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Questions and Answers
What is the primary function of the thoracic duct in the lymphatic system?
What is the primary function of the thoracic duct in the lymphatic system?
Which mechanism helps propel lymph through the lymphatic system?
Which mechanism helps propel lymph through the lymphatic system?
Which type of lymphoid tissue consists of tightly packed lymphoid cells?
Which type of lymphoid tissue consists of tightly packed lymphoid cells?
What is the primary role of macrophages within lymphoid tissues?
What is the primary role of macrophages within lymphoid tissues?
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What characterizes adaptive defenses in the immune system?
What characterizes adaptive defenses in the immune system?
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Which of the following is NOT a surface membrane barrier?
Which of the following is NOT a surface membrane barrier?
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What is the function of defensins in the immune system?
What is the function of defensins in the immune system?
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What role do valves serve in the lymphatic system?
What role do valves serve in the lymphatic system?
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What is the main function of natural killer (NK) cells?
What is the main function of natural killer (NK) cells?
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What role does fever play in the immune response?
What role does fever play in the immune response?
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How do interferons enhance the immune response?
How do interferons enhance the immune response?
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What is NOT a cardinal sign of acute inflammation?
What is NOT a cardinal sign of acute inflammation?
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What initiates the inflammatory process when tissues are injured?
What initiates the inflammatory process when tissues are injured?
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What effects do inflammatory chemicals have on local arterioles?
What effects do inflammatory chemicals have on local arterioles?
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What is formed when a phagocyte engulfs particles during phagocytosis?
What is formed when a phagocyte engulfs particles during phagocytosis?
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What consequence results from the leakiness of local capillaries during inflammation?
What consequence results from the leakiness of local capillaries during inflammation?
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What is one of the primary traits of adaptive immunity?
What is one of the primary traits of adaptive immunity?
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What occurs during the process of chemotaxis in relation to leukocytes?
What occurs during the process of chemotaxis in relation to leukocytes?
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During maturation, T lymphocyte precursors migrate to which organ?
During maturation, T lymphocyte precursors migrate to which organ?
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What are the main products of the humoral immune response?
What are the main products of the humoral immune response?
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What is the role of memory cells in adaptive immunity?
What is the role of memory cells in adaptive immunity?
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What does immunocompetence refer to in lymphocytes?
What does immunocompetence refer to in lymphocytes?
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What is the lag period associated with the primary immune response?
What is the lag period associated with the primary immune response?
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Which type of lymphocyte primarily carries out cellular immunity?
Which type of lymphocyte primarily carries out cellular immunity?
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What happens during the secondary immune response when re-exposed to the same antigen?
What happens during the secondary immune response when re-exposed to the same antigen?
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Which of the following describes naturally acquired active humoral immunity?
Which of the following describes naturally acquired active humoral immunity?
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Which statement about passive humoral immunity is correct?
Which statement about passive humoral immunity is correct?
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What is the function of antibodies in the immune response?
What is the function of antibodies in the immune response?
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Which defensive mechanism involves the masking of dangerous parts of pathogens?
Which defensive mechanism involves the masking of dangerous parts of pathogens?
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What occurs during the transport of respiratory gases in the body?
What occurs during the transport of respiratory gases in the body?
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Which of the following processes is NOT part of respiration?
Which of the following processes is NOT part of respiration?
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Which process describes the movement of air into and out of the lungs?
Which process describes the movement of air into and out of the lungs?
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What percentage of carbon dioxide is transported in blood as bicarbonate ions?
What percentage of carbon dioxide is transported in blood as bicarbonate ions?
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Which process more rapidly induces the formation of bicarbonate ions in red blood cells compared to plasma?
Which process more rapidly induces the formation of bicarbonate ions in red blood cells compared to plasma?
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What effect does increasing blood carbon dioxide levels have on blood pH?
What effect does increasing blood carbon dioxide levels have on blood pH?
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Which of the following statements about the Bohr effect is true?
Which of the following statements about the Bohr effect is true?
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During the chloride shift, what ion moves from the plasma into the red blood cells?
During the chloride shift, what ion moves from the plasma into the red blood cells?
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What is the primary region of the brain responsible for controlling respiration?
What is the primary region of the brain responsible for controlling respiration?
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Which of the following is a common symptom of chronic obstructive pulmonary disease (COPD)?
Which of the following is a common symptom of chronic obstructive pulmonary disease (COPD)?
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What happens to bicarbonate ions in the lungs?
What happens to bicarbonate ions in the lungs?
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Study Notes
Lymphatic System
- Thoracic Duct: Drains lymph from the entire body except the right upper limb, right side of head, and right thorax.
