Respiratory System PDF

12/17/2023 CHAPTER 13 Organs of the Respiratory System The Respiratory System...

12/17/2023 CHAPTER 13 Organs of the Respiratory System The Respiratory System ▪ Nose ▪ Pharynx ▪ Larynx ▪ Trachea ▪ Bronchi ▪ Lungs—alveoli © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 1 2 Figure 13.1 The major respiratory organs shown in relation to surrounding structures. Functional Anatomy of the Respiratory System Nasal cavity ▪ Gas exchanges between the blood and external Oral cavity Nostril Pharynx environment occur only in the alveoli of the lungs Larynx ▪ Upper respiratory tract includes passageways from the nose to larynx Trachea ▪ Lower respiratory tract includes passageways Right main Left main (primary) from trachea to alveoli (primary) bronchus bronchus ▪ Passageways to the lungs purify, humidify, and warm Right lung Left lung the incoming air Diaphragm © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 3 4 The Nose ▪ The only externally visible part of the respiratory system ▪ Nostrils (nares) are the route through which air enters the nose ▪ Nasal cavity is the interior of the nose ▪ Nasal septum divides the nasal cavity © 2018 Pearson Education, Ltd. © 2015 Pearson Education, Inc. 5 6 1  12/17/2023 Figure 13.2b Basic anatomy of the upper respiratory tract, sagittal section. Cribriform plate of ethmoid bone The Nose Sphenoidal sinus Frontal sinus Posterior nasal Nasal cavity aperture Nasal conchae (superior, Nasopharynx middle, and inferior) ▪ Olfactory receptors are located in the mucosa on Pharyngeal tonsil Nasal meatuses (superior, middle, and inferior) the superior surface Opening of pharyngotympanic tube Nasal vestibule ▪ The rest of the cavity is lined with respiratory Nostril Uvula mucosa, which Hard palate Oropharynx Palatine tonsil Soft palate ▪ Moistens air Lingual tonsil Tongue ▪ Traps incoming foreign particles ▪ Enzymes in the mucus destroy bacteria chemically Laryngopharynx Hyoid bone Larynx Esophagus Epiglottis Thyroid cartilage Trachea Vocal fold Cricoid cartilage (b) Detailed anatomy of the upper respiratory tract © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 7 8 The Nose The Nose ▪ Conchae are projections from the lateral walls ▪ Paranasal sinuses ▪ Increase surface area ▪ Cavities within the frontal, sphenoid, ethmoid, and ▪ Increase air turbulence within the nasal cavity maxillary bones surrounding the nasal cavity ▪ Increased trapping of inhaled particles ▪ Sinuses: ▪ Lighten the skull ▪ The palate separates the nasal cavity from the ▪ Act as resonance chambers for speech oral cavity ▪ Produce mucus ▪ Hard palate is anterior and supported by bone ▪ Soft palate is posterior and unsupported © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 9 10 Figure 13.2b Basic anatomy of the upper respiratory tract, sagittal section. Cribriform plate of ethmoid bone The Pharynx Sphenoidal sinus Frontal sinus Posterior nasal Nasal cavity aperture Nasal conchae (superior, Nasopharynx middle, and inferior) ▪ Commonly called the throat Pharyngeal tonsil Nasal meatuses (superior, Opening of middle, and inferior) ▪ Muscular passageway from nasal cavity to larynx pharyngotympanic Nasal vestibule tube Nostril Uvula Hard palate ▪ Three regions of the pharynx Oropharynx Palatine tonsil Soft palate 1. Nasopharynx—superior region behind nasal cavity Lingual tonsil Tongue 2. Oropharynx—middle region behind mouth 3. Laryngopharynx—inferior region attached to larynx Laryngopharynx Hyoid bone Larynx Esophagus Epiglottis Thyroid cartilage Trachea Vocal fold Cricoid cartilage (b) Detailed anatomy of the upper respiratory tract © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 11 12 2  12/17/2023 Figure 13.2a Basic anatomy of the upper respiratory tract, sagittal section. The Pharynx ▪ Oropharynx and laryngopharynx serve as common passageway for air and food ▪ Epiglottis routes food into the posterior tube, the