Ch19 Respiratory System.docx

CHAPTER 19: RESPIRATORY SYSTEM OBJECTIVES: 1. Fully explain the process (5 parts of) respiration. 2. Describe the significance of oxygen and carbon dioxide in human cells. 3. Explain the structure and function of mucous membranes that line most of the respiratory tract. 4. Locate the upper respiratory organs on a diagram, describe their structure and any specific functions they may have (both respiratory and other functions, if applicable). 5. Name the four skull bones that contain sinuses. 6. Name the three parts of the pharynx. 7. Explain the significance of the epiglottis and glottis. 8. Give the scientific name for the "Adam's Apple". 9. Describe how and where sound originates and how it is then converted into recognizable speech. 10. Locate the lower respiratory organs on a diagram, describe their structure and any specific functions they may have. 11. Define the terms C-ring, trachealis muscle, and carina. 12. Name the type of cartilage that composes the trachea. 13. Distinguish between a primary, secondary, and tertiary bronchus. 14. Explain what happens to the epithelial lining, cartilage and smooth muscle of the bronchi as they branch deep into the lungs to form terminal bronchioles. 15. Explain the effects that histamine and epinephrine have on terminal bronchioles. 16. Discuss the structure and function of the pleural membranes. 17. Distinguish between a lobe and lobule of the lung. 18. Discuss the microscopic anatomy of the lung. 19. Track a breath of air from the nose to an alveolus, noting what happens to the air as it meets each structure. 20. Distinguish between Type I and Type II Alveolar cells, in terms of structure and function. 21. Define the term surfactant and describe its important function. 22. Sketch a diagram of the respiratory membrane and then describe its structure in terms of tissue components and thickness. Name the process that occurs through this membrane and explain this process in terms of what is being transported and how, using numerical values. 23. Define the term pulmonary ventilation, and describe its two actions in terms of forces, muscles, and membranes involved. 24. Starting with the diaphragm muscle in its relaxed position, describe, in order, the events that occur during inspiration. 25. Explain how Boyle's Law relates to ventilation. 26. Explain why the serous fluid between the pleural membranes has high surface tension. 27. Define the term atelectasis, explain what is usually lacking within the alveoli when it occurs, and name the disease of premature newborns when it occurs. 28. Name the instrument used to measure lung volumes. 29. List, define, give estimate values, and correlate different lung volume measurements. 30. Define the term external respiration. 31. State Dalton's Law and explain its significance in respiration. 32. List the percentages of N2, O2, and CO2 in air. 33. Define what is meant by the partial pressure (pp) of a gas in a mixture and list the pp values of O2 and CO2 in air and in the lung capillaries. 34. Discuss the factors that influence the rate at which a gas diffuses. 35. Define the term internal respiration. 36. Discuss how oxygen, carbon monoxide and carbon dioxide are transported in the blood. 37. Discuss the factors that cause oxygen to be released from hemoglobin. 38. Define the term hypoxia, and describe how it occurs during carbon monoxide poisoning. 39. Write the chemical equation that involves carbon dioxide, water, carbonic acid, a hydrogen ion, and a bicarbonate ion, and explain its significance. 40. Locate the neural respiratory center on a diagram. 41. Distinguish between the medullary rhythmicity area and pneumotaxic area of the neural respiratory center. 42. Explain how respiration is affected by varying chemical (CO2 and O2) concentration in the blood. INTRODUCTION Respiration: 5 parts: Pulmonary ventilation* = breathing; External respiration* = air into lungs; gas exchange (O2 load/ CO2 unload); air out; Transport of respiratory gases = gases in blood transported from lungs to body cells and back to lungs; Internal respiration = exchange of gases at body capillaries (O2 unload/CO2 load). Cellular respiration = use of oxygen by cells to produce energy (production of CO2). * Only these two portions are included in the respiratory system. ORGANS OF THE RESPIRATORY SYSTEM: See Fig 19.1, page 733 and Summary Table 19.1, page 744. Upper Respiratory Organs (UROs): See Fig 19.2, page 734. 1. The UROs are lined with mucous membranes: See Fig 19.3, page 734. a. ET/CT with many goblet cells (mucus); b. Specifically, pseudostratified columnar ET in the trachea, The mucus functions to trap debris. The cilia beats the debris to the pharynx to be swallowed and destroyed by digestive enzymes. This tissue also serves to warm and moisten incoming air. 2. Nose (external nares or nostrils) a. bone & cartilage with internal hairs; traps large particles (i.e. filters air). 3. Nasal cavity (separated by nasal septum) a. bone & cartilage lined with mucous membranes; b. warms and moistens incoming air; olfactory reception; resonating chambers for speech. II. ORGANS OF THE RESPIRATORY SYSTEM A. Upper Respiratory Organs (UROs): (continued) 4. Nasal conchae (within nasal cavity) See Fig 19.2, page 734. a. superior, middle & inferior; b. divide nasal cavity into a series of groove-like passageways; c. lined by mucous membranes; d. increase turbulence of incoming air (to better warm, moisten and filter). 5. Paranasal sinuses Fig 9.4, page 736 a. within 4 skull bones (frontal, ethmoid, sphenoid, maxillary); b. drain into nasal cavity; c. lined with mucous membranes; d. reduce weight of skull; e. resonating chambers for speech. 6. Pharynx (or throat) See Fig 19.2, page 734. a. wall of skeletal muscle lines with mucous membranes; b. passageway for air and food; c. resonant chamber for speech sounds; d. three parts: nasopharynx (uppermost); oropharynx (middle); laryngopharynx (lowest). 7. Larynx (or voice box) See Fig 19.5 and 19.6, pages 737. a. Anatomy (9 pieces of cartilage) thyroid cartilage (Adam's apple); epiglottis closes off the airway during swallowing; two pairs of vocal folds (false over true vocal cords); glottis = triangular slit; opening between two pairs of vocal cords. cricoid cartilage = ring of hyaline cartilage attached to first ring of trachea; site of tracheotomy. arytenoid cartilages; corniculate cartilages; cuneiform cartilages. II. ORGANS OF THE RESPIRATORY SYSTEM A. Upper Respiratory Organs (UROs): (continued) 7. Larynx (or voice box) See Fig 19.7, page 738. b. Voice production Mucous membranes form 2 pairs of folds: upper ventricular folds (false vocal cords); lower vocal folds (true vocal cords); space between them = glottis. Sound originates from vibration of the vocal folds, but other structures (pharynx, mouth, nasal cavity, and paranasal sinuses) convert that sound into recognizable speech. Lower Respiratory Organs: Trachea (windpipe) See Fig 19.8, page 738. Location = mediastinum; anterior to esophagus; extends from larynx to T5; Structure: 16-20 incomplete rings of hyaline cartilage = C-rings; Rings are completed by trachealis muscle and elastic CT facing esophagus; See Fig 19.9, page 739. lined by mucous membranes (pseudostratified columnar ET); See Fig 19.10, page 739. Carina = point where trachea divides into right & left bronchus; Function = support against collapse; continue to warm, moisten & filter air. II. ORGANS OF THE RESPIRATORY SYSTEM B. Lower Respiratory Organs: 2. Bronchial tree within lungs See Fig 19.12, page 740. a. primary (1o) bronchus leads into each lung and then branches into b. secondary (2o) bronchi, which branch to each lobe and then branch into c. tertiary (3o) bronchi which each serve one of 10 lobules (bronchopulmonary segment); that divide into bronchioles which branch several times into tubes called e. terminal bronchioles. 