BIOLOGY NOTES RESPIRATORY PHYSIOLOGY IS THE RESPIRATORY SYSTEM JUST A PUMP AND A LOT OF TUBING Analogy the respiratory system is an open set of tubes through which air flows in and out driven by a pump AIRWAY AND LUNGS THE TUBES AND MORE Air enters exits through the nose s nostrils and the mouth Nasal and oral cavities join to form pharynx the back of the throat Pharynx divides into 2 tracts o Esophagus leads to digestive system Epiglottis a flap like structure that blocks the entrance to the esophagus during breathing but swallowing shifts the epiglottis position to block the entrance to the trachea the larynx during eating drinking o Trachea leads to lungs subdivides into the left and right primary bronchi singular bronchus then further into bronchioles in left right lungs Larynx contains the vocal chords o Air flowing through causes vibrations of tissues in the larynx creates sounds pitch is controlled by larynx muscles and air flow ex Speaking and yelling Branching of the bronchioles is similar to branching to blood vessels however air in the lungs does not run in a circuit Airways terminate in alveoli singular alveolus which are the interface between the respiratory system and the cardiovascular system ALVEOLI FUNCTIONAL UNITS OF THE RESPIRATORY SYSTEM Spherical air filled structures at the end of each bronchiole o Surrounded by capillaries from the pulmonary circulation o A large number of alveoli in the lungs procures a large surface area for respiratory gas exchange o Alveoli are the sites of diffusion exchange of O2 and CO2 between the air and the blood surfactant o Alveoli consist of a thin layer of flattened lung cells a fluid layer and a layer of Pulmonary surfactant a lipoprotein an assembly of apolipoprotein molecules with many lipid molecules Critical for the structure and function of alveoli Enables alveoli to stay at least partially filled with air during breathing cycle to expand more easily and fill during inhale and to prevent collapse during exhale o A large total surface area of the respiratory system results in loss of water and heat pulmonary surfactant enables it to reduce water loss PROTECTIVE STRUCTURES AND MECHANISMS IN THE AIRWAYS Lungs are open to atmosphere susceptible to particulates and infectious agents in inhaled air o Bent part of upper respiratory system and branching of airway into bronchi and bronchioles redirects air flow so that it runs into airway walls as it moves into the lungs o As nasal and oral cavities curve into pharynx the pathway turns by 90 degrees o Division and subdivision into smaller bronchi bronchioles occurs at angles sometimes more acute than 90 degrees Larger particles less likely to move deep into airways o Walls of airways are coated with sticky fluid mucus produced by goblet cells Mucus is mostly water but contains glycoproteins proteins modified by carbohydrate groups traps particles from the air o Most airway cells have cilia that face the airway and mucus lining Inside cilia are portions of cytoskeleton that allow cilia to move like fingers Transports mucus and particles stuck in mucus out of the lungs toward the pharynx o Increased mucus production is part of infection fighting response however abnormal amounts are component of some respiratory diseases Pulmonary surfactant has a protective role o Has detergent like properties that protect against infectious organisms DIAPHRAGM AND OTHER RESPIRATORY MUSCLES Lungs and heart are enclosed in thoracic cavity chest surrounded and protected by walls of the thorax ie the ribs and the muscles that make the motions for breathing Inhalation is an active process because muscles contract o Two motions that expand the thorax Upward and outward movement of the ribs due to rib muscle contraction Downward movement of the floor of the thorax due to contraction of the diaphragm o Lung volume increases during inhalation because the volume of alveoli and the volume of air within them increases Gas O2 and CO2 Exchange in the Lungs Measuring lung volumes Normal breathing occurs without thinking about it Inhale increase exhale decrease Spirometer See Figure 4 7b in book Measuring lung volumes and O2 use and more during exercise Biking running exercise Figure 4 7c Lung volumes Figure 2 7a Tidal volume normal breath Vital capacity deep breath Pulmonary Circulation of Blood Figure 4 8 Cardiovascular chapter Systemic deoxygenated blood vena cava right atrium to right ventricle to pulmonary artery to lungs from lungs becomes oxygenated and goes to left side then to aorta Q The main pump of the respiratory system is Diaphragm and rib muscles DIFFUSION NOT movement driven by a pump as in cardiovascular circulation or respiration Diffusion is random movement of molecules from regions of high concentration to low concentration Effective for transport of small molecules over short distances o O2 and CO2 are small molecules 2 3 atoms o Typical cell dimensions are short distances Note that lung cells of alveolus and endothelial cells of capillaries have very short dimensions for gas exchange Diffusion of Gasses O2 and CO2 across alveoli Gas O2 and CO2 exchange between air and blood occurs by diffusion Figure 4 9 Note concentration gradients for O2 and CO2 between air and blood Also note that gas concentrations in alveoli are not the same as in the atmosphere o Recall residual volume some air remains in lungs after exhalation Review Carbon dioxide CO2 is transported in blood converted to carbonic acid H2CO3 and bicarbonate HCO3 Carbonic anhydrase enzyme in RBCs converts carbonic acid H2CO3 back to CO2 in lungs Q Gas molecules from the air e g O2 and N2 are distributed throughout the body In the blood Control of Breathing Figure 4 11 Cerebrum voluntary activation of respiratory muscles Brainstem Involuntary activation of respiratory muslces Neural connections Chemosensors Detect variations in CO2 HCO3 carotid arteries Respiratory muscles intercostals and diaphragm Respiratory Diseases H and O2 Concentrated in aorta and Asthma a condition where bronchioles are swollen and smooth muscles of the bronchioles tighten so the airway is smaller than normal o Restricts air flow into and out of the lungs difficulty breathing o Reduced delivery of O2 and removal of CO2 from tissues o Symptoms coughing wheezing shortness of breath increased HR sweating o Constriction of bronchioles can result from inhaling irritants dust pollen mold and tightness in the chest pet dander cigarette smoke Cystic fibrosis A
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