EHD Review of Resp Func & Airway Control 243 PDF

BMED13-125: Exploring Human Disease Review of Normal Lung Function & Airway Control  Learning Objectives LO1. Review previous knowledge of normal lung function LO2. Explain the nervous & hormonal control of airways LO3. Outline respiratory defence mechanisms Useful text...

BMED13-125: Exploring Human Disease Review of Normal Lung Function & Airway Control  Learning Objectives LO1. Review previous knowledge of normal lung function LO2. Explain the nervous & hormonal control of airways LO3. Outline respiratory defence mechanisms Useful texts: Marieb & Hoehn, 12th Ed., Chapter 22 Guyton & Hall, 14th Ed., Chapters 38-43  REVIEW OF NORMAL LUNG FUNCTION  Respiratory Pressures Described relative to atmospheric pressure (Patm) ~ 760 mmHg  Negative (760 mmHg) Intrapulmonary pressure (Ppul)  ↑ and ↓ with the phases of breathing  Eventually equalizes with atmos. press.  Determines direction of air flow Intrapleural pressure (Pip)  Pressure in the pleural cavity  Always ~ 4 mmHg less than Ppul  Maintains pull on lungs Transpulmonary pressure (PTpul)  Difference between Ppul and Pip  Prevents lungs from collapsing LO1. Review previous knowledge of normal lung function Pressure Changes during Inhalation and Exhalation LO1. Review previous knowledge of normal lung function Mechanics & Pressure Changes during Inspiration LO1. Review previous knowledge of normal lung function Mechanics & Pressure Changes during Expiration LO1. Review previous knowledge of normal lung function Airway Disorders LO1. Review previous knowledge of normal lung function  Factors Affecting Pulmonary Ventilation 1. Airway resistance 2. Alveolar surface tension 3. Lung compliance LO1. Review previous knowledge of normal lung function 1. Airway resistance  Resistance to airflow - friction  Inversely proportional to airway diameter  Normally insignificant  Disease increases resistance:  Mucus narrows airways  Irritants, inflammatory chemicals activate parasympathetic reflexes causing bronchoconstriction  Bronchodilators decrease resistance and increase air flow LO1. Review previous knowledge of normal lung function Resistance to airflow  Greatest in bronchi near trachea and in large bronchioles  Smooth muscle in bronchiolar wall is very sensitive to neural control and chemicals  Resistance in smaller bronchioles important in some disease states:  smaller in size  muscle contraction  oedema in walls  mucus collection in lumen LO1. Review previous knowledge of normal lung function 2. Alveolar Surface Tension  Caused by alveolar fluid  At water/air interface water molecules on the surface have a strong attractive force for one another  Inside alveoli, water surfaces attempt to contract and force air out of lungs  Alveoli collapse  Net effect: Elastic contractile force in the lungs Surfactant  Secreted by Type II alveolar epithelial cells  Detergent like substance containing phospholipids, proteins and ions  Reduces surface tension  Increases lung compliance LO1. Review previous knowledge of normal lung function 3. Lung compliance  Extent to which the lung volume will expand for a given increase in transpulmonary pressure  Due to:  Elasticity of lung tissue  Alveolar surface tension  Healthy lungs have high compliance  Reduced compliance results in increased force required to fill and empty the lungs   elasticity of lungs (e.g. fibrosis)   compliance   surfactant production   compliance   thoracic mobility (arthritis, paralysis)   compliance  Alveolar damage (emphysema)   compliance LO1. Review previous knowledge of normal lung function  AIRWAY CONTROL  Nervous control of bronchial smooth muscle  Direct control of bronchioles by sympathetic nerves is very minor in humans  Parasympathetic innervation dominates LO2. Explain the nervous & hormonal control of airways  Neurohumoral control of bronchial smooth muscle Brain stem c eti th Spinal cord pa m sy ra Pa Se ns Circulating adrenaline or Acts on β2-adrenoceptors in y smooth muscle Bronchodilation Parasympathetic innervation Vagus nerve Airway Acetylcholine Smooth Muscle Acts on muscarinic receptors containing (M3) in smooth muscle M3 muscarinic receptors Bronchoconstriction and β2-adrenoceptors LO2. Explain the nervous & hormonal control of airways Neurohumoral control of bronchial smooth muscle Parasympathetic innervation Fibres innervate:  Airway smooth muscle → bronchoconstriction  Vascular smooth muscle → vasodilation (via endothelium)  Glands → mucus secretion www.lwms.ac.uk/resources/clinicalpharm/lectures/drugsactingontheairways.pdf LO2. Explain the nervous & hormonal control of airways Neurohumoral control of bronchial smooth muscle Sympathetic  Very little symp. innervation of bronchial smooth muscle in human  β2-adrenoceptors located on human airway smooth muscle, mast cells, epithelium, glands  Circulating adrenaline released from adrenal medulla via sympathetic stimulation causes:  Bronchodilation  Mediator release from mast cells (anti-inflammatory role)  Increase mucociliary clearance www.lwms.ac.uk/resources/clinicalpharm/lectures/drugsactingontheairways.pdf LO2. Explain the nervous & hormonal control of airways Neurohumoral control of bronchial smooth muscle Other neurotransmitters/modulators (Non-adrenergic, non-cholinergic, NANC) Inhibitory (cause bronchodilation)  Nitric oxide (NO) - inhibitory neurotransmitter  Vasoactive intestinal peptide (VIP) - co-transmitter with ACh Excitatory (cause inflammation, bronchoconstriction)  Substance P, neurokinin A (neurokinins) - peptide neurotransmitters  5-HT (serotonin) LO2. Explain the nervous & hormonal control of airways Local control of bronchial smooth muscle  Local secretory factors often cause bronchoconstriction  Histamine  Slow reactive substance of anaphylaxis  Released by mast cells in the lungs during allergic reaction eg. to pollen  Irritants such as smoke, dust, sulphur dioxide, and acid smog can act directly on lung tissue to initiate local, non- nervous reactions that cause constriction  Prostaglandins, leukotrienes, cytokines LO2. Explain the nervous & hormonal control of airways Summary of Factors Affecting Airway Resistance LO2. Explain the nervous & hormonal control of airways RESPIRATORY DEFENCE MECHANISMS  Respiratory defence mechanisms Inhalation of debris/pathogens will cause damage to respiratory exchange surface Defense mechanisms include: Nose  Coarse hairs in nostrils remove large particles  Turbulent precipitation of particles Airways  Nasal passageway warms and moistens (conditions) air  Goblet cells & submucosal glands in respiratory passageways produce mucus to trap particles & moisten airways  Ciliated epithelium continually sweeps mucus down to & up to pharynx  'Mucociliary escalator‘ Lungs  Alveolar macrophages engulf trapped particles LO3. Outline respiratory defence mechanisms Nasal conchae  During inhalation, the conchae and nasal mucosa filter, heat and moisten air  During exhalation these structures reclaim heat and moisture LO3. Outline respiratory defence mechanisms  Mucociliary escalator - airway epithelium  Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus LO3. Outline respiratory defence mechanisms Mucociliary escalator - airway epithelium www.quizlet.com LO3. Outline respiratory defence mechanisms The respiratory membrane LO3. Outline respiratory defence mechanisms