Lymphatic, Immune, and Respiratory Systems: Comprehensive Study Guide

Lymphatic System

Anatomy of the Lymphatic System

The lymphatic system is a network of vessels, tissues, and organs that help maintain fluid balance and defend the body against pathogens.

• Lymphatic Capillaries: Small, blind-ended vessels that collect interstitial fluid (now called lymph).

• Lacteals: Specialized lymphatic capillaries in the small intestine that absorb dietary fats.

• Major Lymphatic Vessels: The right lymphatic duct drains the right upper body; the thoracic duct drains the rest. Both empty into the venous system at the subclavian veins.

• Origin of Lymph: Lymph is derived from interstitial fluid that enters lymphatic capillaries.

• Mechanism of Circulation: Lymph moves via skeletal muscle contraction, respiratory movements, and valves preventing backflow.

• Pathology: Blockage can cause lymphedema; infection can cause swollen nodes.

Lymphoid Cells, Organs, and Tissues

Lymphoid tissues are sites of immune cell development and function.

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

• Lymphoid Organs: Primary (bone marrow, thymus) and secondary (lymph nodes, spleen, MALT).

• Localization: Lymphoid tissues are found throughout the body, especially in mucosal surfaces.

Lymph Nodes: Anatomy and Histology

Lymph nodes filter lymph and house immune cells.

• Structure: Capsule, cortex (with follicles), medulla.

• Cells: B cells in follicles, T cells in paracortex, macrophages in medullary cords.

• Pathology: Buboes are swollen, infected nodes; nodes can be sites of cancer metastasis.

Spleen: Location, Anatomy, Functions, Pathology

The spleen is the largest lymphoid organ, located in the left upper abdomen.

• Anatomy: White pulp (immune function), red pulp (filters blood, removes old RBCs).

• Functions: Immune surveillance, blood filtration, storage of platelets.

• Pathology: Rupture can cause life-threatening bleeding.

MALT (Mucosa-Associated Lymphoid Tissue)

MALT protects mucosal surfaces.

• Localization: Tonsils (pharynx), Peyer's patches (small intestine), appendix.

• Functions: Tonsils trap pathogens; Peyer's patches monitor intestinal bacteria; appendix may aid immunity.

Thymus: Anatomy, Function, Age-Dependent Evolution

The thymus is the site of T cell maturation.

• Anatomy: Located in the mediastinum; lobulated structure.

• Function: Educates and matures T lymphocytes.

• Age-Dependent Evolution: Largest in childhood; shrinks (involutes) with age.

Immune System

General Description: Lines of Defense

The immune system protects against pathogens via three lines of defense.

• First Line: Physical and chemical barriers (skin, mucous membranes).

• Second Line: Innate immune cells and responses (inflammation, phagocytes).

• Third Line: Adaptive immunity (specific responses by lymphocytes).

Innate Defenses

• First Line: Epithelia produce defenses like mucus, acid, enzymes.

• Second Line:

  • Cells: Phagocytes (neutrophils, macrophages), NK cells (kill abnormal cells).

  • Inflammation: Signs: redness, heat, swelling, pain, loss of function. Triggered by tissue damage; stages include vasodilation, increased permeability, leukocyte recruitment. Chemicals: histamine, cytokines.

  • Antimicrobial Proteins:

    • Interferons: Produced by virus-infected cells; block viral replication.

    • Complement: Activated by classical, alternative, or lectin pathways; C3 activation leads to MAC (membrane attack complex), opsonization.

  • Fever: Regulated by hypothalamus; triggered by pyrogens; inhibits pathogen growth.

Adaptive Defenses

• Classification: Cellular (T cells) and humoral (B cells/antibodies).

• Antigens: Substances recognized by the immune system. Types: complete, incomplete, self antigens. MHC labels self and presents antigens; two types: I (all cells), II (APCs).

• Cells: B and T lymphocytes; maturation in bone marrow (B) and thymus (T).

• Receptor Diversity: Generated by gene rearrangement.

• Lymphocyte Education: Positive and negative selection in thymus.

• APCs: Dendritic cells, macrophages, B cells.

Humoral Response

• Primary Response: First exposure; clonal selection of B cells.

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

• Immunity: Active (body produces antibodies), passive (antibodies given).

• Antibodies: Y-shaped proteins; classes: IgG, IgM, IgA, IgE, IgD. Functions: neutralization, agglutination, opsonization, complement activation.

• Monoclonal Antibodies: Produced from a single B cell clone; used in diagnostics and therapy.

Cellular Immune Response

• MHC: Class I presents to CD8+ T cells; Class II to CD4+ T cells.

• T Cells: CD4 (helper), CD8 (cytotoxic); maturation and activation require antigen presentation.

