Respiratory System Anatomy and Physiology PDF

20: Respiratory System Anatomy and Physiology in Context Chapter 20 20.1 Structures of the Respiratory System Chapter 20: Respiratory System Major Process of the Respiratory System 1. Ventilation : moving air in and out of lungs 2. External Respiration : exchange...

20: Respiratory System Anatomy and Physiology in Context Chapter 20 20.1 Structures of the Respiratory System Chapter 20: Respiratory System Major Process of the Respiratory System 1. Ventilation : moving air in and out of lungs 2. External Respiration : exchange of O2 and CO2 between air → alveoli alveoli → blood supply 3. Transport : O2 and CO2 between 4. Internal Respiration : exchange of O2 and CO2 between blood → metabolically active cells 5. Others : speech generation, balance of blood 20.1.1 Overall Components of the Respiratory System Divided into: 1. Conducting Division Provides passageway for air to move Warms, humidifies and cleanses air 2. Respiratory Division Provides site of gas exchange between lungs and blood sometimes divided into upper and lower division separated buy vocal 20.1.2 Structures of the Conducting Division: The Mouth  Primarily an organ of the digestive system  Role in respiration: acts in parallel with nose as conduit for air entry and exit  Especially important when breathing under exertion Air Treatment : warm, humidify and cleanse?? 20.1.3 Structures of the Conducting Division: External Nose Anatomy ANATOMY FEATURES Apex: Tip of the nose Nares (nostrils): Openings to the nose; contain hair and filter large particles Ala nasi: Cartilaginous flap on lateral side of each nostril Dorsum nasi: Length of nose Bridge: Connects root to rest of nose Root: Region located between the eyebrows 20.1.4 Structures of the Conducting Division: Internal Structures of the Nose ANATOMY FEATURES Nasal septum: Divides nasal cavity into left and right sides Superior, middle and inferior conchae: Three pairs of C- shaped bones extending laterally from the nasal septum Meatuses: Passageways surrounding the conchae for air to flow 20.1.5 Structures of the Conducting Division: Nasal Sinuses ANATOMY FEATURES The nasal cavity is connected to four pairs of sinuses Sinuses are air-filled spaces Serve to warm and humidify incoming air Contribute to resonance of voices 20.1.6 Structures of the Conducting Division: The Pharynx ANATOMY FEATURES Nasopharynx: Conduit for air only Adenoids lie in posterior wall Oropharynx: Conduit for digestion and respiration Tonsils found at the border Laryngopharynx: shortest Conduit for both air and food Opens into larynx and esophagus  20.1.7 Structures of the Conducting Division: The Larynx ANATOMY FEATURES Directs air into trachea and food into esophagus Contains vocal cords Superior portion lined with stratified squamous epithelium Inferior portion lined with mucous membrane that moves trapped debris into pharynx for  20.1.8 Structures of the Conducting Division: The Glottis and Laryngeal Cartilage ANATOMY FEATURES Cartilage in the larynx prevents it from collapsing  Large cartilage: epiglottis, thyroid, cricoid  Small cartilage: arytenoid, corniculate, cuneiform Glottis: vocal apparatus of the larynx 20.1.9 VIDEO: Vocal Cords Please insert the following video: Stroboscopy: Normal Female Vocal Cords https://www.youtube.com/watch?v=9Tlpkdq8a8c  20.1.10 Structures of the Conducting Division: The Trachea ANATOMY FEATURES The trachea extends from the larynx to its division into left and right bronchi Contains hyaline cartilage between fibrous tissue ligaments The carina is a ridge of cartilage that senses solid or liquid substances and triggers violent coughing to expel them Ciliated cells on the interior form 20.1.11 Structures of the Conducting Division: Bronchi Through Terminal Bronchioles ANATOMY FEATURES Primary bronchi  secondary bronchi  tertiary bronchi  primary bronchioles  terminal bronchioles Bronchi: Supported by cartilage; interior contain ciliated mucous cells Bronchioles: Lack cartilage but have smooth muscle instead; lack mucous but still have ciliated cells  20.1.12 Structures of the