3. Structure of the Respiratory Tubes a. Each terminal bronchiole subdivides into microscopic branches called… Fig 19.14, page 741. respiratory bronchioles (lined by simple squamous epithelium), which subdivide into several (2-11)… alveolar ducts, which terminate into numerous… alveoli and alveolar sacs (2-3 alveoli that share a common opening). With this extensive branching: Epithelium changes from ciliated pseudostratified columnar epithelium to non-ciliated simple columnar epithelium in terminal bronchioles; Cartilage decreases; Smooth muscle increases (innervated by ANS and hormones): Parasympathetic and histamine constrict bronchioles (i.e. bronchoconstriction); Sympathetic and epinephrine dilate bronchioles (i.e. bronchodilation). II. ORGANS OF THE RESPIRATORY SYSTEM B. Lower Respiratory Organs: 4. Function of the Respiratory Tubes and Alveoli ALVEOLI (microscopic air sacs) See Fig 19.15, page 741 & Fig 19.33, page 757. wall consists of two types of epithelial cells and macrophages; Type I Alveolar cells form a continuous simple squamous lining of the alveolar wall; Type II Alveolar cells interrupt above lining and secrete surfactant: complex mixture = detergent; lowers surface tension and prevents alveolar collapse. Alveolar Macrophages remove dust particles and other debris from alveolar spaces. See scanning electron micrographs of alveoli on page 742. Alveolar-Capillary (Respiratory) Membrane See Fig 19.33, page 757. Composition: simple squamous epithelium of alveolus; basement membrane of alveolus; endothelium of the lung capillary; basement membrane of lung cap. Structure = thin (0.5 um in thickness). Function = allows for rapid diffusion of gases (from [high] to [low]). External Respiration. *The lungs contain more than 300 million alveoli = SA of 70m2 for gas exchange at one time! Blood Supply to Lungs (two fold): pulmonary circuit (deoxygenated blood); Oxygenated blood is delivered through bronchial arteries (off thoracic aorta). II. ORGANS OF THE RESPIRATORY SYSTEM B. Lower Respiratory Organs: LUNGS See Fig 19.12, page 740. Location = thoracic cavity; Description: paired, cone-shape organs; covered by pleural (serous) membranes: visceral pleura; parietal pleura; pleural cavity filled with serous fluid. * In contrast to the lubrication function we attributed to serous fluid in the past, the pleural fluid has a very high surface tension that allows the two membranes to act as one. Gross Anatomy: Each lung is divided into lobes by fissures: Right lung has 3 lobes; Left lung has 2 lobes. Each lobe: receives a secondary bronchus; is divided into lobules (bronchopulmonary segment) Each lobule: See Fig 19.14, page 741. is wrapped in elastic CT; contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole. PHYSIOLOGY OF RESPIRATION Recall that the function of the respiratory system is to supply cells with oxygen and remove carbon dioxide. The three basic processes are pulmonary ventilation, external respiration and internal respiration. Breathing Mechanism (Pulmonary Ventilation) Breathing involves two actions, inspiration & expiration. Inspiration (inhalation) = breathing air in. Force necessary is atmospheric pressure: Fig 19.21, page 746. When the diaphragm is at rest (curved upward): The air pressure outside the lungs is equal to the air pressure inside the lungs (1 atm or 760 mm Hg). The thoracic cavity has a given size and volume. During inspiration: See Fig 19.23, page 747. The diaphragm muscle pushes downward; The size of thoracic cavity increases; The pressure in the thoracic cavity decreases (758 mm Hg) (Boyles' Law); The air pressure inside the thoracic cavity (lungs) is less than the atmospheric pressure and therefore air rushes into lungs to equalize the pressure gradient. Pleural Membranes aid in inspiration: See Fig 19.20, page 744. Serous fluid between membranes primarily contains water; The water in the serous fluid has great surface tension and therefore, Membranes move together: thoracic cage expands; parietal pleura expands; visceral pleura expands; lungs expand. Contraction of the external intercostal muscles also aid inspiration. PHYSIOLOGY OF RESPIRATION Breathing Mechanism (Pulmonary Ventilation) Expiration = breathing out depends on two factors: See Fig 19.25, page 749. the elastic recoil of tissues that were stretched during inspiration (i.e. tissues bouncing back to shape). the inward pull of surface tension due to the alveolar fluid. * See Summary of inspiration and expiration in Table 19.2, page 747 and Table 19.3, paged 749. Atelectasis (Collapsed Lung) At the end of an expiration, the alveoli tend to recoil inward and collapse on themselves; Surfactant (mixture of phospholipid & proteins) produced by Type II Alveolar cells decreases the surface tension in the lungs; As the alveoli become smaller during expiration, the surfactant overcomes the pressure differential and allows the alveoli to remain inflated. * Respiratory Distress Syndrome (RDS) in newborns (collapsed lungs) occurs due to the lack of surfactant in the alveoli. * See purple box on page 747. PHYSIOLOGY OF RESPIRATION Breathing Mechanism (Pulmonary Ventilation) 4. Respiratory Volumes and Capacities See Fig 19.26, page 749. a. are measured by a spirometer; include the following 4 volumes from which 4 capacities may be calculated: Tidal Volume = amount (volume) of air that enters the lungs during normal inspiration and leaves the lungs during normal expiration; approximately 500 ml; Inspiratory Reserve Volume (IRV) = the amount of air the can be forcibly inhaled after a normal tidal inspiration; approximately 3000 ml; Expiratory Reserve Volume (ERV) = the amount of air that can be forcibly exhaled after a normal tidal expiration; approximately 1100 ml; Residual Volume (RV) = amount of air that always remains in lungs; 1200 ml; Vital Capacity (VC) = the maximum amount of air that can be exhaled after a maximum inhalation; VC = TV + IRV + ERV = 4600 ml. Inspiratory Capacity = total amount of air that can be inspired after a tidal expiration. IC = TV + IRV Functional Residual Capacity = amount of air left in the lungs after a tidal expiration. FRC = ERV + RV Total Lung Capacity = VC + RV; approximately 6 L. See Summary Table 19.4, page 750. 5. Alveolar Ventilation Minute Ventilation (MV) = TV X RR (respiratory rate) Amount of air that enters and exits respiratory system in one minute About 6000mL Anatomic dead space (ADS) – air space in respiratory passageways not involved in gas exchange = 150mL Alveolar ventilation = the actual amount of air involved in gas exchange AV = (TV – ADS) X RR AV = (500mL – 150mL) X 12 breaths per minute AV = 350mL X 12 b/m AV = 4200mL PHYSIOLOGY OF RESPIRATION A. Breathing Mechanism (Pulmonary Ventilation) 6. Non-Respiratory Air Movements Table 19.5, page 751 Modified respiratory movements occur in addition to normal breathing; usually the result of reflexes. a. Cough = sends blast of air through and clears lower respiratory tract; b. Sneeze = forcefully expels air through nose & mouth; c. Laugh = a deep breath released in a series of short convulsive expirations; d. Hiccup = spasmodic contraction of diaphragm; e. Yawn = deep inspiration through open mouth; (ventilates alveoli). CONTROL OF BREATHING Normal breathing = rhythmic; involuntary. Nervous Control = Respiratory Center: located in pons & medulla of brain stem; See Fig 19.28, page 753. Medullary Rhythmicity area composed of dorsal respiratory group which controls the basic rhythm of breathing; ventral respiratory group which controls forceful breathing. Pneumotaxic area = pons: controls rate of breathing. * See Fig 19.29, page 754 for Summary of Nervous Control of Breathing CONTROL OF BREATHING C. Factors Affecting Breathing See Fig 19.30, page 755. Chemoreceptors in carotid & aortic bodies of some arteries are sensitive to: Low levels of oxygen; High levels of CO2 ; affect chemosensitive areas (central chemoreceptors) of respiratory center and breathing rate and depth increases. Effector Sites: diaphragm/intercostals smooth muscle of terminal bronchioles Hyperventilation rapid, shallow breathing increases O2 level; breathing into paper bag rich in CO2 normalizes gas concentrations Factors that influence breathing: See Table 19.6, page 756. Stretch of Tissues; Inflation Reflex – prevent over inflation Low blood oxygen; High Blood carbon dioxide; Low pH; Others: temperature, pain, and irritation of airways. ALVEOLAR GAS EXCHANGES (External Respiration) See Fig 19.33, page 757, and Fig 19.35, page 758. Definition = the exchange of oxygen and carbon dioxide between the alveoli and lung blood capillaries. The pressure of gas determines the rate at which it will diffuse from region to region (Dalton's Law). Air is a mixture of gases: 78% Nitrogen 21% Oxygen .04% Carbon Dioxide In a mixture of gases, the amount of pressure that each gas creates = partial pressure. In air: O2 = 21%; PO2 = 104 mm Hg CO2 = .04%; PCO2 = 40 mm Hg The partial pressure of a gas is directly related to the concentration of that gas in a mixture.