esophagus Pharynx ▪ Pharyngotympanic tubes (eustachean tube) open Nasopharynx into the nasopharynx Oropharynx ▪ Drain the middle ear Laryngopharynx (a) Regions of the pharynx © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 13 14 Figure 13.2b Basic anatomy of the upper respiratory tract, sagittal section. Cribriform plate The Pharynx of ethmoid bone Sphenoidal sinus Frontal sinus Posterior nasal Nasal cavity aperture Nasal conchae (superior, ▪ Tonsils are clusters of lymphatic tissue that play a Nasopharynx middle, and inferior) role in protecting the body from infection Pharyngeal tonsil Nasal meatuses (superior, middle, and inferior) Opening of ▪ Pharyngeal tonsil (adenoid), a single tonsil, is located pharyngotympanic Nasal vestibule tube in the nasopharynx Uvula Nostril ▪ Palatine tonsils (2) are located in the oropharynx at the Oropharynx Hard palate end of the soft palate Palatine tonsil Soft palate ▪ Lingual tonsils (2) are found at the base of the tongue Lingual tonsil Tongue Laryngopharynx Hyoid bone Larynx Esophagus Epiglottis Thyroid cartilage Trachea Vocal fold Cricoid cartilage (b) Detailed anatomy of the upper respiratory tract © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 15 16 The Larynx The Larynx ▪ Commonly called the voice box ▪ Epiglottis ▪ Functions ▪ Spoon-shaped flap of elastic cartilage ▪ Routes air and food into proper channels ▪ Protects the superior opening of the larynx ▪ Plays a role in speech ▪ Routes food to the posteriorly situated esophagus and routes air toward the trachea ▪ Located inferior to the pharynx ▪ During swallowing, the epiglottis rises and forms a lid ▪ Made of eight rigid hyaline cartilages over the opening of the larynx ▪ Thyroid cartilage (Adam’s apple) is the largest © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 17 18 3  12/17/2023 Figure 13.2b Basic anatomy of the upper respiratory tract, sagittal section. Cribriform plate The Larynx of ethmoid bone Sphenoidal sinus Frontal sinus Posterior nasal Nasal cavity aperture Nasal conchae (superior, ▪ Vocal folds (true vocal cords) Nasopharynx middle, and inferior) Pharyngeal tonsil ▪ Vibrate with expelled air Nasal meatuses (superior, middle, and inferior) Opening of ▪ Allow us to speak pharyngotympanic Nasal vestibule tube Nostril Uvula Hard palate ▪ The glottis includes the vocal cords and the Oropharynx Palatine tonsil Soft palate opening between the vocal cords Lingual tonsil Tongue Laryngopharynx Hyoid bone Larynx Esophagus Epiglottis Thyroid cartilage Trachea Vocal fold Cricoid cartilage (b) Detailed anatomy of the upper respiratory tract © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 19 20 Figure 13.3a Anatomy of the trachea and esophagus. The Trachea Posterior Mucosa ▪ Commonly called the windpipe ▪ 4-inch-long tube that connects to the larynx ▪ Walls are reinforced with C-shaped rings of hyaline cartilage, which keep the trachea patent Esophagus (open) Submucosa Trachealis Lumen of Seromucous ▪ Lined with ciliated mucosa muscle gland in trachea ▪ Cilia beat continuously in the opposite direction of submucosa incoming air Hyaline ▪ Expel mucus loaded with dust and other debris away cartilage from lungs Adventitia (a) Anterior © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 21 22 Figure 13.3b Anatomy of the trachea and esophagus. The Main Bronchi ▪ Formed by division of the trachea ▪ Right bronchus is wider, shorter, and straighter than left ▪ Bronchi subdivide into smaller and smaller branches (b) © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 23 24 4  12/17/2023 Figure 13.1 The major respiratory organs shown in relation to surrounding structures. The Lungs Nasal cavity ▪ Occupy the entire thoracic cavity except for the Oral cavity Nostril Pharynx central mediastinum Larynx ▪ Apex of each lung is near the clavicle (superior portion) Trachea ▪ Base rests on the diaphragm Left main Right main (primary) ▪ Each lung is divided into lobes by fissures (primary) bronchus bronchus ▪ Left lung—two lobes Left lung Right lung ▪ Right lung—three lobes Diaphragm © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 25 26 The Lungs ▪ Serosa covers the outer surface of the lungs ▪ Pulmonary (visceral) pleura covers the lung surface ▪ Parietal pleura lines the walls of the thoracic cavity ▪ Pleural fluid fills the area between layers ▪ Allows the lungs to glide over the thorax ▪ Decreases friction during breathing ▪ Pleural space (between the layers) is more of a potential space © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 27 28 Figure 13.4b Anatomical relationships of organs in the thoracic cavity. Posterior Vertebra Esophagus (in posterior mediastinum) Root of lung at hilum Right lung Left main bronchus Parietal pleura Left pulmonary artery Left pulmonary vein Visceral pleura Left lung Pleural cavity Thoracic wall Pulmonary trunk Pericardial membranes Heart (in mediastinum) Anterior mediastinum Sternum Anterior (b) Transverse section through the thorax, viewed from above © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 29 30 5  12/17/2023 The Lungs ▪ The bronchial tree ▪ Main bronchi subdivide into smaller and smaller branches ▪ Bronchial (respiratory) tree is the network of branching passageways ▪ All but the smallest passageways have reinforcing cartilage in the walls ▪ Bronchioles (smallest conducting passageways) © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 31 32 Figure 13.5a Respiratory zone structures. Respiratory Zone Structures and the Respiratory Membrane ▪ Terminal bronchioles lead into respiratory zone structures and terminate in alveoli Alveolar duct Alveoli ▪ Respiratory zone includes the: ▪ Respiratory bronchioles Respiratory bronchioles Alveolar duct ▪ Alveolar ducts Terminal ▪ Alveolar sacs bronchiole Alveolar sac ▪ Alveoli (air sacs)—the only site of gas exchange (a) Diagrammatic view of respiratory bronchioles, alveolar ducts, and alveoli © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 33 34 Figure 13.5b Respiratory zone structures. Respiratory Zone Structures and the Respiratory Membrane ▪ Alveoli Alveolar Alveolar ▪ Simple squamous epithelial cells largely compose the duct pores walls ▪ Alveolar pores connect neighboring air sacs ▪ Pulmonary capillaries cover external surfaces of Alveolus alveoli (b) Light micrograph of human lung tissue, showing the final divisions of the respiratory tree (120×) © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 35 36 6  12/17/2023 Respiratory Zone Structures and the Respiratory Zone Structures and the Respiratory Membrane Respiratory Membrane ▪ Respiratory membrane (air-blood barrier) ▪ Alveolar macrophages (“dust cells”) ▪ On one side of the membrane is air, and on the other ▪ Add protection by picking up bacteria, carbon particles, side is blood flowing past and other debris ▪ Formed by alveolar and capillary walls ▪ Surfactant (a lipid molecule) ▪ Gas crosses the respiratory membrane by ▪ Coats gas-exposed alveolar surfaces diffusion ▪ Secreted by cuboidal surfactant-secreting cells ▪ Oxygen enters the blood ▪ Carbon dioxide enters the alveoli © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 37 38 Figure 13.6 Functional anatomy of the respiratory membrane (air-blood barrier). Respiratory Physiology Red blood cell Endothelial cell nucleus Capillary ▪ Functions of the respiratory system Alveolar pores ▪ Supply the body with oxygen Capillary O2 ▪ Dispose of carbon dioxide CO2 Macrophage Alveolus Nucleus of squamous epithelial cell Respiratory Alveolar epithelium membrane Fused basement membranes Capillary endothelium Alveoli Red blood Surfactant- Squamous (gas-filled cell in secreting cell epithelial cell air spaces) capillary of alveolar wall © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 39 40 Mechanics of Breathing Mechanics of Breathing ▪ Inspiration (inhalation) ▪ Inspiration = inhalation ▪ Diaphragm and external intercostal muscles contract ▪ Flow of air into lungs ▪ Intrapulmonary volume increases ▪ Expiration = exhalation ▪ Gas pressure decreases ▪ Air leaving lungs ▪ Air flows into the lungs until intrapulmonary pressure equals atmospheric pressure © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 41 42 7  12/17/2023 Figure 13.7a Rib cage and diaphragm positions during breathing. Mechanics of Breathing Changes in anterior-posterior and Changes in lateral superior-inferior dimensions dimensions ▪ Expiration (exhalation) Ribs are elevated as external ▪ Largely a passive process that depends on natural intercostals lung elasticity contract ▪ Intrapulmonary volume decreases External Full inspiration ▪ Gas pressure increases intercostal (External muscles intercostals contract) Diaphragm moves inferiorly during contraction (a) Inspiration: Air (gases) flows into the lungs © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 43 44 Figure 13.7b Rib cage and diaphragm positions during breathing. Changes in anterior-posterior and Changes in lateral superior-inferior dimensions dimensions Mechanics of Breathing ▪ Intrapleural pressure Ribs are depressed ▪ The pressure within the pleural space is always as external intercostals relax negative ▪ Major factor preventing lung collapse Expiration ▪ If intrapleural pressure equals atmospheric pressure, External (External intercostal intercostals relax) the lungs recoil and collapse muscles Diaphragm moves superiorly as it relaxes (b) Expiration: Air (gases) flows out of the lungs © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 45 46 Respiratory Volumes and Capacities Respiratory Volumes and Capacities ▪ Factors affecting respiratory capacity ▪ Inspiratory reserve volume (IRV) ▪ Size ▪ Amount of air that can be taken in forcibly over the ▪ Sex tidal volume ▪ Age ▪ Usually around 3,100 ml ▪ Physical condition ▪ Expiratory reserve volume (ERV) ▪ Tidal volume (TV) ▪ Amount of air that can be forcibly exhaled after a tidal ▪ Normal quiet breathing expiration ▪ 500 ml of air is moved in/out of lungs with each breath ▪ Approximately 1,200 ml © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 47 48 8  12/17/2023 Respiratory Volumes and Capacities Respiratory Volumes and Capacities ▪ Residual volume ▪ Vital capacity ▪ Air remaining in lung after expiration ▪ The total amount of exchangeable air ▪ Cannot be voluntarily exhaled ▪ Vital capacity = TV + IRV + ERV ▪ Allows gas exchange to go on continuously, even ▪ 4,800 ml in men; 3,100 ml in women between breaths, and helps keep alveoli open ▪ Dead space volume (inflated) ▪ Air that remains in conducting zone and never reaches ▪ About 1,200 ml alveoli ▪ About 150 ml © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 49 50 Figure 13.9 Graph of the various respiratory volumes in a healthy young adult male. Respiratory Volumes and Capacities 6,000 ▪ Functional volume 5,000 Inspiratory ▪ Air that actually reaches the respiratory zone reserve volume ▪ Usually about 350 ml Milliliters (ml) 4,000 3,100 ml Vital capacity 3,000 4,800 ml Total lung ▪ Respiratory capacities are measured with a Tidal volume 500 ml capacity Expiratory 6,000 ml spirometer 2,000 reserve volume 1,200 ml 1,000 Residual volume 1,200 ml 0 © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 51 52 Table 13.1 Nonrespiratory Air (Gas) Movements Nonrespiratory Air Movements ▪ Can be caused by reflexes or voluntary actions ▪ Examples ▪ Cough and sneeze—clears lungs of debris ▪ Crying—emotionally induced mechanism ▪ Laughing—similar to crying ▪ Hiccup—sudden inspirations ▪ Yawn—very deep inspiration © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 53 54 9  12/17/2023 Respiratory Sounds Gas Transport in the Blood ▪ Sounds are monitored with a stethoscope ▪ For carbon dioxide to diffuse out of blood into the ▪ Two recognizable sounds