L27 - Respiratory System PDF

L27- RESPIRATORY SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES Describe the gross anatomy of larynx Describe Ventilation and Lung mechanics. Describe the factors affecting air flow. ...

L27- RESPIRATORY SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES Describe the gross anatomy of larynx Describe Ventilation and Lung mechanics. Describe the factors affecting air flow.  LARYNX  Hollow musculo-ligamentous structure with a cartilaginous framework that caps the lower respiratory tract  It is composed of: Three large unpaired cartilages (cricoid, thyroid, and epiglottis) Three pairs of smaller cartilages (arytenoid, corniculate, and cuneiform) A fibroelastic membrane and numerous intrinsic muscles. 9-Oct-24 3 SITUATION Lies in the anterior midline of the neck extending from the root of the tongue to trachea CARTILAGES LARYNGEAL INLET Laryngeal inlet is formed by Anteriorly - mucosa covering the superior margin of the epiglottis Lateral borders - mucosal folds (aryepiglottic folds), which enclose the superior margins of the quadrangular membranes Posteriorly - transverse mucosal fold between the two arytenoids  CAVITY OF LARYNX  Interior presents vestibular & vocal folds  Space between 2 vestibular folds – Rima vestibule  Space between 2 vocal folds – Rima glottidisSpace between vestibular and vocal folds – Ventricle of Larynx or Sinus of Larynx CAVITY OF LARYNX  SUMMARY The spaces between aryepiglottic folds – Laryngeal inlet The spaces between vestibular folds – Rima vestibule The spaces between vocal folds – Rima glottides Vestibule – extends from the aryepiglottic folds to the vestibular folds Sinus of the larynx – intervenes between the vestibular folds and vocal folds Infraglottic – lies below the vocal folds 9-Oct-24 9 LARYNGOSCOPIC VIEW True Vocal cord False vocal cord/ vestibular Aryepiglott fold ic fold  NERVE SUPPLY Sensory Above vocal cord- Internal laryngeal nerve Below vocal cord- Recurrent laryngeal nerve Motor All muscles supplied by Recurrent laryngeal nerve except cricothyroid supplied by External laryngeal nerve MECHANICS OF BREATHING  Mechanics means science that deals with forces  Breathing mechanics is interplay of force generated by pressure, volume and flow changes occurring during the breathing cycle  Role of respiratory muscles  Alveolar, Pleural and Trans pulmonary pressures  Compliance of lungs, chest wall & together  Lung recoil due to elastic & collagen fibers  Work of breathing. MUSCLES OF RESPIRATION Muscles of inspiration Muscles of normal expiration Normal expiration is due to  Principal muscles elastic recoil of lungs and Diaphragm associated structures External intercostals  Accessory muscles Muscles of forced expiration Sternocleidomastoid Internal intercostal Scaleni External oblique abdominis Serratus anterior Internal oblique abdominis Pectoralis minor Rectus abdominis Transversus abdominis MUSCLES OF RESPIRATION MUSCLES OF RESPIRATION FUNCTIONS OF THE RESPIRATORY MUSCLES FUNCTIONS OF THE RESPIRATORY MUSCLES FUNCTIONS OF THE RESPIRATORY MUSCLES Introduction to External Respiration The Processes of External Respiration (air from the atmosphere to cells undergoing metabolism, ie muscles, etc.) Pulmonary ventilation (breathing) bringing air into the lungs from the environment Gas exchange across alveolar membranes lung air space to capillaries to RBC cytoplasm Transport of O2 and CO2: movement via RBCs in alveolar capillaries movement via RBCs in capillary beds systemically and to target tissues (muscle, etc.) Gas exchange from systemic capillaries RBC cytoplasm in systemic capillaries to interstitium/cells 19  Pulmonary Ventilation Requires movement of rib cage by respiratory muscles The Mechanics of Breathing Inhalation Always active – requires skeletal muscle contraction Exhalation Passive or active The Respiratory Muscles Most important are: The diaphragm External