Pulmonary Ventilation

1. Pulmonary Ventilation http://www.edumedia-sciences.com/a385_l2-respiratory-system.html

2. Respiratory System Functions • Gas exchange: Oxygen enters blood and carbon dioxide leaves • Regulation of blood pH: Altered by changing blood carbon dioxide levels • Voice production: Movement of air past vocal folds makes sound and speech • Olfaction: Smell occurs when airborne molecules drawn into nasal cavity • Protection: Against microorganisms by preventing entry and removing them

3. Respiration can be divided into 4 major functions: • Pulmonary Ventilation • Diffusion of O2 and CO2 between the alveoli and blood • Transport of O2 and CO2 in the blood and body fluids • Regulation of ventilation and other aspects of respiration

4. Mechanics of Pulmonary Ventilation • How do we breath? • Inspiration is normally active • Expiration is normally passive.

5. Muscles of Respiration • Inspiratory muscles • Diaphragm. • External intercostals. • Accessory muscles. • Include sternomastoids, scalene muscles, and alae nasi. • Expiratory muscles • Abdominal muscles. • Internal intercostals.

7. Chest Wall Muscles

8. Diaphragm Undersurface

10. The Pleura

11. Movement of Air in and out of the Lungs • The lung is an elastic structure that collapses … • There are no attachments between the lung and the walls of the chest cage except where it is suspended at its hilum from the mediastinum • The lungs float in the thoracic cavity, surrounded by a thin layer of pleural fluid • Continual suction of excess fluid into lymphatics maintains a slight suction between the two layers of the pleura • The lungs are held to the thoracic wall as if glued

12. The Pressures and Ventilation

13. Compliance of the Lungs

14. Compliance of the Lungs • The elastic forces of the lung tissue is determined mainly by elastin and collagen fibers in the lung parenchyma

15. A water molecule deep within the liquid is pulled equally from all sides A water molecule at the surface lacks neighboring water molecules (toward the interface) net force is not zero! net force = zero This unequal attraction causes the water at the air-water interface to act as a cohesive surface. and the liquid to shrink to the smallest possible surface area.

16. Surfactant, surface tension and collapse of the alveoli

17. Surfactant, surface tension and collapse of the alveoli • Surfactant is a surface active agent in water, it greatly reduces the surface tension of water • It is secreted by special surfactant-secreting epithelial cells called Type II Alveolar Epithelial Cells • Surfactant is a complex mixture of several phospholipids, proteins and ions. • The fluid-air surface tension elastic forces of the lungs increase when Surfactant is not present in the alveolar fluid

18. Effect of the thoracic cage on lung expansibility • Compliance of the thorax and the lungs together • Twice as much pressure is needed as to inflate the same lungs after removal from the chest cage • Work of breathing (inspiration) • Compliance or elastic work • Tissue resistance work • Airway resistance work • Energy required for respiration • During normal quiet respiration, only 3-5 % of the total body energy is required for pulmonary ventilation • During heavy exercise, it increases as much as 50-fold

19. Pulmonary Volumes and Capacities • Spirometry: A simple method for studying pulmonary ventilation is to record volume movement of air into and out of the lungs

20. Pulmonary Volumes • Tidal Volume is the volume of air inspired or expired with each normal breath. It amounts 500 ml in adult male • The inspiratory reserve volume is the extra volume of air that can be inspired over and above the normal tidal volume (it is about 3000 ml) • The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration (1100 ml) • The residual volume is the volume of air remaining in the lungs after the most forceful expiration (1200 ml)

21. Pulmonary Capacities • Two or more combinations of the volumes are called pulmonary capacities • The inspiratory capacity equals the tidal volume and inspiratory reserve capacity (500 ml + 3000 ml : 3500 ml) • The functional residual capacity equals the expiratory reserve volume and residual volume (1100 ml+1200 ml) • The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume (it is about 4600 ml) • The total lung capacity is the maximum volume to which lungs can be expanded (about 5800 ml)

22. Pulmonary Volumes and Capacities

23. Abbreviations and Symbols for Pulmonary Function

24. Minute respiratory volume • Minute respiratory volume = respiratory rate X Tidal volume • Tidal volume (500 ml) x respiratory rate (12) = 6000 ml/min

25. Alveolar Ventilation • Pulmonary ventilation areas: alveoli, alveolar sacs, alveolar ducts and respiratory bronchioles • The rate at which new air reaches these areas is called alveolar ventilation • Dead Space and its effect on alveolar ventilation: • Nose, pharynx, larynx and trachea • It is about 150 ml • VA = Freq •VT-VD

26. Anatomic Dead Space. • Volume of the lung not involved in gas exchange • (includes: the nose, pharynx, larynx, trachea, and bronchi) • Ventilation of these areas results in no gas exchange. • Estimating anatomical dead space: • Anatomic dead space in ml = ideal body weight measured in pounds.

27. Alveolar Dead Space • Treat lung as if only two types of alveoli exist: • those with ideal gas exchange • those with no gas exchange at all • Partition poorly ventilated units • Alveolar Dead Space. “as if” volume contained in the units with no gas exchange.

28. Physiological Dead Space • DEFINITION: The total effective volume of the lung NOT involved in ideal gas exchange • Physiological dead space = Anatomical Dead Space + Alveolar Dead Space

29. Functions of Respiratory Passageways

30. Nasal Cavity and Pharynx

31. Tracheobronchial Tree

32. Bronchioles and Alveoli

33. Muscular wall of the bronchi and bronchioles and its control • In all areas of the trachea and bronchi not occupied by cartilage plates, the walls are composed mainly of smooth muscle • Walls of the bronchioles are almost completely smooth muscle • Except the terminal bronchiole (also called respiratory bronchiole) which is pulmonary epithelium

34. Nervous and Local Control of Bronchiolar Musculature • Sympathetic dilation of the bronchioles • Epinephrine and norepinephrine • Acting via beta-adrenergic receptors • Paracympathetic constriction of bronchioles • Acetylcholine causes mild to moderate constriction of bronchioles • In presence of asthma parasympathetic stimulation worsens the condition • Local secretory factors often cause bronchiolar constriction • Mast cells release histamine and slow reactive substance of anaphylaxis

35. Mucus Lining the Respiratory Passageways and Action of Cilia to Clear the Passageways • A layer of mucus coats the entire surface of respiratory passageways • Ciliary epithelium • Respiratory functions of nose: • Warming • Humidification and • Filtration of the air

36. Cough Reflex • Inspiratory phase • Epiglottis closes and the vocal cords shut tightly to entrap the air within the lungs • Compressive phase • Expulsive phase • Afferent nerve impulses pass from the respiratory passages mainly thorugh N. Vagus to the medulla of the brain • Sneeze reflex: Signal transmission thorugh Cranial Nerve V to the medulla

37. Vocalization • Speech is composed of two mechanical actions: • Phonation which is achieved by the larynx • Articulation which is achieved by structures of the mouth

38. Vocal Cords