Lung Volumes - Introduction PDF

Dr. Mina Atef Anatomy of Respiratory System  The respiratory system consists of organs:  Nose  Mouth (oral cavity)  Pharynx (throat)  Larynx (voice box)  Trachea (windpipe)  Bronchi  Lungs Organs of the Respiratory System  Divided into Conducting zone Respiratory zone ...

Dr. Mina Atef Anatomy of Respiratory System  The respiratory system consists of organs:  Nose  Mouth (oral cavity)  Pharynx (throat)  Larynx (voice box)  Trachea (windpipe)  Bronchi  Lungs Organs of the Respiratory System  Divided into Conducting zone Respiratory zone  Nose  Provides an airway for respiration  Moistens and warms air  Filters inhaled air  Resonating chamber for speech The Trachea  Descends into the mediastinum  C-shaped cartilage rings keep airway open  Carina  Marks where trachea divides into two primary bronchi Bronchi Bronchial tree: Primary bronchi (main bronchi)  Secondary (lobar) bronchi Three on the right Two on the left  Tertiary (segmental) bronchi Branch into each lung segment  Bronchioles Little bronchi, less than 1 mm in diameter  Terminal bronchioles  Less than 0.5 mm in diameter Structures of the Respiratory Zone  Consists of air-exchanging structures  Respiratory bronchioles – branch from terminal bronchioles  Lead to alveolar ducts  Lead to alveolar sacs Gross Anatomy of the Lungs  Major landmarks of the lungs  Apex, base, hilum, and root  Left lung  Superior and inferior lobes  Fissure – oblique  Right lung  Superior, middle, and inferior lobes  Fissures – oblique and horizontal Anterior View of Thoracic Structures The Pleurae  A double-layered sac surrounding each lung  Parietal pleura  Visceral pleura  Pleural cavity  Potential space between the visceral and parietal pleurae The Mechanisms of Ventilation Two phases of pulmonary ventilation Inspiration – inhalation Expiration – exhalation Inspiration -The principal muscles are: 1. The diaphragm 2. Intercoastal muscles - Volume of thoracic cavity increases - Decreases internal gas pressure -Action of the diaphragm  Diaphragm flattens -Action of intercoastal muscles  Contraction raises the ribs Inspiration  Accessory muscles are typically only used when the body needs to process energy quickly (e.g. during strenuous exercise, during the stress response, or during an asthma attack):  Scalenes  Sternocleidomastoid  Pectoralis major  Pectoralis minor  Erector spinae – extends the back Expiration  Quiet expiration – chiefly a passive process  Inspiratory muscles relax  Diaphragm moves superiorly  Volume of thoracic cavity decreases  Forced expiration – an active process  Produced by contraction of  Internal and external oblique muscles  Transverse abdominal muscles Neural Control of Ventilation  Most important respiratory center  Ventral respiratory group  Located in reticular formation in the medulla oblongata  Neurons generate respiratory rhythm Lung Volumes and Capacities 6000 IRV IC Volume (ml) VC VT TLC ERV FRC RV 0 Primary Lung Lung Capacities Volumes Basic Lung Volumes  There are 4 volume subdivisions: 1. Tidal Volume: TV 2. Inspiratory Reserve Volume: IRV 3. Expiratory Reserve Volume: ERV 4. Residual Volume: RV Basic Lung Volumes  There are 4 volume subdivisions:  They do not overlap  They can not be further divided  When added together equal total lung capacity Basic Lung Volumes  There are 4 volume subdivisions: Tidal Volume: TV  The amount of gas inspired or expired with each normal breath.  About 500 ml Basic Lung Volumes Inspiratory Reserve Volume: IRV Maximum amount of additional air that can be inspired from the end of a normal inspiration. Basic Lung Volumes Expiratory Reserve Volume: ERV The maximum volume of additional air that can be expired from the end of a normal expiration. Basic Lung Volumes  Residual Volume: RV  The volume of air remaining in the lung after a maximal expiration. This is the only lung volume which cannot be measured with a spirometer. Lung Capacities  Are subdivisions of the total volume that include two or more of the 4 basic lung volumes Lung Capacities  Total Lung Capacity: TLC  Vital Capacity: VC  Functional Residual Capacity: FRC  Inspiratory Capacity: IC Lung Capacities Total Lung Capacity: TLC  The volume of air contained in the lungs at the end of a maximal inspiration.  Called a capacity because it is the sum of the 4 basic lung volumes  TLC= RV+IRV+TV+ERV Lung Capacities  Vital Capacity: VC  The maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration.  Called a capacity because it is the sum of inspiratory reserve volume, tidal volume and expiratory reserve volume.  VC= IRV+TV+ERV = TLC - RV Lung Capacities  Functional Residual Capacity: FRC  The volume of air remaining in the lung at the end of a normal expiration.  Called a capacity because it equal residual volume plus expiratory reserve volume.  FRC= RV+ERV Lung Capacities  Inspiratory Capacity: IC  Maximum volume of air that can be inspired from end expiratory position.  Called a capacity because it is the sum of tidal volume and inspiratory reserve volume.  This capacity is of less clinical significance than the other three.  IC= TV+IRV Respiratory Diseases  Restrictive Disease:  Makes it more difficult to get air in to the lungs.  They “restrict” inspiration.  Decreased VC; Decreased TLC, RV, FRC  Includes:  Fibrosis  Sarcoidosis  Muscular diseases  Chest wall deformities  Tumors  Pleural Effusion, Pneumothorax Respiratory Diseases  Obstructive Disease  Make it more difficult to get air out of the lungs.  Decrease VC; Increased TLC, RV, and FRC  Includes:  Emphysema  Chronic bronchitis  Asthma