Chapter 25, f 09

Human Anatomy, Second Edition McKinley & O'Loughlin Chapter 25 Lecture Outline: Respiratory System 25-

Introduction Respiratory system is used for gas exchange: oxygen in and carbon dioxide out Works closely with the cardiovascular system 25-

General Organization and Functions of the Respiratory System Consists of an upper respiratory tract and a lower respiratory tract . Conducting portion transports air . From the nose to the bronchioles Respiratory portion carries out gas exchange . composed of small airways called respiratory bronchioles and alveolar ducts as well as air sacs called alveoli 25-

Respiratory System Functions Breathing (pulmonary ventilation). Inhalation (inspiration) Exhalation (expiration) Gas exchange, gas conditioning, sound production, olfaction, regulation of blood pH, and defense. 25-

Cystic Fibrosis Most common serious genetic disease in Caucasians (1/3200 births - 5% are carriers) A missing chloride pump causes sodium and water to move from the mucus back into the secretory cells, dehydrating the mucus covering the epithelial surface Mucus becomes thick and sticky clogging lungs, and ducts of the pancreas and salivary glands. Pulmonary infections and destruction of pancreas. In the skin, the chloride transport protein works in the opposite direction making skin salty tasting. Treatment: break up mucus, replace pancreatic enzymes, etc. Also insertion of healthy gene. 25-

Upper Respiratory Tract Composed of the nose and nasal cavity, paranasal sinuses, pharynx (throat), and associated structures. All part of the conducting portion of the respiratory system. 25-

Nose and Nasal Cavity Warms air, moistens, traps and moves gunk Smell Resonating chamber for speech Pseudostratified ciliated columnar epithelium (cilia beat toward the throat) 25-

Paranasal Sinuses Four bones of the skull contain paired air spaces called the paranasal sinuses. decrease skull bone weight give resonance to voice Named for the bones in which they are housed. 25-

Pharynx (12 cm) The throat. Originates posterior to the nasal and oral cavities and extends to the bifurcation of the larynx and esophagus. Common pathway for both air and food . 25-

Pharynx Walls are lined by a mucosa and contain skeletal muscles that are primarily used for swallowing . Flexible lateral walls are distensible in order to force swallowed food into the esophagus. Has three regions 25-

Nasopharynx Posterior to the nasal cavity and superior to the soft palate . Normally, only air passes through . Material from the oral cavity and oropharynx is typically blocked from entering the nasopharynx by the soft palate, which elevates when we swallow. In the lateral walls, paired auditory tubes connect to the middle ear. Posterior wall has a single pharyngeal tonsil (commonly called the adenoids). 25-

Oropharynx Posterior to the oral cavity. Bounded by the edge of the soft palate superiorly and the hyoid bone inferiorly. Common respiratory and digestive pathway . 2 pairs of muscular arches form the entrance from the oral cavity. Lymphatic organs, tonsils, here provide the “first line of defense” against ingested or inhaled foreign materials. 25-

Laryngopharynx Inferior, narrowed region of the pharynx. Extends inferiorly from the hyoid bone and is continuous with the larynx and esophagus. Terminates at the superior border of the esophagus and is equivalent to the inferior border of the cricoid cartilage in the larynx. The larynx (voice box) forms the anterior wall Lined with a nonkeratinized stratified squamous epithelium Permits passage of both food and air. 25-

Lower Respiratory Tract Conducting airways (larynx, trachea, bronchi, bronchioles and their associated structures). Respiratory portion of the respiratory system (respiratory bronchioles, alveolar ducts, and alveoli). 25-

Larynx Voice box is a short airway bounded posteriorly by the laryngopharynx and inferiorly by the trachea. Prevents swallowed materials from entering the lower respiratory tract. Conducts air into the lower respiratory tract. Produces sounds. Supported by a framework of nine pieces of cartilage that are held in place by ligaments and muscles. Pseudostratified ciliated columnar epithelium begins below the vocal cords. 25-

Laryngeal Cartilages Unpaired epiglottis - covers the opening of the larynx when swallowing thyroid - has prominence called the “Adam’s apple” cricoid - base of the others. Airway landmark for a tracheostomy Paired arytenoid - attachment point for vocal cords corniculate - attachment point for false vocal cords cuneiform 25-

Sound Production The inferior vocal ligaments, covered by a mucous membrane, are called the vocal folds . the “true vocal cords” produce sound when air passes between them attached to arytenoid cartilages the tension, length, and position of the vocal folds determine the quality of the sound. The superior vestibular ligaments, along with the mucosa covering them, are called the vestibular folds . the “false vocal cords” have no function in sound production, but protect the vocal folds. attached to the corniculate cartilages . 25-