- Right Lymphatic Duct: Drains lymph from the right upper limb, right side of head, and right thorax.
- Lymph Empties into Venous Circulation: Both lymphatic ducts empty lymph into the venous circulation at the junction of the internal jugular and subclavian veins on their respective sides of the body.
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Lymph Transport: The lymphatic system lacks a central pump; Instead, lymph is propelled by:
- Milking Action of Skeletal Muscles: Contraction of skeletal muscles squeezes lymphatic vessels, propelling lymph forward.
- Pressure Changes in Thorax during Breathing: Inhalation expands the thoracic cavity, drawing lymph from abdominal vessels towards the thoracic duct.
- Valves: Prevent backward flow of lymph, ensuring unidirectional movement.
Lymphoid Tissue
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Lymphoid Tissue: Loose reticular connective tissue containing:
- Lymphoid Cells: Includes lymphocytes, macrophages, and other immune cells.
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Two Types:
- Diffuse Lymphoid Tissue: Scattered throughout the body, providing an initial line of defense against pathogens.
- Lymphoid Follicles: Solid, spherical bodies densely packed with lymphoid cells, found in lymph nodes, spleen, and other organs.
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Functions of Lymphoid Tissue:
- Houses and Provides Proliferation Site for Lymphocytes: Lymphoid tissue serves as a reservoir and breeding ground for lymphocytes.
- Surveillance Vantage Point: Lymphocytes and macrophages within lymphoid tissue constantly monitor for invading pathogens.
Lymph Nodes
- Cleansing the Lymph: Lymph nodes act as filters for lymph, removing microorganisms, cellular debris, and foreign substances.
- Macrophages: The primary phagocytes within lymph nodes, destroying pathogens and debris.
Spleen
- Functions of Lymphoid Organs: The spleen, like other lymphoid organs, houses and proliferates lymphocytes, and serves as a surveillance vantage point for immune cells.
- Cleanses Blood: The spleen contains macrophages that remove aged red blood cells, debris, and pathogens from circulating blood.
Immune System
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Innate Defenses (Non-Specific): The body's first and second lines of defense, providing immediate but general protection against pathogens.
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Surface Barriers (First Line of Defense):
- Skin: A physical barrier that prevents pathogen entry.
- Mucous Membranes: Line body cavities, trapping and removing pathogens.
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Internal Defenses (Second Line of Defense):
- Phagocytes: Cells (neutrophils, macrophages) that engulf and destroy pathogens.
- Natural Killer (NK) Cells: Lymphocytes that directly kill virus-infected cells and cancer cells.
- Inflammation: A localized response to injury, characterized by redness, heat, swelling, pain, and potentially impairment of function.
- Antimicrobial Proteins: Proteins (interferons, complement proteins) that inhibit microbial growth and promote pathogen destruction.
- Fever: An increase in body temperature that enhances immune responses.
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Surface Barriers (First Line of Defense):
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Adaptive Defenses (Specific) (Third Line of Defense): A more specific and long-lasting response to pathogens, targeting specific antigens.
- Humoral Immunity (B Cells): Mediated by antibodies produced by B lymphocytes.
- Cellular Immunity (T Cells): Mediated by cytotoxic T cells that directly kill cells infected with pathogens.
Surface Membrane Barriers
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Physical Barriers:
- Keratin: The tough protein in skin, resistant to many chemicals, enzymes, and toxins.
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Secretions:
- Acid: Low pH of skin and vaginal secretions inhibits microbial growth.
- Enzymes: Lysozyme (found in saliva, respiratory mucus, and tears) breaks down bacterial cell walls.
- Mucin: Thick sticky mucus traps microorganisms, preventing them from reaching delicate tissues.
- Defensins: Antimicrobial peptides that inhibit microbial growth.
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Respiratory System Modifications:
- Mucus-Coated Hairs in Nose: Trap airborne particles.
- Cilia: Hair-like structures in the upper respiratory tract sweep trapped particles towards the throat for expectoration.
Natural Killer Cells
- Lyse and Induce Apoptosis: NK cells directly kill virus-infected cells and cancer cells by causing cell lysis (rupture) or apoptosis (programmed cell death).
- Attack Cells Lacking "Self" Receptors: NK cells target cells that lack normal cell-surface receptors, indicating compromised or abnormal cells.
Fever
- Pyrogens: During infection, leukocytes release pyrogens, which act on the hypothalamus, raising body temperature.
- Increased Metabolic Rate: Fever increases metabolic rate by speeding up chemical reactions within cells, potentially enhancing immune defenses and repair processes.
Interferons
- Enhanced Innate Defenses: Interferons, antiviral proteins, contribute to our innate defenses by directly attacking viruses or hindering their ability to replicate.
