(Chapter 22)

1. The Respiratory System I (Chapter 22) Lecture # 8 Anatomy of the Respiratory System and Pulmonary Ventilation Objectives 1- State the functions of the respiratory system. 2- Name and describe the organs of this system. 3- Trace the flow of air from the nose to the pulmonary alveoli. 4- Relate the function of any portion of the respiratory tract to its gross and microscopic anatomy. 5-Describe the brainstem centers that control breathing. 6- Explain how pressure gradients account for the flow of air in and out of the lungs, and how those gradients are produced. 7- Explain the significance of anatomical dead space to alveolar ventilation. 8- Define the clinical measurement of pulmonary volume and capacity.

2. Breathing represents life. The first breath of a newborn baby and the last gasp of a dying person are two of the most dramatic moments of human experience Why do we breathe? • All our body processes directly or indirectly require ATP and ATP synthesis requires oxygen and produces carbon dioxide O2 + Food CO2 + H2O + We need to breathe to take in oxygen, and eliminate carbon dioxide

3. O2 CO2 • The respiratory and cardiovascular systems work together to deliver oxygen to the tissues and remove carbon dioxide Alveoli in lung O2 CO2 • They are often considered jointly as cardiopulmonary system. Disorders of lungs directly effect the heart and vise versa • The respiratory system and the urinary system collaborate to regulate the body’s acid base balance Tissue cells Excess of CO2 reacts with water and releases H+ - + H2O H2CO3 HCO3 + H+ CO2 O2 Food CO2 H2O

4. Functions of Respiratory System • 1- O2 and CO2 exchange between blood and air 2- Speech and other vocalizations (laughing, crying) 3- It provides the sense of smell 4- It helps to control the pH of body fluids by eliminating CO2 • 5- It helps to regulate blood pressure by synthesis of a vaso-constrictor called angiotensin II • 6- Breathing creates pressure gradients between thorax and abdomen that promote the flow of lymph and venous blood 7- Breath-holding helps expel abdominal contents during urination, defecation, and childbirth

5. Principal Organs of the Respiratory System Nose Pharynx Larynx Trachea Lungs Bronchi

6. The Nose Anatomy of the Nasal Region (a) External anatomy. (b) Connective tissues that shape the nose

7. The Nasal Cavity: It is the internal chamber of the nose The nasal cavity is divided into right and left halves (nasal fossae) by the nasal septum NASAL SEPTUM Perpendicular plate of ethmoid Septal cartilage Vomer Middle nasal concha Inferior nasal concha

8. The Nasal Cavity Meatuses: Functions of the nose • 1- It warms, cleanses, and humidifies inhaled air. Superior Nasal conchae: Middle • 2- It detects odors in the airstream. Inferior • 3- It serves as a resonating chamber that amplifies the voice. Superior Posterior nasal aperture Middle Inferior Vestibule The respiratory epithelium lines the rest of nasal cavity except vestibule. It is a ciliated pseudostratified columnar epithelium with goblet cells.

9. The Pharynx Posterior nasal aperture Pharynx: Nasopharynx It is a passageway for air It is lined by a pseudostratified columnar epithelium Oropharynx Laryngopharynx It is a passageway for air, food and drink It is lined by a stratified squamous epithelium It is a passageway for air, food and drink Esophagus It is lined by a stratified squamous epithelium Larynx Trachea

10. The Pharynx Nasopharynx • (posterior to nasal apertures and above soft palate) Pharyngeal tonsil Auditory tube Oropharynx (space between soft palate and epiglottis) Palatine tonsil Laryngopharynx • (from the epiglottis to the cricoid cartilage)

11. The Larynx It is a cartilaginous chamber about 4 cm (1.5 in.) 1- To keep food and drink out of the airway Functions: • 2- Production of sound (phonation) Epiglottis Epiglottis It closes the airway during swallowing Hyoid bone Epiglottic cartilage Hyoid bone Thyroid cartilage Thyroid cartilage Arytenoid cartilage Corniculate cartilage Vestibular fold Vocal cord Cricoid cartilage Arytenoid cartilage Cricoid cartilage Trachea Tracheal cartilage (a) Anterior (b) Posterior (c) Median

