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Pulmophysiology

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how the lung works with invormantal relation to respiratory system

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Pulmophysiology

  1. 1. VS
  2. 2. Dr: Ayub Abdulcadir Sheikh:  Postgraduate MBBS, at University of Somalia.  Resident physician at Sureya Medical Center.  A lecturer physiology at Frontier University. Dedication: To all my family especially may parents (Allah may bless you), also my student in frontier university.
  3. 3. TABLE OF CONTENTS 1. Introduction to Respiratory system ……………………...……………..…………. 1 - 2 2. Mechanism of Respiration …………………………………………………….…… 3 - 4 3. Lung Volume and capacity changes ………………………………………………...… 5 4. Pulmonary Circulation ……………………………….……………………………...… 6 5. Diffusion of gases across respiratory membrane …….………………………...…..… 7 6. Transport of Gases (O2 & CO2) …………………………………………….…….. 8 - 10 7. Regulation Of Respiration …………………………………………...……….… 11 – 15 8. High altitude, Avian, Space physiology …………………………………...……. 16 - 17 9. Deep Sea Physiology ………………………………………………...…………… 17 - 18
  4. 4. Page 1 of 18 The respiratory system starts from the nose and ends to the alveoli The lungs are contained in a space with a volume of approximately 4 L (~ 6-8L).  The respiratory system dividedinto: 1. Upper respiratory system: includes all structures from nose to larynx. 2. Lower respiratory system: includes trachea, bronchi, and lungs.  The Types Of Respiration: 1. External respiration: that involvesexchange of respiratory gases, i.e. (oxygen and carbon dioxide between lungs and blood). 2. Internal respiration: that involves exchange of gases between blood and tissues). 3.  The Phases Of Respiration: 1. Inspiration: air enters the lungs from atmosphere. 2. Expiration: air leaves the lungs.  The Stages Of Respiration: 1. Ventilation stage. 2. Transport stage. 3. Exchange stage. 4. Tissue stage.  The Respiratory zone: 1. Conductive zone: no gas exchange, but humidified air and prevent foreign substance. 2. Respiratory zone: site for gas exchange.  Respiratory Protective Reflexes: 1. Cough reflexes. 2. Sneezing reflex. 3. Swallowing reflex.  Autonomic nervous system on bronchial conductive zone: 1. Sympathetic “Adrenergic receptor”: Adrenaline (relaxation and dilation of smooth muscle cells) – Nor adrenaline (decrease mucosal secretion). 2. Parasympathetic “Cholinergic Muscarinic receptor”: Acetylcholine (Contraction and Constriction of smooth muscle cell) – Acetylcholine (increase mucosal secretion).  Mechanism of Cough Reflexes: 1. Pick up to 2.5 liters of air are rapidly inspired. 2. The epiglottis closes, and the vocal cords shut tightly to entrap the air within the lungs. 3. The abdominal muscles contract forcefully, pushing against the diaphragm while other expiratory muscles, such as the internal intercostals, also contract forcefully. 4. The vocal cords and the epiglottis suddenly open widely, so that air under this high pressure in the lungs explodes outward. 4.
  5. 5. Page 2 of 18  Pleura layer: 1. Inner Visceral Layer: that attached firmly to the surface of the lungs. 2. Outer Parietal Layers: that attaches to the wall of thoracic cavity. A. Intrapleural Space or Pleural Cavity: the narrow space in between the two layers of pleura. B. Intrapleural Fluid: thin film of serous fluid, which is secreted by the visceral layer. B 1. Serve as lubricant to prevent friction between two layers of pleura (during respiration). B2. Serve creating the negative pressure called intrapleural pressure within intrapleural space.  Alveolar Cells or Pneumocytes: A. Type I alveolar cells: Site of gaseousexchange between the alveolus and blood. B. Type II alveolar cells: Secrete alveolar fluid and surfactant.
