The Respiratory System Chapter 22 The Respiratory System

Functions and Divisions of the Respiratory System Ventilation - breathing (external respiration) (bold - internal respiration) Gas exchange - between air and blood in lungs and blood and other tissues Oxygen utilization - Energy-liberating reactions of cell respiration Divisions Conducting division all structures which conduct air to the respiratory system Respiratory division - alveoli of lungs - where gas exchange occurs

Organs of the Conducting System Nose - nasal bones and cartilages - where air enters the respiratory system Pharynx - funnel-shaped passageway that connects the oral and nasal cavities Larynx - composed of several cartilages and keeps the passageway to the trachea open for breathing closed for swallowing - voice box Trachea - rigid tube - supported by rings of cartilage - connects larynx and bronchiole tubes Bronchial tree - right and left primary bronchus, secondary bronchi (3 on right, 2 on left), tertiary bronchi and bronchioles.

Organs of the Respiratory Division Lungs - Right and Left lungs - separated by mediastinum - 3 lobes on right, 2 lobes on left Alveoli - functional unit of lungs - where gas exchange occurs Serous Tissues Visceral Pleura- covers lungs Parietal Pleura- lines thoracic cavity

Respiratory Physiology Intrapleural pressure - pressure outside the lungs- always less than intrapulmonary pressure - subatmospheric - less than atmospheric pressure Intrapulmonary pressure - pressure inside the lungs - falls below atmospheric pressure during inspiration and rises above atmospheric pressure during expiration Transpulmonary pressure - the difference between the intrapulmonary and intrapleural Acts to expand the lungs as the thoracic volume increases during inspiration Boyle’s Law= the pressure of a gas is inversely proportional to its volume

Pulmonary Ventilation inspiration - Diaphragm and external intercostal and internal intercostal muscles contract - increase volume of lungs expiration - These muscles relax - elastic recoil of lung an thorax - decrease in volume of lungs Lungs are stuck to the wall of the thorax because - interpulmonary pressure is greater than intrapleural pressure.

Respiratory Volumes tidal volume - amount of air inspired or expired in each unforced respiratory cycle (quiet breath) inspiratory reserve volume - maximum volume of gas inspired during forced respiratory cycle in addition to tidal volume expiratory reserve volume - maximum volume of gas that can be expired during forced breathing in addition to tidal volume vital capacity - maximum amount of air that can be forcefully exhaled after a maximum inhalation sum of inspiratory reserve volume and expiratory reserve volume

Respiratory Volumes residual volume - volume of gas remaining in the lungs and after a maximum expiration total lung capacity - Total amount of gas in the lungs at the end of a maximum inspiration dead spaces - anatomical - conducting zone, of the respiratory system- where no gas exchange takes place physiological - anatomical dead space plus underventilated or underperfused alveoli that do not contribute normally to blood-gas exchange

Regulation of Breating aspects of breathing - voluntary (cerebral cortex controlled) and involuntary (medulla oblongota controlled) - influenced by sensory feedback from receptors sensitive to partial pressure of carbon dioxide (PCO2), pH, and PO2 of arterial blood. portions of the brain stem rhythmicity center -(in medulla oblongata)- controls automatic breathing I neurons stimulate spinal motor neurons which innervate respiratory muscles during inspiration. E neurons inhibit I neurons apneustic center - (in pons) - promote inspiration - stimulate I neurons pneumotaxic center- (in pons) antagonize apneustic- center - inhibits inspiration

Regulation of Respiration chemoreceptors central chemoreceptors - in medulla oblongata peripheral chemoreceptors - aortic and the carotid bodies - not aortic and carotid sinuses pressure/stretch receptors - Hering-Breuer reflex - stimulated by pulmonary stretch receptors - inhibits inspiration control of normal ventilation in newborns - exercise ventilation in adults irritant receptors - stimulate reflex constriction of bronchioles in response to smog or smoke sneezing, sniffing, and coughing - stimulated by irritant receptors in nose, larynx, and trachea hyperventilation - excessive ventilation - results from abnormally low blood CO2

Respiratory Disorders Asthma - dyspnea, wheezing, etc.. - obstruction of air flow through the bronchioles - caused by inflammation and increased mucus secretion and bronchoconstriction - stimulated by leukotrienes and histamine released by mast cells and leukocytes - provoked by allergic reaction or by release of acetylcholine from parasympathetic nerve endings Chronic obstructive pulmonary diseases - Emphysema - Characterized by destroyed alveolar tissue - fewer, but larger alveoli - reduces surface area and decreased ability of bronchioles to remain open during expiration - bronchioles close during expiration and cause “air trapping” which further decreases the efficiency of gas exchange in the alveoli Chronic bronchitis - inflammation of the bronchioles

Respiratory Infections Pneumonia - acute infection and inflammation of the lung tissue - accompanied by accumulation of fluid (exudation). Tuberculosis - inflammatory disease of lungs caused by presence of tubercle bacilli - leads to ulceration of lung tissue Pleurisy - inflammation of the pleura - usually associated with other respiratory diseases

The End.