12. The Larynx Vestibular fold They play no role in speech but close the larynx during swallowing Vocal cord (from the thyroid cartilage to the arytenoid cartilage) They produce sound when air passes between them Median

14. The Trachea The trachea (windpipe) is a rigid tube about 12 cm (4.5 in.) long and 2.5 cm (1 in.) in diameter. • It is found anterior to the esophagus and it is supported by 16 to 20 C-shaped rings of hyaline cartilage, which reinforces the trachea and keeps it from collapsing when you inhale. Trachea Ciliated pseudostratified columnar epithelium with goblets cells

15. Mucociliary escalator It is a mechanism that moves debris-laden mucus to the pharynx to be swallowed. Epithelium: Goblet cell Ciliated cell Mucus Mucous gland

16. The Lungs They are conical organs with a broad, concave base, resting on the diaphragm, and a blunt peak called the apex projecting slightly above the clavicle. Apex of lung Superior lobe Costal surface Superior lobe Horizontal fissure Middle lobe Mediastinal surface Oblique fissure Oblique fissure Inferior lobe Inferior lobe Diaphragmatic surface Base of lung

17. Bronchial Tree Thyroid cartilage All bronchi are lined with ciliated pseudostratified columnar epithelium. Larynx Cricoid cartilage • The lamina propria has an abundance of mucous glands and lymphocyte nodules (bronchus-associated lymphoid tissue, BALT) positioned to intercept inhaled pathogens. Trachea Carina Main bronchi Superior lobar bronchus Superior lobar bronchus Middle lobar bronchus Inferior lobar bronchus Inferior lobar bronchus Segmental bronchi Segmental bronchi (8 on left) (10 on right) Bronchopulmonary segment: It is a functionally independent unit of the lung tissue.

18. Conducting Division of Respiratory System Main bronchus (lung) It consists of those passages that serve only for airflow: 1- Nostrils 2- Nasal cavity 3- Pharynx 4- Larynx Lobar bronchus 5- Trachea 6- Main (primary) bronchi (lungs) (lobe) 7- Lobar (secondary) bronchi (lobes) 8- Segmental (tertiary) bronchi (segments) 9- Bronchioles (lobules) 10- Terminal bronchioles (the final branches) Bronchioles and terminal bronchioles lack of supportive cartilages) Segmental bronchus Respiratory Division of Respiratory System (segment) Bronchiole (pulmonary lobule) It consists of those structures that participate in gas exchange Terminal bronchioles 1- Respiratory bronchioles 2- Alveolar duct (final branches of conducting division) 3- Atrium 4- Alveoli

19. Pulmonary venule Pulmonary arteriole Openings of alveolar ducts Bronchiole Alveolar sac Terminal bronchioles Respiratory bronchioles Every respiratory bronchiole divides into 2 to 10 alveolar ducts, which end in the alveolar sac Alveoli

20. Pulmonary Alveoli Fluid with surfactant Squamous alveolar cell (type I) Respiratory membrane Great alveolar Cell (type II) Capillary endothelial cell • They repair the alveolar epithelium when the squamous (type I) cells are damaged, and secrete pulmonary surfactant Alveolar macrophage • They are phagocytic cells that engulf invaders and activate the immune system

21. The Respiratory Membrane Squamous alveolar cell O2 O2 O2 Respiratory membrane Shared basement membrane Capillary endothelial cell CO2 CO2 CO2

22. Epithelium Type Changes in the Respiratory System Nasal cavity Ciliated pseudostratified columnar epithelium Nasopharynx Ciliated pseudostratified columnar epithelium Oropharynx Stratified squamous epithelium Laringopharynx Stratified squamous epithelium Larynx (superior part) Stratified squamous epithelium Larynx (inferior part) Ciliated pseudostratified columnar epithelium Trachea Ciliated pseudostratified columnar epithelium Bronchi Ciliated pseudostratified columnar epithelium Bronchioles Ciliated simple columnar epithelium Terminal bronchioles Simple cuboidal epithelium Alveoli Simple squamous epithelium (with 5% of round or cuboidal cells (type II alveolar cells)

