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1 Respiratory System Respiratory System For the body to survive, there must be a constant supply of O2 and a constant disposal of CO2 Respiratory System Respiratory System - Overview: Assists in the detection Protects system of odorants (debris / pathogens / dessication) 5 3 4 Produces sound (vocalization) Provides surface area for gas exchange (between air / blood) 1 2 Moves air to / from gas exchange surface Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Table 19.1 1 Respiratory System Functional Anatomy: Epiglottis Upper Respiratory • Conduction of air System • Gas exchange • Filters / warms / humidifies Lower Respiratory incoming air System 1) External nares 5) Larynx 2) Nasal cavity • Provide open airway • Resonance chamber • channel air / food 3) Uvula • voice production (link) 4) Pharynx 6) Trachea • Nasopharynx 7) Bronchial tree 8) Alveoli • Oropharynx • Laryngopharynx Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.1 Respiratory System Functional Anatomy: Trachea Naming of pathways: • > 1 mm diameter = bronchus • < 1 mm diameter = bronchiole Primary • < 0.5 mm diameter = terminal bronchiole Bronchus Bronchi bifurcation (23 orders) Green = Conducting zone Purple = Respiratory zone Bronchiole Terminal Bronchiole Respiratory Bronchiole Alveolus Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 2 Respiratory System Functional Anatomy: Respiratory Mucosa / Submucosa: Near Near trachea alveoli Epithelium: Pseudostratified Simple columnar cuboidal Cilia No cilia Mucosa: Lamina Propria (areolar tissue layer): Mucous membrane (epithelium / areolar tissue) smooth smooth muscle muscle Mucous No glands mucous glands Cartilage: Rings Plates / none Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Respiratory System Functional Anatomy: How are inhaled debris / pathogens cleared from respiratory tract? Nasal Cavity: Particles > 10 µm Conducting Zone: Particles 5 – 10 µm Respiratory Zone: Mucus Escalator Particles 1 – 5 µm Macrophages Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.2 3 Respiratory System Functional Anatomy: Pseudostratified ciliated columnar epithelium Trachea Goblet cells: Unicellular mucous secreting glands Esophagus Tough, flexible tube 15 – 20 tracheal (~ 1” diameter) cartilages (C-shaped) • Protect airway • Allow for food passage Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Respiratory System Functional Anatomy: Right primary bronchus wider, shorter & steeper ( blockage hazard) Bronchus (> 1 mm diameter) • 1º = Extrapulmonary bronchi • 2º = Intrapulmonary bronchi Bronchitis: Inflammation of airways Pseudostratified ciliated columnar epithelium Smooth muscle Cartilage plate Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 4 Respiratory System Functional Anatomy: Mucous glands rare – Why? Pseudostratified ciliated columnar epithelium Cartilage plates? Thick smooth muscle Allergic attack = Histamine = Bronchoconstriction Sympathetic stimulation (NE; 2 receptors) • Leads to bronchodilation Synthetic drugs (e.g., albuterol) E (medulla) triggers Bronchiole trigger response response (< 1 mm diameter) Parasympathetic stimulation (ACh; muscarinic receptors) • Leads to bronchoconstriction Alveoli (300 million / lung) Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.9 Respiratory System Functional Anatomy: Surrounded by fine elastic fibers Respiratory bronchiole Terminal Alveolar bronchiole sac Type I Pneumocytes: • Simple squamous; forms wall of alveoli Total surface area: • Alveolar pores (1 – 6 / alveoli) 75 - 90 m2 (~1/2 tennis court) Type II Pneumocytes: 200 m • Cuboidal / round; secrete surfactant • Reduces surface tension (stops alveoli collapse) Alveolar macrophages: • Clear debris on alveolar surface Alveolar pores Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.8 5 Respiratory System Pneumonia: Functional Anatomy: Thickening of respiratory membrane Gas exchange occurs readily in the alveoli of the lung via simple diffusion across the respiratory membrane 0.1 – 0.5 m thick Respiratory Membrane: 1) Type I pneumocytes 2) Endothelial cells of capillaries 3) Fused basement membranes Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.9 Respiratory System Respiratory Physiology: 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 