(Dalton’s Law of Partial Pressure) 199453526606500Diffusion of gases through the respiratory membrane proceeds from where a gas is at high pp low pp. Alveolus PCO2 = 40 mm Hg PO2 = 104 mm Hg __________________________________________________________________ PCO2 = 45 mm Hg PO2 = 40 mm Hg Capillary 43948359715500 Therefore, CO2 will flow from lung capillary alveolus & 359473514605000O2 will flow from alveolus lung capillary. The rate of diffusion of gases also depends on a number of factors, including the following: gas exchange surface area; diffusion distance; breathing rate and depth. INTERNAL RESPIRATION Definition = the exchange of oxygen and carbon dioxide between tissue capillaries and tissue cells. In tissue cell: pCO2 = 45; pO2 = 40; In tissue cap: pCO2 = 40; pO2 = 95. See Figure 19.37, page 761. Therefore, oxygen moves from the tissue cap into the tissue cell and carbon dioxide moves from the tissue cell into the tissue cap. GAS TRANSPORT (in Blood) Oxygen binds with hemoglobin (Hb) in red blood cells to form oxyhemoglobin; A weak bond is formed so oxygen can be delivered (released into) to tissues when needed. The release of oxygen from hemoglobin depends on many factors: high blood [CO2]; low blood pH (acidity); high blood temperature. See oxyhemoglobin dissociation curves Figures 19.38, 19.39, page 761 To remember these conditions, think of what happens in a skeletal muscle during exercise, when oxygen is required. Carbon Monoxide (CO) binds to hemoglobin more efficiently than oxygen. If the hemoglobin (that is suppose to bind with oxygen) is bound to CO, much less Hb is available to bind and transport oxygen to the tissues; Hypoxia results. GAS TRANSPORT Carbon Dioxide (CO2) CO2 is transported in 3 forms: dissolved CO2= 7% carbaminohemoglobin= 23% bicarbonate ions= 70% In tissues, CO2 is produced by cellular respiration. This CO2 combines with H2O to form H2CO3 (Carbonic acid) which then dissociates under the influence of carbonic anhydrase to release H+ and bicarbonate ion (HCO3-): 3251835546100021088355461000CO2 + H2O H2CO3 H+ + HCO3- RXN is reversed in lungs & CO2 is expelled during expiration. LIFE SPAN CHANGES Exposure to pollutants, smoke, etc., increases the risk of developing respiratory illnesses. Loss of cilia, thickening of mucus, and impaired macrophages increases the risk of infection as one ages. Breathing becomes more difficult as one ages due to: calcified cartilage skeletal changes altered posture replacement of bronchiole smooth muscle by fibrous connective tissue. Vital Capacity decreases with age. Homeostatic Imbalances: Disorders of the Respiratory System Deviated Septum. See purple box on page 733. Effects of Cigarette Smoking. See Clinical Application 19.1, pages 735. Epiglottitis. See purple box on page 739. Cystic Fibrosis. See purple box on page 743. Lung Irritants. See Clinical Application 19.2, page 745. Respiratory Distress Syndrome. See purple box on page 747. Pneumothorax. See purple box on page 748. Respiratory Disorders that Decrease Ventilation. See Clinical Application 19.3, page 752. Disorders Impairing Gas Exchange. See Clinical Application 19.5, page 759. Other Interesting Topics Concerning the Respiratory System Tracheotomy. See page 739 and Fig 19.11, page 739. Bronchoscopy. See purple box on page 742. Artificial Respiration. See purple box on page 743. Exercise and Breathing. See Clinical Application 19.4, page 756. Clinical Terms Related to the Respiratory System See pages 764 and 766. Innerconnections of the Respiratory System See page 765. Chapter 19 Respiratory System Describe the general functions of the respiratory system. It functions to remove particles from incoming air and transport it from outside the body into and out of the lungs. It houses the structures where gas exchange takes place between the air and the blood. Distinguish between the upper and lower respiratory tracts. The upper respiratory tract includes the nose, nasal cavity, sinuses, pharynx, larynx, and the upper portion of the trachea. The lower respiratory tract consists of the lower portion of the trachea, the bronchial tree, and the lungs. Explain how the nose and nasal cavity filter incoming air. The nose contains internal hairs that help prevent the entrance of the relatively large particles sometimes carried in the air. The nasal cavity is lined with a mucous membrane that has goblet cells that secrete sticky mucus. This mucus traps dust and other small particles entering with the air. Name and describe the locations of the major sinuses, and explain how a sinus headache may occur. The major sinuses are located within, and named from, the maxillary, frontal, ethmoid, and sphenoid bones in the skull. Inflamed and swollen mucous membranes due to nasal infections or allergic reactions may block mucous secretion drainage, causing pressure and a headache. Distinguish between the pharynx and the larynx. The pharynx is located behind the oral cavity and between the nasal cavity and the larynx. It functions as a passageway for food from the oral cavity to the esophagus. It also serves as a passageway for air from the nasal cavity to the larynx. It also serves as a resonance chamber for producing the sounds of speech. The larynx is an enlargement at the top of the trachea and below the pharynx. It serves as a passageway for air moving in and out of the trachea, functions to prevent foreign objects from entering the trachea, and houses the vocal cords. Name and describe the locations and functions of the cartilages of the larynx. Thyroid cartilage—located in the front of the neck. Commonly called the Adam’s apple. Protects the larynx. Cricoid cartilage—located below the thyroid cartilage. Marks the lowermost portion of the larynx. Protects the larynx. Epiglottic cartilage—attached to the upper border of the thyroid cartilage and supports the epiglottis. Allows for opening and closing of the epiglottis. Arytenoid cartilage—located above and on either side of the cricoid cartilage. Serves as an attachment for muscles that regulate vocal cord tension for speech. Aids in closing the larynx for swallowing. Corniculate cartilage—attached to the tips of the arytenoid cartilages. Serves as an attachment for muscles that regulate vocal cord tension for speech. Aids in closing the larynx for swallowing. Cuneiform cartilages—small structures in the mucous membrane between the epiglottic and the arytenoid cartilages. They stiffen soft tissue in this region. Distinguish between the false vocal cords and the true vocal cords. The false vocal cords are the upper folds of tissue found in the larynx. They are called false because they do not function in the production of sounds. The true vocal cords are the lower folds of tissue found in the larynx. They contain muscle tissue and elastic fibers that are responsible for vocal sounds. Compare the structure of the trachea with the structure of the branches of the bronchial tree. The trachea is a flexible cylindrical tube. There are about twenty C-shaped pieces of hyaline cartilage one above the other. The open ends are directed posteriorly and the gaps are filled with smooth muscle and connective tissues. The branches of the bronchial tree are similar but the C-shaped cartilaginous rings are replaced with cartilaginous plates. As the branches become finer and finer, the amount of cartilage decreases and finally disappears in the bronchioles. List the successive branches of the bronchial tree, from the primary bronchi to the alveoli. Primary bronchi divide into secondary (lobar) bronchi. The secondary bronchi divide into tertiary (segmental) bronchi. The tertiary bronchi divide into intralobular bronchioles. The intralobular bronchioles divide into terminal bronchioles. The terminal bronchioles divide into respiratory bronchioles. The respiratory bronchioles connect with the alveolar ducts. The ducts lead to alveolar sacs. Alveoli are the microscopic air sacs that make up the alveolar sac. Describe how the structure of the respiratory tube changes as the branches become finer. The C-shaped cartilaginous rings are replaced with cartilaginous plates at the point where the bronchi enter the lung. The amount of cartilage decreases as the tubes become finer and disappear in the bronchioles. As the cartilage decreases, the amount of smooth