  6. 6. Page 3 of 18  Inspiration & Expiration depends: A) Changes of these Pressures:  Atmospheric pressure. 1. intrapleural or intrathoracic pressure. 2. Alveolar or intrapulmonary pressure. 3. Transpulmonary pressure. B) Respiratory Muscles: 1. Primary & accessory inspiratory muscle. 2. Primary & accessory expiratory muscle.  Two recoils of respiratory system: 1. The Lungs recoil. 2. The chest wall recoils.  Three ways to increase lung volume: 1- Anterioposterior diameter. 2- Vertical diameter. 3- Transverse diameter.  Dalton Law: is the sum of all partial pressure of gasses equal total pressure.  Atmospheric pressure = 760 mmHg or 1 Atm.  Pressure gradient: is movement of gases from highest pressure to lowest pressure.  Boyle’s law: whenlung volumes increase the pressure decrease and vice verse. Pressure gradient  Atmospheric pressure = 760 mmHg or 1 Atmosphere.  Intrapulmonary or (intra-alveolar) pressure: during inspiration less than Atmosphere (-1mmHg), during expiration more than Atmosphere (=1mmHg).  Intrapleural or (intrathoracic) pressure: normally less than atmosphere (-4mmHg), during inspiration (-7 mmHg), during expiration (-4mmHg).  Transpulmonary pressure: intrapulmonary pressure – intra-alveolar pressure.  During normal quiet breathing:  Inspiration is the “active process”.  Expiration is the “passive process”.
  7. 7. Page 4 of 18  Process of Inspiration (quite or heavy state): 1- Contraction of diaphragm, external intercostals mus., and accessory muscles leads 2- Increases lung volume & decrease pressure. 3- Then the intra-pleural pressure becomes more negatively from (-4 mmHg to -7mmHg) and 4- The intrapulmonary pressure also decreases (760 mmHg - 1 mmHg = 759 mmHg) means less than atmospheric pressure. 5- Due to these changes the air in the atmosphere will enter the lungs.  Process of Expiration(quite or heavy state): 1. Relaxation of diaphragm, & contraction of internal intercostals mus., and accessory muscles leads 2. Decrease lung volume & increase pressure. 3. Then the intra-pleural pressure becomes back to its normal (-4 mmHg) and 4. The intrapulmonary pressure also increase (760 mmHg +1 mmHg = 760 mmHg) means more than atmospheric pressure. 5. Due to these changes the air in the lungs will exit to the atmosphere.  Compliance: is the ability of the lungs and thorax to expand or it is the expansibility of lungs and thorax. A. Static and Dynamic compliance. B. Old age & emphysema increases lung compliance. C. Kyphosis, pleural fibrosis, paralysis of respiratory muscles, pleural effusion all will decrease lung compliance.  Collapsing Tendency of Lungs:  Factors CausingCollapsing Tendency of Lungs: 1. Elastic property of lung tissues. 2. Surface tension.  Factors Preventing Collapsing Tendency of Lungs: 1. Intrapleural pressure. 2. Surfactant.  About Surfactant: 1. Mixture of several phospholipids, proteins, and ions. 2. Reduces the surface tension of water. 3. Defense within the lungs against infection and inflammation. WORK OF BREATHING: Is work done by respiratory muscles during breathing (inspiration) to overcome the resistance in thorax and respiratory tract. Three types of resistance: 1. Airway resistance. 2. Elastic resistance of lungs and thorax. 3. Non-elastic viscous resistance.
  8. 8. Page 5 of 18  DEAD SPACE: is some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages where gas exchange does not occur, such as the nose, pharynx, and trachea. Normal range = 150 mL.  Lung volumes: 1. Tidal volume (TV) = 500ml. 2. Inspiratory reserve (force) volume (IRV) = 1.9 -3.3ml. 3. Expiratory reserve (force) volume (ERV) = 0.7– 1.2ml. 4. Residual volume (RV) = 1.1 -1.2ml.  Factors that affects lung volume andlung capacities are: A. Age. B. Gender. C. Built. D. Height. E. Level of physical training.  RESPIRATORY MINUTE VOLUME:  Also called; Pulmonary ventilation or minute ventilation.  Is the volume of air breathed in and out of lungs every minute.  ALVEOLAR VENTILATION:  Is the amount of air utilized for gaseous exchange every minute.  TYPES OF DEAD SPACE : 1- Anatomical Dead Space:  It includes nose, pharynx, trachea, bronchi and branches of bronchi up to terminal bronchioles.  Gaseous exchange does not take place in these structures. 2- Physiological Dead Space:  Air in the alveoli, which are non- functioning.  Air in the alveoli, which do not receive adequate blood flow  These two types of respiratory diseases are determined by lung functions tests; particularly Force Expiratory Volume FEV (has great diagnostic value). 1- Restrictive respiratory disease: difficulty in inspiration (FEV- slightly reduced), but expiration not affected. 2- Obstructive respiratory disease: difficulty inexpiration (FEV- very much decreased).
