MPharm PHA112 The Respiratory System PDF

MPharm PHA112 The Respiratory System Dr Steve Darby [email protected] Slide 1 Learning Outcomes Basic anatomy of the respiratory tract The mechanism of Ventilation Gas Exchange Slide 2 5 Main Functions Of The Respiratory System 1. Gas exchange (O2 and CO2) 2. pH Regulation 3. Defence fro...

MPharm PHA112 The Respiratory System Dr Steve Darby [email protected] Slide 1 Learning Outcomes Basic anatomy of the respiratory tract The mechanism of Ventilation Gas Exchange Slide 2 5 Main Functions Of The Respiratory System 1. Gas exchange (O2 and CO2) 2. pH Regulation 3. Defence from pulmonary pathogens – Stage 2 Lectures – asthma, COPD, Cystic Fibrosis, infections – Stage 4 Lectures – advanced infection 4. Vocalisation – Speech due to larynx 5. Slide 3 Facilitates sense of smell Metabolism Consumes O2 and Produces CO2 Slide 4 The Importance of Respiration Our Bodies require a constant supply of oxygen – Metabolic reactions – Generate ATP – Breakdown and conversion of molecules Our bodies generate CO2 waste products The process of providing O2 and removing CO2 from the body is respiration The respiratory system is responsible this process Aerobic Respiration Slide 5 5 Stages of Respiration 1. Ventilation (breathing) 2. Pulmonary gas exchange 3. Transport of O2 and CO2 by the blood. 4. Systemic gas exchange 5. Cellular respiration Slide 6 Basic Anatomy And Physiology Slide 7 The Upper and Lower Respiratory System (Not the focus of today) Upper Respiratory Tract – Nose & Nasal Cavity – Pharynx (throat) – Larynx (voice box) – Epiglottis Lower Respiratory Tract – Trachea (windpipe) – Lungs – Bronchi – Alveoli – Diaphragm Slide 8 The Rib Bones Protect The Lungs Slide 9 The Pleura Of The Lung Pleural membrane – Thin mesothelial layer – Double membrane – Adherent to, surrounds lungs Visceral and parietal layers – Visceral – against lungs – Parietal – “wall” against surrounding tissues Pleural cavity – Potential space – Contains pleural fluid Pleura – Clinical Relevance For Later Years Pleural cavity Pneumothorax Air in pleural cavity Pleural Effusion Fluid in cavity Haemothorax Blood in cavity Collapsed lung Cross Section Through The Body Slide 12 Blood is Pumped Directly From the Heart Slide 13 The Bronchi Are a Branched Network Slide 14 Alveoli Small air sacs of the lungs Place where gases exchange from air into blood Each alveoli has its own blood supply Alveoli increase surface area to allow more gas exchange Slide 15 The Alveolus Slide 16 Ventilation Ventilation = The Mechanical flow of air in and out of the lungs Slide 17 There are Multiple Gas Law’s – Think LUNGS PUT SIMPLY A – as pressure increases the volume decreases B – as temperature increases the volume increases C – all gases (air!) make up the total pressure Slide 18 Pressures Change In The Lungs During Ventilation The lungs needs to change internal pressure when breathing in (inspiration) and again when breathing out (expiration) Atmospheric pressure - the pressure of the air in the atmosphere – This value generally will not change (unless climbing a mountain / deep sea diving etc) Alveolar pressure is the pressure of air within the alveoli of the lungs. This will INCREASE during inspiration and DECREASE during expiration Intrapleural pressure is the pressure within the pleural cavity, this is changed by the diaphragm. 