Respiratory Division: Respiratory Bronchioles and Alveolar Sacs ANATOMY FEATURES Respiratory bronchioles: Minimal smooth muscle Alveolar ducts: Short conduits of mainly connective tissue Alveolar sacs: Grape-like clusters of individual alveoli that opened from the alveolar ducts Structures are very elastic  20.1.13 Structures of the Respiratory Division: Alveoli ANATOMY FEATURES Structures across which gas exchange occurs Thin-walled with large lumen Provide intimate contact between inhaled air and blood in pulmonary capillaries that wrap the alveolar walls Collectively, the alveoli have a surface area of 70 m2 (the size of a singles tennis court)  20.1.14 Structures of the Respiratory Division: Alveolar Cells TYPE I: Most common cell type Connected to a thin basement membrane with a pulmonary endothelial cell on the other side (“respiratory TYPE II: membrane”) Cuboidal cells; make and secrete surfactant Surfactant: reduces surface tension ** 24-28 weeks; before 37 considered premature between water molecules lining TYPE III:alveoli surfaces inner A.k.a. alveolar macrophages; resident alveolar immune cells Scavenge microorganisms, other Infant Respiratory Distress Syndrome (IRDS) particles  20.1.15 Structures of the Respiratory Division: The Lungs ANATOMY FEATURES Occupy most of the thoracic cavity; encased by pleural membrane Right lung has 3 lobes; left lung has 2 Lobes are further divided into bronchopulmonary segments Bronchopulmonary segments are divided into pulmonary lobules  20.1.16 Structures of the Respiratory Division: Lung Pleura ANATOMY FEATURES Each lung is surrounded by a pleural membrane with two layers: 1. Visceral pleura: tightly covers each lung 2. Parietal pleura: lines inner wall of thoracic cavity Pleural cavity: small space between the layers containing pleural fluid (secreted by mesothelial cells)  20.1.17 Pulmonary Blood Flow in the Lungs ANATOMY FEATURES Deoxygenated blood  1. Pulmonary trunk 2. Pulmonary arteries 3. Lobar arteries 4. Capillary beds surrounding alveoli  Oxygenated blood  5. Venules 6. Small veins 7. Pulmonary veins 20.1.18 Zones of Blood Flow in the Lungs Lungs are divided into zones based on pressure differences caused by gravity:  Zone 1 pressure: Capillary < alveoli (close to atm pres, collapse & helps to prevent flow)  Zone 2 pressure: Capillary (systole) > alveoli Capillary (diastole) < alveoli (collapse)  Zone 3 pressure: For adequate gas exchange, ventilation needs to match perfusion Capillary > alveoli (continuous flow) 20.2 Ventilation Chapter 20: Respiratory System 20.2.1 Pressure Differentials and Gradients Pressure differential: the difference in pressure between any two spaces that are occupied by a gas (or fluid), independent of whether or not the gas can move between the spaces. Pressure gradient between Pressure gradient between atmosphere and alveoli alveolar and pleural spaces E.g., Atmosphere pressure = E.g., alveolar pressure = 760 760 mmHg; alveoli pressure mmHg; pleural pressure = = 758 mmHg 754 mmHg Pressure differential = 2 Pressure differential = 6 mmHg mmHg Pressure will flow from No pathway between alveoli atmosphere into alveoli and pleural space, so no 20.2.2 Determinants of Gas Pressure AMOUNT OF GAS PARTICLES BOYLE’S LAW If the number of gas particles in a given volume increases, pressure increases. TEMPERATURE If temperature increases while all other factors remain the same, pressure increases. VOLUME OF SPACE P 1 V1 = P 2 V2 If the volume increases while all other factors remain the same, pressure decreases. 