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Mechanism:
- Virus Enters Cell: A cell becomes infected by a virus.
- Interferon Genes Activated: The infected cell's interferon genes are activated.
- Interferon Production: The cell produces interferon molecules, which are released. The infected cell is ultimately killed by the viral infection.
- Interferon Binding: Released interferon binds to neighboring cells, stimulating their interferon genes.
- Antiviral Protein Production: The neighboring cells produce antiviral proteins that block viral reproduction.
Phagocytosis
- Phagocyte Adherence: Phagocytes (like neutrophils and macrophages) adhere to pathogens or debris.
- Pseudopod Formation: Phagocytes extend pseudopods (finger-like projections) that engulf the target particle.
- Phagosome Formation: The engulfed particle is enclosed within a phagosome.
- Phagolysosome Formation: A lysosome (containing digestive enzymes) fuses with the phagosome, forming a phagolysosome.
- Digestion: Lysosomal enzymes break down the engulfed particle within the phagolysome.
- Exocytosis: Indigestible remnants are expelled from the cell by exocytosis.
Inflammatory Process
- Triggers: Injury by physical trauma, intense heat, irritating chemicals, or infection.
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Functions:
- Prevents Spread of Damaging Agents: Inflammation contains the injury, preventing further damage.
- Disposes of Cell Debris and Pathogens: Phagocytes remove cellular debris and pathogens.
- Alerts Adaptive Immune System: Inflammation signals the adaptive immune system, initiating specific immune responses.
- Sets the Stage for Repair: Inflammation provides an environment conducive to tissue repair.
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Cardinal Signs:
- Redness (Rubor): Caused by dilation of arterioles, increasing blood flow at site of injury.
- Heat (Calor): Increased blood flow increases local temperature.
- Swelling (Tumor): Increased capillary permeability leads to leakage of fluid (exudate), causing swelling.
- Pain (Dolor): Pressure of swelling on nerve endings and the release of pain-inducing chemicals (like bacterial toxins) cause pain.
- Impairment of Function (Functio Laesa): In severe cases, the inflammatory process can impair function of the affected area.
Chemotaxis
- Inflammatory Chemicals: Damaged cells and immune cells release inflammatory chemicals.
- Vasodilation: These chemicals dilate local arterioles, leading to increased blood flow (redness and heat).
- Increased Capillary Permeability: Chemicals make capillaries leaky, allowing exudate to seep into tissues (swelling and pain).
- Exudate: This fluid contains clotting factors and antibodies which help to wall off and repair the affected area.
- Leukocytosis: Increased numbers of white blood cells (leukocytes) in the blood stream.
- Margination: Leukocytes adhere to the walls of capillaries.
- Diapedesis: Neutrophils squeeze out of capillaries.
- Chemotaxis: Neutrophils follow chemical signals (chemotactic factors) released by damaged cells and invading pathogens to the site of injury.
Adaptive Immunity
- Specificity: The adaptive immune system targets unique antigens, providing a tailored response to each pathogen.
- Systemic: Adaptive immune responses can act throughout the body, not just at the site of infection.
- Memory: The adaptive immune system remembers past infections and mounts a more rapid and robust response upon re-exposure to the same antigen.
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Two Arms:
- Humoral (Antibody-Mediated) Immunity: Mediated by antibodies produced by B lymphocytes.
- Cellular (Cell-Mediated) Immunity: Mediated by cytotoxic T cells that directly kill infected or abnormal cells.
Antigens
- Antigens: Substances that can trigger the adaptive immune response.
- Immune Response Targets: All adaptive immune responses are directed against specific antigens.
Lymphocytes
- Origin: B and T lymphocyte precursors originate in red bone marrow.
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Maturation:
- T Cells: Precursors migrate to the thymus and mature there.
- B Cells: Mature in the bone marrow.
- Immunocompetence: During maturation, lymphocytes develop the ability to recognize and bind to a specific antigen.
- Self-Tolerance: Lymphocytes become unresponsive to self-antigens, preventing autoimmune attacks.
- Seeding Lymphoid Organs and Circulation: Mature lymphocytes circulate throughout the body, encountering antigens in lymphoid organs and other tissues.
- Antigen Encounter and Activation: When an immunocompetent but naive (unactivated) lymphocyte encounters its specific antigen, it becomes activated.
- Proliferation and Differentiation: Activated lymphocytes proliferate (multiply) and differentiate into effector cells and memory cells.
Humoral Immunity
- B Cell Activation: B cells become activated when antigens bind to their surface receptors.
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Proliferation and Differentiation: Activated B cells proliferate and differentiate into:
- Plasma Cells: Antibody-secreting cells, which produce antibodies specific for the antigen.
