Chapter 20: The Lymphatic System and Lymphoid Organs and Tissues

Overview of the Lymphatic System

The lymphatic system is a network of vessels, nodes, and organs that helps maintain fluid balance, absorbs fats from the digestive tract, and provides immune defense.

• Lymphatic vessels: Transport leaked plasma proteins and fluids from tissues back to the cardiovascular system. They also serve as sites for immune surveillance.

• Lymph: The fluid transported by lymphatic vessels, similar to interstitial fluid.

• Lymphoid organs: Include lymph nodes, spleen, thymus, tonsils, and MALT (mucosa-associated lymphoid tissue).

Structure and Function of Lymphatic Vessels

• Lymphatic capillaries: Highly permeable, blind-ended vessels that collect interstitial fluid. Entry is promoted by one-way minivalves formed by overlapping endothelial cells.

• Lymphatic ducts: The right lymphatic duct and thoracic duct (originating at the cisterna chyli) return lymph to the venous circulation.

Lymphoid Tissue and Organs

• Lymph nodes: Small, bean-shaped structures that filter lymph and house lymphocytes and macrophages. Densely clustered in axillae, groin, and cervical regions.

• Spleen: Largest lymphoid organ; filters blood, recycles old red blood cells, and stores platelets.

• Thymus: Site of T lymphocyte maturation; most active during youth and atrophies with age.

• Tonsils and MALT: Protect mucosal surfaces from pathogens.

Comparison: Blood, Interstitial Fluid, and Lymph

• Blood: Contains cells (RBCs, WBCs, platelets) and plasma; circulates in blood vessels.

• Interstitial fluid: Fluid between cells; derived from plasma, bathes tissues.

• Lymph: Interstitial fluid that enters lymphatic vessels; returns to blood circulation.

Clinical Applications

• Lymphedema: Swelling due to lymphatic obstruction (e.g., after mastectomy).

• Swollen lymph nodes: Often indicate infection or immune response.

• Tonsillectomy: Now less common due to recognition of immune function.

Chapter 21: The Immune System: Innate and Adaptive Body Defenses

Innate (Nonspecific) Defenses

The innate immune system provides immediate, general defense against pathogens.

• Physical barriers: Skin and mucous membranes.

• Chemical barriers: Lysozyme, acid pH, mucus, keratin.

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

• Inflammation: Local response to injury or infection.

• Antimicrobial proteins: Complement system, interferons.

Adaptive (Specific) Defenses

The adaptive immune system targets specific pathogens and provides memory for future responses.

• Humoral immunity: Mediated by B lymphocytes and antibodies.

• Cellular immunity: Mediated by T lymphocytes (helper, regulatory, cytotoxic T cells).

• Antigen: Any substance that can provoke an immune response.

• Antibody structure: Y-shaped molecules with variable (antigen-binding) and constant regions; composed of heavy and light chains.

Immune Responses and Disorders

• Primary vs. Secondary Response: Secondary is faster and stronger due to memory cells.

• Hypersensitivity: Overreaction of the immune system (e.g., allergies, autoimmune diseases).

• Immunodeficiency: Failure of the immune system (e.g., AIDS, SCID).

• Self-tolerance: Ability to distinguish self from non-self; loss leads to autoimmunity.

Table: Types of Immune Cells and Their Functions

Chapter 22: The Respiratory System

Overview of Respiratory Anatomy

The respiratory system provides for gas exchange between the atmosphere and the blood.

• Major structures: Nasal cavity, pharynx, larynx, trachea, bronchi, lungs.

• Laryngeal cartilages: Include paired (arytenoid, corniculate, cuneiform) and unpaired (epiglottis, thyroid, cricoid) cartilages.

• Phrenic nerve: Innervates the diaphragm; damage causes paralysis of the diaphragm.

Mechanics of Breathing

• Inspiration: Diaphragm and external intercostals contract, increasing thoracic volume and decreasing pressure, drawing air in.

• Expiration: Usually passive; muscles relax, thoracic volume decreases, pressure increases, air flows out.

• Surfactant: Reduces surface tension in alveoli, preventing collapse.

Gas Exchange and Transport

• Gas exchange: Occurs by diffusion across the respiratory membrane in alveoli.

• Oxygen transport: Mostly bound to hemoglobin in red blood cells.

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

Control of Respiration

• Respiratory centers: Located in the medulla and pons; regulate rate and depth of breathing.

• Stimuli: Rising is the most powerful respiratory stimulant.

Clinical Applications

• Pneumothorax: Air in the pleural cavity causes lung collapse.

• Hyperventilation: Rapid breathing decreases , can lead to alkalosis.

• Minute ventilation vs. alveolar ventilation: Alveolar ventilation is a better measure of effective gas exchange.

Table: Comparison of Minute and Alveolar Ventilation

Key Equations

• Partial Pressure Gradient: Drives gas movement

• Minute Ventilation:

• Alveolar Ventilation:

Additional info:

• Some content was inferred and expanded for clarity and completeness, such as the structure of antibody monomers and the clinical significance of lymphatic and respiratory disorders.

• Tables were recreated to summarize immune cell functions and ventilation parameters.