4 Randall et al. (Eckert Animal Physiology, 5th ed.) – Figure 13.19 6 Respiratory System Pulmonary Ventilation: Simplified Model: Trachea Trachea Visceral pleura Lung Parietal Pleural pleura cavity Thoracic wall Lung Pleural cavity Thoracic Diaphragm Diaphragm wall Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.12 Respiratory System Pulmonary Ventilation: Atmospheric pressure = ~ 760 mm Hg (Consider Patmospheric = 0 mm Hg) Pressure relationships in the thoracic cavity: 1) Intrapulmonary Pressure (w/in the alveoli): • Static conditions = 0 mm Hg • Inhalation (inspiration) = Ppul slightly negative Intrapulmonary • Exhalation (expiration) = Ppul slightly positive pressure (P = 0 mm Hg) pul 2) Intrapleural pressure (w/in pleural cavity): • Always relatively negative (~ - 4 mm Hg) • Prevents lungs from collapsing Diaphragm Intrapleural pressure (Pip = - 4 mm Hg) atmospheric pressure = Patm = 0 mm Hg 7 Respiratory System Pulmonary Ventilation: Why is the intrapleural pressure negative? Answer: Interaction of opposing forces Forces equilibrate at Pip = - 4 mm Hg Forces acting to collapse lung: 1) Elasticity of lungs Surface tension of 2) Alveolar surface tension serous fluids keep lungs “stuck” to Force resisting lung collapse: chest wall 1) Elasticity of chest wall Pneumothorax: (“sucking chest wound”) Puncture of chest wall; results in inability to generate negative pressure and expand the lungs Costanzo (Physiology, 4th ed.) – Figure 5.9 Respiratory System Pulmonary Ventilation: Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes Boyle’s Law: P1V1 = P2V2 P = pressure of gas (mm Hg) V = volume of gas (mm3) P1 = initial pressure; V1 = initial volume P2 = resulting pressure; V2 = resulting volume 3 3 Example: 4 mm Hg (2 mm ) = P2 (4 mm ) P2 = 2 mm Hg CHANGING THE VOLUME RESULTS IN INVERSE CHANGE OF PRESSURE Martini et. al. (Fundamentals of Anatomy and Physiology, 7th ed.) – Figure 23.13 8 Respiratory System Pulmonary Ventilation: Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes 0 mm Hg Inspiration: Muscular expansion of thoracic cavity - 4 mm Hg A) Contraction of diaphragm • Lengthens thorax (pushes liver down) B) Contraction of external intercostal muscles • Widens thorax 0 mm Hg Diaphragm Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.13 Respiratory System Pulmonary Ventilation: Pulmonary ventilation is a mechanical process that depends on thoracic cavity volume changes 0 mm Hg Inspiration: Muscular expansion of thoracic cavity - 6 mm Hg A) Contraction of diaphragm • Lengthens thorax (pushes liver down) B) Contraction of external intercostal muscles • Widens thorax - 1 mm Hg Results in: • Reduced intrapleural pressure (Pip) • Reduced intrapulmonary pressure (Ppul) Results in decreased pressure in thoracic cavity and air enters Diaphragm 9 Respiratory System Internal pressure Pulmonary Ventilation: can reach +100 mm Hg (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 Respiratory System Pulmonary Ventilation: Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 22.14 10 Respiratory System Pulmonary Ventilation: Several physical factors exist influence pulmonary ventilation A) Airway resistance Q = Airflow (L / min) Q = P / R P = Pressure gradient (mm Hg) R = Airway resistance (mm Hg / L / sec) Airflow is directly proportional to pressure difference between outside air and alveoli and inversely proportional to resistance of the airway Resistance determined by Why don’t the smallest airways provide the highest resistance? Poiseuille’s Law: Medium-sized bronchi 8Lη Reminder: R = Parasympathetic system produces 4 r bronchial constriction Terminal ( diameter = resistance) R = Resistance bronchioles η = Viscosity of inspired air Resistance Sympathetic system produces L = Length of airway bronchial dilation ( diameter = resistance) r = Radius of airway Bifurcation stage Respiratory System Respiratory Distress Syndrome Pulmonary Ventilation: (e.g., pre-mature babies) Several physical factors exist influence pulmonary ventilation B) Surface tension in alveoli Surface tension generated as neighboring liquid molecules on the surface of alveoli are drawn together by attractive forces Pressure required to keep alveolus open P = Collapsing
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