- Memory Cells: Long-lived cells that provide immunological memory, allowing for a faster and more effective response to future exposures to the same antigen.
- Primary Immune Response: The initial response to an antigen, taking several days (3-6) to develop.
- Secondary Immune Response: Upon re-exposure to the same antigen, a secondary response is quicker, stronger, and more prolonged due to the existence of memory cells.
Active and Passive Humoral Immunity
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Active Humoral Immunity: The body's own immune system produces antibodies against the antigen.
- Naturally Acquired: Develops from a pathogen infection, providing immunity after the individual recovers.
- Artificially Acquired: Develops from vaccination with weakened or inactivated pathogens, providing immunity without causing full disease symptoms.
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Passive Humoral Immunity: Pre-made antibodies are introduced into the body.
- Naturally Acquired: Antibodies are passed from mother to fetus via the placenta or to infant through breast milk.
- Artificially Acquired: Antibodies are injected into the body (e.g., antivenom, rabies antibodies, tetanus antitoxin).
Antibody Targets and Functions
- Neutralization: Antibodies bind to dangerous parts of viruses and bacteria, blocking their ability to bind to and infect target cells.
- Agglutination: Antibodies bind to cell-bound antigens, causing clumping of pathogens, facilitating removal by phagocytes.
- Precipitation: Antibodies bind to soluble antigens, forming complexes that precipitate out of solution, making them easier to remove.
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Complement Fixation: Antibodies bound to pathogens activate the complement system, a cascade of proteins that leads to:
- Cell Lysis: Destruction of pathogen cells.
- Enhances Inflammation: Increases inflammation and recruitment of immune cells.
- Promotes Phagocytosis: Increases phagocytosis of pathogens.
Respiratory System
- Pulmonary Ventilation (Breathing): Movement of air into (inspiration) and out of (expiration) the lungs.
- External Respiration: Exchange of gases between the lungs and blood. Oxygen diffuses from the alveoli into the capillaries, while carbon dioxide diffuses from the capillaries into the alveoli.
- Transport of Respiratory Gases: Oxygen is transported from the lungs to the tissues, and carbon dioxide is transported from the tissues to the lungs.
- Cellular Respiration: The process by which cells use oxygen to produce energy (ATP) and generate carbon dioxide as a byproduct.
Carbon Dioxide Transport in Blood
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Three Forms:
- Dissolved in Plasma (7-10%): CO2 dissolves directly in the plasma.
- Bound to Hemoglobin (20%): CO2 binds to hemoglobin molecules, forming carbaminohemoglobin.
- Bicarbonate Ions (HCO3-) (70%): Most CO2 is transported as bicarbonate ions.
- Conversion in RBCs: CO2 enters red blood cells and reacts with water to form carbonic acid (H2CO3), catalyzed by carbonic anhydrase. Carbonic acid then quickly dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
- Chloride Shift: As HCO3- moves out of RBCs into the plasma, chloride ions (Cl-) move into the RBCs to maintain electrical neutrality.
- Reversal in Lungs: In the lungs, the process reverses. Bicarbonate ions enter RBCs, combine with H+ to form carbonic acid. Carbonic anhydrase then converts carbonic acid back into CO2 and water. CO2 diffuses from the blood into the alveoli.
Influence of CO2 on Blood pH
- Slow, Shallow Breathing: Increased CO2 in the blood leads to a drop in pH (acidosis).
- Rapid, Deep Breathing: Decreased CO2 in the blood leads to an increase in pH (alkalosis).
Control of Respiration
- Respiratory Centers: Neurons in the brain stem (specifically the medulla oblongata) control breathing.
- Chemoreceptors: Chemoreceptors in the brainstem and peripheral tissues monitor levels of oxygen, carbon dioxide, and hydrogen ions in the blood, providing feedback to the respiratory centers.
- Higher Brain Centers: Areas in the brain (like the cerebral cortex) can voluntarily influence breath rate and depth.
Chronic Obstructive Pulmonary Disease (COPD)
- Definition: Irreversible decrease in the ability to force air out of the lungs.
- Common Causes: Smoking (contributes to 80% of cases), air pollution, and genetic predisposition.
- Symptoms: Dyspnea (labored breathing), coughing, frequent pulmonary infections, and eventually respiratory failure.
- Consequences: Hypoventilation (decreased ventilation), respiratory acidosis (low blood pH), and hypoxemia (low blood oxygen levels).
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Test your knowledge of the lymphatic system and its functions with this quiz. Questions cover the thoracic duct, lymph propulsion mechanisms, lymphoid tissues, and the roles of macrophages and defenses in the immune system. Ideal for students studying biology or health sciences.