Laryngitis Inflammation Causes: virus, bacteria, overuse Symptoms: hoarse voice, sore throat, maybe fever Severe cases may spread to epiglottis May dangerously obstruct airway in a child 25-

Trachea (12 cm x 2.5 cm) The “windpipe.” Anterior to the esophagus, inferior to the larynx, and superior to the primary bronchi of the lungs. 15 to 20 C-shaped tracheal cartilages. reinforce and provide some rigidity to ensure that the trachea remains open (patent) at all times 25-

Trachea At the sternal angle (T5), the trachea bifurcates into the right and left primary bronchi. Each primary bronchus projects laterally toward each lung. The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina. The carina is very sensitive and may initiate a cough reflex if something lands there. 25-

Bronchial Tree A highly branched system of air-conducting passages that originate from the bronchi and progressively branch before terminating in terminal bronchioles. Incomplete rings of hyaline cartilage support the walls of the primary bronchi to ensure that they remain open. Right primary bronchus is shorter, wider, and more vertically oriented than the left primary bronchus. Foreign particles are more likely to lodge in the right primary bronchus. 25-

Bronchial Tree The primary bronchi enter the hilum of each lung together with the pulmonary vessels, lymphatic vessels, and nerves. Each primary bronchus then branches into secondary bronchi (or lobar bronchi). The left lung has two secondary bronchi since it has two lobes. The right lung has three lobes and three secondary bronchi. They further divide into tertiary bronchi. The right lung is supplied by 10 tertiary bronchi, and the left lung is supplied by 8 to 10 tertiary bronchi. Each tertiary bronchus is called a segmental bronchus because it supplies a part of the lung called a bronchopulmonary segment. 25-

Bronchial Tree As branching occurs, several structural changes occur Cartilage rings become cartilage plates and then cartilage disappears Pseudostratified ciliated columnar tissue becomes cuboidal in the terminal bronchioles (need macrophages then) and finally simple squamous in the respiratory bronchioles As the cartilage decreases, there is an increase in the smooth muscle which is affected by the ANS and chemicals such as histamine and epinephrine 25-

Bronchitis Inflammation Causes: viruses, bacteria, chemicals, particulate matter, cigarette smoke Acute bronchitis Rapid development after an infection, e.g., a cold Resolves usually in 10-14 days Chronic bronchitis Long-term exposure to irritants Large amounts of mucus with a 3 mo. cough Permanent damage may occur leading to increase chances of bacterial infections and increased chance of pneumonia 25-

Respiratory Bronchioles, Alveolar Ducts, and Alveoli Lungs contain small saccular outpocketings called alveoli. An alveolus is about 0.25 to 0.5 mm in diameter. Its thin wall is specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries. Gas exchange can take place in the respiratory bronchioles and alveolar ducts as well as in the lungs, which contain approximately 300–400 million alveoli (70 m 2 ). Alveoli are the major site for gas exchange. The spongy nature of the lung is due to the packing of millions of alveoli together. 25-

Alveolar Cells Type 1 alveolar (squamous pulmonary epithelial) cells Type 2 alveolar (septal) cells produce surfactant which reduces surface tension in the lungs preventing collapse of the air sacs Alveolar macrophages or “dust cells” 25-

Hyaline Membrane Disease Respiratory distress syndrome Lack of surfactant Often in preemies (less than 7 months) or infants of diabetic mothers 25-

Oxygen Transport 1.5% carried dissolved in the plasma 98.5% carried by the heme of Hb Normally, Hb gives up about 25% of the O 2 to the tissues In active tissues, Hb gives up more O 2 The partial pressure gradient of O 2 , pH, and temperature affect the amount of O 2 released by the Hb 25-

Carbon Monoxide Poisoning CO binds to heme 200x more tightly than oxygen . Symptoms: cherry pink, nausea, sleepiness Treatment: pure oxygen 25-

Carbon Dioxide Transport From the tissues: 7% dissolved in plasma as CO 2 23% binds to globin of Hb forming carbaminohemoglobin 70% is converted to H 2 CO 3 by carbonic anhydrase which then quickly dissociates into H + and HCO 3 - (which quickly moves out of the RBC and is carried in the plasma) In the lungs, the reverse occurs 25-

