Respiratory System Topic 4.1 & 4.2 PDF

MODULE 4 Respiratory System Topic 4.1: Functional Anatomy 1  Learning Objectives ü Identify and describe the organs forming the respiratory passageways from the nose to the alveoli, including the gross anatomy and histology where mentioned. ü List...

MODULE 4 Respiratory System Topic 4.1: Functional Anatomy 1  Learning Objectives ü Identify and describe the organs forming the respiratory passageways from the nose to the alveoli, including the gross anatomy and histology where mentioned. ü List and describe the following protective mechanisms of the respiratory system: o warming and humidification of inspired air o filtration and impaction of inhaled particles, chemical and immunological defence o mucociliary escalator; cough reflex; bronchoconstriction; alveolar macrophages. ü Distinguish between: o conducting and respiratory zone structures. ü Describe the makeup of the respiratory membrane and relate structure to function. ü Pulmonary blood supply (pulmonary arteries and veins), and know that the bronchial arteries supply oxygenate blood to lung tissues. Respiration i. Respirations (rate) § breathing or pulmonary ventilations. § measured as the “number of respirations/min ii. External respiration § exchange of O2 and CO2 across the lungs. iii. Internal respiration § exchange of O2 and CO2 between blood and tissues. Scanning electron microscope image: iv. Cellular respiration Alveoli (alveolus) § consumption of O2 at the biochemical level. ! ↳ at cell level (diff or only ) - 2 Respiratory system Pharynx = Gross Anatomy Common to BOTH respiratory and gastrointestinal tracts Learn ALL of these gross structures and their functions! & Respiratory system Upper respiratory tract i. Nasal cavity § updateecepto Nasal membranes (olfactory epithelium), Nasal conchae som ↑ ii. Paranasal sinuses (frontal, sphenoid ethmoid and maxillary bones) ↳ issue iii. Oral cavity > - route for air good iv. Pharynx § Nasopharynx (posterior to nasal cavity) § Oropharynx (posterior to oral cavity) § Laryngopharynx (posterior to larynx ,passageway for food/air) of soft pallete - PeProduction end & uvular - small pengrim on a How 3  Respiratory system Upper respiratory tract Nasal Cavity It of mucous produced Defenses begin in the nose Mucous contains: § Lysozymes: antibacterial enzymes § Defensins: antimicrobial peptides involved in innate immune response § Nasal conchae (↑ SA & enhance turbulence, moisten air) s m § olfactory mucosa: olfactory receptors, moisten air § respiratory mucosa: goblet cells (mucous), serous glands (watery fluid) , Clinical: Rhinitis (itis = inflammation) § inflammation of the nasal mucosa § symptoms: excessive mucous production, nasal congestion and post-nasal drip. § caused/triggered by: allergens, viruses (i.e. streptococcal bacteria ‘strep throat’) can spread upwards and cause ‘sinusitis’ 4 Protective mechanisms How does the respiratory system counter irritants? § Nasal sensory epithelium: sneezing § Larynx: sensitive to anything other than gases § strong cough reflex when concious > only works - § Carina: bifurcation of the 2 main bronchi § very sensitive cough reflex region § Increased production of mucous § Spasm of smooth muscle (lining smaller airways) All mechanisms work to prevent entry of materials deep into the lungs where defences are much reduced Activity: Label & Learn Upper respiratory tract A Label structures: A, B, C & D B D C 5 Lower Respiratory System > - provides :openairwaaor i. Larynx ↓ Godiround a ii. Trachea ↓ iii. Bronchi ↓ iv. Lungs Consists of two zones: i. respiratory zone > - gaschange (gas exchange) ii. conducting zone (respiratory passageways) Lower Respiratory System Larynx (Thyroid and cricoid cartilage) Whenwater relasticrtilage (protect i -des banchor for vocal cords 6  Larynx Hyoid bone (Thyroid & & cricoid cartilage) Epiglottis Thyroid