19 20 Respiratory Muscles The lungs don’t have their own muscles to inflate/deflate Changes in pressure of the cavity determine lung volume Respiratory muscles and the diaphragm control pressure of the cavity and hence the lungs Respiratory centres control rate of contraction Slide 21 The Diaphragm Is A Major Controller Of Ventilation The diaphragm is a dome shaped muscle It separates the thoracic and abdominal cavities from each other The diaphragm is the primary muscle that is active in inspiration Contraction of the muscle facilitates expansion of the thoracic cavity. Slide 22 This increases volume of the the cavity, which in turn decreases the intrathoracic pressure allowing the lungs to expand and inspiration to occur. The Diaphragm and Pulmonary Ventilation Slide 23 Lung Volumes Slide 24 Spirometry Slide 25 Lung Volumes - Spirometry Slide 26 Slide 27 The Respiratory system is NOT just involved in Ventilation Movement Description A long-drawn and deep inspiration followed by a strong expiration that suddenly Coughing sends a blast of air through the upper respiratory passages. Stimulus for this reflex act may be a foreign body lodged in the larynx, trachea, or epiglottis. Sneezing Spasmodic contraction of muscles of expiration that forcefully expels air through the nose and mouth. Stimulus may be an irritation of the nasal mucosa. Sighing A long-drawn and deep inspiration immediately followed by a shorter but forceful expiration. A deep inspiration through the widely opened mouth producing an exaggerated Yawning depression of the mandible (lower jaw). It may be stimulated by drowsiness, or someone else's yawning, but the precise cause is unknown. Crying An inspiration followed by many short convulsive expirations, during which the vocal cords vibrate; accompanied by characteristic facial expressions and tears. Laughing The same basic movements as crying, but the rhythm of the movements and the facial expressions usually differ from those of crying. Spasmodic contraction of the diaphragm followed by a spasmodic closure of the Hiccupping larynx, which produces a sharp sound on inspiration. Stimulus is usually irritation of the sensory nerve endings of the gastrointestinal tract. Slide 28 Respiratory Control Centres Slide 29 Control of Ventilation At rest, about 200 mL of O2 are used each minute by body cells. During strenuous exercise, however, O2 use typically increases 15- to 20fold in normal healthy adults Several mechanisms help match breathing effort to metabolic demand The Respiratory Centre Controls Breathing – Neurons in the pons and medulla oblongata of the brain stem that regulate breathing We will NOT go into great depth on this topic Slide 30 Chemoreceptors and Ventilation Certain chemical stimuli modulate how quickly and how deeply we breathe. The respiratory system functions to maintain correct levels of CO2 and O2 and is very responsive to changes in the levels of these gases in body fluids – e.g. exercise, illness, environmental changes, drug therapy Chemoreceptors are sensory receptors that are responsive to levels of CO2, H+, and O2 and provide input to the respiratory centre Central chemoreceptors are located in the medulla oblongata in the central nervous system. Peripheral chemoreceptors are located in the aortic bodies and in the carotid bodies Slide 31 Chemoreceptors Can Modulate Ventilation Changes in CO2, O2 or pH is detected by chemoreceptors and then increases or decreases the ventilation response via respiratory muscles Slide 32 Respiratory Centre - Brainstem Key mechanism for CO2 removal System initiates diaphragm and ribs to increase ventilation PaCO2 = Ventilation PaCO2 = Ventilation 33 Gas Exchange Slide 34 Respiratory Quotient (RQ) The respiratory quotient (RQ) is the ratio of carbon dioxide production to oxygen consumption and reflects the relative contributions of fat, carbohydrate, and protein to the oxidation fuel mixture (diet). RQ = CO2 eliminated / O2 consumed When organisms are using carbohydrates only as a fuel, the respiratory quotient—RQ of CO2 produced to O2 consumed is 1 The RQ of fats and proteins is much lower, e.g. RQ = CO2/O2 = 0.7 RQ Use – some patients with lung disorders can adjust their diet