Lymphatic, Immune, and Respiratory Systems: Study Guide

Lymphatic System

Overview of the Lymphatic System

The lymphatic system is a network of vessels, nodes, and organs that returns excess tissue fluid to the bloodstream and plays a vital role in immune defense.

• Lymphatic vessels transport lymph, a fluid containing white blood cells.

• Lymph nodes filter lymph and house lymphocytes.

• Lymphoid organs include the spleen, thymus, tonsils, and MALT (mucosa-associated lymphoid tissue).

20.1 The Lymphatic System: Vessels, Lymph, and Lymph Nodes

• Functions of lymphatic vessels: Return interstitial fluid to the blood, absorb dietary fats, and provide immune surveillance.

• Structure and distribution: Lymphatic capillaries merge to form larger vessels, which pass through lymph nodes before returning lymph to the venous system.

• Lymph transport: Lymph is moved by skeletal muscle contraction, pressure changes during breathing, and smooth muscle in vessel walls.

20.2 Lymphoid Cells and Tissues

• Lymphoid cells: Include lymphocytes (B cells and T cells), macrophages, and dendritic cells.

• Lymphoid tissues: Provide sites for immune cell proliferation and surveillance. Two main types: diffuse lymphoid tissue and follicular lymphoid tissue.

• Follicular tissue: Forms lymphoid follicles, often found in lymph nodes and spleen.

20.3 Lymph Nodes

• Function: Filter lymph and house lymphocytes that respond to pathogens.

• Structure: Cortex (contains follicles with germinal centers) and medulla (contains medullary cords).

20.4 Spleen and Lymph Nodes: Comparison

• Spleen: Filters blood, removes old red blood cells, and stores platelets.

• Lymph nodes: Filter lymph and initiate immune responses to antigens in lymph.

20.5 MALT (Mucosa-Associated Lymphoid Tissue)

• Definition: Lymphoid tissues in mucous membranes throughout the body (e.g., tonsils, Peyer's patches, appendix).

• Function: Protects body entryways from pathogens.

20.6 Thymus and T Lymphocyte Maturation

• Thymus: Site of T lymphocyte maturation; most active during childhood.

• Structure: Consists of cortex (immature T cells) and medulla (mature T cells).

Immune System

21.1 Surface Barriers

Surface barriers, such as skin and mucous membranes, act as the first line of defense against pathogens.

• Physical barriers: Skin, mucous membranes.

• Chemical barriers: Acid mantle, enzymes, mucin, defensins.

21.2 Innate Internal Defenses

• Cells: Phagocytes (neutrophils, macrophages), natural killer (NK) cells.

• Chemicals: Inflammatory mediators, complement proteins, interferons.

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

21.3 Antigens and Adaptive Defenses

• Antigens: Substances that provoke an immune response.

• Adaptive immunity: Specific defense involving B and T lymphocytes.

21.4 B and T Lymphocytes; Antigen-Presenting Cells

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

• T lymphocytes: Directly attack infected cells; responsible for cellular immunity.

• Antigen-presenting cells (APCs): Dendritic cells, macrophages, and B cells that present antigens to T cells.

21.5 Antibodies and Humoral Immunity

• Antibodies: Proteins produced by plasma cells that bind to specific antigens.

• Five classes: IgG, IgA, IgM, IgE, IgD.

• Active immunity: Acquired through exposure to antigen.

• Passive immunity: Acquired through transfer of antibodies.

21.6 Cellular Immunity and T Cells

• Types of T cells: Helper T cells (CD4+), cytotoxic T cells (CD8+), regulatory T cells.

• Functions: Directly kill infected cells, activate other immune cells, regulate immune responses.

Respiratory System

22.1 Upper Respiratory System

• Components: Nose, paranasal sinuses, pharynx.

• Functions: Warms, humidifies, and filters incoming air.

• Protective mechanisms: Mucus, cilia, sneezing, and coughing.

22.2 Lower Respiratory System

• Components: Larynx, trachea, bronchi, lungs.

• Conducting zone: Passages that carry air to the respiratory zone.

• Respiratory zone: Sites of gas exchange (respiratory bronchioles, alveolar ducts, alveoli).

22.3 Pleural Cavities

• Pleura: Double-layered membrane surrounding each lung.

• Pleural cavity: Space between pleural layers, contains lubricating fluid.

22.4 Volume Changes and Pulmonary Ventilation

• Boyle's Law: Pressure and volume of a gas are inversely related at constant temperature.

$P_1V_1 = P_2V_2$

• Inspiration: Diaphragm contracts, thoracic volume increases, pressure decreases, air flows in.

• Expiration: Diaphragm relaxes, thoracic volume decreases, pressure increases, air flows out.

22.5 Measuring Respiratory Volumes and Capacities

• Tidal volume (TV): Air moved in or out during normal breathing.

• Inspiratory reserve volume (IRV): Additional air inhaled after normal inspiration.

• Expiratory reserve volume (ERV): Additional air exhaled after normal expiration.

• Residual volume (RV): Air remaining in lungs after maximal exhalation.

22.6 Gas Exchange

• Dalton's Law: Total pressure of a gas mixture is the sum of the partial pressures of each gas.

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

$P_{total} = P_1 + P_2 + P_3 + \ldots$

22.7 Oxygen and Carbon Dioxide Transport

• Oxygen transport: Mostly by hemoglobin in red blood cells; small amount dissolved in plasma.

• Carbon dioxide transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

• Oxygen-hemoglobin dissociation curve: Shows relationship between partial pressure of oxygen and hemoglobin saturation.

22.8 Respiratory Centers in the Brain Stem

• Medullary respiratory centers: Control basic rhythm of breathing.

• Pontine centers: Modify breathing rhythm.

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

22.9 Exercise and High Altitude

• Exercise: Increases respiratory rate and depth to meet increased oxygen demand.

• High altitude: Lower atmospheric pressure reduces oxygen availability; body acclimatizes by increasing red blood cell production and ventilation.

22.10 Respiratory Diseases

• Chronic bronchitis: Inflammation of bronchi, excess mucus production.

• Emphysema: Destruction of alveolar walls, reduced surface area for gas exchange.

• Asthma: Reversible airway constriction and inflammation.

• Tuberculosis: Infectious disease caused by Mycobacterium tuberculosis.

• Lung cancer: Uncontrolled cell growth in lung tissue.