cartilage Cricoid cartilage Tracheal cartilage Epiglottis Thyroid cartilage Cricoid cartilage 7  Epiglottis Arytenoid Thyroid cartilage cartilage ach Cricoid cartilage Epiglottis Thyroid cartilage Cricoid · Arytenoid cartilage cartilage 8  Larynx Vocal cords ↳ stop food from entering padoset * inflammation of the vocal folds = laryngitis interferes with vibration and changes vocal tone Respiratory Tree zones (i) Conducting zone Trachea to terminal bronchioles § Trachea § Right and left main bronchi § Smaller bronchi (secondary, tertiary) § Conducting bronchioles § Terminal bronchioles (ii) Respiratory zone Gas exchange zone § Respiratory bronchioles § Alveolar ducts § Alveolar sacs § Alveoli 9 Respiratory tree (i) conducting zone Carina T4/5 ↳ Trachea Trachea (windpipe) § descends from larynx to mediastinum pseudonatie § divides into left and right main a bronchi (mid thorax) > - § contains layers: mucosa, submucosa, adventitia ↳ connective § hyaline cartilage § mucosa = goblet cells (pseudostratified epithelium) 10 Trachea & Note: the oesophagus is normally collapsed. and opens only when a bolus of food or fluid passes during swallowing. Ciliated cells = grass-like projections (yellow) Goblet cells = Mucous-secreting cells (orange) Respiratory tree The mucociliary escalator Ciliated mucous § Location: lining of trachea, bronchi, and bronchioles makes up the mucociliary escalator. § Function = beat synchronously and sweep foreign particles trapped in mucous up toward the throat, where it is swallowed and digested by gastric juices! What can make this ‘escalator’ movement sluggish? · § Cold air, smoking (cilia are covered in tar) § Smoking can inhibit and destroy cilia. Coughing is the only way to prevent mucous accumulating in the lungs cillia covered tar which * smoking by > - result destruction inhibits their action can in 11  Respiratory tree (ii) respiratory zone Begins with: i. respiratory bronchioles (smallest bronchioles) ii. alveolar ducts (out pockets of alveoli, SM, connective tissue) iii. alveolar sacs (clusters of alveoli.. like a bunch of grapes) iv. alveoli (individual grape …gas exchange occurs here) / - only macrophages are herefor protecta Contain amount muscle of smooth cells Mastic Respiratory zone Type II alveolar cells § scattered amongst type I Microanatomy § cuboidal § secretes surfactant Respiratory membrane (VERY Thin): 0.5µm think (blood air barrier) § coats gas exposed i. Type I alveolar cells (thin single layer) alveolar surfaces § single layer (squamous epithelial cells) ii. basement membrane (VERY thin and flimsy) iii. pulmonary capillaries (external surface) relied eonly cheavily on as defense a i gas exchange = simple diffusion (O 2 goes from alveolus into blood) *smooth muscle in alvedidate contraction assists alveoli to t in size during experation 12 Blood supply of the Lungs § TWO circulations (pulmonary and bronchial) i. Pulmonary circulation § Deoxygenated blood: delivered from the right ventricle via the pulmonary arteries and feed capillary networks surrounding alveoli and pulmonary veins return to heart ii. Bronchial circulation § provide O2 rich blood to the lung tissues (via bronchial arteries) before being returned via pulmonary veins (some tiny bronchial veins). § Pulmonary tissues are also well served by lymphatic tissue: primary immune function and drain excess fluid from lung to subclavain vein. Questions: Review & Learn na 1. List two common structures associated and/or found within the larynx? 