Lymphatic and Respiratory Systems: Structure, Function, and Physiology

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Chapter 22: The Lymphatic System and Immunity

Components and Organization of the Lymphatic System

The lymphatic system is essential for defending the body against environmental hazards and internal threats. It consists of specialized cells, tissues, and organs that work together to maintain immunity and fluid balance.

Lymphocytes: Primary cells of the lymphatic system; respond to pathogens, abnormal cells, and foreign proteins.
Innate (Nonspecific) Defenses: Present at birth; include skin, fever, macrophages, etc.
Adaptive (Specific) Defenses: Lymphocytes (T cells and B cells) respond to specific threats; known as immune response.
Immunity: The ability to resist infection and disease.

Organization:

Lymphatic vessels: Begin in peripheral tissues and connect to veins.
Lymph: Interstitial fluid traveling through lymph vessels; resembles plasma.
Lymphoid tissues and organs:
- Primary: Sites of lymphocyte formation and maturation (red bone marrow, thymus).
- Secondary: Sites of lymphocyte activation and cloning (appendix, spleen, lymph nodes, tonsils, MALT).
Lymphocytes and lymphophages: T-cells, B-cells, macrophages, microphages.

Functions of the Lymphatic System

Defense: Production, maintenance, and distribution of lymphocytes.
Fluid Balance: Returns excess interstitial fluid to the bloodstream, maintaining blood volume and composition.

Lymphatic Vessels and Capillaries

Lymphatic capillaries are present in most tissues, with unique features for fluid uptake.

Originate as pockets, not continuous tubes.
Large diameters, thin walls, irregular outlines.
One-way valves allow entry of fluids, solutes, viruses, bacteria, and debris.
Lacteals: Specialized capillaries in the small intestine for lipid transport.

Small lymphatic vessels resemble veins, with one-way valves and beaded appearance. Major lymph-collecting vessels are classified as superficial (in subcutaneous and mucous/serous membranes) and deep (accompany deep arteries/veins).

Deep and superficial lymphatics merge into trunks, draining into the right lymphatic duct and thoracic duct.

Lymphadema

Blockage of lymphatic drainage leads to fluid accumulation and swelling, increasing risk of infection and toxin buildup.

Types of Lymphocytes

B-cells: 10-15%; mature in bone marrow; produce antibodies (humoral immunity).
T-cells: 80%; mature in thymus; cell-mediated immunity; cytotoxic, helper, suppressor, memory types.
Natural Killer (NK) cells: 5-10%; nonspecific defense against infected and cancerous cells.

Lymphocyte Production (Lymphopoiesis)

Occurs in bone marrow, thymus, and peripheral tissues. Hemocytoblasts produce lymphoid stem cells; B and NK cells mature in bone marrow, T cells in thymus. Cytokines promote B cell differentiation.

Lymphoid Nodules, MALT, and Tonsils

Lymphoid nodules: Dense lymphocyte clusters in areolar tissue; germinal centers for division.
MALT: Mucosa-associated lymphoid tissue; includes Peyer's patches and appendix nodules.
Tonsils: Five large nodules in pharynx (lingual, palatine, pharyngeal/adenoid).

Lymph Nodes

Small, oval organs with fibrous capsule and trabeculae. Filter lymph, removing 99% of pathogens. Lymph flows through sinuses, encountering B cells, T cells, and macrophages.

Afferent vessels: Bring lymph to node.
Efferent vessels: Carry lymph away.
Function: Purifies lymph, antigen presentation, early warning system.

Thymus

Programs T cells; large in infants, shrinks with age. Divided into lobes and lobules; cortex (active T cell division), medulla (mature T cells). Reticular epithelial cells maintain blood-thymus barrier and secrete thymosins.

Spleen

Highly vascular organ; removes abnormal blood cells, stores iron, initiates immune response. Red pulp (RBCs, macrophages), white pulp (lymphocytes, dendritic cells).

Nonspecific Defenses

Physical barriers: Skin, mucous membranes, secretions.
Phagocytes: Macrophages and microphages; engulf pathogens.
Immunological surveillance: NK cells monitor tissues.
Interferons: Cytokines from infected cells; trigger antiviral proteins.
Complement system: Proteins enhance antibody action; classical and alternate pathways.
Inflammatory response: Mast cells release histamine/heparin; swelling, redness, heat, pain.
Fever: Elevated temperature accelerates defenses; pyrogens reset hypothalamic thermostat.