muscle surrounding the tube increases. The lining of the larger tubes consist of pseudostratified, ciliated columnar epithelium (PCCE) with a lot of goblet cells for mucus secretion. Along the way, the number of goblet cells and the height of the epithelial cells decline. Cilia become scarce. In the finer tubes, beginning with the respiratory bronchioles, the lining is cuboidal epithelium. In the alveoli, the lining consists of simple squamous epithelium. Explain the functions of the respiratory tubes. The respiratory tubes filter the incoming air and distribute it to the alveoli in all parts of the lungs. At the alveolar level, gas exchange can take place. Distinguish between the visceral pleura and the parietal pleura. The visceral pleura is the lining that covers the outside of the lungs. The parietal pleura is the lining that covers the pleural cavity. Name and describe the locations of the lobes of the lungs. The right lung consists of three lobes called the superior, middle, and inferior. It is located in the right side of the chest. The left lung consists of two lobes called the superior and inferior. It is located on the left side of the chest. Explain how normal inspiration and forced inspiration are accomplished. Normal inspiration is the result of the differing air pressures within the lung and in the atmospheric pressure outside the lungs. When the pressure inside the lungs decreases, the air flows into the body by way of the atmospheric pressure. Forced inspiration can be accomplished by further contraction of the diaphragm and the external intercostal muscles. Additional muscles, such as the pectoralis minors and sternocleidomastoids, can also be used to enlarge the thoracic cavity, thereby decreasing the internal pressure to a greater extent. Define surface tension, and explain how it aids breathing mechanism. Surface tension is the great attraction for water molecules to attach to one another. This force is used in breathing to hold the moist surfaces of the pleural membranes together. It also helps to expand the lung in all directions. Define surfactant, and explain its function. Surfactant is a lipoprotein mixture continually secreted into the alveolar air spaces. It acts to reduce the surface tension and decreases the tendency of the alveoli to collapse when the lung volume is low. Define compliance. Compliance (distensibility) is the ease with which lungs can be expanded as a result of pressure changes occurring during breathing. Explain how normal expiration and forced expiration are accomplished. Normal expiration is accomplished by the elastic recoil of the lung tissues and the decrease in the diameter of the alveoli as a result of surface tension. Forced expiration can be accomplished by contracting the internal intercostal muscles to pull the ribs and sternum downward and inward, increasing the pressure in the lungs. The abdominal wall muscles also can be used to squeeze the abdominal organs inward and increase the abdominal cavity pressure. This translates in forcing the diaphragm even higher against the lungs. Distinguish between the vital capacity and total lung capacity. The vital capacity is the maximum amount of air a person can exhale after taking the deepest breath possible. Total lung capacity is the vital capacity added to the residual volume. The residual volume is the amount of air that remains in the lungs even after forceful expiration. Distinguish between anatomic, alveolar, and physiologic dead spaces. Anatomic dead space is the volume of air that remains in the trachea, bronchi, and bronchioles, as these tubes do not participate in gas exchange. Alveolar dead space consists of air sacs in some regions of the lungs that are nonfunctional due to poor blood flow. Physiologic dead space is the combination of anatomic and alveolar dead spaces. Distinguish between minute respiratory volume and alveolar ventilation rate. The minute respiratory volume is the amount of new atmospheric air that is moved into the respiratory passages each minute. This is ascertained by multiplying the tidal volume by the breathing rate. The alveolar ventilation rate is the volume of new air that does reach the alveoli and is available for gas exchange. This is calculated by subtracting the physiologic dead space from the tidal volume and then multiplying the result by the breathing rate. Compare the mechanisms of coughing and sneezing, and explain the function of each. A cough involves taking a deep breath, closing the glottis, and forcing air upward from the lungs against the closure. The glottis is then suddenly opened, and a blast of air is forced upward from the lower respiratory tract. This action clears the lower respiratory passages. A sneeze is usually initiated by a mild irritation in the linings of the nasal cavity, and in response, a blast of air is forced up through the glottis. This time the air is directed into the nasal passages by depressing the uvula, thus closing the opening between the pharynx and the oral cavity. This action clears the upper respiratory passages. Explain the function of yawning. Yawning is thought to aid respiration by providing an occasional deep breath. Describe the location of the respiratory center, and name its major components. The respiratory center is found widely scattered throughout the pons and medulla oblongata in the brain stem. The two major components are the medullary rhythmicity center and the pneumotaxic area. The medullary rhythmicity center is further subdivided into the dorsal respiratory group and the ventral respiratory group. Describe how the basic rhythm of breathing is controlled. The dorsal respiratory group controls the basic rhythm of breathing. The neurons emit bursts of impulses that signal the diaphragm and other inspiratory muscles to contract. The neurons remain inactive during exhalation and then begin the bursts of impulses anew. Explain the function of the pneumotaxic area of the respiratory center. The neurons in this area transmit impulses to the dorsal respiratory group continuously and regulate the duration of the inspiratory bursts originating from the dorsal respiratory group. This is where rate of respiration is controlled. Explain why increasing blood concentrations of carbon dioxide and hydrogen ions have similar effects on the respiratory center. The similarity of the effects of carbon dioxide and hydrogen ions is a consequence of the fact that carbon dioxide combines with water in the cerebrospinal fluid to form carbonic acid. Carbonic acid then ionizes releasing hydrogen ions and bicarbonate ions. If these concentrations rise, the central chemoreceptors signal the respiratory center and the breathing rate increases. Describe the function of the peripheral chemoreceptors in the carotid and aortic bodies of certain arteries. The chemoreceptors, known as the peripheral chemoreceptors, function to detect changes in the blood oxygen concentrations. When changes are detected, impulses are transmitted to the respiratory center, and the breathing rate is increased. These are only triggered by an extremely low blood oxygen concentration. This seems to support the statement that oxygen seems to play only a minor role in the control of normal respiration. Describe the inflation reflex. The inflation reflex occurs when the stretch receptors in the visceral pleura, bronchioles, and alveoli are stimulated as a result of lung tissues being overstretched. Sensory impulses of this reflex travel via the vagus nerves to the pneumotaxic area of the respiratory center. This center causes the duration of the inspiratory movements to shorten. This reflex prevents overinflation of the lungs during forceful breathing. Discuss the effects of emotions on breathing. Strong emotional upset or sensory stimulation may alter the normal breathing pattern. Because control of the respiratory muscles is voluntary, we can alter breathing patterns consciously or even stop it altogether for a short time. Define hyperventilation, and explain how it affects the respiratory center. Hyperventilation is the action of breathing readily and deeply. This causes a lowered blood carbon dioxide concentration. This can result in the ability to hold the breath longer, as it takes a longer time for the carbon dioxide levels to build up to a concentration that will overwhelm the respiratory center. Define respiratory membrane, and