can be heard with a alveoli, it must be released from its bicarbonate stethoscope: form: 1. Bronchial sounds—produced by air rushing through ▪ Bicarbonate ions enter RBC large passageways such as the trachea and bronchi ▪ Combine with hydrogen ions 2. Vesicular breathing sounds—soft sounds of air filling ▪ Form carbonic acid (H2CO3) alveoli ▪ Carbonic acid splits to form water + CO2 ▪ Carbon dioxide diffuses from blood into alveoli © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 55 56 Figure 13.11a The loading and unloading of oxygen (O2) and carbon dioxide (CO2) in the body. (a) External respiration in the lungs (pulmonary gas exchange) Oxygen is loaded into the blood, and carbon dioxide is unloaded. Alveoli (air sacs) O2 CO2 Loading of O2 Unloading of CO2 Hb + O2 HbO2 HCO3− + H+ H2CO3 CO2 + H2O (Oxyhemoglobin Bicar- Carbonic Water is formed) bonate acid ion Plasma Red blood cell Pulmonary capillary © 2018 Pearson Education, Ltd. © 2015 Pearson Education, Inc. 57 58 Figure 13.11b The loading and unloading of oxygen (O2) and carbon dioxide (CO2) in the body. (b) Internal respiration in the body Internal Respiration tissues (systemic capillary gas exchange) Oxygen is unloaded and carbon dioxide is loaded into the blood. ▪ Exchange of gases between blood and tissue cells Tissue cells CO2 O2 ▪ An opposite reaction from what occurs in the lungs Loading Unloading of CO2 ▪ Carbon dioxide diffuses out of tissue cells to blood of O2 (called loading) ▪ Oxygen diffuses from blood into tissue (called CO2 + H2O H2CO3 H+ + HCO3− unloading) Water Carbonic Bicar- acid bonate HbO2 Hb + O2 Plasma ion Systemic capillary Red blood cell © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 59 60 10  12/17/2023 Control of Respiration Control of Respiration ▪ Neural regulation: setting the basic rhythm ▪ Normal respiratory rate (eupnea) ▪ Activity of respiratory muscles is transmitted to and ▪ 12 to 15 respirations per minute from the brain by phrenic and intercostal nerves ▪ Hyperpnea ▪ Neural centers that control rate and depth are located ▪ Increased respiratory rate, often due to extra oxygen in the medulla and pons needs ▪ Medulla—sets basic rhythm of breathing and contains a pacemaker (self-exciting inspiratory center) called the ventral respiratory group (VRG) ▪ Pons—smoothes out respiratory rate © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 61 62 Figure 13.12 Neural control of respiration. Control of Respiration Breathing control centers: Pons centers Medulla centers ▪ Non-neural factors influencing respiratory rate Afferent Efferent nerve impulses from and depth impulses to medulla trigger contraction of medulla inspiratory muscles: ▪ Physical factors Phrenic nerves Intercostal nerves ▪ Increased body temperature Breathing control centers ▪ Exercise stimulated by: ▪ Talking CO2 and H+ increase Nerve impulse in tissue. from O2 sensor Intercostal ▪ Coughing muscles indicating O2 decrease Diaphragm ▪ Emotional factors such as fear, anger, and excitement O2 sensor in aortic body of aortic arch © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 63 64 Control of Respiration Control of Respiration ▪ Factors influencing respiratory rate and depth ▪ Factors influencing respiratory rate and depth ▪ Chemical factors: CO2 levels (continued) ▪ The body’s need to rid itself of CO2 is the most ▪ Chemical factors: oxygen levels important stimulus for breathing ▪ Changes in oxygen concentration in the blood are ▪ Increased levels of carbon dioxide (and thus, a detected by chemoreceptors in the aorta and common decreased or acidic pH) in the blood increase the rate carotid artery and depth of breathing ▪ Information is sent to the medulla ▪ Changes in carbon dioxide act directly on the medulla ▪ Oxygen is the stimulus for those whose systems have oblongata become accustomed to high levels of carbon dioxide as a result of disease © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 65 66 11  12/17/2023 Control of Respiration Control of Respiration ▪ Non-neural factors influencing respiratory rate ▪ Non-neural factors influencing respiratory rate and depth (continued) and depth (continued) ▪ Chemical factors (continued) ▪ Chemical factors (continued) ▪ Hyperventilation ▪ Hypoventilation ▪ Rising levels of CO2 in the blood (acidosis) result in ▪ Results when blood becomes alkaline (alkalosis) faster, deeper breathing ▪ Extremely slow or shallow breathing ▪ Exhale more CO2 to elevate blood pH ▪ Allows CO2 to accumulate in the blood © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 67 68 Respiratory Disorders Respiratory Disorders ▪ Chronic obstructive pulmonary disease (COPD) ▪ Chronic bronchitis ▪ Exemplified by chronic bronchitis and emphysema ▪ Mucosa of the lower respiratory passages becomes ▪ Shared features of these diseases severely inflamed 1. Patients almost always have a history of smoking ▪ Excessive mucus production impairs ventilation and 2. Labored breathing (dyspnea) becomes progressively gas exchange worse ▪ Patients become cyanotic and are sometimes called 3. Coughing and frequent pulmonary infections are “blue bloaters” as a result of chronic hypoxia and common carbon dioxide retention 4. Most COPD patients are hypoxic, retain carbon dioxide and have respiratory acidosis, and ultimately develop respiratory failure © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 69 70 Respiratory Disorders ▪ Emphysema ▪ Alveoli walls are destroyed; remaining alveoli enlarge ▪ Chronic inflammation promotes lung fibrosis, and lungs lose elasticity ▪ Patients use a large amount of energy to exhale; some air remains in the lungs ▪ Sufferers are often called “pink puffers” because oxygen exchange is efficient ▪ Overinflation of the lungs leads to a permanently expanded barrel chest ▪ Cyanosis appears late in the disease © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 71 72 12  12/17/2023 Homeostatic Imbalance 13.13 The pathogenesis of COPD. Tobacco smoke Air pollution Respiratory Disorders Continual bronchial Breakdown of elastin in irritation and connective tissue of lungs ▪ Lung cancer inflammation ▪ Leading cause of cancer death for men and women ▪ Nearly 90 percent of cases result from smoking Chronic bronchitis Emphysema Excessive mucus Destruction of alveolar ▪ Aggressive cancer that metastasizes rapidly produced Chronic productive walls ▪ Three common types Loss of lung elasticity cough 1. Adenocarcinoma 2. Squamous cell carcinoma Airway obstruction or air trapping 3. Small cell carcinoma Dyspnea Frequent infections Respiratory failure © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 73 74 Developmental Aspects of the Respiratory Developmental Aspects of the Respiratory System System ▪ Lungs do not fully inflate until 2 weeks after birth ▪ Respiratory rate changes throughout life ▪ This change from nonfunctional to functional ▪ Newborns: 40 to 80 respirations per minute respiration depends on surfactant ▪ Infants: 30 respirations per minute ▪ Surfactant lowers surface tension so the alveoli do not ▪ Age 5: 25 respirations per minute collapse ▪ Adults: 12 to 18 respirations per minute ▪ Surfactant is formed late in pregnancy, around 28 to ▪ Rate often increases again in old age 30 weeks © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 75 76 Developmental Aspects of the Respiratory Developmental Aspects of the Respiratory System System ▪ Asthma ▪ Aging effects ▪ Chronically inflamed, hypersensitive bronchiole ▪ Elasticity of lungs decreases passages ▪ Vital capacity decreases ▪ Respond to irritants with dyspnea, coughing, and ▪ Blood oxygen levels decrease wheezing ▪ Stimulating effects of carbon dioxide decrease ▪ Elderly are often hypoxic and exhibit sleep apnea ▪ More risks of respiratory tract infection © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd. 77 78 13