Pulmonary Ventilation, Circulation, Edema, and Pleural Fluid PDF

PAGE 1 UNIVERSITÄTSMEDIZIN NEUMARKT A. M. https://www.umfst.ro https://edu.umch.de CAMPUS HAMBURG May Lecture No. 11 – Physiology 1 Associate Professor MD PH...

PAGE 1 UNIVERSITÄTSMEDIZIN NEUMARKT A. M. https://www.umfst.ro https://edu.umch.de CAMPUS HAMBURG May Lecture No. 11 – Physiology 1 Associate Professor MD PHD Adina 2024 Stoian PULMONARY VENTILATION. PULMONARY CIRCULATION, PULMONARY EDEMA. PLEURAL FLUID What is respiration? PAGE 2 Main functions of respiration: provide oxygen to the tissues remove carbon dioxide. Four major components of respiration: pulmonary ventilation , which means the inflow and outflow of air between the atmosphere and the lung alveoli; diffusion of oxygen (O2) and carbon dioxide (CO2) between the alveoli and the blood ; transport of oxygen and carbon dioxide in the blood and body fluids to and from the body’s tissue cells; regulation of ventilation and other facets of respiration.  PAGE 3 Muscles That Cause Lung Expansion and Contraction The lungs can be expanded and contracted in two ways: – by downward or upward movement of the diaphragm to lengthen or shorten the chest cavity – by elevation or depression of the ribs to increase or decrease the anteroposterior diameter of the chest cavity  PAGE 4 Pulmonary Ventilation Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 38, 491-501 Contraction and expansion of the thoracic cage during expiration and inspiration, demonstrating diaphragmatic contraction, function of the intercostal muscles, and elevation and depression of the rib cage. AP, Anteroposterior. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Muscles That Cause Lung Expansion and Contraction PAGE 5 First method Expiration Inspiration the diaphragm simply relaxes, and Normal quiet breathing contraction of the diaphragm the elastic recoil of the lungs, movement of the diaphragm pulls the lower surfaces of the chest wall, and abdominal lungs downward. structures compresses the lungs and expels the air. Heavy breathing Extra force is achieved mainly by contraction of the abdominal muscles, which pushes the abdominal contents upward against the bottom of the diaphragm Muscles That Cause Lung Expansion and Contraction PAGE 6 Second method The second method for expanding the lungs is to raise the rib cage. Raising the rib cage -> expands the lungs – in the natural resting position, the ribs slant downward, thus allowing the sternum to fall backward toward the vertebral column. All the muscles that elevate the chest cage are classified as muscles of inspiration, and the muscles that depress the chest cage are classified as muscles of expiration. Muscles That Cause Lung Expansion and Contraction PAGE 7 sternocleidomastoid muscles, which lift upward on the The most important muscles that raise the sternum; rib cage are the external intercostals, but anterior serrati, which lift many of the ribs; and others that help are the following: scaleni , which lift the first two ribs. (1) the abdominal recti , which have the powerful effect of pulling downward on the lower ribs at the same time The muscles that pull the rib cage downward that they and other abdominal muscles also compress during expiration are mainly the following: the abdominal contents upward against the diaphragm; (2) the internal intercostals. Pressures That Cause Movement of air in and out of the PAGE 8 Lungs No attachments between the lung The lung - elastic structure that and walls of the chest cage, except collapses like a balloon and expels all where it is suspended at its hilum its air through the trachea whenever from the mediastinum , the middle there is no force to keep it inflated. section of the chest cavity. The lung “floats” in the thoracic ! Continual suction of excess fluid into cavity, surrounded by a thin layer lymphatic channels maintains a slight of pleural fluid that lubricates suction between the visceral surface movement of the lungs within the of the lung pleura and the parietal cavity. pleural surface of the thoracic cavity. Pleural Pressure and Its Changes During Respiration PAGE 9 Pleural pressure is the pressure of the fluid in the thin space between the lung pleura and chest wall pleura. This pressure is normally a slight suction, which means a slightly negative pressure. The normal pleural pressure at the beginning of inspiration is about −5 centimeters of water (cm H2O), which is the amount of suction required to hold the lungs open to their resting level. During normal inspiration, expansion of the chest cage pulls outward on the lungs with greater force and creates more negative pressure to an average of about −7.5 cm H 2 O. Alveolar Pressure—Air Pressure Inside the Lung Alveoli PAGE 10 the pressures in all parts of the respiratory tree, all the way to When the glottis is open, and no air is the alveoli, are equal to atmospheric pressure flowing into or out of the lungs: is considered to be zero reference pressure in the airways = 0 cm H2O pressure. To cause inward flow of air into the the pressure in the alveoli must fall to a value slightly below atmospheric pressure (below 0). alveoli during inspiration: This slight negative pressure is enough to pull 0.5 liter of air into the lungs in the 2 seconds required for normal quiet inspiration. alveolar pressure