explain its function. The respiratory membrane consists of at least two thicknesses of epithelial cells and a layer of fused basement membranes separating the air in an alveolus from the blood in the capillaries. This membrane is the site at which gas exchange occurs between the blood and the alveolar air. Explain the relationship between the partial pressure of a gas and its rate of diffusion. The partial pressure of a gas within the blood will use diffusion to equalize the pressure between its blood concentration and its surroundings. Summarize the gas exchanges that occur through the respiratory membrane. The PO2 level in the atmospheric pressure is higher than that in the blood. This allows for diffusion of oxygen into the blood. The PCO2 level is higher in the blood than in the atmosphere so diffusion occurs out of the blood into the atmosphere. Describe how oxygen is transported in blood. Over 98% of the oxygen is transported in the blood on the hemoglobin molecules. The remainder is dissolved in the blood plasma. List three factors that increase release of oxygen from the blood. The blood concentration of carbon dioxide. The blood pH. The blood temperature. Explain why carbon monoxide is toxic. The toxic effect of carbon monoxide occurs because it combines with the hemoglobin more effectively than does oxygen. It also does not dissociate readily from hemoglobin, thereby leaving less hemoglobin available for oxygen transport. List three ways that carbon dioxide is transported in blood. It can be dissolved in the blood plasma. It can combine with hemoglobin and form carbaminohemoglobin. It can be transported as part of a bicarbonate ion. Explain the function of carbonic anhydrase. Carbonic anhydrase is an enzyme that catalyzes the reaction between carbon dioxide and water to form carbonic acid. Define chloride shift. Chloride shift is the movement of chloride ions from the blood plasma into the red blood cells as bicarbonate ions diffuse out of the red blood cells into the plasma. Describe the changes that make it harder to breathe with advancing years. Cartilage between the sternum and ribs calcifies and stiffens. Changes in shape of thoracic cavity into a “barrel chest.” In the bronchioles, fibrous connective tissue replaces some smooth muscle, decreasing contractility. Chapter 19: Respiratory System I. Introduction A. The respiratory system consists of B. Respiration is called C. Respiration consists of D. Ventilation is E. External respiration is F. Internal respiration is G. Cellular respiration is II. Why We Breathe A. Respiration enables cells to B. Without oxygen as a final electron acceptor, much energy C. A metabolic waste of respiration is D. Carbon dioxide, when it reacts with water, forms which contributes to the pH of E. Too much carbon dioxide will lower F. explain why we must obtain oxygen and get rid of carbon dioxide. III. Organs of the Respiratory System A. Introduction 1. The upper respiratory tract includes 2. The lower respiratory tract includes B. Nose 1. The nose is supported internally by 2. Nostrils are 3. Internal hairs of nostrils prevent C. Nasal Cavity 1. The nasal cavity is 2. The nasal septum is 3. The nasal cavity is separated from the cranial cavity by ___________________ and from the oral cavity by 4. Nasal conchae are located and divide the nasal cavity into 5. Nasal conchae function to 6. The lining of the upper portion of the nasal cavity contains 7. Most of the nasal cavity conducts air 8. The mucous membrane lining the nasal cavity contains 9. The functions of the mucous membrane of the nasal cavity are 10. Cilia of the nasal cavity function to D. Sinuses 1. Sinuses are 2. Bones that contain sinuses are 3. The functions of sinuses are E. Pharynx 1. The pharynx is located 2. Functions of the pharynx are F. Larynx 1. The larynx is 2. The functions of the larynx are 3. The larynx is composed of 4. The cartilages of the larynx are 5. The thyroid cartilage is located 6. The cricoid cartilage is located 7. The epiglottic cartilage is located 8. The epiglottis is 9. The functions of the epiglottis are 10. The arytenoid cartilages are located 11. The corniculate cartilages are located 12. The arytenoids and corniculate cartilages are attachment sites for 13. The cuneiform cartilages are located and function to 14. False vocal cords are located and are composed of 15. The function of the false vocal cords is 16. The true vocal cords are located and are composed of 17. The functions of the true vocal cords are 18. A higher pitch of the voice is produced by and a lower pitch is produced by 19. The loudness of a vocal sound depends on 20. The glottis is 21. The mucous membrane that lines the larynx continues to filter incoming air by G. Trachea 1. The trachea is and is located 2. The trachea splits into 3. The inner wall of the trachea is lined with 4. The mucous membrane of the trachea functions to 5. The wall of the trachea is composed of 6. The cartilaginous rings of the trachea prevent 7. The soft tissues that complete the rings in the back of the trachea allow 8. A blocked trachea causes 9. A tracheostomy is H. Bronchial Tree 1. Introduction a. The bronchial tree consists of b. Primary bronchi are c. The carina is d. Each bronchus, accompanied by , enters its respective lung. 2. Branches of the Bronchial Tree a. Primary bronchi branch into b. Secondary bronchi branch into c. Tertiary bronchi branch into d. A bronchopulmonary segment is e. Intralobular bronchioles branch into f. Terminal bronchioles branch into g. Respiratory bronchioles branch into h. Alveolar ducts give rise to i. Alveolar sacs are j. Alveoli are 3. Structure of the Respiratory Tubes a. The structure of a bronchus is similar to that of the trachea except b. Finer branches of the respiratory tree have decreased amounts of __________________ and increased amounts of c. fibers are scattered throughout the lungs. d. Other changes in the tubes of the respiratory tree as they get smaller are 4. Functions of the Respiratory Tubes and Alveoli a. The branches of the bronchial tree function to b. The alveoli function to I. Lungs 1. The lungs are _____________ shaped and located 2. The right and left lungs are separated by ______________ and enclosed by 3. The hilus of the lung is 4. Visceral pleura is 5. Parietal pleura is 6. The pleural cavity is 7. The functions of serous fluid in the pleural cavity are 8. The lobes of the right lung are 9. The lobes of the left lung are 10. Lobules of the lungs are IV. Breathing Mechanism A. Introduction 1. Breathing or ventilation is 2. Inspiration is 3. Expiration is B. Inspiration 1. The force that moves air into the lungs is 2. If the pressure inside the lungs and alveoli decreases, outside air will 3. The diaphragm is located and is composed of 4. The nerves that stimulate the diaphragm are 5. When the diaphragm contracts it moves and the thoracic cavity 6. When the thoracic cavity enlarges, the intra-alveolar pressure 7. When intra-alveolar pressure falls, air is 8. The action of external intercostals muscles is _________________________ which the size of the thoracic cavity. 9. When intercostals muscles move the thoracic wall upward and outward, the ________________________ and move. 10. Movement of the parietal and visceral pleura upward and outward expands 11. Surface tension is 12. Surfactant is located and functions to 13. If a person needs to take a deeper than normal breath, the diaphragm and external intercostals muscles 14. Other muscles that can be used to enlarge the thoracic cavity are 15. Compliance is 16. In a normal lung, compliance as lung volume increases because 17. Factors that lead to a decrease in lung compliance are C. Expiration 1. The forces responsible for normal expiration come from 2. As the diaphragm and external intercostals muscles relax, the elastic tissues cause the lungs to 3. Air is forced out of respiratory passageways because 4. Muscles that aid in a more forceful exhalation than normal are D. Respiratory Volumes and Capacities 1. Spirometry is 2. A respiratory cycle is 3. Tidal volume is 4. Inspiratory reserve volume is 5. Expiratory reserve volume is 6. Residual volume is 7. Vital capacity is 8. Inspiratory capacity is 9. Functional residual capacity is 10. Total lung capacity is 11. Anatomic dead space is 12. Alveolar dead space is 13. Physiologic dead space is 14. A spirometer measures 15. Respiratory volumes and capacities are used to evaluate E. Alveolar Ventilation 1. Minute ventilation is and equals 2. The volume of air that reaches alveoli is calculated by 3. Alveolar ventilation rate is and is a major factor affecting F. Nonrespiratory Air Movements 1. Nonrespiratory air movements are 2. Examples of nonrespiratory air movements are 3. Nonrespiratory air movements usually result from 4. Coughing involves 5. The function of a sneeze is 6. Laughing involves 7. A hiccup is caused by 8. The function of a yawn is V. Control of Breathing A. Respiratory Center 1. The respiratory center is 2. The functions of the respiratory center are 3. The components for the respiratory center are located 4. The medullary rhythmicity includes 5. The dorsal respiratory group is responsible for 6. The functions of the ventral respiratory center are 7. The functions of the pneumotaxic area are B. Factors Affecting Breathing 1. Partial pressure of a gas is 2. High concentrations of carbon dioxide in blood are detected by 3. In response to high carbon dioxide levels, the respiratory center triggers in alveolar ventilation, which decreases in blood. 