Pleura and Pleural Cavities The outer surface of each lung is tightly covered by the visceral pleura, while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura. The parietal and visceral pleural layers are continuous at the hilum of each lung. The pleura are serous membranes , simple squamous on top of connective tissue. 25-

Pleura and Pleural Cavities The potential space between these serous membrane layers is the pleural cavity. The pleural membranes produce a thin, serous fluid that circulates in the pleural cavity and acts as a lubricant. 25-

Pneumothorax Free air in pleural cavity from an external injury or internally (e.g., broken rib) Collapsed lung or part of lung results = atelectasis Large amount requires a tube for removal Dangerous type is tension pneumothorax where hole acts as a one-way valve Fluids may accumulate in pleural cavity Hemothorax if blood Hydrothorax if serous fluid Empyema if pus 25-

Pleurisy Inflammation of pleura May get decreased pleural fluid leading to pain or May get increased pleural fluid leading to pressure on the lungs 25-

Gross Anatomy of the Lungs Cone shaped. Its base rests upon the diaphragm. Its apex projects superiorly to a point that is slightly superior and posterior to the clavicle. Both lungs are bordered by the thoracic wall anteriorly, laterally, and posteriorly, and supported by the rib cage. The lungs are separated from each other by the mediastinum. Surface in contact with the thoracic wall is called the costal surface of the lung. 25-

Segmental Resection Each segment is an autonomous unit. Therefore, a segment may be removed if diseased leaving the other segments intact. 25-

Pneumonia Infection in the alveoli Causes: viruses, bacteria, and sometimes fungi Tissue swelling and WBCs accumulate decreasing gas exchange Contagious Symptoms: cough, fever, rapid breathing, sputum Treatment: antibiotics, respiratory support, and medications for symptoms and possibly supplemental oxygen 25-

Blood Supply To and From the Lungs Pulmonary trunk and its branches carry deoxygenated blood Bronchial arteries bring oxygenated blood from the systemic circuit Two blood supplies communicate and most of the blood returns to the heart through the pulmonary veins 25-

Lymphatic Drainage Lymph nodes and vessels are located within the connective tissue of the lung as well as around the bronchi and pleura. 25-

Pulmonary Ventilation Pulmonary ventilation or breathing Exchange between atmosphere and lungs About 16x/minute About 500 ml of air exchanged/breath Pulmonary or external respiration Exchange between lungs and blood Transport by blood Tissue respiration or internal respiration Between blood and cells (Cellular respiration in mitochondria) 25-

Boyle’s Law “ The pressure of a gas decreases if the volume of the container increases, and vice versa.” 25-

Thoracic Wall Dimensional Changes During External Respiration Elevation of the ribs increases the lateral dimensions of the thoracic cavity, while depression of the ribs decreases the lateral dimensions of the thoracic cavity. Diaphragm actively moves down with inspiration and passively up during normal expiration. Most important muscle for breathing. 25-

Muscles that Move the Ribs Inhalation The scalenes help increase thoracic cavity dimensions by elevating the first and second ribs during forced inhalation. The ribs elevate upon contraction of the external intercostals , thereby increasing the transverse dimensions of the thoracic cavity during inhalation. Exhalation Contraction of the internal intercostals depresses the ribs, but this only occurs during forced exhalation . Normal exhalation requires no active muscular effort. A small transversus thoracis extends across the inner surface of the thoracic cage and attaches to ribs 2–6. It helps depress the ribs. 25-

Muscles that Move the Ribs Two posterior thorax muscles also assist with respiration. In addition, some accessory muscles assist with respiratory activities. 25-

Factors Influencing Respiratory Rate and Depth Physical factors Volition (conscious control) Emotional factors Chemical factors (most important) Concentration of oxygen has little effect usually Concentration of carbon dioxide has the most important effect 25-

Factors Influencing Respiratory Rate and Depth Concentration of carbon dioxide has the most important effect Increased arterial partial pressure of CO 2 Increases partial pressure of CO 2 or decreases pH in CSF stimulate central chemoreceptors in the medulla (70% of response) Stimulates peripheral chemoreceptors in the carotid and aortic bodies mediate 30% of response Afferent impulses go to medullary respiratory centers Efferent impulses go to respiratory muscles Increased ventilation (more CO 2 exhaled) Arterial pCO 2 and pH return to normal 25-

Innervation of the Respiratory System The trachea, bronchial tree, and lungs are innervated by the autonomic nervous system. The autonomic nerve fibers that innervate the heart also send branches to the respiratory structures. Pulmonary plexus Sympathetic innervation mainly causes bronchodilation Parasympathetic innervation mainly causes bronchoconstriction The involuntary, rhythmic activities that deliver and remove respiratory gases are regulated in the brainstem. 25-