rises to about +1 cm H2O, which forces the During expiration 0.5 liter of inspired air out of the lungs during the 2 to 3 seconds of expiration. Transpulmonary Pressure—Difference between Alveolar PAGE 11 and Pleural Pressures Transpulmonary pressure A measure of the elastic The pressure difference forces in the lungs that tend between that in the alveoli to collapse the lungs at each and that on the outer instant of respiration, called surfaces of the lungs (pleural the recoil pressure. pressure); Compliance of the Lungs PAGE 12 Lung compliance = The extent to which the lungs will expand for each unit increase in transpulmonary pressure (if enough time is allowed to reach equilibrium). Total compliance of both lungs together in the normal adult averages about 200 ml of air/cm H2O transpulmonary pressure. Every time the transpulmonary pressure increases by 1 cm H2O, the lung volume, after 10 to 20 seconds, will expand 200 ml. Characteristics of the lung compliance PAGE 13 The elastic forces of the lung tissue - determined Determined by the elastic These forces can be divided mainly by elastin and forces of the lungs. into two parts: collagen fibers interwoven among the lung parenchyma. elastic forces caused by surface tension of the fluid elastic forces of the lung that lines the inside walls tissue of the alveoli and other lung air spaces = surfactant Principle of Surface Tension PAGE 14 If water forms a surface with air, the The water surface is always attempting to This is what holds raindrops together water molecules on the surface of the contract. a tight contractile membrane of water water have an especially strong attraction molecules around the entire surface of for one another. the raindrop. Surfactant, Surface Tension, and Collapse of the Alveoli PAGE 15 What happens on the inner surfaces of the alveoli? Here, the water surface is also attempting to contract. This tends to force air out of the alveoli through the bronchi and, in doing so, causes the alveoli to try to collapse. The net effect is to cause an elastic contractile force of the entire lungs, which is called the surface tension elastic force. Surfactant and Its Effect on Surface Tension PAGE 16 It is secreted by special it means that it greatly is a surface-active agent surfactant-secreting reduces the surface in water epithelial cells - type II tension of water. alveolar epithelial cells These cells are granular, containing lipid inclusions 10% of the surface area that are secreted in the of the alveoli. surfactant into the alveoli. Surfactant and Its Effect on Surface Tension PAGE 17 The dipalmitoyl phosphatidylcholine Surfactant: and several less important several phospholipids phospholipids are responsible for Proteins reducing the surface tension!!! Ions The most important components: phospholipid dipalmitoyl phosphatidylcholine surfactant apoproteins calcium ions Thoracic Cage - Lung Expansibility and Compliance PAGE 18 The thoracic cage even if the lungs were not present in the thorax, muscular effort has its own elastic and viscous characteristics would still be required to expand the thoracic cage. The compliance of the entire pulmonary system (the lungs and thoracic cage together) is measured while expanding the lungs of a totally relaxed or paralyzed subject. To measure compliance, air is forced into the lungs a little at a time while recording lung pressures and volumes. Compliance of Thorax and Lungs Together PAGE 19 The compliance of the combined To inflate this total pulmonary lung-thorax system is almost system, almost twice as much exactly half that of the lungs LIMITS - the lungs are expanded pressure is required compared alone—110 ml/cm H2O pressure to high volumes or compressed with the same lungs after for the combined system, to low volumes removal from the chest cage. compared with 200 ml/cm H2O for the lungs alone. the compliance of the combined the limitations of the chest lung-thorax system can be less become extreme than 20% of that of the lungs alone. Work of Breathing PAGE 20 The work of inspiration can be divided During normal quiet breathing into three fractions: all respiratory muscle contraction expand the lungs against the lung occurs during inspiration and chest elastic forces = compliance expiration is almost entirely a work or elastic work; passive process caused by elastic overcome the viscosity of the lung recoil of the lungs and chest cage. and chest wall structures = tissue resistance work; overcome airway resistance to movement of air into the lungs = airway resistance work; Energy Required for Respiration PAGE 21 One of the major limitations on the During normal quiet respiration intensity of exercise that can be only 3% to 5% of the total energy expended by performed is the person’s ability to the body is required for pulmonary ventilation. provide enough muscle energy for the respiratory process alone. During heavy exercise energy required can increase as much as 50-fold especially if the person has any degree of increased airway resistance or decreased pulmonary compliance. Pulmonary Volumes and Capacities PAGE 22 Recording Changes in Pulmonary Volume—Spirometry Spirometry = recording the volume movement of air into and out of the lungs It consists of a drum inverted over a chamber of water, with the drum counterbalanced by a weight. In the drum is a breathing gas, usually air or oxygen a tube connects the mouth with the gas chamber. When the person breathes into and out of the chamber, the drum rises and falls, and an appropriate recording is made. Pulmonary Ventilation Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 38, 491-501 Spirometer. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Spirometry - > Spirogram PAGE 23 The Spirogram indicates the changes in lung volume under different conditions of breathing The air in the lungs has been subdivided in this diagram in: – four volumes – four capacities Lung volumes vary considerably depending on physical fitness, age, height, sex, and other factors, such as the altitude at which a person resides. Pulmonary Ventilation Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 38, 491-501 Respiratory excursions during normal breathing and during maximal inspiration and maximal expiration. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Pulmonary Volumes – 4! PAGE 24 The inspiratory The expiratory The tidal volume The residual reserve volume reserve volume = CV volume = RV = IRV = ERV is the extra volume of air is the maximum extra is the volume of air is the volume of air inspired that can be inspired over volume of air that can be remaining in the lungs after or expired with each and above the normal tidal expired by forceful the most forceful normal breath volume when the person expiration after the end of expiration inspires with full force a normal tidal expiration this volume normally it amounts to about 500 ml it is usually equal to about this volume averages about amounts to about 1100 ml in the average healthy man 3000 ml 1200 ml in men Pulmonary Capacities – 4! PAGE 25 The functional residual The inspiratory capacity (IC) The vital capacity (VC) The total lung capacity (TLC) capacity (FRC) equals the tidal volume plus equals the expiratory reserve equals the inspiratory is equal to the vital the inspiratory reserve volume plus the residual reserve volume plus the tidal capacity plus the residual volume. volume. volume plus the expiratory volume This capacity is the amount This capacity is the amount reserve volume. is the maximum volume to of air (≈3500 ml) that a of air that remains in the This capacity is the which the lungs can be person can breathe in, lungs at the end of normal maximum amount of air a expanded with the greatest beginning at the normal expiration ≈2300 ml) person can expel from the possible effort (≈5800 ml) expiratory level and FRC = RV + ERV lungs after first filling the TLC = CV +IRV + ERV + RV distending the lungs to the lungs to their maximum maximum amount extent and then expiring to IC = CV + IRV the maximum extent (≈4600 ml) VC = CV + IRV + ERV Average Pulmonary Volumes and Capacities PAGE 26 Pulmonary Volumes and Men Women Capacities Volume (ml) Tidal volume 500 400 Inspiratory reserve volume 3000 1900 Expiratory volume 1100 700 Residual volume 1200 1100 Capacities (ml) Inspiratory capacity 3500 2400 Functional residual capacity 2300 1800 Vital capacity 4600 3100 Total lung capacity 5800 4200 Functional Residual Capacity, Residual Volume, and Total PAGE 27 Lung Capacity The spirometer cannot be used in to measure the FRC directly To measure FRC, the The functional residual because the air in the residual spirometer must be used in an capacity (FRC) - changes volume of the lungs cannot be indirect manner, usually by markedly in some types of expired into the spirometer, means of a helium dilution pulmonary disease and this volume constitutes method. about half of the FRC. Residual Volume and Total Lung Capacity - Determination PAGE 28 The residual volume (RV) can be determined by subtracting expiratory reserve volume (ERV), as measured by normal spirometry, from the FRC. RV=FRC−ERV The total lung capacity (TLC) can be determined by adding the inspiratory capacity (IC) to the FRC. TLC=FRC+IC  PAGE 29 Minute Respiratory Volume The minute respiratory volume – is the total amount of new air moved into the respiratory passages each minute – is equal to the tidal volume times the respiratory rate per minute. – The normal tidal volume is about 500 ml – the normal respiratory rate is about 12 breaths/min. – the minute respiratory volume averages about 6 L/min. A person can live for a short period with a minute respiratory volume as low as 1.5 L/min and a respiratory rate of only 2 to 4 breaths/min. The respiratory rate occasionally rises to 40 to 50 breaths/min, and the tidal volume can become as great as the vital capacity, about 4600 ml in a young man. Alveolar Ventilation PAGE 30 The ultimate importance of These areas include the pulmonary ventilation is to alveoli, alveolar sacs, alveolar renew the air in the gas ducts, and respiratory exchange areas of the lungs bronchioles. The rate at which continually, where air is in new air reaches these areas is proximity to the pulmonary called alveolar ventilation. blood. Dead Space and its Effect on Alveolar Ventilation PAGE 31 Some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages, such as the nose, pharynx, and trachea, where gas exchange does not occur. This air is called dead space air because it is not useful for gas exchange. On expiration, the air in the dead space is expired first, before any of the air from the alveoli reaches the