Mechanics of Respiration

Topics: Respiratory physiology, Lung, Respiratory system Pages: 9 (2141 words) Published: September 1, 2013
Mechanics of Respiration Angelica D. Francisco, MD, MSc Edited to Word Format by: GASES KINETIC THEORY OF GASES o MOLECULES IN CONSTANT MOTION > TEMPERATURE > PRESSURE > VOLUME AVOGADRO’S LAW: V n CHARLES’ LAW: V=kT

THE VOLUME OF A GAS IS PROPORTIONAL TO THE TEMPERATURE V = kT, P is constant IDEAL GAS EQUATION V = kn, T and P are constant EQUAL VOLUMES OF GASES, CONTAIN EQUAL NUMBER OF MOLECULES. PV= nRT P, PRESSURE V, VOLUME OF GAS n, NUMBER OF MOLECULES OF GAS R, GAS CONSTANT T, TEMPERATURE P1V1 = P2V2 n1T1 n2T2 What is atmospheric air? Nitrogen, PN2 Oxygen, PO2 Carbon Dioxide, PCO2 Total Partial Pressure of gases o Pressure exerted by any one gas in a mixture of gases o Equal to the total pressure times the fraction of the total amount of gas it represents DALTON’S LAW PARTIAL PRESSURE, PX THE PRESSURE EXERTED BY A GAS IN A GAS MIXTURE IS PROPORTIONATE TO ITS FRACTIONAL CONCENTRATION IN THE MIXTURE. Px = Fx x P Total Px = Fx x P Total Percentage 79 20.8 .04 100

BOYLE’S LAW: PV=k

AT CONSTANT TEMPERATURE, THE VOLUME OF A GAS IS INVERSELY PROPORTIONAL TO PRESSURE PV = k, then V = 1/P

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Therefore, THE TOTAL PRESSURE OF A GAS MIXTURE IS THE SUM TOTAL OF THE PARTIAL PRESSURES OF ITS COMPONENTS. PTotal = P1 + P2 + P3 + Pn Composition of Dry, Atmospheric Air Percentage Partial Pressure (mmHg) Nitrogen, PN2 79 600 Oxygen, PO2 20.8 159 Carbon Dioxide, .04 0.3 PCO2 Total 100 760 TYPES OF RESPIRATION EXTERNAL RESPIRATION o THE ABSORPTION OF O2 AND REMOVAL OF CO2 FROM THE BODY AS A WHOLE INTERNAL RESPIRATION o THE UTILIZATION OF O2 AND THE PRODUCTION OF CO2 BY CELLS AND THE GASEOUS EXCHANGES BETWEEN THE CELLS AND THE INTERSTITIAL FLUID THE RESPIRATORY SYSTEM

REMOVES LEUKOTRIENES, SEROTONIN, ACETYLCHOLINE, BRADYKININ CONVERTS ANGIOTENSIN I TO ANGIONTENSIN II (most potent vasoconstrictor) SYNTHESIS OF VASOACTIVE SUBSTANCES EX. HISTAMINE, HEPARIN, PLATELET ACTIVATING FACTOR (PAF) SYNTHESIS OF PULMONARY SURFACTANT Humidification of Inspired Air Highly vascularized mucus membranes in turbinates and nasopharynx FILTRATION AND REMOVAL OF INSPIRED PARTICLES PARTICLES 10-15 um o IMPACTION/SEDIMENTATION o VIBRISSAE & TURBINATES o TONSILS & ADENOIDS PARTICLES 2-5 um o SEDIMENTATION BY GRAVITY IN SMALLER AIRWAYS PARTICLES 0.1 - 0.5 um o SUSPENDED AS AEROSOL IN ALVEOLAR DUCTS AND ALVEOLI o EXHALED PARTICLES LESS THAN 0.1um o DEPOSIT DUE TO BROWNIAN MOTION MUCOCILIARY ESCALATOR o MUCUS-COVERED CILIATED EPITHELIUM o SPEED: 5-20 mm/min IN TRACHEA AND BRONCHI o IMPAIRED BY CIGARETTE SMOKE ALVEOLAR MACROPHAGES o REMOVAL OF PARTICULATES AND BACTERIA PULMONARY CIRCULATION vs. SYSTEMIC CIRCULATION PULMONARY CIRCULATION o RECEIVES THE SAME STROKE VOLUME FROM THE HEART o LOW PRESSURE SYSTEM o LOW RESISTANCE VESSELS

FUNCTIONS OF THE RESPIRATORY SYSTEM 1. RESPIRATION GAS EXCHANGE: TRANSPORT O2 & CO2 2. ACID-BASE BALANCE 3. PHONATION 4. PROTECTION REMOVAL OF SUBSTANCES IN BLOOD EX. BLOOD CLOTS, MICROORGANISMS WARMING & UMIDIFICATION OF INSPIRED AIR FILTRATION OF INSPIRED AIR 5. ABSORPTION OF DRUGS ANESTHETICS, AEROSOL DRUGS 6. METABOLISM OF SUBSTANCES 2|Page

PULMONARY CIRCULATION and BRONCHIAL CIRCULATION

VELOCITY OF AIRFLOW IN THE RESPIRATORY AIRWAYS

PULMONARY CIRCULATION FUNCTIONAL DELIVERS UNOXYGENATED BLOOD FROM THE HEART (RIGHT VENTRICLE) BRONCHIAL CIRCULATION NUTRITIVE DELIVERS OXYGENATED BLOOD FROM THE HEART (LEFT VENTRICLE) INNERVATION IN THE BRONCHI AUTONOMIC NERVOUS SYSTEM o MAINLY TO SMOOTH MUSCLES IN THE AIRWAYS PARASYMPATHETIC INNERVATION SYMPATHETIC INNERVATION NONCHOLINERGIC/NONADRENERGIC INNERVATION PARASYMPATHETIC INNERVATION MUSCARINIC RECEPTORS o ACTION: BRONCHOCONSTRICTION SYMPATHETIC INNERVATION α1-ADRENEGIC RECEPTORS o ACTION: INHIBIT SECRETION β2-ADRENERGIC RECEPTORS o ACTION: BRONCHODILATION NONCHOLINERGIC/NONADRENERGIC INNERVATION VASOACTIVE INTESTINAL PEPTIDE, VIP o ACTION: BRONCHODILATION RESPIRATORY AIRWAYS

Airways DIVIDED INTO CONDUCTING ZONE & RESPIRATORY ZONE MOVEMENT OF AIR IN THE...


References: GANONG, REVIEW OF MEDICAL PHYSIOLOGY, Chapter 35, 23RD ed GUYTON & HALL, MEDICAL PHYSIOLOGY, Chapters 37, 12th ed BERNE & LEVY, Chapters 25, 26 & 27, 5th ed COSTANZO L, PHYSIOLOGY, 3rd ed
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