4. High concentrations of hydrogen ions in blood or cerebrospinal fluid are detected by 5. In response to high hydrogen ion levels, the respiratory center triggers in alveolar ventilation, which decreases in blood. 6. Low concentrations of oxygen in blood are detected by 7. When blood levels of oxygen are low, ventilation and the concentration of oxygen in blood 8. The inflation reflex helps regulate 9. The inflation reflex occurs when 10. The inflation reflects prevents 11. Hyperventilation is and it lowers VII. Alveolar Gas Exchanges A. Alveoli 1. Alveoli are 2. An alveolus consists of 3. Alveolar pores are 4. Alveolar macrophages are and function to B. Respiratory Membrane 1. The respiratory membrane is composed of 2. The respiratory membrane is the site of C. Diffusion Through the Respiratory Membrane 1. Molecules diffuse from 2. Carbon dioxide diffuses from blood in pulmonary capillaries to alveolar air because 3. Oxygen diffuses from alveolar air to blood in pulmonary capillaries because 4. Factors that affect diffusion across the respiratory membrane are 5. Diseases that harm respiratory membranes are 6. Breath analysis can detect alcohol in the blood because VIII. Gas Transport A. Introduction 1. The blood transports oxygen and carbon dioxide between 2. As oxygen and carbon dioxide enter blood, they B. Oxygen Transport 1. Almost all the oxygen carried in blood is bound to 2. A small amount of oxygen is carried in blood dissolved 3. Hemoglobin consists of 4. Each heme group contains an 5. Oxyhemoglobin is 6. Deoxyhemoglobin is 7. Factors that promote the release of oxygen from hemoglobin are C. Carbon Dioxide Transport 1. Blood flowing through capillaries gains carbon dioxide because 2. Carbon dioxide is transported to lungs in one of the following three forms: 3. Carbaminohemoglobin is 4. Hemoglobin can carry oxygen and carbon dioxide at the same time because 5. The most important carbon dioxide transport mechanism involves 6. Carbon dioxide forms when it reacts with water. 7. Carbonic anhydrase is and is located 8. Carbonic acid dissociates into 9. The chloride shift is and functions to 10. When blood reaches the pulmonary capillaries, _____________________ recombine to form 11. In the pulmonary capillaries, carbonic acid becomes 12. In the lungs, carbon dioxide diffuses IX. Life-Span Changes A. Changes in the respiratory system over a lifetime reflect B. People who have been exposed to foul air are more likely to develop C. The factors that change the ability of the respiratory system to clear pathogens from The lungs are D. Factors that contribute to an overall increase in effort required to breathe are E. The microscopic changes that occur in the lungs are Chapter 19: Respiratory System I. Introduction A. The respiratory system consists of passages that filter incoming air and transport it to the body, into the lungs, and to the many microscopic air sacs where gases are exchanged. B. Respiration is the entire process o exchanging gases between the atmosphere and body cells. C. Respiration consists of ventilation, external respiration, transport of gases be the blood between lungs and body cells, internal respiration, and cellular respiration. D. Ventilation is the movement of air in and out of the lungs. E. External respiration is the exchange of gases between the air in the lungs and the blood F. Internal respiration is the exchange of gases between the blood and the body cells. G. Cellular respiration is oxygen utilization and production of carbon dioxide in body cells. II. Why We Breathe A. Respiration enables cells to harness the energy held in chemical bonds of nutrient molecules. B. Without oxygen as a final electron acceptor, much energy remains locked in nutrients. C. A metabolic waste of respiration is carbon dioxide. D. Carbon dioxide, when it reacts with water, forms carbonic acid which contributes to the pH of blood. E. Too much carbon dioxide will lower blood pH. F. Cellular respiration and control of blood pH explain why we must obtain oxygen and get rid of carbon dioxide. III. Organs of the Respiratory System A. Introduction 1. The upper respiratory tract includes nose, nasal cavity, sinuses, and pharynx. 2. The lower respiratory tract includes larynx, trachea, bronchial tree, and lungs. B. Nose 1. The nose is supported internally by muscle, bone, and cartilage. 2. Nostrils are openings through which air can enter and leave the nasal cavity. 3. Internal hairs of nostrils prevent entry of large particles carried in air. C. Nasal Cavity 1. The nasal cavity is a hollow space behind the nose. 2. The nasal septum is a structure that divides the nasal cavity into left and right halves. 3. The nasal cavity is separated from the cranial cavity by the cribiform plate of the ethmoid bone and from the oral cavity by by the hard palate. 4. Nasal conchae are located on the lateral walls of the nasal cavity and divide the nasal cavity into superior, inferior, and middle meatuses. 5. Nasal conchae function to support the mucous membranes that line the nasal cavity and to increase the surface area of the nasal cavity. 6. The lining of the upper portion of the nasal cavity contains olfactory receptors. 7. Most of the nasal cavity conducts air to and from the nasopharynx. 8. The mucous membrane lining the nasal cavity contains pseudostratified ciliated epithelium that is rich in mucous-secreting goblet cells. 9. The functions of the mucous membrane of the nasal cavity are to warm the air, to moisten the air, and to trap small particles entering the nasal cavity. 10. Cilia of the nasal cavity function to move mucous and any entrapped particles toward the pharynx. D. Sinuses 1. Sinuses are air-filled spaces located within skull bones. 2. Bones that contain sinuses are maxillae, frontal, ethmoid, and sphenoid. 3. The functions of sinuses are to reduce the weight of the skull and to serve as resonant chambers that affect the quality of the voice. E. Pharynx 1. The pharynx is located posterior to the oral cavity and between the nasal cavity and the larynx. 2. Functions of the pharynx are to move food into the esophagus, to move air into the larynx, and to aid in the production of sound. F. Larynx 1. The larynx is an enlargement in the airway superior to the trachea and inferior to the pharynx. 2. The functions of the larynx are to move air into the trachea, prevent foreign objects from entering the trachea, and to house vocal cords. 3. The larynx is composed of a framework of muscles and cartilages bound by elastic tissue. 4. The cartilages of the larynx are thyroid, cricoid, and epiglottic. 5. The thyroid cartilage is located just superior to the thyroid gland. 6. The cricoid cartilage is located inferior to the thyroid cartilage. 7. The epiglottic cartilage is located attached to the upper border of the thyroid cartilage. 8. The epiglottis is flaplike structure supported by the epiglottic cartilage. 9. The functions of the epiglottis are to prevent foods and liquids from entering the air passages and to allow air to pass into the trachea. 10. The arytenoid cartilages are located superior to and on either side of the cricoid cartilage. 11. The corniculate cartilages are located attached to the tips of the arytenoid cartilages. 