Specific Resistance (Immunity)

T cells: Cellular immunity; respond to antigens presented by MHC I.
B cells: Humoral immunity; produce antibodies.
Innate immunity: Genetically determined, present at birth.
Adaptive immunity: Acquired through exposure; active (natural/induced) or passive (natural/induced).

Properties of Immunity

Specificity: Targets specific antigens.
Versatility: Responds to diverse antigens.
Memory: Remembers past pathogens.
Tolerance: Distinguishes self from non-self.

Antigen Presentation and Recognition

MHC I: All nucleated cells; present antigens to cytotoxic T cells.
MHC II: APCs and lymphocytes; present antigens to helper T cells.
CD markers: CD8 (cytotoxic/suppressor T cells), CD4 (helper T cells).
Co-stimulation: Second signal required for T cell activation; prevents self-attack.

T-Cell Activation

CD8: Cytotoxic T cells destroy infected cells; memory and suppressor T cells regulate response.
CD4: Helper T cells secrete cytokines; stimulate B cells and other defenses.

B-Cell Sensitization and Activation

Sensitization: B cell binds antigen, presents via MHC II.
Activation: Helper T cell confirms; B cell divides into plasma cells (antibody production) and memory B cells.

Antibody Structure and Classes

Structure: Two heavy and two light chains; variable and constant segments; antigen-binding sites.
Actions: Neutralization, precipitation/agglutination, complement activation, phagocyte attraction, opsonization, inflammation stimulation, prevention of adhesion.

Antibody Class	Function
IgG	Most abundant; crosses placenta; resistance to viruses/bacteria
IgE	Allergic response; binds basophils/mast cells
IgD	Surface of B cells; activation
IgM	First produced; agglutination; anti-A/B blood types
IgA	Secretions (mucus, saliva); protects surfaces

Primary vs. Secondary Response

Primary: Slow, initial exposure; IgM appears first, then IgG.
Secondary: Rapid, strong response; memory cells produce antibodies quickly.

Immunological Competence

Ability to mount an immune response; develops in fetal life, with passive immunity from maternal IgG.

Immune Disorders

Autoimmune: Loss of tolerance; antibodies target self.
Immunodeficiency: Failure of immune development or function (e.g., SCID, AIDS).
Allergies: Hypersensitivity; IgE-mediated; anaphylaxis possible.

Stress and Immune Response

Long-term glucocorticoid secretion depresses inflammation, phagocyte activity, and interleukin secretion.

Chapter 23: The Respiratory System

Functions of the Respiratory System

Gas exchange (O2 and CO2) at alveoli
Air movement to/from exchange surfaces
Protection of surfaces from dehydration, temperature, pathogens
Sound production
Olfaction (smell)

Organization of the Respiratory System

Upper: Nose, nasal cavity, sinuses, pharynx
Lower: Larynx, trachea, bronchi, bronchioles, alveoli
Conducting portion: Air passageways
Respiratory portion: Alveoli and smallest bronchioles

Respiratory Mucosa and Defense

Mucosa: Lines conducting portion; contains mucous glands and smooth muscle.
Epithelium types: Pseudostratified ciliated columnar (nasal cavity, pharynx), stratified squamous (lower pharynx), cuboidal (bronchioles), simple squamous (alveoli).
Defense: Mucus, cilia, macrophages; mucus escalator moves debris to pharynx.

Upper Respiratory Structures

Nose/Nasal cavity: Primary air entry; warms, humidifies, filters air.
Pharynx: Shared by respiratory and digestive systems; divided into nasopharynx, oropharynx, laryngopharynx.

Larynx Structure and Function

Cartilages: Thyroid, cricoid, epiglottis, arytenoid, corniculate, cuneiform.
Vocal folds: Produce sound; pitch depends on tension, length, diameter.
Vestibular folds: Protect vocal folds.
Cough reflex: Clears airway.

Trachea and Bronchi

Trachea: Windpipe; C-shaped cartilages; trachealis muscle adjusts diameter.
Primary bronchi: Right larger and steeper; branches at carina; enters lung at hilum.

Lung Anatomy

Right lung: 3 lobes; left lung: 2 lobes, cardiac notch.
Bronchial tree: Primary → secondary → tertiary bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli.

