Lymphatic System

Overview of the Lymphatic System

The lymphatic system is a network of vessels, nodes, and organs that returns leaked fluids to the blood, filters pathogens, and supports immune function.

• 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 excess interstitial fluid to the bloodstream, absorb fats from the digestive tract, 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.

• Location: Found in lymphoid organs and scattered in connective tissues of other organs.

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.

20.5 MALT (Mucosa-Associated Lymphoid Tissue)

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

• Function: Guards body entryways against pathogens.

20.6 Thymus and T Lymphocyte Maturation

• Thymus: Site of T lymphocyte (T cell) maturation.

• Structure: Bilobed organ in the mediastinum; most active during childhood.

Immune System

21.1 Surface Barriers

Surface barriers are the first line of defense, preventing pathogen entry.

• Physical barriers: Skin and mucous membranes.

• Protective functions: Secretion of acids, enzymes, and mucins.

21.2 Innate Internal Defenses

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

• Chemicals: Inflammatory mediators, complement proteins, interferons.

• Inflammatory response: Redness, heat, swelling, pain, and loss of function.

21.3 Antigens and Adaptive Defenses

• Antigens: Substances that provoke an immune response.

• Adaptive immunity: Specific, involves B and T lymphocytes.

21.4 B and T Lymphocytes; Antigen-Presenting Cells

• B lymphocytes: Produce antibodies (humoral immunity).

• T lymphocytes: Directly attack infected cells (cellular immunity).

• Antigen-presenting cells (APCs): Dendritic cells, macrophages, B cells.

21.5 Antibodies and Humoral Immunity

• Antibodies: Proteins that bind specific antigens; five classes (IgG, IgM, IgA, IgD, IgE).

• Humoral immunity: Involves B cells and antibody production.

• Active vs. passive immunity: Active (exposure or vaccination), passive (antibody transfer).

21.6 Cellular Immunity and T Cells

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

• Functions: Direct adaptive immunity, attack infected or abnormal cells.

Respiratory System

22.1 Upper Respiratory System

• Components: Nose, paranasal sinuses, pharynx.

• Functions: Warms, humidifies, and filters air.

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

22.2 Lower Respiratory System

• Components: Larynx, trachea, bronchi, lungs.

• Conducting vs. respiratory zones: Conducting (air passageways), respiratory (gas exchange).

22.3 Pleural Cavities

• Pleura: Double-layered membrane surrounding each lung.

• Pleural cavity: Contains pleural fluid, reduces friction during breathing.

22.4 Volume Changes and Pulmonary Ventilation

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

• 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 per breath.

• Vital capacity (VC): Maximum air exhaled after maximum inhalation.

• Spirometry: Measures lung volumes and capacities.

22.6 Gas Exchange

• Dalton's Law: Total pressure is the sum of partial pressures of gases.

• Henry's Law: Gas solubility in liquid is proportional to partial pressure.

• External respiration: Gas exchange between alveoli and blood.

• Internal respiration: Gas exchange between blood and tissues.

22.7 Oxygen and Carbon Dioxide Transport

• Oxygen transport: Mostly by hemoglobin in red blood cells.

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

• Factors affecting oxygen loading/unloading: Temperature, pH, BPG, , .

22.8 Respiratory Centers in the Brain Stem

• Neural control: Medullary respiratory centers regulate breathing rhythm.

• Chemoreceptors: Detect changes in , , and pH.

• Higher brain centers: Influence voluntary control and emotional responses.

22.9 Exercise and High Altitude

• Exercise: Increases respiratory rate and depth (hyperpnea).

• High altitude: Triggers acclimatization, increased red blood cell production.

22.10 Respiratory Diseases

• Chronic bronchitis, emphysema, asthma, tuberculosis, lung cancer: Major causes of disability and death.

• Comparison: Each disease has distinct causes, symptoms, and effects on lung function.