2. What purpose do the ‘nasal conchae’ serve? dehumidity a , enhance Piglottarynt 3. Name the two divisions of the respiratory tree? conducting i respiration lobe 4. Name two structural differences between the left and right lung? Left long has I where Left contains Right long has 3 cadaa 5. What structures make up the respiratory membrane? as. Type I sill alredi alls Basement membrane pulmonary capillaries alveoli cells - secrete surfactantl Type 2 13 Summary of key concepts: Respiratory System Topic 4.1 § Upper respiratory system: nasal cavity, paranasal sinuses, oral cavity, pharynx § Protective mechanisms of the respiratory system: § Nasal cavity (olfactory epithelium), mucosa (lysozymes, defensins), nasal conchae (turbinate’s), olfactory mucosa, respiratory mucosa § sneezing, cough reflex, carina, bronchoconstriction; alveolar macrophages. § Lower respiratory system: larynx, trachea, bronchi and lungs § Conducting zone structures (respiratory passageways) and respiratory zones structures (gas exchange) § Larynx: cricoid, thyroid cartilage, vocal cords § Trachea: mucosa (ciliated pseudostratified epithelium), goblet cells (mucous) § Respiratory membrane: Type I and Type II alveolar cells, basement membrane, pulmonary capillaries § Blood supply to lungs: Pulmonary and bronchial circulations 14  MODULE 4 Respiratory System Topic 4.2: Mechanics of Breathing 1  Learning Objectives ü Describe inspiration and expiration (active vs. passive) ü Relate Boyle’s Law to the events of inspiration and expiration ü Explain the relative roles of the respiratory muscles and lung elasticity in producing volume changes ü Explain intrapleural pressure and its role ü Describe pulmonary pressures during pulmonary ventilation ü Describe the following factors and how they influence pulmonary ventilation: § airway resistance; alveolar surface tension; lung compliance ü Describe the role of surfactant ü Define the various lung volumes and capacities, explaining what they represent, and values ü Define the two types of dead space and values ü Indicate types of information that can be gained from pulmonary function tests Lung Gross anatomy § Apex of the lung: clavicle, 1st rib § Base of the lung: Diaphragm § Mediastinum: heart § Left lung: 2 lobes, cardiac notch § Right lung: 3 lobes Pleura (membranes) i. Parietal: against chest wall (outer) ii. Visceral: against lung (inner) 2  Pulmonary ventilation Breathing (at REST) § Breathing in at REST § active process due to contraction of the diaphragm flattens it downwards, and the external intercostal muscles pull the rib cage up and out. § Breathing out at REST > - passive § passive process due to muscle relaxation and recoil of the lung alveoli and stretched elastic tissues in the chest wall. § Heavy breathing (i.e. exercise): BOTH inspiration and expiration become active processes Dependent on two primary facts: Very thin fluid layer between two pleural surfaces → Wet gladwrap analogy i. Boyle’s Law → P1V1 = P2V2 ii. relationship between > resistance and gas flow in airways → F = ∆P/R ↳ usually doesn't impact adults The lungs are not “a closed container”, but air must flow through the Boyle’s Law upper airways to reach the lungs. P 1V 1 = P 2V 2 P 1V 1 = P 2V 2 Boyle’s Law drives breathing § Molecular kinetic theory = molecules of gas are constantly in motion exerting pressure on walls § Product of = volume and pressure volume ↓ volume = pressure volume ↑ pressure ↑ pressure ↓ (is constant in an enclosed container) Adriver movement of air in out of longs due relaxation > occurs - to contraction I of diaphrams intercostals. 3  of rises intercostals rib contraction > - cage * Cop is out) diaphram moves inferiorly - causes ↓ polmananary (lower than bressure to -Immig atmospheric pressure ↳ air flows in to get pressure back to equilibrium Inspiration: at rest dar Heavy breathing Extra muscle activity needed to lift (expand) the rib cage Muscles = sternocleidomastoid, levator scapulae, scalenes Expiration: at rest With exertion (heavy breathing), additional muscles are employed for force air out. Muscles = abdominal muscles (contract to push diaphragm superiorly). - When (active process exercising ↳ opposite although - is a passive process process addition recoil ! in elastic longs 