Pulmonary Lobule and Alveoli

Bronchioles: Terminal branches; lack cartilage; smooth muscle controls diameter.
Alveolar ducts/sacs: Connect bronchioles to alveoli; site of gas exchange.
Alveoli: Simple squamous cells (type I), macrophages, type II cells (surfactant).
Respiratory membrane: Epithelium, endothelium, fused basement membrane.

Blood Supply and Pleura

Pulmonary circuit: Deoxygenated blood to lungs; oxygenated blood to left atrium.
Bronchial arteries: Supply conducting passageways.
Pleura: Visceral and parietal; pleural fluid lubricates.

Respiration Types

External respiration: Gas exchange between lungs and environment.
Internal respiration: Gas exchange between blood and tissues.

External Respiration Steps

Pulmonary ventilation
Gas diffusion across respiratory membrane
Transport of O2 and CO2

Pressure-Volume Relationship (Boyle's Law)

Pressure is inversely proportional to volume:

Inhalation: Thoracic volume increases, pressure decreases, air flows in.
Exhalation: Volume decreases, pressure increases, air flows out.

Compliance

Expandability of lungs; affected by surfactant, tissue elasticity, and rib cage mobility.

Pressures in Respiration

Intrapulmonary pressure: Inside alveoli; varies with breathing.
Intrapleural pressure: Between pleurae; always negative relative to atmospheric.

Muscles of Breathing

Inhalation: Diaphragm, external intercostals, accessory muscles.
Exhalation: Internal intercostals, transversus thoracis, abdominal muscles (forced).

Breathing Types

Quiet breathing: Diaphragmatic (deep) and costal (shallow); passive exhalation.
Forced breathing: Accessory muscles active; forced exhalation.

Respiratory Rates and Volumes

Respiratory rate: 12-15 breaths/min (adults).
Minute volume:
Alveolar ventilation:
Tidal volume: 500 ml
Expiratory reserve volume: Male 1000 ml, Female 700 ml
Residual volume: Male 1200 ml, Female 1100 ml
Inspiratory reserve volume: Male 3300 ml, Female 1900 ml

Capacity	Male (ml)	Female (ml)
Inspiratory Capacity (IC)	3600	2400
Functional Residual Capacity (FRC)	2400	1800
Vital Capacity (VC)	4800	3400
Total Lung Capacity (TLC)	6000	4200

Gas Laws in Respiration

Dalton's Law: Total pressure is sum of partial pressures.
Henry's Law: Gas solubility in liquid is proportional to partial pressure.

Respiratory Membrane Features

Large partial pressure differences
Short diffusion distance
Lipid solubility of gases
Large surface area
Coordinated blood flow and airflow

Partial Pressures in Gas Exchange

Location	Po2 (mm Hg)	Pco2 (mm Hg)
Alveolus	100	40
Pulmonary capillary	40	45
Systemic capillary	95	40
Peripheral tissue	40	45

Oxygen Transport

Oxyhemoglobin: Hb binds up to 4 O2 molecules; reversible.
Hemoglobin saturation: % of heme units with O2; affected by Po2, pH, temperature, BPG.

Hemoglobin Relationships

pH: Lower pH (acidic) increases O2 release (Bohr effect).
Temperature: Higher temperature increases O2 release.
BPG: Higher BPG increases O2 release.
Fetal hemoglobin: Higher O2 affinity than adult.

Bohr effect equation:

Carbon Dioxide Transport

Converted to carbonic acid (70%)
Binds to hemoglobin (23%)
Dissolves in plasma (7%)
Chloride shift: Bicarbonate exchanged for chloride in RBCs.

Respiratory Centers

Medulla oblongata: Respiratory rhythmicity centers (DRG, VRG).
Pons: Apneustic and pneumotaxic centers regulate depth/rate.

Chemoreceptors and Reflexes

Chemoreceptors: Monitor Pco2, pH, Po2; stimulate respiration as needed.
Baroreceptors: Monitor blood pressure; affect respiratory rate.
Hering-Breuer reflexes: Prevent overexpansion/deflation of lungs.
Protective reflexes: Coughing, sneezing, laryngeal spasms.

Hypercapnia and Hypocapnia

Hypercapnia: High Pco2; stimulates increased respiration.
Hypocapnia: Low Pco2; decreases respiratory rate.

Voluntary Control of Respiration

Conscious and emotional influences via hypothalamus and ANS.
Chemoreceptor reflexes override voluntary control if Pco2 rises.

Additional info: All equations are provided in LaTeX format as required. Tables are rendered in HTML. Academic context has been expanded for clarity and completeness.