atmosphere. Therefore, the dead space is very disadvantageous for removing the expiratory gases from the lungs. The normal dead space air in a young man is about 150 ml. Dead space air increases slightly with age. Anatomical Versus Physiological Dead Space PAGE 32 Anatomic dead space - the Some of the alveoli are volume of all the space of the nonfunctional or only partially These alveoli must also be respiratory system other than the functional because of absent or considered dead space. alveoli and their other closely poor blood flow through the related gas exchange areas adjacent pulmonary capillaries. Partially functional or nonfunctional alveoli in some Physiological dead space - the Healthy lungs - the anatomical parts of the lungs - the alveolar dead space is included in and physiological dead spaces are physiological dead space may be the total measurement of dead nearly equal because all alveoli as much as 10 times the volume space are functional in the normal lung of the anatomical dead space, or 1 to 2 liters. Functions of Respiratory Passageways PAGE 33 Trachea, Bronchi, and Bronchioles One of the most important challenges in the respiratory passageways = keep them open and allow easy passage of air to and from the alveoli. To keep the trachea from In the walls of the bronchi These plates The bronchioles collapsing multiple cartilage rings less extensive curved become progressively are not prevented from extend about five-sixths cartilage plates also less extensive in the later collapsing by the rigidity of the way around the maintain a reasonable generations of bronchi of their walls. trachea. amount of rigidity yet are gone in the they are kept expanded allow sufficient motion bronchioles, which mainly by the same for the lungs to expand usually have diameters transpulmonary and contract. less than 1.5 millimeters. pressures that expand the alveoli. That is, as the alveoli enlarge, the bronchioles also enlarge, but not as much.  PAGE 34 Pulmonary Ventilation Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 38, 491-501 Respiratory passages. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Muscular Wall of the Bronchi and Bronchioles PAGE 35 In all areas of the trachea and bronchi not occupied by cartilage plates, the walls are composed mainly of smooth muscle. The walls of the bronchioles are almost entirely smooth muscle, with the exception of the most terminal bronchiole, called the respiratory bronchiole pulmonary epithelium Respiratory bronchiole underlying fibrous tissue a few smooth muscle fibers Resistance to Airflow in the Bronchial Tree PAGE 36 normal respiratory conditions air flows through the respiratory passageways so easily that less than 1 cm H2O pressure gradient from the alveoli to the atmosphere is sufficient to cause enough airflow for quiet breathing. The greatest amount of resistance to airflow occurs not in the tiny air passages of the terminal bronchioles in some of the larger bronchioles and bronchi near the trachea Why? there are relatively few of these larger bronchi in comparison with the approximately 65,000 parallel terminal bronchioles, through each of which only a minute amount of air must pass. Sympathetic Dilation of the Bronchioles PAGE 37 Direct sympathetic control - bronchioles relatively weak few of fibers penetrate to the central portions of the lung. The bronchial tree is very much expose: To norepinephrine To epinephrine released into the blood by sympathetic stimulation of the adrenal gland medullae Both these hormones (epinephrine because of its greater stimulation of beta-adrenergic receptors) cause dilation of the bronchial tree. Parasympathetic Constriction of the Bronchioles PAGE 38 Parasympathetic nerves are also Asthma – Obstructive Respiratory Parasympathetic – vagus nerve activated by reflexes that Disfunction originate in the lungs A few parasympathetic nerve already caused some bronchiolar irritation of the epithelial penetrate the lung parenchyma. constriction membrane of the respiratory acetylcholine causes mild to superimposed parasympathetic passageways moderate constriction of the nervous stimulation - worsens initiated by noxious gases, dust, bronchioles. the condition cigarette smoke, or bronchial administration of drugs that infection block the effects of bronchiolar constrictor reflex acetylcholine, (atropine) often occurs when microemboli relax the respiratory passages occlude small pulmonary arteries enough to relieve the obstruction Mucus Lining the Respiratory Passageways PAGE 39 Secreted partly by All the respiratory individual mucous passages, from the nose Keeps them moist goblet cells in the to the terminal epithelial lining of the bronchioles passages The mucus traps small The mucus is removed Secreted partly by small particles out of the from the passages in submucosal glands inspired air the following manner.  