12. The arytenoids and corniculate cartilages are attachments sites for muscles that help regulate tension on the vocal cords during speech and aid in closing the larynx during swallowing. 13. The cuneiform cartilages are located between the epiglottic and arytenoid cartilages and function to stiffen soft tissue in this region. 14. False vocal cords are located inside the larynx and are composed of muscle tissue and connective tissue with a covering of mucous membrane. 15. The function of the false vocal cords is to help close the larynx during swallowing. 16. The true vocal cords are located inferior to the false vocal cords and are composed of elastic fibers. 17. The functions of the true vocal cords are to produce sounds of speech. 18. A higher pitch of the voice is produced by increasing tension on true vocal cords and a lower pitch is produced by decreasing the tension on the cords. 19. The loudness of a vocal sound depends on upon the force of air passing over the vocal cords. 20. The glottis is the opening between vocal cords. 21. The mucous membrane that lines the larynx continues to filter incoming air by entrapping particles and moving them toward the pharynx by ciliary action. G. Trachea 1. The trachea is a flexible cylindrical tube and is located anterior to the esophagus in the thoracic cavity. 2. The trachea splits into right and left bronchi. 3. The inner wall of the trachea is lined with a ciliated mucous membrane that contains many goblet cells. 4. The mucous membrane of the trachea functions to filter incoming air and to move entrapped particles upward into the pharynx where the mucous can be swallowed. 5. The wall of the trachea is composed of C shaped pieces of hyaline cartilage, smooth muscle, and connective tissues. 6. The cartilaginous rings of the trachea prevent the trachea from collapsing and blocking the airway. 7. The soft tissues that complete the rings in the back of the trachea allow the esophagus to expand as food moves through it on the way to the stomach. 8. A blocked trachea causes asphyxiation. 9. A tracheostomy is the production of a temporary hole in the trachea. H. Bronchial Tree 1. Introduction a. The bronchial tree consists of branched airways leading from the trachea to the microscopic air sacs in the lungs. b. Primary bronchi are the first branches of the trachea. c. The carina is ridge of cartilage that separates the primary bronchi. d. Each bronchus, accompanied by blood vessels and nerves, enters its respective lung. 2. Branches of the Bronchial Tree a. Primary bronchi branch into secondary bronchi. b. Secondary bronchi branch into tertiary bronchi. c. Tertiary bronchi branch into intralobular bronchioles. d. A bronchopulmonary segment is a portion of a lung supported by a tertiary segment. e. Intralobular bronchioles branch into terminal bronchioles. f. Terminal bronchioles branch into respiratory bronchioles. g. Respiratory bronchioles branch into alveolar ducts. h. Alveolar ducts give rise to alveolar sacs. i. Alveolar sacs are thin-walled, closely packed outpouchings of the alveolar ducts. j. Alveoli are thin-walled, microscopic air sacs that open to an alveolar sac. 3. Structure of the Respiratory Tubes a. The structure of a bronchus is similar to that of the trachea except the C shaped cartilaginous rings are replaced with cartilaginous plates where the bronchus enters the lung. b. Finer branches of the respiratory tree have decreased amounts of cartilage and increased amounts of smooth muscle. c. Elastic fibers are scattered throughout the lungs. d. Other changes in the tubes of the respiratory tree as they get smaller are the changes in cells types that line the airways. 4. Functions of the Respiratory Tubes and Alveoli a. The branches of the bronchial tree function to filter incoming air and distribute it to the alveoli in all parts of the lungs. b. The alveoli function to provide a large surface area of thin epithelial cells through which gas exchanges can occur. I. Lungs 1. The lungs are cone shaped and located the thoracic cavity. 2. The right and left lungs are separated by the heart and the mediastinum and enclosed by the diaphragm and thoracic cage. 3. The hilus of the lung is an indention on the medial surface of a lung. 4. Visceral pleura are serous membranes attached to the surfaces of the lungs. 5. Parietal pleura is a serous membrane that lines the thoracic cavity. 6. The pleural cavity is the potential space between the visceral pleura and parietal pleura. 7. The functions of serous fluid in the pleural cavity are to lubricate serous membranes and reduce friction during lung movements. 8. The lobes of the right lung are superior, middle, and inferior. 9. The lobes of the left lung are superior and inferior. 10. Lobules of the lungs are divisions of lung lobes. IV. Breathing Mechanism A. Introduction 1. Breathing or ventilation is the movement of air from outside the body into the bronchial tree and alveoli, followed by a reversal of this air movement. 2. Inspiration is inhalation. 3. Expiration is exhalation. B. Inspiration 1. The force that moves air into the lungs is atmospheric pressure. 2. If the pressure inside the lungs and alveoli decreases, outside air will flow into the airways. 3. The diaphragm is located just inferior to the lungs and is composed of skeletal muscle. 4. The nerves that stimulate the diaphragm are the phrenic nerves. 5. When the diaphragm contracts it moves inferiorly and the thoracic cavity enlarges. 6. When the thoracic cavity enlarges, the intra-alveolar pressure decreases. 7. When intra-alveolar pressure falls, air is moved into the airways. 8. The action of external intercostals muscles is to raise the ribs and elevates the sternum, which increases the size of the thoracic cavity. 9. When intercostals muscles move the thoracic wall upward and outward, the parietal pleura and visceral pleura move. 10. Movement of the parietal and visceral pleura upward and outward expands the lungs in all directions. 11. Surface tension is the attraction certain molecule to each other. 12. Surfactant is located in alveolar spaces and functions to reduce the alveoli’s tendency to collapse. 13. If a person needs to take a deeper than normal breath, the diaphragm and external intercostals muscles may contract to a greater extent. 14. Other muscles that can be used to enlarge the thoracic cavity are the pectoralis minors and sternocleidomastoids. 15. Compliance is the ease at which the lungs can expand as a result of pressure changes occurring during breathing. 16. In a normal lung, compliance decreases as lung volume increases because an inflated lung is more difficult to expand that a lung at rest. 17. Factors that lead to a decrease in lung compliance are conditions that obstruct air passages, destroy lung tissue, or impede lung expansion in other ways. C. Expiration 1. The forces responsible for normal expiration come from elactic recoil of lung tissues and from surface tension. 2. As the diaphragm and external intercostals muscles relax, the elastic tissues cause the lungs to recoil. 3. Air is forced out of respiratory passageways because intra-alveolar pressure rises above atmospheric pressure. 4. Muscles that aid in a more forceful exhalation than normal are internal intercostal muscles and abdominal wall muscles. D. Respiratory Volumes and Capacities 1. Spirometry is the measure of air volumes. 2. A respiratory cycle is one inspiration plus the following expiration. 3. Tidal volume is the amount of air that enters of leaves during a respiratory cycle. 4. Inspiratory reserve volume is the additional quantity of air after the resting tidal volume that can enter the lungs. 5. Expiratory reserve volume is the additional quantity of air that can exit the lungs after a resting tidal volume. 6. Residual volume is the amount of air that remains in the lungs after a forceful expiration. 7. Vital capacity is maximum amount of air that can be exhaled after taking the deepest breath possible. 8. Inspiratory capacity is maximum volume of air that can be inhaled following exhalation of tidal volume. 9. Functional residual capacity is volume of air that remains in the lungs following exhalation of tidal volume. 10. Total lung capacity is total volume of air that the lungs can hold. 11. Anatomic dead space is the space in airways. 12. Alveolar dead space is space in alveoli that do not carry out gas exchange due to poor blood flow. 13. Physiologic dead space is anatomical dead space plus alveolar dead space. 