Immunity and Respiratory System: Key Concepts and Study Guide

Immunity and the Lymphatic System

Overview of Immune Responses

The immune system protects the body from pathogens and foreign substances through a complex network of cells, tissues, and molecules. It includes both innate (nonspecific) and adaptive (specific) defenses.

• Innate Immunity: The body's first line of defense, including physical barriers (skin, mucous membranes), chemical barriers (enzymes, acids), and cellular defenses (phagocytes).

• Adaptive Immunity: A targeted response involving lymphocytes (B cells and T cells) and the production of antibodies.

• Key Terms: Leukocytosis, margination, diapedesis, apoptosis, histamine, pyrogen, antigen, hapten, MHC (Major Histocompatibility Complex), cytokine.

Nonspecific Surface Barriers and Internal Defenses

Nonspecific defenses act against a wide variety of pathogens and include:

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

• Internal Defenses: Phagocytes (neutrophils, macrophages), natural killer cells, inflammation, antimicrobial proteins (complement, interferons).

• Functions: Destroy pathogens, remove debris, and signal adaptive responses.

Phagocyte Mobilization and Phagocytosis

Phagocytes are white blood cells that ingest and destroy microbes and debris.

• Steps of Phagocyte Mobilization: Leukocytosis, margination, diapedesis, chemotaxis.

• Phagocytosis: The process by which phagocytes engulf and digest pathogens.

Inflammation

Inflammation is a protective response to injury or infection, characterized by redness, heat, swelling, and pain.

• Cardinal Signs: Redness, heat, swelling, pain, and sometimes loss of function.

• Purpose: Isolate and eliminate pathogens, remove damaged tissue, and initiate repair.

Antigen-Presenting Cells (APCs)

APCs are immune cells that process and present antigens to T cells, initiating adaptive immunity.

• Examples: Dendritic cells, macrophages, B cells.

• Function: Display antigen fragments on MHC molecules to activate T cells.

Lymphocyte Selection, Proliferation, and Differentiation

Lymphocytes undergo selection to ensure self-tolerance and effective immune response.

• Selection: Eliminates self-reactive cells (central tolerance).

• Proliferation: Activated lymphocytes multiply.

• Differentiation: Lymphocytes become effector or memory cells.

Humoral and Cell-Mediated Immunity

The immune system uses two main mechanisms to fight pathogens:

• Humoral Immunity: Mediated by antibodies produced by B cells; targets extracellular pathogens.

• Cell-Mediated Immunity: Involves T cells; targets infected or abnormal cells.

Primary and Secondary Immune Responses

Immune responses differ upon first and subsequent exposures to an antigen.

• Primary Response: Slow, occurs after first exposure; involves activation and clonal expansion of lymphocytes.

• Secondary Response: Faster and stronger due to memory cells.

• Active Immunity: Results from direct exposure to antigen (infection or vaccination).

• Passive Immunity: Results from transfer of antibodies (maternal antibodies, antiserum).

Classes of Antibodies

Antibodies (immunoglobulins) are classified into five main types, each with distinct functions:

Class	Main Function
IgG	Main antibody in blood; provides long-term immunity
IgM	First antibody produced; effective in agglutination
IgA	Found in mucous membranes; protects body surfaces
IgE	Involved in allergic reactions and defense against parasites
IgD	Functions mainly as a B cell receptor

T Cell Types and Functions

T cells are critical for cell-mediated immunity and include several subtypes:

• Helper T Cells (CD4+): Activate B cells and other immune cells.

• Cytotoxic T Cells (CD8+): Destroy infected or abnormal cells.

• Regulatory T Cells: Suppress immune responses to prevent autoimmunity.

Immunodeficiency, Autoimmunity, and Hypersensitivity

Disorders of the immune system can lead to various clinical conditions:

• Immunodeficiency: Reduced immune function (e.g., HIV/AIDS).

• Autoimmunity: Immune system attacks self-tissues (e.g., lupus, rheumatoid arthritis).

• Hypersensitivity: Excessive or inappropriate immune responses (e.g., allergies).

Respiratory System

Key Terms and Concepts

The respiratory system is responsible for gas exchange, supplying oxygen, and removing carbon dioxide. Understanding its structure and function is essential for physiology.

• ValSalva/Heimlich Maneuvers: Techniques affecting airway pressure and clearance.

• Boyle's Law: Pressure and volume of a gas are inversely related ($P_1V_1 = P_2V_2$).

• Dalton's Law: Total pressure of a mixture of gases equals the sum of partial pressures.

• Henry's Law: Amount of gas dissolved in a liquid is proportional to its partial pressure.

• Surfactant: Substance that reduces surface tension in alveoli, preventing collapse.

• Compliance: Measure of lung expandability.

• Resistance: Opposition to airflow in airways.

• Hypoxia: Low oxygen levels in tissues.

• Hypercapnia: Elevated carbon dioxide levels.

• Hyperventilation: Increased rate and depth of breathing.

Structure and Function of the Nasal Cavity, Sinuses, Pharynx, and Larynx

These structures filter, warm, and humidify air, and play roles in speech and protection.

• Nasal Cavity: Filters and humidifies air.

• Sinuses: Air-filled spaces that lighten the skull and produce mucus.

• Pharynx: Passageway for air and food.

• Larynx: Contains vocal cords; protects lower airways.

Conducting vs. Respiratory Zones

The respiratory tract is divided into conducting and respiratory zones:

• Conducting Zone: Includes nose, pharynx, larynx, trachea, bronchi, and bronchioles; transports air.

• Respiratory Zone: Includes respiratory bronchioles, alveolar ducts, and alveoli; site of gas exchange.

Bronchial and Pulmonary Circulations

Two circulatory systems supply the lungs:

• Bronchial Circulation: Supplies oxygenated blood to lung tissue.

• Pulmonary Circulation: Carries deoxygenated blood to alveoli for gas exchange.

Respiratory Pressures and Gas Exchange

Gas exchange depends on pressure gradients and laws of physics:

• Intrapulmonary Pressure: Pressure within alveoli.

• Intrapleural Pressure: Pressure within pleural cavity.

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

• Oxygen Transport: Carried by hemoglobin; affected by pH, BPG, and CO2 levels.

Neural and Chemical Regulation of Breathing

Breathing is controlled by neural centers in the brainstem and chemical signals.

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

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

Respiratory Disorders

Several diseases affect the respiratory system:

Disorder	Main Features
Laryngitis	Inflammation of the larynx; hoarseness
Pleurisy	Inflammation of pleura; chest pain
Pneumothorax	Air in pleural cavity; lung collapse
Asthma	Airway inflammation and constriction; wheezing
Infant RDS	Respiratory distress due to lack of surfactant
COPD	Chronic obstructive pulmonary disease; airflow limitation
Emphysema	Destruction of alveoli; reduced gas exchange
Lung Cancer	Uncontrolled cell growth in lung tissue
Cystic Fibrosis	Genetic disorder; thick mucus obstructs airways

Additional info:

• Some definitions and explanations have been expanded for clarity and completeness.

• Equations for Boyle's Law and gas exchange have been provided in LaTeX format.