PAGE 40 Cilia Action to Clear the Passageways The entire surface of the respiratory passages, in the nose and the lower passages, down as far as the terminal bronchioles, is lined with ciliated epithelium, with about 200 cilia on each epithelial cell. These cilia beat continually at a rate of 10 to 20 times/sec and the direction of their “power stroke” is always toward the pharynx. – The cilia in the lungs beat upward – The cilia in the the nose beat downward The continuous beating causes the coat of mucus to flow slowly, at a velocity of a few millimeters per minute, toward the pharynx. Then the mucus and its entrapped particles are swallowed or coughed to the exterior. Cough Reflex PAGE 41 The bronchi and The terminal Mechanism of the The larynx and carina trachea bronchioles + alveoli cough reflex sensitive to light Carina - the point are sensitive to Afferent nerve touch where the trachea corrosive chemical impulses pass from slight amounts of divides into the stimuli the respiratory foreign matter or bronchi E.g. sulfur dioxide gas passages mainly other causes of Especially sensitive or chlorine gas. through the vagus irritation initiate the nerves to the cough reflex. medulla of the brain. An automatic sequence of events is triggered by the neuronal circuits of the medulla, causing the following effects. Events of the cough reflex PAGE 42 Up to 2.5 liters of air are rapidly inspired. The epiglottis closes The vocal cords shut tightly to entrap the air within the lungs. The abdominal muscles contract forcefully pushing against the diaphragm Other expiratory muscles, such as the internal intercostals, also contract forcefully. Consequently, the pressure in the lungs rises rapidly, to as much as 100 mm Hg or more. The vocal cords and epiglottis suddenly open widely The air under this high pressure in the lungs explodes outward. Importantly! The strong compression of the lungs collapses the bronchi and trachea by causing their noncartilaginous parts to invaginate inward, The exploding air actually passes through bronchial and tracheal slits. The rapidly moving air usually carries with it any foreign matter that is present in the bronchi or trachea. Sneeze Reflex PAGE 43 The initiating stimulus of the EXEPTION - it applies to the sneeze reflex The sneeze reflex – same idea nasal passageways instead of irritation in the nasal passageways as the cough reflex the lower respiratory the afferent impulses pass in the fifth cranial nerve to the medulla, where passages. the reflex is triggered. DD – cough reflex – vagus nerve A series of reactions similar to those for the cough reflex takes Large amounts of air pass Helping clear the nasal place, but the uvula is rapidly through the nose passages of foreign matter. depressed Normal Respiratory Functions of the Nose PAGE 44 the air is warmed by the the air is almost extensive surfaces of the completely the air is partially conchae and septum, a humidified, even before filtered. total area of about 160 it passes beyond the square centimeters nose; and Filtration Function of the Nose PAGE 45 The hairs - important for filtering out large particles Turbulent precipitation – the conchae The conchae: obstructing vanes the air passing through the nasal passageways hits the conchae, the septum, pharyngeal wall also called turbinates , because they cause turbulence of the air The air: each time air hits one of these obstructions, it must change its direction of movement The particles: the particles suspended in the air, having far more mass and momentum than air, cannot change their direction of travel as rapidly as the air can. they continue forward, striking the surfaces of the obstructions, and are entrapped in the mucous coating and transported by the cilia to the pharynx to be swallowed. Vocalization PAGE 46 Speech involves not only the Speech is composed of two respiratory system but also the mechanical functions: following: specific speech nervous control phonation, which is achieved by centers in the cerebral cortex the larynx; respiratory control centers of the articulation, which is achieved by brain; the structures of the mouth. the articulation and resonance structures of mouth and nasal cavities. Phonation PAGE 47 The larynx - especially adapted to act as a vibrator. The vibrating elements are the vocal folds , commonly called the vocal cords. The vocal cords protrude from the lateral walls of the larynx toward the center of the glottis. are stretched and positioned by several specific muscles of the larynx itself.  Phonation PAGE 48 Pulmonary Ventilation Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 38, 491- 501 A, Anatomy of the larynx. B, Laryngeal function in phonation, showing the positions of the vocal cords during different types of phonation. Modified from Greene MC: The Voice and Its Disorders, 4th ed. Philadelphia: JB Lippincott, 1980. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Phonation PAGE 49 The B figure shows the vocal cords as During normal breathing they are seen when looking into the the cords are wide open to allow easy passage of air. glottis with a laryngoscope. During phonation the cords move together so that passage of air between them will cause vibration. The pitch of the vibration is determined mainly: by the degree of stretch of the cords by how tightly the cords are approximated to one another by the mass of their edges. Phonation PAGE 50 Figure A shows: a dissected view of the vocal folds after removal of the mucous epithelial lining. Immediately inside each cord is a strong elastic ligament called the vocal ligament. The vocal ligament is attached anteriorly to the large thyroid cartilage the large thyroid cartilage is the cartilage that projects forward from the anterior surface of the neck and is called the Adam’s