4  Pulmonary pressures Atmospheric pressure (P atm) 760 mmHg i. Intrapulmonary pressure (inside lung) § Within the alveolar spaces § -1 to +1 mmHg g ii. Intrapleural pressure (space) § Within the pleural cavity -4 mmHg · iii. Transpulmonary pressure § Difference between pulmonary and intrapleural pressures ~4 mmHg How do lungs stay inflated? Answer = Negative intrapleural pressure § Coupling of lungs to thoracic wall by visceral pleural membrane ‘stuck’ to parietal pleural membrane (wet ‘glad wrap’ analogy) § Atelectasis (lung collapse) → may arise If / intrapleural pressure equalises with intrapulmonary pressure causes atelectasis (lung collapse). What is a Pneumothorax? = air in the pleural cavity (space). Caused by: § Traumatic wound to parietal pleura § Spontaneous rupture of visceral pleura 5  Ona * reate ↓ Pulmonary ventilation Only 2 mmHg is required to create the tidal volume of Pressures that drive inhalation/exhalation ~500ml per breath equilibrium Intrapulmonary pressure = -ve during inspiration and +ve during expiration Transpulmonary pressure = keeps lungs inflated de Intrapleural pressure = -ve during BOTH -access inspiration and expiration What happens during Exercise? § oxygen requirements increaseà § increased breathing rate and depth. § Increased activity of abdominal muscles As thoracic volume ↑, what help to push diaphragm superiorly happens to the intrapulmonary and intrapleural pressures? ↓ as thoracic volume ↑ intrapolmanary pressure t "intrapleural pressure Airway resistance F = ΔP/R Airway resistance = minimal (healthy lungs) § Large airway diameters in conducting zone, relative to the low viscosity of air lasthma-t diameter) § Large number of bronchioles = ↑ total cross- sectional area § Where is the greatest resistance to gas flow? § medium-sized bronchi (less numerous) tas they cosectio, numerous a § ↳ Terminal bronchi meaning § gas diffusion is main force driving for gas movement, § Airways resistance is no longer important in determining gas movement ↳ gas diffusion is main thus resistance is force irrelevant ! 6 Alveolar Soant! surface tension reason Surface tension = occurs at an air-water interface § How? liquid (water) molecules are more strongly attracted to each other compared to gas molecules. § ↑ Surface tension = ↑ force which tends to collapse alveoli. § The surface tension of water increases with decreasing radius. § Smaller alveoli tend to collapse into larger ones. How do alveoli overcome surface tension? § Surfactant = phospholipid complex secreted by the type II alveolar cells, reduces surface tension forces between adjacent water molecules. § helps expand the lungs during inspiration and § inhibits the tendency for alveolar collapse at end of expiration. primary function of surfactant surface tension A - reduce between adjacent to molecules especially during expiration Reduces of long inflation ! > - word Surface tension The pressure generated in a sphere is inversely LaPlace’s Law proportional to the radius of the sphere. [A] small sphere = ↑ surface tension (higher pressure) compared to larger sphere. § Effect = air moves from the small sphere (higher pressure) to the larger sphere. persona § What happens? the small sphere collapses and the large sphere become overdistended (stretched). [B] Surfactant (dark purple) § produces a greater ↓ in surface tension in t collapse the smaller sphere vs. larger sphere. overdistended § RESULT? similar pressures in smaller and larger [A] Surfactant [B] (↓ in surface tension) spheres (i.e. stabilised). Clinical: IRDS (infant respiratory distress syndrome). Too little surfactant ↳ infants can cause to become hypoxic 7  distendibility of long tissues alveolar Long compliance t * tension ! Surfaze Lung compliance Healthy lung tissue is COMPLIANT. It is easily stretched and is distensible (stretchy). § For a given change in transpulmonary