  9. 9. Page 6 of 18  Lung (pulmonary) vessels: 1- Bronchial artery (High-pressure, low-flow circulation): A. Branch of aorta, B. Less than aortic pressure. C. Supplies: trachea bronchus, supportive connective tissue of lung,& outer coat of vessels. 2- Pulmonary artery (low-pressure, high-flow circulation): A. 1/3 thickness of that aorta. B. Large compliance, larger diameters. C. Carries deoxygenated blood from heart to lungs. 3- Lymphatic vessels: A. Present in all the supportive tissues of the lung. B. Empties to right thoracic lymph duct C. Prevent pulmonary edema. Physiological shunt: A diversion through which the venous blood is mixed with arterial blood (1-5% of cardiac output).  The Lungs Serve as a Blood Reservoir.  Cardiac Pathology May Shift Blood From the Systemic Circulation to the Pulmonary Circulation Lung zones  Pulmonary edema:  Increases fluid filtration out of the pulmonary capillaries.  Impedes pulmonary lymphatic function.
  10. 10. Page 7 of 18 Diffusion: is simply the random motion of molecules in all directions through the respiratory membrane and adjacent fluids.  Respiratory (Pulmonary) Membrane: 1) A layer of fluid containing surfactant. 2) The alveolar epithelium. 3) An epithelial basement membrane. 4) A thin interstitial space. 5) A capillary basement membrane. 6) The capillary endothelial membrane. 7) Blood plasma. 8) Red blood cell membrane. 9) Red blood cell cytoplasm. 10) Hemoglobin. • For diffusion to occur these factors mast be done: A. A source of energy provided by the kinetic motion of the molecules. B. A constant temperature. “Partial Pressures” of Individual Gases: Is the pressure of a single type of gas in a mixture of gases. Henry’s law: is the solubility of gases in a liquid and depends on:  Solubility.  Temperature.  Factors that affect the rate of gas diffusion through the respiratory membrane: 1. The thickness of the membrane. 2. The surface area of the membrane. 3. The diffusion coefficient of the gas 4. The partial pressure difference of the gas between the two sides of the membrane. Multiple breaths are required to exchange most of the alveolar air.
  11. 11. Page 8 of 18 • Transport of oxygen from alveoli to the tissue: 1. As simple physical solution(3%). 2. In combination with hemoglobin (97%) as Oxyhemoglobin.  Poor solubility of oxygen in water content of plasma as in simple physical solution.  Oxygen Carrying Capacity of Hemoglobin & Blood:  Each Hb can carry 4 oxygen.  One RBC contains 250 million Hb molecules: 250 X 4 = 1 billion oxygen (one RBC).  1g of Hb combines 1.34ml of Oxygen.  100ml of blood contains 15g of Hb, so  15g X 1.34ml/g = 20 ml of oxygen.  OXYGEN-HEMOGLOBIN DISSOCIATION CURVE:  Hemoglobin’s affinity for oxygen.  Under normal conditions, oxygen-hemoglobin dissociation curve is ‘S’ shaped or sigmoid shaped. A. Upper part of the curve indicates the uptake of oxygen by hemoglobin depending upon partial pressure of oxygen (shift to left). B. Lower part of the curve indicates dissociation of oxygen from hemoglobin (shift to right).  Bohr Effect:  Christian Bohr in 1904.  Is the effect by which presence of carbon dioxide decreases the affinity of hemoglobin for oxygen.  Due to continual metabolic activity in the tissue there is high P co2 and Low P o2 in tissue.  Oxygen dissociation curve is shifted to right.
