Chapter 20: Lymphatic System & Immunity

General Functions of the Lymphatic System

The lymphatic system is essential for fluid balance, immune defense, and absorption of dietary fats. It works closely with the circulatory and immune systems.

• Fluid Balance: Returns excess interstitial fluid to the bloodstream.

• Immune Defense: Houses and transports immune cells, filters pathogens.

• Absorption of Fats: Lacteals in the small intestine absorb dietary lipids.

Lymph and Lymphatic Vessels

Lymphatic vessels transport lymph, a fluid derived from interstitial fluid, throughout the body. Their structure and function differ from blood vessels.

• Lymph: Clear fluid containing white blood cells, proteins, and fats.

• Comparison: Lymphatic vessels have thinner walls, more valves, and carry lymph in one direction toward the heart, unlike blood vessels.

• Circulation: Lymph is moved by skeletal muscle contraction, respiratory movements, and valves preventing backflow.

• Formation: Lymph forms when interstitial fluid enters lymphatic capillaries.

Lymphatic Cells, Tissues, and Organs

Lymphatic tissues and organs are specialized for immune responses and filtration of lymph.

• Basic Structure: Composed of reticular connective tissue and lymphocytes.

• Major Organs: Lymph nodes, spleen, thymus, tonsils, and MALT (mucosa-associated lymphoid tissue).

• Functions: Lymph nodes filter lymph; spleen filters blood; thymus matures T cells; tonsils protect against inhaled/ingested pathogens.

Introduction to Innate (Nonspecific) and Adaptive (Specific) Immune Responses

The immune system is divided into innate (nonspecific) and adaptive (specific) responses, each with distinct mechanisms and cell types.

• Innate Immunity: First line of defense, includes barriers and general responses (e.g., phagocytes, inflammation).

• Adaptive Immunity: Specific responses involving lymphocytes (T and B cells) and memory formation.

• Leukocytes: White blood cells classified by function in each immunity type.

Innate (Nonspecific) Defenses

Innate defenses provide immediate protection against pathogens through physical, chemical, and cellular mechanisms.

• Surface Barriers: Skin and mucous membranes block pathogen entry.

• Chemical Defenses: Enzymes, acids, and antimicrobial proteins.

• Cellular Defenses: Phagocytes (neutrophils, macrophages), natural killer cells.

• Inflammation: Local response to injury or infection, characterized by redness, heat, swelling, and pain.

• Fever: Systemic response that inhibits pathogen growth.

Overview of Adaptive (Specific) Immunity

Adaptive immunity targets specific pathogens and involves humoral and cell-mediated responses.

• Humoral Immunity: Mediated by B cells and antibodies.

• Cell-Mediated Immunity: Mediated by T cells attacking infected cells.

• Immunological Memory: Rapid, enhanced response upon re-exposure to the same antigen.

Antigens and Antigen Processing

Antigens are substances that elicit immune responses. Their processing and presentation are crucial for adaptive immunity.

• Antigen: Any molecule recognized as foreign by the immune system.

• Self-Antigen: Molecules belonging to the host, usually not attacked.

• Major Histocompatibility Complex (MHC): Proteins presenting antigens to T cells.

• Class I MHC: Present on all nucleated cells; present endogenous antigens.

• Class II MHC: Present on antigen-presenting cells (APCs); present exogenous antigens.

Lymphocytes and Their Role in Adaptive (Specific, Acquired) Immunity

Lymphocytes are central to adaptive immunity, with distinct roles for B and T cells.

• B Cells: Produce antibodies; responsible for humoral immunity.

• T Cells: Helper T cells (activate other immune cells), cytotoxic T cells (destroy infected cells), regulatory T cells (modulate immune response).

• APCs: Cells that present antigens to lymphocytes (e.g., dendritic cells, macrophages).

Antibodies and Their Role in Adaptive (Specific) Immunity

Antibodies are proteins produced by B cells that neutralize pathogens and facilitate their removal.

• Structure: Y-shaped molecules with variable and constant regions.