intercostal muscles of the ribs Accessory respiratory muscles:  activated when respiration increases 20 significantly Inhalation, Exhalation and the Thoracic cavity 21  Pulmonary Ventilation: quiet vs forced The Mechanics of Breathing Quiet Inhalation Active – diaphragm and external intercostal muscles Quiet Exhalation Passive (allow muscle groups to relax) Forced inhalation (active) the diaphragm external intercostal muscles accessory respiratory muscles: activated when respiration increases significantly Forced exhalation (active) accessory respiratory muscles: activated when respiration increases significantly 22 ALVEOLAR PRESSURE  Intra Alveolar pressure (Alveolar pressure): Pressure inside the alveoli. The process of inspiration and expiration depends upon this pressure.  Normal alveolar pressure is equal to the atmospheric pressure=760 mm Hg. ALVEOLAR PRESSURE  Alveolar pressure during inspiration: The alveolar pressure is lower than the atmospheric pressure during inspiration (760 to 758 mm Hg) so air moves from the atmosphere towards the lung alveoli.  Alveolar pressure during expiration: Alveolar pressure is increased during the process of expiration and is slightly more with respect to the atmospheric pressure (763 mm Hg) so air moves from lungs to the atmosphere. ALVEOLAR PRESSURE PLEURAL AND TRANSPLEURAL PRESSURE  Intrapleural pressure or pleural pressure: Pressure in the narrow space between the lung pleura and chest wall pleura. Negative pressure in the pleural space prevent the collapse of the lungs. -5 cm H2O at the beginning of inspiration -7.5 cm H2O at the peak of inspiration  Transpulmonary pressure: Pressure difference between the alveolar and pleural pressure is called transpulmonary pressure. CHANGING ALVEOLAR VOLUME NORMAL BREATHING CYCLE NORMAL BREATHING CYCLE  ROLE OF NEGATIVE INTRAPLEURAL PRESSURE  At rest the intra pleural pressure is negative (Sub- atmospheric) More negative at apex (-10 cms of water) as compared to base (-2.5 cms of water)  It can become more negative during deep Inspiration and becomes substantially more positive during Forced expiration  Main function is that it prevents the lungs from collapsing and the chest wall from going out. 30 PULMONARY VENTILATION  Pulmonary ventilation (Pulmo=lungs, ventilation=breathing)  Pulmonary ventilation is the inspiration (inflow) and expiration (outflow) of air between the atmosphere and lungs  In ventilation important factor called the pressure gradient exists.  Air moves into the lungs when the pressure inside the lungs is less than that of the atmospheric pressure.  Air moves from the lungs to the atmosphere, when the pressure in the lungs is greater than the atmospheric pressure. PULMONARY VENTILATION [INSPRATION AND EXPIRATION] PULMONARY VENTILATION [INSPRATION AND EXPIRATION] PULMONARY VENTILATION [INSPIRATION] Movement of air into and out of lungs Air moves from area of higher pressure to area of lower pressure Pressure is inversely related to volume PULMONARY VENTILATION [INSPIRATION] PULMONARY VENTILATION [INSPRATION] THORACIC VOLUME THORACIC VOLUME THORACIC VOLUME THORACIC VOLUME PULMONARY VENTILATION [EXPIRATION]  Relaxation of inspiratory muscle  Decreased vertical and antero-posterior diameter of the chest cavity  Increased intra-thoracic pressure  Size of lungs decreases  Increased alveolar pressure from 760-763 mm Hg  Air moves from lung alveoli towards atmosphere  Expiration FACTORS AFFECTING THE AIRFLOW Viscosity: - Viscosity is the measure of a fluid's resistance to flow. Surface roughness: - Surface roughness is caused by the irregularities of the surface that the air comes into contact with.  REFERENCES Drake R.L., Gray’s Anatomy for Students, 2nd Edition, 2009, Churchill Livingstone Moore, Clinically Oriented Anatomy, 6th Edition, 2009, Lippincott Williams & Wilkins Textbook of Medical Physiology – Guyton & Hall Medical Physiology – R.K Marya 9-Oct-24 43