23. The Respiratory Muscles

24. Neural Control of Breathing No autorhythmic pacemaker cells for respiration, as in the heart, have been found. The exact mechanism for setting the rhythm of respiration remains unknown, but we do know that breathing depends on repetitive stimuli of skeletal muscles from brain. 1- Neurons in medulla oblongata and pons control unconscious breathing, enabling us to breath without thinking about it. Breathing is controlled at 2 levels of the brain. 2- The motor cortex provides voluntary control, enabling us to inhale or exhale at will. Automatic, unconscious cycle of breathing is controlled by three pairs of respiratory centers in the reticular formation of the medulla oblongata and the pons. • 1- The ventral respiratory group (VRG) Medulla oblongata • 2- The dorsal respiratory group (DRG) • 3- The pontine respiratory group (PRG) Pons

25. Autonomic (Involuntary) Control of Breathing Pontine respiratory group (PRG) 2 1 3 1 2 4 3 • It modifies rhythm of the VRG by outputs to both the VRG and DRG. It adapts breathing to special circumstances such as sleep, exercise, vocalization, and emotional responses Ventral respiratory group (VRG) • It is the primary generator of the respiratory rhythm and produces a respiratory rhythm of 12 breath per minute. Dorsal respiratory group (DRG) • It modifies the rate and depth of breathing. It receives influences from external sources: They respond to the pH of the CSF, which reflex the CO2 level in the blood A respiratory center on the pons Chemosensitive center of the anterior medulla oblongata They respond to the O2 and CO2 content and the pH of the blood Chemoreceptors in the carotid and aortic bodies Irritant receptors in the airway (they respond to smoke, dust, pollen, chemical fumes, cold air)

26. Voluntary Control of Breathing The voluntary control over breathing originates in the motor cortex of frontal lobe of cerebrum. It sends impulses down corticospinal tracts to respiratory neurons in spinal cord, bypassing brainstem. There are limits to voluntary control. A breaking point is reached when CO2 levels rise to a point when automatic controls override one’s will.

27. Pulmonary Ventilation Pressure, Resistance, and Airflow 1- Pressure The respiratory airflow is governed by the same principles of flow, pressure, and resistance as blood flow. • The flow of a fluid is directly proportional to the pressure difference between two points: 600 mm Hg 600 mm Hg 600 mm Hg 500 mm Hg 600 mm Hg 600 mm Hg 600 mm Hg 600 mm Hg 400 mm Hg 400 mm Hg 400 mm Hg 400 mm Hg No flow • The flow of a fluid is inversely proportional to the resistance

28. Boyle’s Law: At a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume 757 mm Hg 760 mm Hg 763 mm Hg • If the lungs contain a quantity of a gas and the lung volume increases, their internal pressure (intrapulmonary pressure) falls • If the pressure falls below atmospheric pressure the air moves into the lungs Inspiration At rest Expiration Intra-pulmonary pressure 763 mm Hg 760 mm Hg 757 mm Hg No flow Atmospheric pressure 760 mm Hg 760 mm Hg 760 mm Hg

29. Pulmonary Ventilation: It consists of the repetitive cycles of inspiration (inhaling) and expiration (exhaling). Pressure-Volume Relationships in the Lungs Volume Volume Pressure (757 mmHg) Expiration Inspiration -3 +3 Air: 760 mmHg Pressure (763 mmHg) Intercostal muscles elevates the rib cage and diaphragm is contracted Rib cage in normal position and diaphragm is relaxed Boyle’s law: Pressure and volume are inversely proportional

30. Inspiration Rib cage elevates and diaphragm contracts Expiration Rib cage returns to the normal position and diaphragm relaxes

32. 2- Resistance Pressure is one determinant of airflow and resistance is the other • The greater the resistance the slower the flow Three factors influence the airway resistance: • 1- Diameter of the bronchioles • 2- Pulmonary compliance (the ease with which the lungs can expand) • 3- Surface tension of the alveoli and distal bronchioles • 1- Diameter of the bronchioles Bronchodilation: It is an increase in the diameter of a bronchus or bronchiole • Epinephrine and sympathetic stimulation stimulate bronchodilation and increase air flow Bronchoconstriction: It is a decrease in the diameter of a bronchus or bronchiole • Histamine, parasympathetic nerves, cold air, and chemical irritants stimulate bronchoconstriction • Suffocation from extreme bronchoconstriction brought about by anaphylactic shock and asthma

