Respiratory System Respiratory System - Overview: Assists in the detection Protects system of odorants Respiratory (debris / pathogens / dessication) System 5 3 4 Produces sound (vocalization) Provides surface area for gas exchange (between air / blood) 1 2 For the body to survive, there must be a constant supply of Moves air to / from gas O2 and a constant exchange surface disposal of CO 2 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Table 19.1 Respiratory System Respiratory System Functional Anatomy: Functional Anatomy: Trachea Epiglottis Naming of pathways: • > 1 mm diameter = bronchus Upper Respiratory • Conduction of air • < 1 mm diameter = bronchiole System • Gas exchange Primary • < 0.5 mm diameter = terminal bronchiole Bronchus • Filters / warms / humidifies Lower Respiratory Bronchi System incoming air bifurcation (23 orders) 1) External nares 5) Larynx 2) Nasal cavity • Provide open airway Green = Conducting zone • Resonance chamber • channel air / food Purple = Respiratory zone 3) Uvula • voice production (link) 4) Pharynx 6) Trachea 7) Bronchial tree • Nasopharynx Bronchiole 8) Alveoli • Oropharynx Terminal Bronchiole Respiratory Bronchiole • Laryngopharynx Alveolus Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.1 Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Respiratory System Respiratory System Functional Anatomy: Functional Anatomy: Respiratory Mucosa / Submucosa: How are inhaled debris / pathogens cleared from respiratory tract? Near Near trachea alveoli Nasal Cavity: Epithelium: Particles > 10 µm Pseudostratified Simple columnar cuboidal Conducting Zone: Particles 5 – 10 µm Cilia No cilia Respiratory Zone: Mucus Escalator Particles 1 – 5 µm Mucosa: Lamina Propria (areolar tissue layer): Mucous membrane (epithelium / areolar tissue) smooth smooth muscle muscle Mucous No glands mucous glands Cartilage: Rings Plates / none Macrophages Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.2 1 Respiratory System Respiratory System Functional Anatomy: Pseudostratified ciliated Functional Anatomy: columnar epithelium Trachea Right primary bronchus wider, shorter & steeper Goblet cells: ( blockage hazard) Unicellular mucous secreting glands Bronchus (> 1 mm diameter) • 1º = Extrapulmonary bronchi • 2º = Intrapulmonary bronchi Esophagus Bronchitis: Inflammation of airways Pseudostratified ciliated columnar epithelium Tough, flexible tube Smooth muscle 15 – 20 tracheal (~ 1” diameter) cartilages (C-shaped) • Protect airway Cartilage plate • Allow for food passage Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Respiratory System Respiratory System Functional Anatomy: Mucous glands rare – Why? Functional Anatomy: Pseudostratified Surrounded by fine ciliated columnar elastic fibers epithelium Respiratory bronchiole Cartilage plates? Terminal Alveolar bronchiole sac Thick smooth muscle Type I Pneumocytes: • Simple squamous; forms wall of alveoli Allergic attack = Histamine = Bronchoconstriction Total surface area: • Alveolar pores (1 – 6 / alveoli) 75 - 90 m2 (~1/2 tennis court) Type II Pneumocytes: Sympathetic stimulation (NE; 2 receptors) • Leads to bronchodilation 200 m • Cuboidal / round; secrete surfactant • Reduces surface tension (stops alveoli collapse) Synthetic drugs (e.g., albuterol) E (medulla) triggers Alveolar macrophages: Bronchiole trigger response response (< 1 mm diameter) • Clear debris on alveolar surface Parasympathetic stimulation (ACh; muscarinic receptors) • Leads to bronchoconstriction Alveoli Alveolar (300 million / lung) pores Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.8 Respiratory System Respiratory System Pneumonia: Functional Anatomy: Thickening of respiratory membrane Respiratory Physiology: Gas exchange occurs readily in the alveoli of the lung via simple diffusion across the respiratory membrane 0.1 – 0.5 m thick Respiration includes: 1 1) Pulmonary ventilation (pumping air in / out of lungs) 2) External respiration (gas exchange @ blood-gas barrier) 2 3) Transport of respiratory gases (blood) 4) Internal respiration (gas exchange @ tissues) 3 Respiratory Membrane: 1) Type I pneumocytes 2) Endothelial cells of capillaries 4 3) Fused basement membranes Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.9 Randall et al. (Eckert Animal Physiology, 5th ed.) – Figure 13.19 2 Respiratory System Respiratory System Pulmonary Ventilation: Pulmonary Ventilation: Simplified Model: Atmospheric pressure = ~ 760 mm Hg (Consider Patmospheric = 0 mm Hg) Trachea Trachea