to produce LESS CO2 – lessen stress on the lungs Slide 35 Red Blood Cells At Alveoli Surface 36 Gas Exchange At The Alveoli Slide 37 Arterial Blood Gases (ABG) Arterial Blood Gases enable measurement of effectiveness of blood exchange of O2 and CO2 Partial pressure = contribution of an individual gas to the total gas mixture e.g. Air Gases move from areas of high pressure to low pressure Lungs  high PO2 in alveoli and high PCO2 in blood CO2 – main waste product from respiration – PCO2 – PaCO2 blood – partial pressure – partial pressure in arterial 38 Haemoglobin Carries Oxygen in RBC Plus O2 39 Foetal Haemoglobin Has A Higher Affinity For O2 Foetal Haemoglobin is slightly different in structure that maternal Hb It has a higher affinity for O2 Naturally occurring inhibitors of Hb don’t effect Foetal Hb Thus, when O2 is low, HbFoetal can carry up to 30% more O2 than maternal Hb 40 Muscle Contains Myoglobin Muscle transports O2 using myoglobin NOT haemoglobin Myoglobin has 1 Haem group not 4 Myoglobin’s affinity for oxygen is higher than the haemoglobin, even at lower levels Myoglobin has a simpler job than haemoglobin - store and release oxygen to the muscles Haemoglobin is responsible for carrying and releasing the oxygen at tissues throughout the entire blood stream 41 Several Factors Affect the Affinity of Haemoglobin for Oxygen Acidity (pH) - As acidity increases (pH decreases), the affinity of haemoglobin for O2 decreases, and O2 dissociates more readily from haemoglobin Partial pressure of carbon dioxide – CO2 can also bind to haemoglobin, and the effect is similar to that of H+. As CO2 rises, haemoglobin releases O2 more readily Temperature (Within limits) – As temperature increases, so does the amount of O2 released from haemoglobin These factors must also be considered when disease states occur that may impact these parameters – e.g. pathology, drug overdose and lung diseases (covered at later stages of MPharm) 42 43 Oxygenation of Blood O2 has a key role in “aerobic” respiration Unbound O2 versus O2 bound to Haemoglobin (Hb) Hb concentration is also critical PO2 PaO2 SO2 SaO2 – partial pressure – partial pressure in arterial blood – O2 saturation of Hb – O2 saturation of Hb in arterial blood SaO2 (not CO2) can be simply measured using a finger probe called a pulse oximeter – quick & simple 44 CO2 ‘Waste’ Is Transported In 3 Forms Dissolved CO2 – The smallest percentage—about 7%—is dissolved in blood plasma. Upon reaching the lungs, it diffuses into alveolar air and is exhaled Bound to Haemoglobin - about 23%, combines Haemoglobin that has bound CO2 is termed carbaminohaemoglobin (Hb–CO2) As Bicarbonate ions – about 70%—is transported in blood plasma as bicarbonate ions. As CO2 diffuses into systemic capillaries and enters erythrocytes, it reacts with water in the presence of the enzyme carbonic anhydrase to form carbonic acid 45 Gas Exchange – RBC to Tissue Hb = Haemoglobin Erythrocyte = Red Blood Cell Key Enzyme = Carbonic Anhydrase 46 Respiration Controls Blood pH - Buffering Respiration – Simple but KEY equation Promotes Acidic conditions CO2 + LUNGS Promotes Alkali conditions H2O HCO3- H2CO3 Carbonic Acid + Bicarbonate Buffer Enzyme = carbonic anhydrase H+ URINE 47 Gas Exchange Is Key To pH Control What Happens when you undertake intense Exercise? 48 Why Is This Important To A Pharmacist? Hypoxia – tissues receive inadequate O2 to support aerobic respiration – Causes - impaired oxygenation, impaired blood supply Acute and chronic lung conditions Need to ensure correct respiratory function Need to be aware of Lung Function Testing 49 Lung Function Testing Spirometry Fractional Exhaled Nitric Oxide (FeNO) Pulse oximeter Peak flow measurements Exercise tolerance test 50 Why Is All This Important To A Pharmacist? Slide 51