn to areas of infection to inflammation signals.
Natural Killer Cells (NK Cells)
- Cell Actions: Induce apoptosis (programmed cell death) in infected cells to destroy pathogens, especially intracellular pathogens.
- Recognition Mechanisms: Identify infected cells using unclear surface receptors.
- Two Apoptosis Mechanisms: Fas ligand interaction; Granule release (perforins and granzymes).
Inflammation
- Definition: Complex cellular process involving various immune cells, proteins, and signaling molecules
- Versus Infection: Inflammation is the body's protective, cellular response to infection (bacteria or virus multiplication)
- Inflammatory effects: Heat, redness, pain, swelling, loss of function. Infections lead to inflammation and can cause these effects. E.g cuts.
Inflammatory Response (Diagram)
Inflammatory response-Injury
- Tissue injury: Injured cells trigger mast cells- release inflammatory mediators- swelling and increased blood flow.
- Vasodilation: Resulting blood flow increase causes redness and warmth.
- Increased Vascular Permeability: Mediators make blood vessels more permeable- fluid leakage and swelling.
- Recruitment of Phagocytes: Mediators attract immune cells, remove debris and fight infection.
- Overall Role: Eliminate pathogens, debris, clot, initiate wound repair, and facilitate adaptive immunity.
Active vs. Passive Immunity
- Active Immunity:
- Naturally Acquired: Develops after encountering a pathogen.
- Artificially Acquired: Develops after vaccination (killed or weakened pathogens).
- Passive Immunity:
- Naturally Acquired: Transfer of immune components from an immune individual to a non-immune individual.
- Artificially Acquired: Direct transfer of antibodies or immune components for immediate but short-term protection against specific diseases.
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Description
Test your knowledge on the immune system with this quiz. Learn about the functions of phagocytes, lymphocytes involved in antibody secretion, and the role of lymph nodes. Explore how different antibody classes participate in allergic reactions.