apple. Posteriorly, the vocal ligament is attached to the vocal processes of two arytenoid cartilages. The thyroid cartilage and the arytenoid cartilages articulate from below with another cartilage, the cricoid cartilage. Phonation PAGE 51 The vocal cords can be The thyroarytenoid Slips of these stretched: muscles: muscles in the vocal cords: by forward rotation of Muscles located in the can change the shapes the thyroid cartilage vocal cords lateral to the and masses of the vocal by posterior rotation of vocal ligaments cord edges the arytenoid cartilages Can pull the arytenoid Effect: sharpening the The cartilages are cartilages toward the vocal cord edges to emit activated by muscles thyroid cartilage high-pitched sounds and stretching from the Loosen the vocal cords. blunting them for the thyroid cartilage and more bass sounds. arytenoid cartilages to the cricoid cartilage.  PAGE 52 PULMONARY CIRCULATION  PAGE 53 The lung has two circulations: a high-pressure, low-flow circulation a low-pressure, high-flow circulation Pulmonary Circulation PAGE 54 The high-pressure, low-flow circulation - bronchial arteries supplies systemic arterial blood to the trachea, bronchial tree (including the terminal bronchioles) supporting tissues of the lung, and outer coats (adventitia) of the pulmonary arteries and veins. The bronchial arteries are branches of the thoracic aorta supply most of this systemic arterial blood at a pressure that is only slightly lower than the aortic pressure. The low-pressure, high-flow circulation - pulmonary artery and vein supplies venous blood from all parts of the body to the alveolar capillaries where oxygen (O2) is added and carbon dioxide (CO 2) is removed. The pulmonary artery receives blood from the right ventricle carry blood through its arterial branches to the alveolar capillaries for gas exchange The pulmonary veins return the blood to the left atrium to be pumped by the left ventricle through the systemic circulation.  PAGE 55 PHYSIOLOGICAL ANATOMY OF THE PULMONARY CIRCULATORY SYSTEM Pulmonary Vessels PAGE 56 The pulmonary artery: extends only 5 centimeters beyond the apex of the right ventricle then divides into right and left main branches supply blood to the two respective lungs has a wall thickness one-third from that of the aorta. The pulmonary arterial branches are short all the pulmonary arteries, even the smaller arteries and arterioles, have larger diameters than their counterpart systemic arteries. the vessels are thin and distensible => the pulmonary arterial tree a large compliance , averaging almost 7 ml/mm Hg, which is similar to that of the entire systemic arterial tree This large compliance allows the pulmonary arteries to accommodate the stroke volume output of the right ventricle Bronchial Vessels PAGE 57 Blood also flows to the lungs through small bronchial arteries that originate from the systemic circulation amounting to 1% to 2% of the total cardiac output. This bronchial arterial blood is oxygenated blood in contrast to the partially deoxygenated blood in the pulmonary arteries. supplies the supporting tissues of the lungs, including the connective tissue, septa, and large and small bronchi. After this bronchial and arterial blood passes through the supporting tissues, it empties into the pulmonary veins enters the left atrium, rather than passing back to the right atrium. Lymphatics PAGE 58 Lymph vessels are present in all the supportive tissues of the lung in the connective tissue spaces that surround the terminal bronchioles coursing to the hilum of the lung mainly into the right thoracic lymph duct What is removed by these lymph vessels? Particulate matter entering the alveoli is partly removed Plasma protein leaking from the lung capillaries is also removed from the lung tissues thereby helping to prevent pulmonary edema. Pressures in the Pulmonary System PAGE 59 Pressures in the Right Ventricle The pressure pulse curves of the right ventricle and pulmonary artery are shown in the lower portion of the next figure. The normal systolic pressure in the right ventricle averages about 25 mm Hg The diastolic pressure averages about 0 to 1 mm Hg, values that are only one-fifth those for the left ventricle. Pulmonary Circulation, Pulmonary Edema, and Pleural Fluid Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 39, 503-510 Pressure pulse contours in the right ventricle, pulmonary artery, and aorta. Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Pressures in the Pulmonary Artery PAGE 60 During systole the pressure in the pulmonary artery is essentially equal to the pressure in the right ventricle. after the pulmonary valve closes at the end of systole the ventricular pressure falls precipitously the pulmonary arterial pressure falls more slowly as blood flows through the lungs. The systolic pulmonary arterial pressure normally averages about 25 mm Hg in the human being The diastolic pulmonary arterial pressure is about 8 mm Hg The mean pulmonary arterial pressure is 15 mm Hg. - !!!!!!!!!! – Pulmonary Hypertension! Pulmonary Capillary Pressure PAGE 61 The mean pulmonary capillary pressure – is about 7 mm Hg. – The importance of this low capillary pressure is discussed in detail later in relation to fluid exchange functions of the pulmonary capillaries. Left Atrial and Pulmonary Venous Pressures PAGE 62 