Chapter 22 Respiratory System PDF

Chapter 22: The Respiratory System  Learning Objectives 1. Describe the different events that make up respiration, and distinguish between the conducting and respiratory zones. 2. List all of the structures that make up the respiratory system, including the bronchioles and alveoli. 3...

Chapter 22: The Respiratory System  Learning Objectives 1. Describe the different events that make up respiration, and distinguish between the conducting and respiratory zones. 2. List all of the structures that make up the respiratory system, including the bronchioles and alveoli. 3. Describe the different regions of the pharynx, with respect to the passage of air or food. 4. Describe the respiratory membrane, and explain how gas is exchanged there. 5. Describe the structure of the lungs and the function of the pleurae. 6. Explain the relationship between pressure, volume and breathing. 7. Define the various respiratory volumes and capacities. 8. Describe several lung diseases (asthma, bronchitis, emphysema). 9. Explain how gas exchange occurs with the help of red blood cells. 10. Explain how carbon dioxide is converted into bicarbonate for transport.  Respiratory System Major functions: – Provide oxygen to body tissues for cellular respiration – Remove carbon dioxide (waste product) – Acid-base balance Portions of the respiratory system are also used for non-vital functions. – Sensing odors, producing speech, straining and coughing  Functional classification 1. Conducting zone: includes the organs and structures not directly involved in gas exchange (nose, pharynx, trachea, bronchi) 2. Respiratory zone: where gas exchange occurs (capillaries and alveoli)  Regional classification 1. Upper respiratory: includes nose and adjacent structures and pharynx 2. Lower respiratory: includes larynx, trachea, bronchi and branches, lungs and alveoli.  Nose Major point of entry and exit Two major sections: 1. the external nose 2. the nasal cavity or internal nose Moistens and filters the air coming into the body Contains receptors for smelling  Pharynx Tube formed by skeletal muscle and lined by mucosa; continuous with that of the nasal cavities. Three major regions: 1. Nasopharynx 2. Oropharynx 3. laryngopharynx  Larynx Cartilaginous structure inferior to the laryngopharynx Connects the pharynx to the trachea Regulates the volume of air that enters and leaves lungs Three large cartilage pieces form the major structure of the larynx: 1. the thyroid cartilage (anterior) 2. epiglottis (superior) 3. cricoid cartilage (inferior)  Larynx The thyroid cartilage makes up the wall of larynx. The thick cricoid cartilage forms a ring connects larynx to trachea. The epiglottis is made of elastic cartilage and covers the opening of the trachea to prevent entry of solid objects.  Larynx When epiglottis closes, its unattached end rests on the glottis. The glottis is composed of the vestibular folds, the true vocal cords, and the space between these folds. 1=vocal folds, 2=vestibular fold, 3=epiglottis, By I, Welleschik, CC BY-SA 3.0, 4=plica aryepiglottica, 5=arytenoid cartilage, https://commons.wikimedia.org/w/index.php? 6=sinus piriformis, 7=dorsum of the tongue curid=2468726  Trachea AKA “windpipe” Extends from the larynx toward the lungs. Formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage connected by dense connective tissue. Branches into the right and left primary bronchi.  Bronchi The primary bronchi enter the lungs at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter the lungs. A bronchial tree (or respiratory tree) is the multiple-branched bronchi. The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung.  Bronchioles As bronchi branch into bronchioles, their diameter decreases (1 mm diameter). – Bronchioles do not contain cartilage – Wall contains smooth muscles to increase or decrease airflow Terminal bronchioles lead to the site of gas exchange.  Respiratory Zone Site of gas exchange. Begins where the terminal bronchioles join a respiratory bronchiole, the smallest type of bronchiole. Respiratory bronchioles lead to an alveolar duct, opening into a cluster of alveoli.  Alveoli alveolar duct: tube composed of smooth muscle and connective tissue which opens into an alveolar sac. alveolar sac: cluster of many individual alveoli that are responsible for gas exchange. An alveolus is one of the many small, grape-like sacs that are attached to the alveolar ducts.  Alveoli Elastic walls allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange. Alveoli are connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the Alveoli  Alveolar cells The alveolar wall consists of three major cell types: – Type I alveolar cells: squamous epithelial cells that are highly permeable to gases. – Type II alveolar cells: interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins that reduces the surface tension of the alveoli. – Alveolar macrophage roams around the alveoli and remove debris and pathogens that have  Respiratory membrane Type I alveolar cells are attached to a thin, elastic basement membrane which is extremely thin and borders the endothelial membrane of capillaries. The alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 mm thick. By Delmalani18 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.p hp?curid=69613938  Respiratory membrane Allows gases to cross by simple diffusion oxygen is picked up by the blood for transport and CO2 is released into the alveoli. By Katherinebutler1331 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=69564061  The Lungs main function is to perform the exchange of oxygen and carbon dioxide with air from the atmosphere. Pyramid-shaped, paired organs that are connected to the trachea. Rest on the diaphragm. The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right.  