Visceral pleura Lung Pressure relationships in the thoracic cavity: Parietal Pleural 1) Intrapulmonary Pressure (w/in the alveoli): pleura cavity • Static conditions = 0 mm Hg Thoracic wall • Inhalation (inspiration) = Ppul slightly negative Intrapulmonary • Exhalation (expiration) = Ppul slightly positive Lung pressure (Ppul = 0 mm Hg) 2) Intrapleural pressure (w/in pleural cavity): • Always relatively negative (~ - 4 mm Hg) • Prevents lungs from collapsing Pleural cavity Diaphragm Intrapleural pressure Diaphragm Thoracic Diaphragm (Pip = - 4 mm Hg) wall atmospheric pressure = Patm = 0 mm Hg Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.12 Respiratory System Respiratory System Pulmonary Ventilation: Pulmonary Ventilation: Why is the intrapleural pressure negative? Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes Answer: Interaction of opposing forces Forces equilibrate at P = - 4 mm Hg ip Boyle’s Law: Forces acting to collapse lung: P1V1 = P2V2 1) Elasticity of lungs Surface tension of 2) Alveolar surface tension serous fluids keep lungs “stuck” to P = pressure of gas (mm Hg) Force resisting lung collapse: chest wall V = volume of gas (mm3) 1) Elasticity of chest wall P1 = initial pressure; V1 = initial volume P2 = resulting pressure; V2 = resulting volume Pneumothorax: 3 3 Example: 4 mm Hg (2 mm ) = P2 (4 mm ) P2 = 2 mm Hg (“sucking chest wound”) Puncture of chest wall; results in inability to CHANGING THE VOLUME RESULTS IN INVERSE generate negative pressure CHANGE OF PRESSURE and expand the lungs Costanzo (Physiology, 4th ed.) – Figure 5.9 Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.13 Respiratory System Respiratory System Pulmonary Ventilation: Pulmonary Ventilation: Pulmonary ventilation is a mechanical process that depends on Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes thoracic cavity volume changes 0 mm Hg 0 mm Hg Inspiration: Inspiration: Muscular expansion of thoracic cavity - 4 mm Hg Muscular expansion of thoracic cavity - 6 mm Hg A) Contraction of diaphragm A) Contraction of diaphragm • Lengthens thorax (pushes liver down) • Lengthens thorax (pushes liver down) B) Contraction of external intercostal muscles B) Contraction of external intercostal muscles • Widens thorax • Widens thorax 0 mm Hg - 1 mm Hg Results in: • Reduced intrapleural pressure (Pip) • Reduced intrapulmonary pressure (Ppul) Results in decreased pressure in thoracic Diaphragm cavity and air enters Diaphragm Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.13 3 Respiratory System Respiratory System Internal pressure Pulmonary Ventilation: can reach +100 mm Hg Pulmonary Ventilation: (e.g., why you should exhale when lifting weights) Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes Results in increased pressure 0 mm Hg Expiration: in thoracic cavity; air exits Retraction of thoracic cavity - 4 mm Hg A) Passive Expiration • Diaphragm / external intercostals relax • Elastic rebound (lungs rebound) B) Active (“Forced”) Expiration +10 mm Hg • Abdominal muscles contract • Internal intercostals contract Eupnea: Hyperpnea: Quiet breathing Forced breathing Diaphragm (active inspiration; (active inspiration; (passive expiration) (active expiration) Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.13 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.14 Respiratory System Respiratory System Respiratory Distress Syndrome Pulmonary Ventilation: Pulmonary Ventilation: (e.g., pre-mature babies) Several physical factors exist influence pulmonary ventilation Several physical factors exist influence pulmonary ventilation A) Airway resistance B) Surface tension in alveoli Q = Airflow (L / min) Surface tension generated as neighboring liquid molecules on the surface P = Pressure gradient (mm Hg) of alveoli are drawn together by attractive forces Q = P / R Pressure required to R = Airway resistance (mm Hg / L / sec) keep alveolus open P = Collapsing pressure on alveolus (dynes / cm2) Airflow is directly proportional to pressure difference between outside air 2T T = Surface tension (dynes / cm) and alveoli and inversely proportional to resistance of the airway Law of Laplace: P = r r = Radius of alveolus (cm) Resistance determined by Why don’t the smallest airways provide the highest resistance? Poiseuille’s Law: Medium-sized Surfactant bronchi 8Lη Reminder: R = Parasympathetic system produces 4 r bronchial constriction Problem? Terminal ( diameter = resistance) R = Resistance bronchioles η = Viscosity of inspired air Resistance