Ventilation Control by Respiratory Centers of the Brain Regulatory respiratory centers are located within the reticular formation through both the medulla oblongata and pons. Medulla sets mainly the rate (basic rhythm) Dorsal group is the inspiratory center Ventral group is the expiratory center for forced expiration Pons sets the depth Apneustic center gives inspiratory drive Pneumotaxic center inhibits apneustic center and limits the length of inspiration and promotes expiration Phrenic nerve serves the diaphragm Intercostal nerves serve the external intercostals 25-

Aging and the Respiratory System Less efficient with age due to structural changes. Decrease in elastic connective tissue in the lungs and the thoracic cavity wall. Loss of elasticity reduces the amount of gas that can be exchanged with each breath and results in a decrease in the ventilation rate. Vital capacity of lung decreases by 35% by age 70. Emphysema may cause a loss of alveoli or their functionality Reduced capacity for gas exchange can cause an older person to become “short of breath” upon exertion. Carbon, dust, and pollution material gradually accumulate in our lymph nodes and lungs (less macrophages and ciliary function) Cardiovascular and respiratory systems affect each other. Increase in pulmonary disorders. 25-

Factors Influencing Gas Exchange Thickness of respiratory membrane Ex., edema increases thickness Surface area of the respiratory membrane Ex., emphysema and cancer decrease S.A. Partial pressure of gas Ex., less partial pressure at high altitude 25-

Chronic Obstructive Pulmonary Disease (COPD) Common features Smoking, difficult breathing, coughing and infections common, most hypoxic, retain carbon dioxide so acidosis. Disability and ultimately develop respiratory failure (death) 25-

Chronic Obstructive Pulmonary Disease (COPD) Emphysema Alveoli enlarge. Inflammation leads to fibrosis and airways lose elasticity. Hard to exhale and leads to exhaustion Overinflation leads to a barrel chest Air retained - > ”pink puffers” (cyanosis late) Chronic bronchitis Inflammation of mucosa of lower respiratory passages -> increased mucus -> impaired ventilation and gas exchange -> increased risk of lung infection (e.g., pneumonia) Hypoxia and carbon dioxide retention early in disease and cyanosis is common -> “blue bloaters” 25-

Asthma A chronic condition characterized by episodes of bronchoconstriction and wheezing, coughing, shortness of breath and excess pulmonary mucus. Usually a sensitivity to an airborne agent. Upon reexposure, a localized immune reaction occurs in the bronchi and bronchioles. Usually lasts an hour or two. Eventually, the walls may become permanently thickened. Severe attacks may be fatal. Treatment: inhaled steroids and bronchodilators. Important to avoid triggering agent. Allergy shots may help some. 25-

Smoking and Lung Cancer Smoking increases the risk and severity of atherosclerosis and is directly related to the development of cancers of the lung, esophagus, stomach, and urinary bladder. Smoking also increases wrinkling and impotency. 25-

Smoking and Lung Cancer Lung cancer: smoking causes 85%. Increases mucus Paralyzes cilia and decreases macrophage activity Has many carcinogens Highly aggressive and frequently fatal . 1/3 cancer deaths in U.S, 7% 5 year cure rate. Detection is late and it spreads fast. Average 9 month survival after diagnosis. Treatment Resection is best if not too late Chemotherapy and radiation may be the only options 25-

Lung Cancer Three major types Squamous cell carcinoma most common type from transformed epithelial cells. Adenocarcinoma from mucin-producing glands. Small-cell (oat-cell) carcinoma arises from the primary bronchi and eventually invades the mediastinum. From neuroendocrine cells and may produce hormones. Aggressive and early metastasis. 25-

Sudden Infant Death Syndrome (SIDS) Sudden and unexplained death of an infant younger than 1 year (usually 2-4 months old and 60% male) SIDS babies have trouble regulating and maintaining B.P., breathing and body temperature. Stress plus one or more of these three factors appears to be involved. “ Back-to-sleep” campaign has reduced incidence. 25-

Respiratory Changes at Birth At birth, Powerful contractions of diaphragm and external intercostal muscles cause inhalation Rib cage expands and never returns to its former shape (important forensically). We never completely empty our lungs after birth. More breaths increase inflation and surfactant helps prevent collapse. 25-

Chapter 25, f 09

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Chapter 25, f 09