BIOL 320 1 st Edition Lecture 15 Outline of Last Lecture I Respiratory System II Nose III Nasal Cavity IV Paranasal Sinuses V Pharynx VI Larynx VII Trachea VIII Bronchi Bronchioles Outline of Current Lecture IX Respiratory Zone X Respiratory Membrane XI Lungs XII Pleural Cavity XIII Breathing XIV Pressure Relationships XV Forces Acting on Lungs XVI Boyle s Law XVII Inspiration XVIII Expiration XIX Resistance to Airflow XX Lung Compliance XXI Gas Exchange XXII Oxygen Transport XXIII Carbon Dioxide Transport Current Lecture Respiratory 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 exchange Respiratory Membrane Air blood barrier fused wall of alveoli capillaries Alveolar walls 1 Type I simple squamous epithelial 2 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 lungs o For oxygenation pulmonary artery to lungs and pulmonary vein to left atrium o For lung tissue nourishment bronchial artery Pleural 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 friction Breathing Two stages o Inspire Inhale o Expire Exhale Pulmonary ventilation o Mechanical process o Depends upon volume changes o Volume changes lead to pressure changes o Pressure changes lead to mechanical moving of gas or airflow Pressure Relationships Atmospheric pressure Patm o 760 mm Hg at sea level Respiratory pressures relative to Patm o Negative respiratory pressure Patm o Positive respiratory pressure Patm o Zero respiratory pressure Patm Intrapulmonary press Ppul Press in alveoli o Fluctuates w breathing o Always eventually equalizes w Patm Forces Acting on Lungs Forces promoting lung collapse Elasticity of lungs Surface tension of alveolar surfactant Forces promoting lung expansion o Elasticity of chest wall o 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 breathe Boyle s Law In English pressure and volume are inversely proportional If volume increases then pressure decreases Inspiration Expiration Muscles utilized in forced expiration abdominal muscles internal intercostal muscles Resistance 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 Inflammation 3 Increased mucous production o Triggers multiple many o Treatment bronchiodilators inflammatory suppressors steroids o Epinephrine natural bronchiodilator decrease resistance to allow better airflow Lung Compliance Homeostatic imbalances that reduce compliance o Deformities of thorax o Ossification of the costal cartilage o Paralysis of intercostal muscles Gas 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 mixture 2 The partial pressure of each gas is directly proportional to its percentage in the mixture Henry s Law 1 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 soluble o O2 1 20th as soluble o N practically insoluble in plasma External Respiration Driven by pressure gradients o Ventilation amount of air reaching alveoli o Perfusion amount of blood circulating by alveoli o Ventilation Perfusion coupling these two factors are tightly regulated for efficient gas exchange HOW vasodilation vasoconstriction Internal Respiration o Driven by pressure gradient Oxygen 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 decreases 3 Blood pH If pH decreases then affinity of Hb for oxygen decreases 4 P CO2 If increased then affinity decreases 5 BPG byproduct of glycolysis concentration If BPG increases then affinity decreases 6 Cigarette smoking decreases number of binding sites Carbon 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 acid 2 Carbonic acid split by carbonic anhydrase CO2 H20 3 CO2 diffuses from RBC to alveoli