1. Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Chapter 13 The Respiratory System Presented by Dr. Mohammad Alqudah Department of Physiology

2. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiration General function is to obtain O 2 for use by the body’s cells and to eliminate the CO 2 the body cells produce Encompasses two separate but related processes –Internal respiration –External respiration

3. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Internal Respiration Cellular respiration Refers to metabolic processes carried out within the mitochondria, which use O 2 and produce CO 2, while deriving energy from nutrient molecules

4. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning External Respiration Refers to sequence of events involved in the exchange of O 2 and CO 2 between the external environment and the cells of the body Four steps –Ventilation – movement of air into and out of the lungs –O 2 and CO 2 are exchanged between air in alveoli and blood within the pulmonary capillaries by means of diffusion –Blood transports O 2 and CO 2 between lungs and tissues –O 2 and CO 2 are exchanged between tissues and blood by process of diffusion across systemic (tissue) capillaries

5. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning External and Internal Respiration

6. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Nonrespiratory Functions of Respiratory System Route for water loss and heat elimination Enhances venous return Helps maintain normal acid-base balance Enables speech and other vocalizations Defends against inhaled foreign matter Removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation Nose serves as the organ of smell

7. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory System Consists of –Respiratory airways leading into the lungs –Lungs –Structures of the thorax involved in producing movement of air through the airways into and out of the lungs

8. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Airways Tubes that carry air between the atmosphere and the air sacs –Nasal passages (nose) –Pharynx (common passageway for respiratory and digestive systems) –Trachea (windpipe) –Larynx (voice box) –Right and left bronchi –Bronchioles Alveoli (air sacs) are clustered at ends of terminal bronchioles

9. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Airways Trachea and larger bronchi –Fairly rigid, nonmuscular tubes –Rings of cartilage prevent collapse Bronchioles –No cartilage to hold them open –Walls contain smooth muscle innervated by autonomic nervous system –Sensitive to certain hormones and local chemicals

10. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Alveoli Thin-walled inflatable sacs Function in gas exchange Walls consist of a single layer of flattened Type I alveolar cells Pulmonary capillaries encircle each alveolus Type II alveolar cells secrete pulmonary surfactant Alveolar macrophages guard lumen

11. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Lungs Occupy much of thoracic cavity –Heart, associated vessels, esophagus, thymus, and some nerves also occupy space Two lungs –Each is divided into several lobes –Tissue consists of highly branched airways, the alveoli, the pulmonary blood vessels, and large quantities of elastic connective tissue Outer chest wall (thorax) –Formed by 12 pairs of ribs which join sternum anteriorly and thoracic vertebrae posteriorly

12. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Lungs Diaphragm –Dome-shaped sheet of skeletal muscle –Separates thoracic cavity from the abdominal cavity Pleural sac –Double-walled, closed sac that separates each lung from the thoracic wall –Pleural cavity – interior of plural sac –Intrapleural fluid Secreted by surfaces of the pleura Lubricates pleural surfaces

13. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Pleural Sac

14. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Mechanics Interrelationships among pressures inside and outside the lungs are important in ventilation Three different pressure considerations important in ventilation –Atmospheric (barometric) pressure –Intra-alveolar pressure (intrapulmonary pressure) –Intrapleural pressure (intrathoracic pressure)

15. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Pressures Important in Ventilation

16. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Mechanics Changes in intra-alveolar pressure produce flow of air into and out of the lungs If this pressure is less than atmospheric pressure, air enters the lungs. If the opposite occurs, air exits from the lungs. Boyle’s law states that at any constant temperature, the pressure exerted by a gas varies inversely with the volume of a gas. Boyle’s Law

17. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Mechanics Major inspiratory muscles –Diaphragm Major inspiratory muscle Innervated by phrenic nerve –External intercostal muscles Activated by intercostal nerves 75 % of the enlargement of the thoracic cavity during quiet respiration is due to the contraction and flattening of the diaphragm. This expansion decreases the intrapleural pressure (down to 754). The lungs are drawn into this area of lower pressure. They expand. This increase in volume lowers the intra- alveolar pressure to a level below atmospheric pressure. By this difference, air enters the lungs. The action of accessory inspiratory muscles can further enlarge the thoracic cavity.

18. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Anatomy of the Respiratory Muscles

19. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Mechanics Onset of expiration begins with relaxation of inspiratory muscles –Relaxation of diaphragm and muscles of chest wall, plus the elastic recoil of the alveoli, decrease the size of the chest cavity –Intrapleural pressure increases and lungs are compressed –Intra-alveolar pressure increases. When pressure increases to level above atmospheric pressure, air is driven out – expiration occurs –Forced expiration can occur by contraction of expiratory muscles Abdominal wall muscles Internal intercostal muscles

20. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Muscle Activity During Inspiration

21. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Respiratory Muscle Activity During Expiration

22. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Airway Resistance Primary determinant of resistance to airflow is the radius of the conducting airway Autonomic nervous system controls contraction of smooth muscle in walls of bronchioles (changes the radii) Chronic obstructive pulmonary disease abnormally increases airway resistance –Expiration is more difficult than inspiration –Diseases Chronic bronchitis Asthma Emphysema F = Pressure difference/ resistance

23. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Compliance Lungs have elastic recoil – rebound if stretched Compliance –Refers to how much effort is required to stretch or distend the lungs –The less compliant the lungs are, the more work is required to produce a given degree of inflation –Decreased by factors such as pulmonary fibrosis

24. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Elastic Recoil Refers to how readily the lungs rebound after having been stretched Responsible for lungs returning to their preinspiratory volume when inspiratory muscles relax at end of inspiration Depends on two factors –Highly elastic connective tissue in the lungs –Alveolar surface tension Thin liquid film lines each alveolus

25. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Work of Breathing Normally requires 3% of total energy expenditure for quiet breathing Lungs normally operate at about “half full” Work of breathing is increased in the following situations –When pulmonary compliance is decreased –When airway resistance is increased –When elastic recoil is decreased –When there is a need for increased ventilation

26. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Lung Volumes and Capacities Can be measured by a spirometer Spirogram is a graph that records inspiration and expiration

27. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Lung Volumes and Capacities DescriptionAverage Value Tidal volume (TV)Volume of air entering or leaving lungs during a single breath 500 ml Inspiratory reserve volume (IRV) Extra volume of air that can be maximally inspired over and above the typical resting tidal volume 3000 ml Inspiratory capacity (IC) Maximum volume of air that can be inspired at the end of a normal quiet expiration (IC =IRV + IV) 3500 ml Expiratory reserve volume (ERV) Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume 1000 ml Residual volume (RV) Minimum volume of air remaining in the lungs even after a maximal expiration 1200 ml

28. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Lung Volumes and Capacities DescriptionAverage Value Functional residual capacity (FRC) Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV) 2200 ml Vital capacity (VC)Maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV) 4500 ml Total lung capacity (TLC)Maximum volume of air that the lungs can hold (TLC = VC + RV) 5700 ml Forced expiratory volume in one second (FEV 1 ) Volume of air that can be expired during the first second of expiration in a VC determination

29. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Variations in Lung Volume

30. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Pulmonary Ventilation Minute ventilation Volume of air breathed in and out in one minute Pulmonary ventilation = tidal volume x respiratory rate (ml/min) (ml/breath) (breaths/min)

31. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Alveolar Ventilation More important than pulmonary ventilation Volume of air exchanged between the atmosphere and the alveoli per minute Less than pulmonary ventilation due to anatomic dead space –Volume of air in conducting airways that is useless for exchange –Averages about 150 ml in adults Alveolar ventilation = (tidal volume – dead space) x respiratory rate O2 CO2 Anatomic dead space Alveolus

32. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Effect of Different Breathing Patterns on Alveolar Ventilation

33. Chapter 13 The Respiratory System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Alveolar Ventilation Alveolar dead space –Quite small and of little importance in healthy people –Can increase even to lethal levels in several types of pulmonary disease Local controls act on smooth muscle of airways and arterioles to match airflow to blood flow –Accumulation of carbon dioxide in alveoli decreases airway resistance leading to increased airflow –Increase in alveolar oxygen concentration brings about pulmonary vasodilation which increases blood flow to match larger airflow

34. Next lecture: Gas Exchange Gas Transport