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1. 2. 3. 4. 5. Provides extensive gas exchange surface area (alveoli) between air and blood Moves air to and from alveoli Protects respiratory surfaces from outside environment Produces sounds Participates in olfactory sense (smell) The organs of the respiratory system are the nose, pharynx, larynx, trachea, bronchi and the smaller branches, and the lungs and the alveoli. Branch from the pulmonary vein (oxygen-rich blood) Branch from the pulmonary artery (oxygen-poor blood) Terminal bronchiole Nasal cavity Pharynx Left lung Alveol 50 µm Larynx Esophagus Trachea 50 µm Right lung Bronchus Bronchiole Diaphragm Heart SEM Colorized SEM Conducting Passageways Consists of the nose and pharynx Figure 23–3 Air enters the nasal cavity through the nostrils. Nasal hairs prevent the entry of large particles carried in the air. Nasal cavity is a hollow space behind the nose. The nasal septum divides it into left and right sides. Superior portion of nasal cavity is the olfactory region • Lines the nasal cavity • Rests on a rich network of thin-walled blood vessels that warm and humidify the air as it flows • Breathing through mouth bypasses this important step create a gentle current that moves contaminated mucus toward the pharynx, where it is swallowed and digested by stomach juices. When external temp is extremely cold, these cilia become sluggish, allowing mucus to dribble out nostrils. The nasal cavity is surrounded by a ring of paranasal sinuses, which are air filled spaces in skull Reduce weight of skull Resonating chambers that affect speech The tear ducts also empty into the nasal cavities Located in the frontal, sphenoid, ethmoid, and maximally bones. A chamber shared by digestive and respiratory systems Both food and air share the passageway Superior portion of the pharynx Contains pharyngeal tonsils (adenoids) and openings to left and right auditory tubes Middle portion of the pharynx Communicates with oral cavity Inferior portion of the pharynx Extends from hyoid bone to entrance to larynx and esophagus Contagious VIRAL respiratory infection Indirect causes: chilling, fatigue, lack of proper food, and not enough slepp Handwashing is the best preventative measure Sometimes called an upper respiratory infection Red, inflammed throat Inflammation of the larynx of voice box Often secondary to other respiratory infections Symptoms: Sore throat, loss of voice, dysphagia (difficulty swallowing) Infection of the mucusou membrane that lines sinus cavities Can be caused by bacteria or virus Symptoms: headache or pressure, thick nasal discharge, loss of voice resonance (sounds different) Consists of the larynx, trachea, bronchi, and the lungs The lungs consist of bronchioles and alveoli Figure 23–4 ▪ Routes air and food into the proper channels ▪ Plays a role in speech ▪ vocal cords: vibrate with expelled air 3 large, unpaired cartilages form the larynx: the epiglottis the thyroid cartilage the cricoid cartilage Ligaments attach to thyroid cartilage and hyoid bone guardian of the airways Also called the Adam’s apple Support and protect the glottis, the entrance to the trachea Form lower portion of larynx Support and protect the glottis, the entrance to the trachea Prevents entry of food and liquids into respiratory tract During swallowing: the larynx is elevated the epiglottis folds back over glottis When we are not swallowing, the epiglottis does not restrict the passage of air into the lower respiratory passages. When we swallow food or fluids, the larynx is pulled upward and the epiglottis tips forming a lid over the opening of the larynx This routes food into the esophagus • • Air passing through glottis vibrates vocal folds and produces sound waves Sound is varied • Changing the shapes of the pharynx and oral cavity and using the tongue and lips to transform the sound waves into words • Contracting and relaxing muscles alter the tension on the vocal cords to control the pitch. During normal breathing, the vocal cords are relaxed and the opening between them, the glottis, is a triangular slit When food or liquid is swallowed, muscles within the false vocal cords close the glottis, which also helps to prevent food or liquid from entering the trachea. Figure 23–5 Figure 23–6 Common Term: windpipe Located anterior to the esophagus and into the thoracic cavity, where it splits into right and left bronchi 15–20 tracheal cartilages: strengthen and protect airway discontinuous where trachea contacts esophagus ▪ open parts of the rings allow the esophagus to expand when we swallow a large piece of food. ▪ solid portion support the trachea walls and keep it open in spite of the pressure changes that occur during breathing. Lined with lined with ciliated mucosa beat continuously and in a direction opposite to that of incoming air. propel mucus, loaded with dust and other debris, away from lungs to the throat, where it can be swallowed or spat out. Smoking inhibits ciliary activity and ultimately destroys the cilia. Without these cilia, coughing is the only means of preventing mucus from accumulating in the lungs. Since the trachea is the only way that air can enter the lungs, tracheal obstruction is lifethreatening Heimlich maneuver: procedure in which the air in a person’s own lungs in used to pop out an obstruction piece of food. In emergency situations, a tracheotomy is done to provide an alternate route for air to reach the lungs Temporary surgical procedure which involves making an opening so that air can bypass a structure in the trachea. Branched airways leading from the trachea to the microscopic air sacs in the lungs. ① Primary bronchi (left and right) ② Secondary bronchi ③ Tertiary bronchi ④ Bronchioles ⑤ Aleveolar ducts ⑥ Alveolar sacs ⑦ Alveoli Inflammation of the mucous membrane of the trachea and bronchiole tubes, producing excess mucous Causes constriction and breathing difficulty Provides a large surface area of thin simple squamous epithelial cells through which gases can be easily exchange In both lungs, ~300 mil alveoli ½ size of tennis court Oxygen diffuses from the alveoli into the blood in nearby capillaries Carbon dioxide diffuses from the blood into the alveoli Lungs are soft and spongy and coneshaped Base of lung rests on the diaphragm Each lung enclosed in a pleural cavity 3 lobes superior, middle, & inferior separated by horizontal and oblique fissures Displaced upward by liver Wider than left lung 2 lobes superior and inferior separated by an oblique fissure Longer than right lung Displaced leftward by the heart Pneumonia is an inflammation of the lungs caused by an infection. Alveoli fill with exudates (thick fluid) Many different organisms can cause