  12. 12. Page 9 of 18 • Transport of carbon dioxide from tissue to the alveoli: 1. As dissolved form (7%) 2. As carbonic acid(negligible) 3. As bicarbonate (63%) 4. As carbamino compounds (30%).  Carbonic acid is very unstable immediately dissociates into bicarbonate and hydrogen ions.  CARBON DIOXIDE DISSOCIATION CURVE: Is the curve that demonstrates the relationship between the 1) partial pressure of carbon dioxide and the 2) quantity of carbon dioxide that combines with blood.  Haldane Effect:  John Scott Haldane in 1860.  Is the effect by which combination of oxygen with hemoglobin displaces carbon dioxide from hemoglobin.  Excess of oxygen content in blood & Highly acidic hemoglobin has low tendency to combine with carbon dioxide  Carbon dioxide dissociation curve is shifted to right.
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  14. 14. Page 11 of 18 Regulation of Respiration: Nervous or neural mechanism Chemical mechanism Nervous or neural mechanism Afferent nerves Respiratory centers Efferent nerves A. Medullary centers: 1. Dorsal respiratory group of neurons (DRGN) 2. Ventral respiratory group of neurons (VRGN) B. Pontine centers: 3. Apneustic center 4. Pneumotaxic center. 1. Phrenic nerve fibers (C3, C4, C5), which supply the diaphragm.  Phrenic nerve: motor, sensory, sympathetic. 2. Intercostals nerve fibers (T1 to T11), which supply the intercostals muscles.  Intercostals nerve: Right & Left internal intercostals , Right & Left external intercostals 1. Peripheral chemoreceptors and baroreceptors via branches of glossopharyngeal and vagus nerves. 2. Stretch receptors of lungs via vagus nerve. 3. Others
  15. 15. Page 12 of 18 A= MEDULLARY CENTERS: 1. Dorsal Respiratory Group of Neurons: a) Situated in the nucleus of tractus solitarius (NTS). b) Inspiratory neurons and generate inspiratory ramp. c) During quite breathing (2 second inspiration followed 3 second expiration). 2. Ventral Respiratory Group of Neurons: a) Present in nucleus ambiguous and nucleus retroambiguous. b) Earlier, expiratory center. c) Both inspiratory and expiratory neurons. d) During forced breathing. B= PONTINE CENTERS: 1. Apneustic Center: a) Situated in the reticular formation of lower pons. b) Increases depth of inspiration. 2. Pneumotaxic Center: a) Situated in the dorsolateral part of reticular formation. b) Neurons of medial parabrachial and subparabrachial (kölliker-fuse) nuclei. c) Inhibits the apneustic center, so inspiration stops and expiration starts.
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  17. 17. Page 14 of 18 CHEMICAL MECHANISM: Changesin Chemical Constituents of Blood which Stimulate Chemoreceptors: 1. Hypoxia (decreased pO2) 2. Hypercapnea (increased pCO2) 3. Increased hydrogen ion concentration. A) Central Chemoreceptors:  Present in the brain.  Deeper part of medulla oblongata, close to the (DRGN).  In close contact with blood and cerebrospinal fluid (CSF).  Sensitive for CO2 , H+ . B) Peripheral Chemoreceptors:  Carotid and aortic region (glomus cells).  Sensitive for Oxygen. • Mechanism action OfGLOMUS CELLS:  Decreased PO2 in blood.  Activation of O2 sensor and closure of K channel.  Entrance of Ca+2 ions and depolarization of Glomus cell.  Release of neurotransmitter in synaptic cleft then taking by sensory fiber to respiratory center. Peripheral Chemoreceptors
  18. 18. Page 15 of 18 • Mechanism action OfCentral Chemoreceptors:  CO2 enters the extracellular fluid of the brain.  CO2also is permeable across the brain-CSF barrier and enters the CSF.  CO2 is converted to H+ and HCO3−, thus increases in arterial PCO2 produce increases in the PCO2 of CSF, which results in an increase in H+ concentration of CSF (decrease in pH).  The central chemoreceptors are in close proximity to CSF and detect the decrease in pH. A decrease in pH then signals the inspiratory center to increase the breathing rate (hyperventilation). Central Chemoreceptors
