BIOL 320 1st EditionLecture 15Outline of Last Lecture I. Respiratory SystemII. NoseIII. Nasal CavityIV. Paranasal SinusesV. PharynxVI. LarynxVII. TracheaVIII. Bronchi/BronchiolesOutline of Current Lecture IX. Respiratory ZoneX. Respiratory MembraneXI. LungsXII. Pleural CavityXIII. BreathingXIV. Pressure RelationshipsXV. Forces Acting on LungsXVI. Boyle’s LawXVII. InspirationXVIII. ExpirationXIX. Resistance to AirflowXX. Lung ComplianceXXI. Gas ExchangeXXII. Oxygen TransportXXIII. Carbon Dioxide TransportCurrent LectureRespiratory Zone = presence of alveoli- Order of flow: terminal bronchiole --> respiratory bronchiole --> alveolar duct --> alveoli- Volume: mostly located in the ~300 million alveoli- Surface area: 40 sq. meters in alveoli; massive increase in surface area for gas exchangeRespiratory Membrane- Air-blood barrier: fused wall of alveoli/capillaries- Alveolar walls:1. Type I simple squamous epithelial2. Permit gas exchange via simple diffusion- Surfactant: secreted by Type II cells; like a detergent that breaks up grease…help keep alveoli open- Features:o -Smooth muscle (aid elasticity but resist over-filling)o -Elastic fibers (aid elasticity but resist over-filling)o -Alveolar pores (help equalize the pressure)o -Macrophages (keep surface clean)Lungs- Space occupied: thoracic cavity- Left lung: 2 lobes- Right lung: 3 lobes- Blood supply to lungso -For oxygenation: pulmonary artery to lungs and pulmonary vein to left atriumo -For lung tissue nourishment: bronchial arteryPleural Cavity- Pleural lining: thin, double-layered serosal membrane (secretes fluid to reduce friction)- Parietal pleura: - Visceral pleura:- Pleural space: filled with fluid- Pleurisy: inflammation of lining; very painful due to frictionBreathing- Two stages:o -Inspire (Inhale)o -Expire (Exhale)- Pulmonary ventilation:o -Mechanical processo -Depends upon: volume changeso -Volume changes lead to: pressure changeso -Pressure changes lead to: mechanical moving of gas or airflowPressure Relationships- • Atmospheric pressure (Patm)o 760 mm Hg at sea level- • Respiratory pressures = relative to Patmo Negative respiratory pressure < Patmo Positive respiratory pressure > Patmo Zero respiratory pressure = Patm- • Intrapulmonary press. (Ppul) = Press. in alveolio Fluctuates w/ breathingo Always eventually equalizes w/ PatmForces Acting on Lungs- Forces promoting lung collapse:- -Elasticity of lungs- -Surface tension of alveolar surfactant- Forces promoting lung expansion:o -Elasticity of chest wallo -Low intrapleural space pressure- Pneumothorax: excess air in the intrapleural space- Hemothorax: excess/introduction of blood in intrapleural space- Pressure of inside the lungs is greater than the intrapleural space allowing you to breatheBoyle's Law- In English: pressure and volume are inversely proportional- If volume increases, then pressure decreasesInspirationExpirationMuscles utilized in forced expiration: abdominal muscles & internal intercostal musclesResistance to Airflow- The greatest natural resistance to airflow in the lungs is in the medium sized bronchi (greatest change in diameter)- Constricted or obstructed bronchioles can prevent: pulmonary ventilation- Asthma attacks:o -Primary reactions:1. Constricted airway (smooth muscle in deep with no supporting cartilage to keep open)2. Inflammation3. Increased mucous productiono -Triggers: multiple; manyo -Treatment: bronchiodilators; inflammatory suppressors (steroids)o -Epinephrine: natural bronchiodilator (decrease resistance to allow better airflow)Lung Compliance- Homeostatic imbalances that reduce complianceo Deformities of thoraxo Ossification of the costal cartilageo Paralysis of intercostal musclesGas Exchange- Air is a mixture of gasses in unequal parts.- Dalton’s Law of Partial Pressures (Ptot = P1+P2+P3…)1. Total pressure exerted by a mixture of gasses = sum of pressures exerted by each gas in mixture2. The partial pressure of each gas is directly proportional to its percentage in the mixture.- Henry’s Law1. When mixture of gasses in contact w/ a liquid, each gas will dissolve in liquid in proportion to its partial pressure.2. The amount of gas that will dissolve in a liquid also depends upon its solubility.o CO2 = most solubleo O2 = 1/20th as solubleo N = practically insoluble in plasma- External Respiration- -Driven by: pressure gradientso -Ventilation: amount of air reaching alveolio -Perfusion: amount of blood circulating by alveolio -Ventilation-Perfusion coupling: these two factors are tightly regulated for efficient gas exchange…HOW? vasodilation & vasoconstriction- Internal Respiration:o -Driven by: pressure gradientOxygen Transport- Hemoglobin: carries 98.5% of oxygen- The rest: dissolved in plasma- Factors affecting Hb's affinity for oxygen:1. P (O2) - only 25% of bound oxygen is released from Hb; if more is needed, then released…HOW?2. Temperature - If temperature increases, then affinity of Hb for oxygen decreases3. Blood pH - If pH decreases, then affinity of Hb for oxygen decreases4. P (CO2) - If increased, then affinity decreases5. BPG (byproduct of glycolysis) concentration - If BPG increases, then affinity decreases6. Cigarette smoking - decreases number of binding sitesCarbon Dioxide Transport- CO2 is picked up in tissues & transported in blood in three forms:1. Bicarbonate ion in plasma (70%)2. Bound to Hb (20%)3. Dissolved in plasma (10%)- O2:1. Bound to Hb (98.5%)2. Dissolved in plasma (1.5%)- At lungs:1. Bicarbonate ions move into RBCs & bind with H+ --> carbonic acid2. Carbonic acid split by carbonic anhydrase --> CO2 + H203. CO2 diffuses from RBC to