The mean pressure in the left atrium and major pulmonary veins averages about 2 mm Hg in the recumbent person varying from as low as 1 mm Hg to as high as 5 mm Hg. The left atrial pressure can be estimated with moderate accuracy by measuring the so-called pulmonary wedge pressure. The pulmonary wedge pressure is measured by inserting a catheter first through a peripheral vein to the right atrium then through the right side of the heart through the pulmonary artery into one of the small branches of the pulmonary artery finally pushing the catheter until it wedges tightly in the small branch. Left Atrial and Pulmonary Venous Pressures PAGE 63 The pressure measured through the catheter, called the “wedge pressure,” is about 5 mm Hg. Attention!!! – Because all blood flow has been stopped in the small wedged artery – Because the blood vessels extending beyond this artery make a direct connection with the pulmonary capillaries – The wedge pressure is usually only 2 to 3 mm Hg higher than the left atrial pressure. When the left atrial pressure rises to high values the pulmonary wedge pressure also rises. Wedge pressure measurements can be used to estimate changes in pulmonary capillary pressure and left atrial pressure in patients with congestive heart failure. Blood Volume of the Lungs PAGE 64 The blood volume of the lungs: – is about 450 ml – about 9% of the total blood volume of the entire circulatory system. – Approximately 70 ml - pulmonary capillaries; – Divided about equally between the pulmonary arteries and veins.  PAGE 65 PHYSIOLOGICAL ANATOMY OF THE PULMONARY CIRCULATORY SYSTEM Cardiac Pathology May Shift Blood From Systemic PAGE 66 Circulation to Pulmonary Circulation Left Side Heart Failure (LSHF) + Because the volume of the systemic Increased resistance to blood flow circulation is about nine times that of through the mitral valve as a result of the pulmonary system, a shift of blood mitral stenosis or mitral regurgitation from one system to the other causes blood to dam up in the affects the pulmonary system greatly pulmonary circulation usually has only mild systemic sometimes increasing the pulmonary circulatory effects. blood volume as much as 100% and causing large increases in the pulmonary vascular pressures. Blood Flow Through the Lungs And its Distribution PAGE 67 Blood flow through the lungs equal to the cardiac output. The factors that control cardiac output also control pulmonary blood flow. The pulmonary vessels act as distensible tubes that enlarge with increasing pressure narrow with decreasing pressure. Decreased Alveolar Oxygen Reduces Local Alveolar Blood PAGE 68 Flow and Regulates Pulmonary Blood Flow Distribution When the concentration of O2 in the air of the alveoli decreases below normal especially when it falls below 70% of the adjacent blood vessels constrict increase vascular resistance more than normal (i.e. these channels are blocked leading to depolarization of the cell membrane activation of calcium channels causing the influx of calcium ions. The rise of calcium concentration then causes constriction of small arteries and arterioles. Decreased Alveolar Oxygen Reduces Local Alveolar Blood Flow and Regulates Pulmonary Blood Flow Distribution PAGE 72 The increase in pulmonary vascular resistance as a result of low O2 concentration has the important function of distributing blood flow where it is most effective. – if some alveoli are poorly ventilated and have a low O2 concentration, the local vessels constrict. This constriction causes: – the blood to flow through other areas of the lungs that are better aerated, – providing an automatic control system for distributing blood flow to the pulmonary areas in proportion to their alveolar O 2 pressures. Effect of Hydrostatic Pressure Gradients in the Lungs on PAGE 73 Regional Pulmonary Blood Flow This difference is The pulmonary arterial ? caused by hydrostatic In lungs – same effect: pressure pressure The blood pressure in Why? In the upright adult, in the uppermost the foot of a standing by the weight of the the lowest point in portion of the lung of person can be as blood itself in the the lungs is normally a standing person is much as 90 mm Hg blood vessels. about 30 cm below about 15 mm Hg less greater than the the highest point than the pulmonary pressure at the level represents a 23 arterial pressure at of the heart. mmHg pressure the level of the heart difference the pressure in the about 15 mm Hg of lowest portion of the which is above the lungs is about 8 mm heart and 8 below. Hg higher Effect of Hydrostatic Pressure Gradients in the Lungs on PAGE 74 Regional Pulmonary Blood Flow Such pressure differences => profound effects on blood flow through the different Note that in the standing position at rest: areas of the lungs. This effect is demonstrated by the lower there is little flow in the top of the lung curve in the next figure, which depicts but about five times as much flow in the blood flow per unit of lung tissue at bottom. different levels of the lung in the upright To help explain these differences, the person. lung is often described as being divided into three zones, as shown in in the second next figure. In each zone, the patterns of blood flow are quite different.  