PET3322 Fall 2012 Final Exam Study Guide Ch 23 The Respiratory System Excessive CO2 produces acidity and can be toxic to cells Conducting Zone nose nasal cavity pharynx larynx trachea bronchi broncioles and terminal bronchioles filter warm moisten and conduct air Respiratory Zone where gas exchange occurs respiratory bronchioles alveolar ducts alveolar sacs and alveoli Nose open to pharynx through internal nares or choane Ducts from the paranasal sinuses which drain mucus and the nasolacrimal ducts which drain tears also open into the nasal cavity Nasal conchae moisten warm and trap dust particles in air Pharynx throat Larynx voicebox starts at internal nares and extends to the level of the cricoid cartilage the most inferior cartilage if the larynx voicebox connects laryngopharynx with trachea epiglottis during swallowing the pharynx and larynx rise and cause the epiglottis to move down and form a lid over the glottis closing it off Voice production ventricular folds false vocal cords vocal folds true vocal cords Bronci At the superior border of 5th thoracic trachea divides into left and ride primary broncus this internal ridge is called the carina Air passages undergo 23 orders of branching in the lungs Secondary bronchi split to supply each lobe Path Trachea cid 224 primary bronchi cid 224 secondary bronchi cid 224 tertiary bronchi cid 224 bronchioles cid 224 terminal bronchioles cid 224 microscopic resp bronchioles bronchioles consist of cuboidal epithelium have a complete layer of circular smooth muscle and lack cartilage support and mucus producing cells Lungs seperated from each other by the heart and other structures of the mediastinum which divides the thoracic cavity into two anatomically distinct chambers As a result if trauma occurs to one lung and it collapses the other one may remain expanded Alveoli An alveolus is a cup shaped outpouched line by simple squamous epithelium and supported by a thin elastic basement membrane An alveolar sac consists of 2 alveoli that share a common opening Terminal bronchioles cid 224 resp bronchioles cid 224 alveolar ducts cid 224 alveolar sacs cid 224 alveoli Air blood barrier is composed of Alveolar and capillary walls Their fused basal membranes Alveolar walls Area single layer of type 1 epithelial cells Permit gas exchange by simple diffusion Secrete angiotensin converting enzyme ACE Pulmonary Ventilation The process of gas exchange in the body called respiration has 3 basic steps 1 Pulmonary ventilation or breathing is the inhalation inflow and exhalation outflow of air and involves the exchange of air between the atmosphere and alveoli of lungs 2 External pulmonary respiration is the exchange of gases between the alveoli of the lungs and the blood in the pulmonary capillaries across the pulmonary membrane Blood gains O2 and loses CO2 3 Internal tissue respiration is the exchange of gases between blood in the systemic capillaries and tissue cells Blood loses O2 and gains CO2 Within cells the metabolic reactions that consume O2 and give off CO2 during the production of ATP are termed cellular respiration Pressure Changes During Pulmonary Ventilation Air moves into the lungs when the air pressure inside the lungs is less than the air pressure in the atmosphere Air moves out of the lungs when the air pressure inside the lungs is greater than the air pressure in the atmosphere Negative respiratory pressure Patm Positive repiratory pressure Patm The first step in expanding the lungs during normal quiet breathing involves contraction of muscles of inhalation the diaphragm 75 and external intercostals 25 elevate ribs Scalenes and sternocleidomastoids also during exercises or forced breathing During quiet inhalation the pressure between the two pleural layers in the pleural cavity called intrapleural intrathoracic pressure is always subatmospheric Exhalation Passive process quite exhale Active only during forceful breathing exercise playing an instrument Abdominal and internal intercostal contract Other Factors Affecting Pulmonary Ventilation A Surface tension of alveolar fluid Surface tension arises at all air water surfaces because the polar water molecules are more strongly attracted to each other than to gas molecules in the air In the lungs surface tension causes the alveoli to assume the smallest possible diameter size of alveoli during exhalation Surface tension also accounts for 2 3 of lung elastic recoil which decreases the Surfactant reduces its surface tension to less than that of water Deficiency in premature babies increases surface tension so that the alveoli collapse at the end of each exhalation and great effort is the next inhalation to reopen the collapsed alveoli needed in B Compliance of the lungs refers to how much effort is required to stretch the lungs and chest wall High compliance stretches easily Like bloodflow rate of airflow depends on both the pressure difference and the C Airway resistance resistance Airflow DP Resistance Greatest resistance in medium sized bronchi inhalation walls expand bronchioles expand less resistance Opposite for exhalation Lung Volumes and Capacities Tidal Volume VT volume of one breath Minute Volume MV total volume inhaled and exhaled in one minute MV 12 breaths min x 500mL breath 6 liters min Anatomic respiratory dead space the conducting airways with air that does not undergo respiratory exchange 150mL Alveolar Ventilation rate AVR measure the flow of fresh gases into and out of the alveoli during a particular time AVR frequency x TV dead space Slow deep breathing cid 221 AVR Rapid shallow breathing cid 223 AVR Exchange of Oxygen and Carbon Dioxide Total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gad in the mixture Each gas exerts its own pressure as if no other gas were present Daltons Law the partial pressure Px of each gas is directly proportional to its percentage in the mixture Atmospheric pressure 760 mmHg O2 20 93 160 mmHG CO2 0 0003 0 3 mmHg N2 79 04 600 mmHg Henry s Law the quantity of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility More gas molecules are soluble at a higher pressure cid 221 P cid 221 solubility Although CO2 has a lower partial pressure gradient It has 20x more soluble membranes than O2 It diffuses in equal amounts with oxygen While O2 is diffusing from alveolar air into deoxygenated blood CO2 is diffusing in the opposite direction Saturated hb
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