33. 2- Pulmonary compliance (the ease with which the lungs can expand) • It determines the change in lung volume relative to a given pressure change. The thoracic cage expands normally but the lungs expand relatively little. • Pulmonary compliance reduced by degenerative lung diseases in which the lungs are stiffened by scar tissue (tuberculosis, black lung disease *). • 3- Surface tension of the alveoli and distal bronchioles Water molecules in the alveolar epithelium are attracted to each other by hydrogen bonds, creating a surface tension. Surface tension draws the walls of the alveoli inward toward the lumen and resisting the reinflation. A surfactant is a substance produced by the great alveolar cells (type II cells) that disrupts the hydrogen bonds and allows the lungs to expand. Premature infants often have a deficiency of pulmonary surfactant and experience great difficulty breathing. The result is the “infant respiratory distress syndrome (IRDS), which is treated with artificial surfactant. * Black lung disease is a chronic occupational lung disease contracted by the prolonged breathing of coal mine dust. Black lung disease is also called anthracosis, black lung, black spittle, coal worker's pneumoconiosis, miner's asthma, pneumoconiosis, and silicosis.

34. Only air that enters the alveoli is available for gas exchange But not all inhaled air gets there, about 150 mL fills the conducting division of the airway (anatomical dead space). When a person inhales 500 mL of air, 150 mL stays in anatomical dead space, and 350 mL reaches alveoli. In pulmonary diseases, some alveoli may be unable to exchange gases because they lack blood flow or there respiratory membrane has been thickened by edema or fibrosis. Physiologic (total) dead space: • It is the sum of anatomic dead space and any pathological alveolar dead space. Alveolar ventilation rate (AVR): In a healthy person: Anatomical dead space = Physiologic (total) dead space • It is the air that ventilates alveoli (350 mL) X respiratory rate (12 bpm) = 4200 mL/min. The alveoli never completely empty during expiration. Residual volume: It is the air that cannot be exhaled with maximum effort (1300 mL).

35. Measurements of Ventilation Spirometer It is a device that recaptures expired breath and records such variables such as rate and depth of breathing, speed of expiration, and rate of oxygen consumption. Respiratory Volumes 1- Tidal volume (TV): It is volume of air inhaled and exhaled in one cycle during quiet breathing (500 mL). 2- Inspiratory reserve volume (IRV): It is the air in excess of tidal volume that can be inhaled with maximum effort (3000 mL). 3- Expiratory reserve volume (ERV): It is the air in excess of tidal volume that can be exhaled with maximum effort (1200 mL). 4- Residual volume (RV): It is the air remaining in lungs after maximum expiration (1300 mL).

36. 1- Tidal volume (TV): It is volume of air inhaled and exhaled in one cycle during quiet breathing (500 mL) 2- Inspiratory reserve volume (IRV): It is the air in excess of tidal volume that can be inhaled with maximum effort (3000 mL) 3- Expiratory reserve volume (ERV): It is the air in excess of tidal volume that can be exhaled with maximum effort (1200 mL) 4- Residual volume (RV): It is the air remaining in lungs after maximum expiration (1300 mL) Maximum possible inspiration 2- Inspiratory reserve volume (IRV) 1- Tidal volume (TV) 3- Expiratory reserve volume (ERV) Maximum voluntary expiration 4- Residual volume (RV)

37. Pulmonary Capacities 1-Vital capacity (VT): It is the total amount of air that can be inhaled and then exhaled with maximum effort (4700mL) 2-Inspiratory capacity (IC): It is the maximum amount of air that can be inhaled after a normal tidal expiration (3500 mL) 3-Functional residual capacity (FRC): It is the amount of air remaining in lungs after a normal tidal expiration (2500 mL) 4-Total lung capacity (TLC) It is the maximum amount of air the lungs can contain Maximum possible inspiration 2- Inspiratory reserve volume (IRV) Inspiratory capacity Vital capacity 1- Tidal volume (TV) Total lung capacity 3- Expiratory reserve volume (ERV) Maximum voluntary expiration Functional residual capacity 4- Residual volume (RV)