20.2.3 Determinants of Flow F = ΔP / R F = flow rate ΔP = pressure differential R = resistance to flow  20.2.4 Respiratory Pressures Pressure in the atmosphere that surrounds the body Pressure differential between Pressure in the space intrapulmonary and between the visceral intrapleural and parietal pleura pressures; represents force that Pressure in the alveoli tends to collapse the lungs 20.2.5 VIDEO: Mechanics of Breathing Please insert the following video: 3D Medical Mechanics of Breathing L V 10 https://www.youtube.com/watch?v=MPovpAXcmIU  20.2.6 Process of Ventilation: Resting Breathing Just prior to Lungs start Air moves Pressures During Air moves out inspiration, to expand, from return to expiration, of lungs until atmospheric so atmospher equilibriu thoracic pressure pressure = intrapulmona e to lungs m volume equilibrates intrapulmonar ry pressure declines and again y pressure decreases intrapulmonar y pressure > 20.2.7 Non-Breathing Air Movements Coughing and sneezing: Respiratory system trying to clear irritants from the airways Yawn: Results from deepest possible breath Hiccup: Spasm of the diaphragm that causes rapid bursts of air Image courtesy of the U.S. Air Force in the through the vocal cords Public Domain. Laughing/crying: When emotional states drive the ventilatory pattern 20.2.8 Ventilatory Volumes and Capacities IRV IC VC TV TL C ER V RV FR C 20.2.9 Ventilatory Flow Rates Flow rates provide information about the resistance of airways PEF = peak expiratory flow rate FEV = forced expiratory volume FVC = forced vital capacity 20.3 Gas Exchange Chapter 20: Respiratory System 20.3.1 Diffusion and Partial Pressures of Gases Partial Pressure represents the contribution of any gas in a mixture to the mixture’s total pressure. Partial Pressure = Total Pressure x Fraction of Gas  20.3.2 Gas Diffusion Between Air and Blood External respiration occurs between air in the alveoli and blood in the capillaries. The rate of gas diffusion depends on the solubility coefficient of the gas. Amount of gas dissolved in a liquid = partial pressure x solubility coefficient Initial At equilibrium conditions E.g. 20.3.3 Key Points About Gas Diffusion and Partial Pressures  The equilibrium values for partial pressure are not the average of the initial partial pressure values.  Larger partial pressure changes result from a greater percentage change in gas volumes.  If a gas has a higher solubility coefficient, a greater volume will transfer into (or out of) the liquid.  Higher solubility coefficients are associated with a higher rate of diffusion.  The “amount” of gas in a liquid is most commonly expressed as the equivalent volume that is transferred from the gas mixture and does not represent an actual additional volume added to the liquid. 20.3.4 Gas Exchange in the Lungs (External Respiration) and Tissues (Internal Respiration) Diffusion is based on the gas’ partial pressures In the lungs:  O2 moves from air to blood  CO2 moves from blood to air In the tissues:  O2 moves from blood to tissue  CO2 moves from tissue to blood 20.4 O2 and CO2 Transport in Blood Chapter 20: Respiratory System 20.4.1 Transport of Oxygen in Blood by Hemoglobin Hemoglobin transports more than 98% of blood’s O2 Each RBC contains 250- 300 million hemoglobin molecules Each RBC can carry up to 1.2 billion oxygen molecules 20.4.2 Oxyhemoglobin Dissociation Curves ↑ saturation ↓ saturation As O2 molecules bind hemoglobin, Certain conditions can cause shifts in the it is easier for more O2 molecules curve (e.g., changes in pH, temperature) to bind. 20.4.3 Carbon Dioxide Transport in Blood 70% 23% CO2 bound to bicarbonate Hemoglobin The Haldane effect: CO2 more readily binds to unoxygenated 20.4.4 Gas Exchange Between Blood and Tissues Removes the end products so the reaction can continue 20.4.5 Gas Exchange Between Blood and Air 20.4.6 Overall Control of Ventilation Sensors: Chemoreceptors that detect chemicals in blood (e.g., PaCO2, PaO2) Integrators: Respiratory center in brainstem (neurons in medulla oblongata and pons)  20.4.7 Brainstem Regions Involved in Control of Ventilation The respiratory center contains pattern-generating neurons with intrinsic depolarizing capacities Provides stimulatory Provides inhibitory inputs to inputs to the DRG the DRG Dorsal respiratory group: responds to blood CO2 and O2 levels; impacts VRGin breathing Also participates Retrotrapezoid nucleus: rhythm receives input from Provides the main stimulus for chemoreceptors in breathing brainstem and lung Ventral respiratory stretch; impacts VRG group 20.4.8 Sensitivity of Ventilation to Blood O2 and CO2 Levels and pH Sensitivity to Sensitivity to Sensitivity to PCO2 PO2 pH