pressure (ΔP), the change in volume (ΔV) depends on the “stretchiness” of the lungs (compliance). Compliance (C) where: C= ΔV/ ΔP (ΔP= the change in intrapulmonary pressure) § Compliant lungs are easily stretched. Only a small ΔP will change lung volume § Compliance: determined by the distensibility of the lung tissue and alveolar surface tension Clinical examples: i. Decreased lung compliance: need to generate a larger ΔP to move air into the alveoli i. Pulmonary fibrosis (excessive connective tissue in the alveolar walls) ii. Infant respiratory distress syndrome (IRDS) (absence of adequate surfactant) ↑ ii. Increased lung compliance: decreases the pressure required to inflate the lung i. Emphysema: large, floppy bags of over-inflated alveoli 9 as elasticity is lost) ↳ obstructive disease Respiratory volumes and capacities IRV - forcibly ! ERV after Lexpelled tidal volume ↳ forced ↳ cannot be found using spirometry anatomical dead space = approx. 150mL of air (trapped air in respiratory passageways) alveolar dead space = volume of air trapped in collapsed or obstructed alveoli total dead space (both ofabotogether * create own ! values ! memorise 8  Respiratory volumes and capacities we ing ↳ Remember that a CAPACITY is always equal to the sum of 2 or more volumes. awa Clinical: Chronic bronchitis and Emphysema -almosta edi Chronic obstructive i. Chronic bronchitis pulmonary disease (COPD) § Chronic bronchial § Irreversible inflammation § >80% caused by smoking § Excess mucous § Air trapping § Chronic cough § Dyspnoea ii. Emphysema § Frequent infections § Loss of elastic § Hypoventilation recoil a § Destruction of nocompare § Hypoxaemia § Respiratory acidosis alveoli ↳ cillia, * smoking-damage to also cause damage to macrophages > changes functioning > change from predistratified ciliated - - epithelium to non-ciliated squamous up thelium 9 presence of carcenogens > the ↳ When in resultsis - ↳> resut in Lung cancer ! Clinical: Asthma Chronically inflamed airways (abnormal immune response) § Oedema in the walls of small airways § Excess mucous production § Decreased airway diameter = increased resistance to flow § Cause: Irritants or allergens induce bronchoconstriction = asthma attack Prevention: corticosteroids to reduce inflammation Relief (alleviate symptoms): bronchodilators, relax smooth muscle in bronchioles due to bronchio constriction Tresistance Activity: Label & Learn B A Answer the following (include values): C 1. What is the Patm? 2. Label the two pleura (A & B) 3. Label the transpulmonary pressure (C) D 4. Label the intrapleural pressure (D) 5. Label the intrapulmonary pressure (E) E 10 Questions: Review and Learn 1. Name the two pleura? 2. Boyle’s Law describes the relationship between ____ and ____ 3. What is a normal tidal volume? (in healthy lungs) 4. Describe the role of surfactant? 5. Compliance is a measure of ______ Summary of key concepts: Respiratory System Topic 4.2 § Inspiration: active at rest and Expiration: passive at rest § Exercise (heavy breathing): active § Boyle’s Law: product of pressure and volume. (i.e., as volume ↓ pressure ↑ OR volume ↑ then pressure ↓) § Respiratory muscles: § Inspiration: inspiratory muscles contract diaphragm descends, rib cage rises. Lung elasticity in producing volume changes § Expiration: inspiratory muscles relax, diaphragm rises, rib cage descends due to recoil) § Pulmonary Pressures: intrapleural pressure (pressure inside pleural cavity/space); intrapulmonary pressure (inside lung/alveoli); Transpulmonary ( difference between pulmonary and intrapleural pressures) § Factors that influence pulmonary ventilation: airway resistance; alveolar surface tension; lung compliance § What is surfactant?: reduce surface tension § Lung volumes and capacities: pulmonary functional testing (spirometry) § Pathologies of lung function: COPD, bronchitis, emphysema, asthma 11