PAGE 75 Pulmonary Circulation, Pulmonary Edema, and Pleural Fluid Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 39, 503-510 Blood flow at different levels in the lung of an upright person at rest (red curve) and during exercise (blue curve). Note that when the person is at rest, the blood flow is very low at the top of the lungs; most of the flow is through the bottom... Copyright © 2021 Copyright © 2021 by Pulmonary Circulation, Pulmonary Edema, and Pleural Fluid Elsevier, Inc. All rights Hall, John E., PhD, Guyton and Hall Textbook of Medical Physiology, Chapter 39, 503-510 reserved. Mechanics of blood flow in the three blood flow zones of the lung: zone 1, no flow— alveolar air pressure ( PALV) is greater than arterial pressure; zone 2, intermittent flow— systolic arterial pressure rises higher than alveolar air pressure, but d... Copyright © 2021 Copyright © 2021 by Elsevier, Inc. All rights reserved. Zones 1, 2, and 3 of Pulmonary Blood Flow PAGE 76 are distended by the blood pressure inside them The capillaries in the alveolar walls: simultaneously are compressed by the alveolar air pressure on their outsides. Whenever the lung alveolar air the capillaries close pressure becomes greater than the there is no blood flow. capillary blood pressure Zones 1, 2, and 3 of Pulmonary Blood Flow PAGE 77 Zone 1 Zone 2 Zone 3 No blood flow during Intermittent blood flow Continuous blood flow all portions of the only during the peaks because the alveolar cardiac cycle of pulmonary arterial capillary pressure because the local pressure because the remains greater than alveolar capillary systolic pressure is then alveolar air pressure pressure in that area of greater than the during the entire the lung never rises alveolar air pressure cardiac cycle higher than the alveolar The diastolic pressure is air pressure during any less than the alveolar part of the cardiac cycle air pressure Exercise Increases Blood Flow Through All Parts of the PAGE 78 Lungs The blood flow in all parts of the lung increases during exercise. The pulmonary vascular pressures rise enough during exercise to convert the lung apices from a zone 2 pattern into a zone 3 pattern of flow. Exercise Increases Blood Flow Through All Parts of the PAGE 79 Lungs During heavy exercise, This extra flow is blood flow through the accommodated in the lungs may increase lungs in three ways fourfold to sevenfold. by distending all the by increasing the number capillaries and increasing by increasing the of open capillaries, the rate of flow through pulmonary arterial sometimes as much as each capillary more than pressure. threefold; twofold; Exercise Increases Blood Flow Through All Parts of the PAGE 80 Lungs The ability of the lungs to accommodate greatly increased blood flow during exercise: – Is made without increasing the pulmonary arterial pressure – conserves the energy of the right side of the heart. – also prevents a major rise in pulmonary capillary pressure – the development of pulmonary edema. Function of Pulmonary Circulation When Left Atrial PAGE 81 Pressure Rises as a Result of Left-Sided Heart Failure The left atrial pressure in a healthy These small changes in left atrial person pressure never rises above +6 mm Hg, even have virtually no effect on during the most strenuous exercise. pulmonary circulatory function because this merely expands the pulmonary venules and opens up more capillaries so that blood continues to flow with almost equal ease from the pulmonary arteries. Function of Pulmonary Circulation When Left Atrial PAGE 82 Pressure Rises as a Result of Left-Sided Heart Failure Left Heart Failure: blood begins to dam up in the left atrium the left atrial pressure can rise on occasion from its normal value of 1 to 5 mm Hg to as high as 40 to 50 mm Hg. The rise of the left atrial preasure: The initial rise - about 7 mm Hg - has little effect on pulmonary circulatory function. The pressure rises to greater than 7 or 8 mmHg - further increases in left atrial pressure cause almost equally great increases in pulmonary arterial pressure, Causing a concomitant increased load on the right heart. Any increase in left atrial pressure above 7 or 8 mm Hg increases capillary pressure almost equally as much. When the left atrial pressure rises above 30 mm Hg, causing similar increases in capillary pressure, pulmonary edema is likely to develop. Capillary Exchange of Fluid in the Lungs and Pulmonary PAGE 83 Interstitial Fluid Dynamics The dynamics of fluid exchange across the lung capillary membranes are: Qualitatively the same as for peripheral tissues. Quantitatively – 4 important differences 1. The pulmonary capillary pressure is low, about 7 mm Hg The functional capillary pressure in many peripheral tissues of about 17 mm Hg. 2. The interstitial fluid pressure in the lung is slightly more negative than that in peripheral subcutaneous tissue. Capillary Exchange of Fluid in the Lungs and Pulmonary PAGE 84 Interstitial Fluid Dynamics 3. The colloid osmotic pressure of the pulmonary interstitial fluid is about 14 mm Hg, in comparison with less than half this value in most peripheral tissues. 4. The alveolar walls are extremely thin the alveolar epithelium covering the alveolar surfaces is so weak that it can be ruptured by any positive pressure in the interstitial spaces greater than alveolar air pressure (>0 mm Hg) Lows dumping of fluid from the interstitial spaces into the alveoli.