  19. 19. Page 16 of 18  High altitude: Is the region of earth located at an altitude of above 8,000 feet from mean sea level.  Partial pressure of gases, particularly oxygen proportionally decreases.  Carbon dioxide in high altitude is very much negligible and it does not create any problem.  CHANGES IN THE BODY AT HIGH ALTITUDE: a) Hypoxia. b) Expansion of gasesin Alveoli, and Gastrointestinal. c) Fall in atmospheric temperature (-400 C). d) Injury from Light rays especially (skin, eye).  MOUNTAIN SICKNESS (Condition characterized by adverse effects of hypoxia at high altitude) like: a) Loss of appetite, nausea and vomiting b) Heart rate and force of contraction of heart increases. c) Increase pulmonary blood pressure & pulmonary edema. d) Headache, depression, disorientation, irritability, lack of sleep, weakness and fatigue (cerebral edema).  ACCLIMATIZATION: Adaptations or the adjustments by the body in high altitude despite a low oxygen tension.  Changes during cclimatization:  RBC count increases and packed cell volume rises from normal value of 45% to about 59% (Hb15g- 20g).  Increase in rate and force of heart contraction & vascularity.  Pulmonary ventilation increases and pulmonary hypertension.  Elevation both cellular oxidative enzymes and mitochondria.  does not create any  AVIATION PHYSIOLOGY: Is the study of physiological responses of the body in aviation environment.  Flyingexerts great effects on the body through accelerative forces (velocity) and gravitational forces.  GRAVITATIONAL FORCE: Is the major factor that develops accelerative force.  Increase inG unit is called positive G (acceleration).  Decrease inG unit is called negative G (deceleration).  EFFECTS OF GRAVITATIONAL FORCES ON THE BODY:  Effects of Positive G:  When G unit increases to about 4 to 5 G, blood is pushed toward the lower parts of the body including abdomen.  Reduced blood supply to the brain and eyes leads: 1. Graying of vision that occurs when blood flow to eyes starts diminishing. 2. Complete loss of vision. 3. Loss of consciousness. 4. When force increases to about 20 g, bones, particularly the spine, becomes susceptible for fracture even during sitting posture.  Effects of Negative G:  Negative G develops while flying downwards (inverted flying). 1. The blood is pushed towards head. 2. Blurring of vision and sudden reddening of visual field. 3. Loss of consciousness (it increases the pressure in the blood vessels of chest and neck).
  20. 20. Page 17 of 18  SPACE AND SPACECRAFTS: Is the study of physiological responses of the body in space and spacecrafts.  Major differences between the environments of earth and space are: a) Atmosphere. b) Radiation. c) Gravity.  Astronauts also wear launch and entry suit (LES: is a pressurized suit) that protects the body from space environment.  Another factor which affects the body in the space is WEIGHTLESSNESS due to absence of gravity.  EFFECTS OF WEIGHTLESSNESS IN SPACECRAFT ARE: 1. Accumulation of blood and other fluid in the head and upper trunk, firstly the heart enlarged and after a while times it become gradually shrinking and small in size. 2. The kidney compensate the excess fluid in the body by excreted the fluid and electrolyte, so the person not feel thirst. 3. Space anemia due to decrease both blood volume and RBC. 4. Suppression of immune system in the body. 5. Decrease in muscle mass and muscle strength, also osteoclast activity increased. Astronauts move by floating instead of using their legs. 6. Abnormal stimulation of vestibular apparatus and fluid shift causes space motion sickness - It is characterized by nausea, vomiting, headache and malaise.  Deep Sea Physiology:  In deepsea or mines, the problem is with high barometric pressure.  Increased pressure creates two major problems: 1. Compression effect on the body and internal organs. 2. Decrease in volume of gases.
  21. 21. Page 18 of 18  NITROGEN NARCOSIS:  As the person going more depth in the sea his may suffer a condition knowing as nitrogen narcosis which is means “nitrogen intoxication”.  Nitrogen narcosis is common in deep sea divers, who breathe compressed air (air under high pressure).  Mechanism of nitrogen narcosis:  Nitrogen is soluble in fat.  Nitrogen escapes from blood vessels and gets dissolved in neuronal membranes and act like anesthetic agent.  Nitrogen narcosis can be prevented by mixing helium with oxygen  Nitrogen narcosis may be prevented by limiting the depth of dives. 

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