The Lungs The cardiac notch is an indentation on the surface of the left lung, and it allows space for the heart. The apex of the lung is the superior region, whereas the base is the opposite region near the diaphragm. Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other.  The Lungs The right lung consists of three lobes: the superior, middle, and inferior lobes. The left lung consists of two lobes: the superior and inferior lobes. Oblique fissure separates the superior and inferior lobes of the left lung and the middle and inferior lobes of the right lung. Horizontal fissure separates the superior and middle lobes  Pleura of the Lungs pleura (plural = pleurae) two layer serous membrane that surrounds the lungs. visceral pleura is superficial to the lungs and extends into and lines the lung fissures. parietal pleura is the outer layer that connects to the thoracic wall, the mediastinum, and the diaphragm. The pleural cavity is the space between the visceral and parietal  The Process of Breathing Pulmonary ventilation is the act of breathing, which can be described as the movement of air into and out of the lungs. The major factors that drive pulmonary ventilation are – atmospheric pressure (Patm) – intra-alveolar pressure (Palv): pressure within the alveoli – intrapleural pressure (Pip): pressure within the pleural cavity  Pressure Relationships Gases move from areas of high pressure to areas of low pressure. The reference point for ventilation is the atmospheric pressure (760mmHg). Because the alveoli are connected to the atmosphere via the tubing of the airways, the intrapulmonary pressure of the alveoli always equalizes with the  Pressure Relationships Intrapleural pressure is the pressure of the air within the pleural cavity. Due to certain characteristics of the lungs, the intrapleural pressure is always lower than the intra-alveolar pressure and atmospheric pressure). It remains approximately –4 mm Hg throughout the breathing cycle.  Pressure Relationships In a gas, pressure is a force created by the movement of gas molecules that are confined. Boyle’s law describes the inverse relationship between volume and pressure in a gas at a constant temperature. – If volume increases, pressure decreases. – if volume decreases, pressure increases. Pulmonary ventilation is  Respiration 1. Pulmonary ventilation: The movement of air in and out of the lungs. 2. External respiration: exchange of O2 and CO2 between lungs and blood 3. Transport: of O2 and CO2 in blood 4. Internal respiration: exchange of O2 and CO2 between blood and cells  Pulmonary Ventilation Pulmonary ventilation comprises two major steps: inspiration and expiration. Inspiration is the process that causes air to enter the lungs, and expiration is the process that causes air to leave the lungs Respiratory cycle is one sequence of inspiration and expiration. Two muscle groups are used during normal inspiration: the  Pulmonary Ventilation: Inspiration Diaphragm and External Intercostals contract, lifting the ribcage, and lowering the diaphragm, resulting in more space in the thoracic cavity. The expansion of the thoracic cavity forces the lungs to stretch and expand. Increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure.  Pulmonary Ventilation: Expiration Diaphragm and External Intercostals relax, Internal intercostals contract, pulling the ribcage down and decreasing the volume in the thoracic cavity. lungs shrink. intra-alveolar pressure increases, creating a pressure higher than atmospheric pressure. As a result, a pressure gradient is created that  Pulmonary Ventilation Air flows into the lungs largely due to a difference in pressure; atmospheric pressure is greater than intra- alveolar pressure. Air flows out of the lungs during expiration based on the same principle; pressure within the lungs becomes greater than the atmospheric pressure.  Respiratory Volumes and Capacities Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle. Four major types: 1. Tidal volume (TV) is the amount of air that normally enters and exits the lungs during quiet breathing, which is about 500 milliliters.  Respiratory Volumes and Capacities 2. Expiratory reserve volume (ERV) is the amount of air that can forcefully exhale past a normal tidal expiration, up to 1200 milliliters. 3. Inspiratory reserve volume (IRV) is produced by a deep inhalation, past a tidal inspiration. This is the extra volume that can be brought into the lungs during a forced inspiration.  Respiratory Volumes and Capacities 4. Residual volume (RV) is the air remains in the heart ERV. RV keeps lungs open.  Respiratory Volumes and Capacities Additional respiratory volumes : – Total lung capacity (TLC) is the sum of all of the lung volumes (TV, ERV, IRV, and RV), which represents the total amount of air a person can hold in the lungs after a forceful inhalation. TLC is about 6000 mL air for men, and about 4200 mL for women. – Vital capacity (VC) is the amount of air a person can move into or out of his or her lungs; the sum of all of the volumes except residual volume (TV, ERV, and IRV), which is between 4000 and 5000 milliliters. Respiratory Volumes and Capacities Additional respiratory volumes : – Inspiratory capacity (IC) is the maximum amount of air that can be inhaled past a normal tidal expiration; the sum of the tidal volume and inspiratory reserve volume. – Functional residual capacity (FRC): is the amount of air that remains in the lung after a normal tidal expiration; the sum of expiratory reserve volume and residual volume.  