14. A spirometer measures respiratory air volumes. 15. Respiratory volumes and capacities are used to evaluate the course of respiratory illnesses. E. Alveolar Ventilation 1. Minute ventilation is the amount of new atmospheric air that is moved into the respiratory passages each minute and equals the tidal volume multiplied by the breathing rate. 2. The volume of air that reaches alveoli is calculated by subtracting the physiologic dead space from the tidal volume. 3. Alveolar ventilation rate is the volume of air that reaches alveoli multiplied by breathing rate and is a major factor affecting the concentrations of oxygen and carbon dioxide in alveoli. F. Nonrespiratory Air Movements 1. Nonrespiratory air movements are air movements that occur in addition to breathing. 2. Examples of nonrespiratory air movements are coughing, sneezing, crying and laughing. 3. Nonrespiratory air movements usually result from reflexes. 4. Coughing involves take a deep breath, closing the glottis, and forcing air upward from the lungs against the closure. Then the glottis is suddenly opened, and a blast of air is forced upward from the lower respiratory tract. 5. The function of a sneeze is to clear the upper respiratory passages. 6. Laughing involves taking a deep breath and releasing it in a series of short expirations. 7. A hiccup is caused by sudden inspiration due to a spasmodic contraction of the diaphragm while the glottis is closed. 8. The function of a yawn is to aid respiration by providing an occasional deep breath. V. Control of Breathing A. Respiratory Center 1. The respiratory center is composed of groups of neurons in the brainstem which controls breathing. 2. The functions of the respiratory center are to cause inhalation and exhalation, and to adjust the rate and depth of breathing. 3. The components for the respiratory center are located widely scattered throughout the pons and medulla oblongata. 4. The medullary rhythmicity area includes two groups of neurons that extend throughout the length of the medulla oblongata. 5. The dorsal respiratory group is responsible for the basic rhythm of breathing. 6. The functions of the ventral respiratory center are to generate impulses for more forceful breathing movements. 7. The functions of the pneumotaxic area are to regulate the duration of inspiratory bursts originating from the dorsal group. This area basically controls the rate of breathing. B. Factors Affecting Breathing 1. Partial pressure of a gas is amount of pressure each gas contributes. 2. High concentrations of carbon dioxide in blood are detected by central chemoreceptors. 3. In response to high carbon dioxide levels, the respiratory center triggers an increase in alveolar ventilation, which decreases carbon dioxide levels and hydrogen ions levels in blood. 4. High concentrations of hydrogen ions in blood or cerebrospinal fluid are detected by central chemoreceptors. 5. In response to high hydrogen ion levels, the respiratory center triggers an increase in alveolar ventilation, which decreases hydrogen ions in blood. 6. Low concentrations of oxygen in blood are detected by peripheral chemoreceptors. 7. When blood levels of oxygen are low, ventilation increases and the concentration of oxygen in blood increases. 8. The inflation reflex helps regulate the depth of breathing. 9. The inflation reflex occurs when stretch receptors in the visceral pleura, bronchioles, and alveoli are stimulated as lung tissues are stretched. 10. The inflation reflex prevents overinflation of the lungs. 11. Hyperventilation is rapid and deep breathing and it lowers the blood concentration of carbon dioxide. VII. Alveolar Gas Exchanges A. Alveoli 1. Alveoli are microscopic air sacs clustered at the distal ends of the finest respiratory tubes. 2. An alveolus consists of a tiny space surrounded by a thin wall that separates it from adjacent alveoli. 3. Alveolar pores are tiny openings in the walls of some alveoli. 4. Alveolar macrophages are phagocytic cells and function to destroy airborne agents that reach alveoli. B. Respiratory Membrane 1. The respiratory membrane is composed of two layers of epithelial cells and two basement membranes. 2. The respiratory membrane is the site of gas exchange between alveolar air and the blood. C. Diffusion Through the Respiratory Membrane 1. Molecules diffuse from regions where they are in higher concentration toward regions where they are in lower concentration. 2. Carbon dioxide diffuses from blood in pulmonary capillaries to alveolar air because the partial pressure of carbon dioxide is higher in the blood of pulmonary capillaries than in alveolar air. 3. Oxygen diffuses from alveolar air to blood in pulmonary capillaries because the partial pressure of oxygen is higher in alveolar air than in the blood of pulmonary capillaries. 4. Factors that affect diffusion across the respiratory membrane are surface area, distance, solubility of gases, partial pressure gradients, and diseases. 5. Diseases that harm respiratory membranes are pneumonia and emphysema. 6. Breath analysis can detect alcohol in the blood because the respiratory membrane is so thin that alcohol can diffuse into alveolar air and be exhaled. VIII. Gas Transport A. Introduction 1. The blood transports oxygen and carbon dioxide between the lungs and the body cells. 2. As oxygen and carbon dioxide enter blood, they dissolve in plasma or combine chemically with other atoms or molecules. B. Oxygen Transport 1. Almost all the oxygen carried in blood is bound to hemoglobin. 2. A small amount of oxygen is carried in blood dissolved in plasma. 3. Hemoglobin consists of two types of components called heme and globin. 4. Each heme group contains an atom of iron. 5. Oxyhemoglobin is the combination of oxygen and hemoglobin. 6. Deoxyhemoglobin is hemoglobin that is not carrying oxygen. 7. Factors that promote the release of oxygen from hemoglobin are a decrease in the partial pressure of oxygen, increasing blood concentrations of carbon dioxide, acidity, and increased temperatures. C. Carbon Dioxide Transport 1. Blood flowing through capillaries gain carbon dioxide because the tissues have a high partial pressure of carbon dioxide. 2. Carbon dioxide is transported to lungs in one of the following three forms: bound to hemoglobin, dissolved in plasma, or as bicarbonate ions. 3. Carbaminohemoglobin is the combination of carbon dioxide and hemoglobin. 4. Hemoglobin can carry oxygen and carbon dioxide at the same time because they bind at different sites on hemoglobin. 5. The most important carbon dioxide transport mechanism involves the formation of bicarbonate ions. 6. Carbon dioxide forms carbonic acid when it reacts with water. 7. Carbonic anhydrase is an enzyme that speeds up the reaction between carbon dioxide and water and is located inside red blood cells. 8. Carbonic acid dissociates into hydrogen ions and bicarbonate ions. 9. The chloride shift is the exchange of chloride ions and bicarbonate ions across the red blood cell membrane and functions to maintain the ionic balance between the red blood cells and the plasma. 10. When blood reaches the pulmonary capillaries, hydrogen ions and bicarbonate ions recombine to form carbonic acid. 11. In the pulmonary capillaries, carbonic acid becomes carbon dioxide and water. 12. In the lungs, carbon dioxide diffuses out of the blood until equilibrium is established between the partial pressure of carbon dioxide of the blood and that of the alveolar air. IX. Life-Span Changes A. Changes in the respiratory system over a lifetime reflect both the accumulation of environmental influences and the effects of aging in other organ systems. B. People who have been exposed to foul air are more likely to develop chronic bronchitis, emphysema, or lung cancer. C. The factors the change the ability of the respiratory system to clear pathogens from the lungs are a decreases in activity of cilia, thickening of mucus, and the slowing of swallowing, gagging and coughing reflexes. D. Factors that contribute to an overall increase in effort required to breathe are calcification of cartilage between the sternum and ribs and changes in skeletal structure of the thoracic cavity. E. The microscopic changes that occur in the lungs are expansion of alveolar walls, an increase in the amount of collagen, and a decreased amount of elastin.