• Effector T Cells: Helper T cells (coordinate responses), cytotoxic T cells (kill infected cells).

• Cytokines: Key signaling molecules (e.g., interferon-gamma, TNF-alpha).

• TH Cells: Central to both humoral and cellular responses.

Immediate Hypersensitivity

• Conditions: Allergies, anaphylaxis.

• Mechanism: Initial exposure sensitizes; subsequent exposure triggers mast cell degranulation (histamine release).

Respiratory System

Functions of the Respiratory System

The respiratory system supplies oxygen, removes carbon dioxide, and regulates acid-base balance.

• Gas exchange

• Vocalization

• Protection from pathogens

Upper Respiratory System: Anatomy and Histology

• Components: Nose, nasal cavity, pharynx.

• Epithelium: Pseudostratified ciliated columnar epithelium (nasal cavity).

• Functions: Filter, warm, humidify air.

Lower Respiratory System: Anatomy, Histology, Pathology

• Larynx: Cartilages (thyroid, cricoid, arytenoid, epiglottis), vocal cords, functions in voice and airway protection.

• Trachea: C-shaped cartilage rings, mucociliary escalator moves debris upward; pathology includes obstruction (Heimlich maneuver).

• Bronchi: Primary, secondary, tertiary divisions; conducting zone (air passage), respiratory zone (gas exchange).

• Alveoli: Type I cells (gas exchange), Type II cells (surfactant production), alveolar macrophages.

• Lungs: Lobes, blood supply (pulmonary and bronchial arteries), innervation, pleurae (visceral and parietal), pleural cavity pathology (e.g., pneumothorax).

Respiratory Physiology: Mechanics and Pressures

• Inspiration/Expiration: Diaphragm and intercostal muscles change thoracic volume.

• Pressures: Pulmonary, pleural, transpulmonary pressure ($P_{tp} = P_{pul} - P_{pleural}$).

• Inward Forces: Elastic recoil, surface tension.

• Stages: Inspiration (active), expiration (passive or active).

• Physical Factors: Airway resistance, lung compliance, alveolar surface tension.

Respiratory Volumes and Capacities

• Tidal Volume (TV): Amount of air inhaled/exhaled per breath.

• Dead Space: Air not involved in gas exchange.

• Restrictive vs. Obstructive Conditions: Restrictive (reduced volumes), obstructive (increased residual volume).

Gas Exchange: Laws and Partial Pressures

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

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

• Partial Pressures:

  • Alveolar air: $PO_2 \approx 104$ mmHg, $PCO_2 \approx 40$ mmHg

  • Pulmonary veins/systemic arteries: $PO_2 \approx 100$ mmHg, $PCO_2 \approx 40$ mmHg

  • Tissues/systemic veins: $PO_2 \approx 40$ mmHg, $PCO_2 \approx 45$ mmHg

External and Internal Respiration

• External Respiration: Gas exchange in lungs; affected by surface area, membrane thickness, partial pressure gradients.

• Ventilation-Perfusion Coupling: Matches airflow to blood flow in local lung regions.

• Internal Respiration: Gas exchange in tissues.

Transport of Gases

• Oxygen: Bound to hemoglobin; dissociation curve is sigmoid, indicating cooperative binding.

• Bohr Effect: Increased CO2 or temperature shifts curve right, promoting O2 release.

• CO2: Transported as dissolved gas, carbaminohemoglobin, and mainly as bicarbonate ($CO_2 + H_2O \leftrightarrow H_2CO_3 \leftrightarrow H^+ + HCO_3^-$).

• Haldane Effect: Low O2 increases CO2 binding to hemoglobin.

Control of Respiration

• Neural Control: Medullary respiratory centers (dorsal, ventral), pontine center; regulate rhythm and depth.

• Regulation: CO2 is the most potent regulator; acts on central chemoreceptors (brainstem) and peripheral chemoreceptors (carotid/aortic bodies).

Pathology

• Obstructive Diseases: COPD (emphysema: alveolar destruction; chronic bronchitis: mucus production), asthma (bronchoconstriction).

• Restrictive Diseases: Lung cancer, cystic fibrosis (affect lung volumes and gas exchange).

Condition	Effect on Lung Volumes	Effect on Gas Exchange
Obstructive (COPD, Asthma)	Increased residual volume, decreased expiratory flow	Impaired O2/CO2 exchange
Restrictive (Fibrosis, Cancer)	Decreased total lung capacity	Reduced O2 uptake

Additional info: The above notes expand on brief review points, providing definitions, examples, and mechanisms for each topic. Equations are rendered in LaTeX as required. Table compares obstructive and restrictive lung diseases as inferred from the review outline.