Respiratory Rate The respiratory rate is the total number of breaths, or respiratory cycles, that occur each minute. – Can be an important indicator of disease, as the rate may increase or decrease during an illness or in a disease condition. Minute ventilation rate: total amount of gas that flows into or out of respiratory tract in 1 minute Alveolar ventilation rate (AVR): flow of gases into and out of alveoli during a particular time. – Better indicator of effective ventilation – It excludes the air in the conducting pathways (dead space)  Gas Exchange Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. – For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen. Total pressure is the sum of all the partial pressures of a gaseous mixture. – Gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower. – The greater the partial pressure difference between the two areas, the more rapid is the movement of gases.  Gas Exchange External respiration: is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. – Performed by respiratory system Internal respiration: is the exchange of gases with the internal environment, and occurs in the tissues. – Performed by cardiovascular system The actual exchange of gases occurs By Ahmed Katsha. Made with Biorender due to simple diffusion.  External Respiration Majority of the oxygen is picked up by erythrocytes (red blood cells) and binds to hemoglobin – Small amount is able to dissolve directly into plasma. External respiration occurs due to partial pressure differences of oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries.  Internal Respiration Carbon dioxide is transported by three major mechanisms. 1. The first mechanism is by blood plasma, as some carbon dioxide molecules dissolve in the blood. 7-10% of total CO2 2. The second mechanism is transport in the form of bicarbonate (HCO3–), which also dissolves in plasma. 70% of total CO2 3. The third mechanism is by binding to hemoglobin. 20% of total CO2  CO2 Transportation CO2 transportation involves the production of bicarbonate HCO3-, which is an important molecule in controlling blood pH. Most bicarbonate is produced in erythrocytes. Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid (H2CO3), which dissociates into two ions: bicarbonate (HCO3–) and hydrogen (H+). The following formula depicts this reaction: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 −  CO2 Transportation About 20 percent of carbon dioxide is bound by hemoglobin and is transported to the lungs. Carbon dioxide does not bind to iron as oxygen does; instead, it binds to the globin portions of hemoglobin to form carbaminohemoglobin. The following formula depicts this reversible reaction: CO2 + Hb ↔ HbCO2  CO2 Transportation Slow breathing (hypoventilation) will lead to slow removal of CO2 from blood, which will shift the reaction toward the right – CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 − – This leads to respiratory acidosis Fast breathing (hyperventilation) like the one during panic attack, leads to fast removal of CO2 beyond what the body needs. – Reaction will shift toward the left and this causes respiratory alkolosis.  Disease of Respiratory System: Asthma chronic disease characterized by inflammation and edema of the airway, which can inhibit air from entering the lungs. excessive mucus secretion can occur, which further contributes to airway occlusion. Cells of the immune system, such as eosinophils, may also be involved in infiltrating the walls of the bronchi and  Disease of Respiratory System: Asthma Bronchospasms occur periodically and lead to an “asthma attack.” – May be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress. Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of  Diseases of the Respiratory System: COPD Chronic Obstructive Pulmonary Disease is a type of obstructive lung disease characterized by long- term breathing problems and poor airflow. – An ongoing cough or a cough that produces a lot of mucus; this is often called smoker's cough. – Shortness of breath, especially with physical activity – Wheezing or a whistling or squeaky sound when you https://www.nhlbi.nih.gov/health-topics/copd  Diseases of the Respiratory System: COPD COPD includes two main conditions: emphysema and chronic bronchitis. Emphysema: involves damage to the air sacs (alveoli) in the lungs so the body doesn’t get enough O2. By Nephron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7935360  Diseases of the Respiratory System: Chronic Bronchitis Chronic bronchitis is an ongoing cough that lasts for several months and comes back two or more years in a row. The lining of the airways stays constantly inflamed. This causes the lining to swell and produce more mucus, which can make it hard to breathe. By National Heart Lung and Blood Institute - National Heart Lung and Blood Institute, Public Domain, https://commons.wikimedia.org/w/index.php? curid=29583164  Lung Cancer Leading cause of cancer deaths in North America 90% of all cases are result of smoking  Lung Cancer (cont.) Three most common types: – Adenocarcinoma (~40% of cases) originates in peripheral lung areas; develops from bronchial glands and alveolar cells – Squamous cell carcinoma (20–40% of cases) arises in bronchial epithelium – Small cell carcinoma (~20% of cases) contains lymphocyte-like cells that originate in primary bronchi and subsequently metastasize  Lung Cancer (cont.) Treatment for lung cancer – Early detection is key to survival – If metastasis has not occurred: surgery to remove diseased lung tissue – If metastasis has occurred: radiation and chemotherapy – Several new therapies are on horizon