• Function: Bind antigens, neutralize toxins, opsonize pathogens for phagocytosis.

• Classes: IgG, IgA, IgM, IgE, IgD (each with specific roles).

Applied Immunology

Immunity can be acquired actively or passively, naturally or artificially.

• Active Immunity: Body produces its own antibodies (e.g., infection, vaccination).

• Passive Immunity: Antibodies are transferred from another source (e.g., maternal antibodies, antibody therapy).

Predictions Related to Disruption of Homeostasis

Disorders of the lymphatic and immune systems can lead to significant health issues.

• Lymphedema: Swelling due to lymphatic obstruction.

• Allergic Reactions: Hypersensitivity of the immune system.

• Immunodeficiency Disorders: SCID, HIV/AIDS.

Chapter 21: Respiratory System

General Functions of the Respiratory System

The respiratory system provides oxygen, removes carbon dioxide, and regulates blood pH.

• Ventilation: Movement of air in and out of the lungs.

• Gas Exchange: Exchange of O2 and CO2 between air and blood, and between blood and tissues.

• Regulation: Maintains acid-base balance and vocalization.

Gross and Microscopic Anatomy of the Respiratory Tract and Related Organs

The respiratory tract includes several anatomical regions, each with specialized functions.

• Upper Respiratory Tract: Nasal cavity, pharynx, larynx.

• Lower Respiratory Tract: Trachea, bronchi, bronchioles, alveoli.

• Larynx: Produces sound, protects airway.

• Trachea: Conducts air, supported by C-shaped cartilage rings.

• Bronchial Tree: Branching system of airways leading to alveoli.

• Alveoli: Site of gas exchange; thin-walled sacs surrounded by capillaries.

Mechanics of Breathing

Breathing involves changes in thoracic volume and pressure, driven by muscle contraction and relaxation.

• Inspiration: Diaphragm and external intercostals contract, increasing thoracic volume.

• Expiration: Muscles relax, thoracic volume decreases.

• Pressure Relationships: Atmospheric, intrapulmonary, and intrapleural pressures govern airflow.

• Boyle's Law: (Pressure and volume are inversely related).

Pulmonary Volumes and Capacities

Pulmonary volumes and capacities measure the amount of air moved during breathing.

• Tidal Volume (TV): Air moved in one breath.

• Inspiratory Reserve Volume (IRV): Extra air inhaled after normal inspiration.

• Expiratory Reserve Volume (ERV): Extra air exhaled after normal expiration.

• Residual Volume (RV): Air remaining after maximal exhalation.

• Vital Capacity (VC):

• Total Lung Capacity (TLC):

Mechanisms of Gas Exchange in the Lungs and Tissues

Gas exchange occurs by diffusion, driven by partial pressure gradients of O2 and CO2.

• Partial Pressure: Pressure exerted by a single gas in a mixture.

• Oxygen Transport: Mostly bound to hemoglobin; some dissolved in plasma.

• Carbon Dioxide Transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

• Bicarbonate Equation:

• Oxygen-Hemoglobin Dissociation Curve: Shows hemoglobin saturation at different partial pressures of oxygen.

Control of Pulmonary Ventilation

Breathing is regulated by neural centers in the brainstem and by chemical stimuli.

• Medullary Respiratory Centers: Control rhythm and rate of breathing.

• Chemoreceptors: Detect changes in CO2, O2, and pH.

• Peripheral vs. Central Chemoreceptors: Peripheral (carotid, aortic bodies); central (medulla oblongata).

• Abnormal Breathing Patterns: Hyperventilation, hypoventilation, apnea.

Predictions Related to Homeostatic Imbalance

Disorders of the respiratory system disrupt gas exchange and homeostasis.

• Acute Disorders: IRDS (Infant Respiratory Distress Syndrome), asthma, pneumonia.

• Chronic Disorders: COPD (chronic bronchitis, emphysema), lung cancer.

Additional info:

• Some content inferred for completeness, such as definitions and equations.