Respiratory System Overview PDF

An Overview on Respiratory System Fac. of Health Sciences Istanbul Atlas University Istanbul Oct. 2024  Learning Outcomes Morphology of respiratory system Respiratory system and blood gases Surface tension , Surfactant and alveoli mecha...

An Overview on Respiratory System Fac. of Health Sciences Istanbul Atlas University Istanbul Oct. 2024  Learning Outcomes Morphology of respiratory system Respiratory system and blood gases Surface tension , Surfactant and alveoli mechanism Lung volume and capacity Regulation of respiration  Respiratory System Functions Gas exchange: Oxygen enters blood and carbon dioxide leaves Regulation of blood pH: Altered by changing blood carbon dioxide levels Voice production: Movement of air past vocal folds makes sound and speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity Protection: Against microorganisms by preventing entry and removing them  Respiration Includes Four major functional events : Pulmonary ventilation : Air moves in and out of lungs Continuous replacement of gases in alveoli (air sacs) External respiration Gas exchange between blood and air at alveoli O2 (oxygen) in air diffuses into blood CO2 (carbon dioxide) in blood diffuses into air  Cont. Transport of respiratory gases Between the lungs and the cells of the body Performed by the cardiovascular system Blood is the transporting fluid Internal respiration Gas exchange in capillaries between blood and tissue cells O2 in blood diffuses into tissues CO2 waste in tissues diffuses into blood  Cont. External Respiration Gas Transport in The Blood  Internal Respiration Exchange of gases between blood and tissue cells Respiratory zone Anatomical Features of the Respiratory Zone  Alveolus and Respiratory Membrane ❑ Almost 300 million air sacs (alveoli). Large surface area (60–80 m2) Each alveolus is 1 cell layer thick Rich blood supply capillaries form Sheet over alveoli Types of alveolar epithelial cells Type I alveolar cells : make up wall of alveoli (Structural cells) Single layer epithelial cells Permit gas exchange by simple diffusion Type II alveolar cells : Secrete surfactant It decreases tension Alveolar macrophages : free floating “dust cells” Surfactant Phospholipid Lowers surface tension Reduces attractive forces of hydrogen bonding by becoming interspersed between water molecules. As alveoli radius decreases, surfactant’s ability to lower surface tension increases. Surfactant prevents alveolar collapse  Physiology Importance of Surfactant Stabilize alveoli Prevent collapse and sticking of alveoli Reduce the work of breathing Maintain the dryness of the alveoli Prevent the edema of the alveoli  Function of the lower Respiratory System Exchange of gases Due to : Huge surface area = 1x105 m2 of type I alveolar cells Associated network of pulmonary capillaries o 80-90% of the space between alveoli is filled with blood in pulmonary capillary networks Exchange distance is approx. 1 µm from alveoli to blood Protection Free alveolar macrophages (dust cells) Surfactant produced by type II alveolar cells Respiratory membrane  Muscles of Respiration Inspiratory muscles increase volume of thoracic cavity Diaphragm External intercostal Expiratory muscles decrease volume of thoracic cavity Internal intercostal Abdominal muscles ❖ Expiration is generally passive (no muscles required)  Inhale ❑ Active process: Contraction of diaphragm, increases thoracic volume vertically. Contraction of parasternal and internal intercostal, increases thoracic volume laterally. Increase in lung volume decreases pressure in alveoli, and air rushes in. Mechanics of breathing  Exhale ❑ Quiet expiration is a passive process. After being stretched, lungs recoil. Decrease in lung volume raises the pressure within alveoli above atmosphere and pushes air out.  Pulmonary ventilation Due to changing pressures in lungs air flows from higher pressure to lower pressure pulling air instead of pushing it.  Law of Laplace Pressure in alveoli is directly proportional to surface tension; and inversely proportional to radius of alveoli. ❖Pressure in smaller alveolus greater. Oxygen and carbon dioxide transportation  Transport of Oxygen ❑ Bound to hemoglobin in red blood cells (98.5%) Heme portion of hemoglobin contains 4 iron atoms – each can bind one O2 molecule ❖Oxyhemoglobin ❑Dissolved in plasma ( 1.5% ) ❖ 280 million hemoglobin/RBC  Carbon Dioxide Transport Carbon dioxide is transported in the blood in three forms: Bicarbonate ions 70% transported in plasma as HCO3- Enzyme carbonic anhydrase forms carbonic acid (H2CO3) which dissociates into H+ and HCO3- Carbamino compounds About 23% combines with amino acids including those in Hb Carbaminohemoglobin Dissolved CO2 Smallest amount, about 7% How Is Carbon Dioxide Transported in Blood?  Carbonic anhydrase Carbon dioxide diffuses into RBCs and combines with water to form carbonic acid (H2CO3), which quickly dissociates into hydrogen ions and bicarbonate ions In RBCs, carbonic anhydrase reversibly catalyzes the conversion of carbon dioxide and water to carbonic acid. Transport and Exchange of Carbon Dioxide Neural control of Ventilation Chemoreceptors  Pathological States that Increase Airway Resistance Asthma : caused by spastic contractions of bronchiolar smooth muscle Chronic obstructive pulmonary diseases – COPD Lung volume & Lung capacity  Pulmonary volume The four pulmonary volumes and representative values for a young adult male: Tidal volume Inspiratory reserve volume Expiratory reserve volume Residual volume  Pulmonary capacity ❑Are the sum of two or more pulmonary volumes. ▪ Some pulmonary capacities follow: Inspiratory capacity Functional residual capacity Vital capacity ❖ Forced vital capacity ( FVC) ❖Forced expiratory volume in 1 s. ( FEV1) Total lung capacity Lung volume & Lung capacity Terms Used to Describe Lung Volumes and Capacities  Respiratory Terms Eupnea : normal respiratory rate (12-17 B/min) Hyperpnea : increased respiratory rate (exercising) Apnea : stopped breathing e.g. Sleep apnea Dyspnea : difficult breathing  Dead Space Anatomical dead space : volume of the conducting respiratory passages (150 ml) Alveolar dead space : alveoli that cease to act in gas exchange due to collapse or obstruction Total dead space : sum of alveolar and anatomical dead spaces THANK YOU