it, including bacteria, viruses, and fungi. Pneumonia is a common illness that affects millions of people each year in the United States. Symptoms – chest pain, fever, chills, dyspnea (difficult, labored, painful breathing) The symptoms of pneumonia range from very mild to very severe, even fatal. Inflammatory airway obstruction Caused by allergen or psychological stress 5% of Americans have asthma Symptoms: difficulty exhaling, dyspnea, wheezing, tightness in chest Contagious bacterial infection that involves the lungs, but may spread to other organs. It causes inflammation, the formation of tubercules within tissue, and even tissue death. Caused by the bacteria Mycobacterium tuberculosis You can get TB by breathing in air droplets from a cough or sneeze of an infected person. Symptoms: cough, low grade fever in the afternoon, weight loss and night sweats Alveoli become over-dilated, lose their elasticity, can’t rebound, may even eventually rupture Air becomes trapped, can’t exhale- forced exhalation required Reduced exchange of O2 and CO2 Dyspnea increases as disease progresses Found mainly in smokers Symptoms: chronic cough and weight loss Diagnosis: x-ray and bronchoscopy (flexible tube passed through mouth or nose into bronchi and lungs Blood clot breaks off and travels to the lung Occurs after surgery or when a person has been on bed rest Symptoms: sudden severe chest pain, dyspnea Consists of 2 layers Parietal pleura: lines the walls of the thoracic cavity Visceral pleura: lines the surface of each lung No significant space exists between the visceral and parietal pleura, but the potential space between them is what is referred to as the pleural cavity. Pleural fluid lubricates the space between the two layers reducing friction as they move against one another during breathing Notice the relationship between the heart and lungs Notice the pleura and pleural cavities Figure 23–8 Inflammation of the lining of the lungs and chest (the pleura) that leads to chest pain (usually sharp) when you take a breath or cough. May develop when you have lung inflammation due to infections such as pneumonia or tuberculosis. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Breathing Mechanism Ventilation (breathing), the movement of air in and out of the lungs, is composed of inspiration and expiration. 55 Atmospheric pressure is the force that moves air into the lungs. When pressure on the inside of the lungs decreases, higher pressure air flows in from the outside. Air pressure inside the lungs is decreased by increasing the size of the thoracic cavity; due to surface tension between the two layers of pleura, the lungs follow with the chest wall and expand. Muscles involved in expanding the thoracic cavity include the diaphragm and the external intercostal muscles. As the lungs expand in size, surfactant keeps the alveoli from sticking to each other so they do not collapse when internal air pressure is low. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. The forces of expiration are due to the elastic recoil of lung and muscle tissues and from the surface tension within the alveoli. Passive process Forced expiration is aided by thoracic and abdominal wall muscles that compress the abdomen against the diaphragm. 57 58 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. The measurement of different air volumes is called spirometry, and it describes four distinct respiratory volumes : tidal volume, inspiratory reserve volume, expiratory reserve volume and the residual volume One inspiration followed by expiration is called a respiratory cycle Normal adult: 14-20 respirations per minute Increases with exercise, body temperature, disease 59 The amount of air that enters or leaves the lungs during one respiratory cycle is the tidal volume. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. During forced inspiration, an additional volume, the inspiratory reserve volume, can be inhaled into the lungs. IRV + TV gives us the inspiratory capacity. 61 During a maximal forced expiration, an expiratory reserve volume can be exhaled, but there remains a residual volume in the lungs. Adding the two together gives us the functional reserve capacity. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Vital capacity is the tidal volume plus inspiratory reserve and expiratory reserve volumes combined. Vital capacity plus residual volume is the total lung capacity. Anatomic dead space is air remaining in the bronchial tree. 63 64 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Normal breathing is a rhythmic, involuntary act even though the muscles are under voluntary control. Breathing controlled by two factors: Neural factors and Chemical factors 65 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Groups of neurons in the brain stem (the medulla oblongata and the pons) comprise the respiratory center, which controls breathing by causing inspiration and expiration and by adjusting the rate and depth of breathing. 66 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemicals, lung tissue stretching, and emotional state affect breathing. Chemosensitive areas (central chemoreceptors) are associated with the respiratory center and are sensitive to changes in the blood concentration of carbon dioxide and hydrogen ions. If either carbon dioxide or hydrogen ion concentrations rise, the central chemoreceptors signal the respiratory center, and breathing rate increases. 67 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peripheral chemoreceptors in the carotid sinuses and aortic arch (heart) sense changes in blood oxygen concentration, transmit impulses to the respiratory center, and breathing rate and tidal volume increase. An inflation reflex, triggered by stretch receptors in the visceral pleura, bronchioles, and alveoli, helps to prevent overinflation of the lungs during forceful breathing. Hyperventilation lowers the amount of carbon dioxide in the blood. 68 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. The alveoli are the only sites of gas exchange between the atmosphere and the blood. The alveoli are tiny sacs clustered at the distal ends of the alveolar ducts. 69 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. The respiratory membrane consists of the epithelial cells of the alveolus, the endothelial cells of the capillary, and the two fused basement membranes of these layers. Gas exchange occurs across this respiratory membrane. 70 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gases diffuse from areas of higher pressure to areas of lower pressure. In a mixture of gases, each gas accounts for a portion of the total pressure; the amount of pressure each gas exerts is equal to its partial pressure. 71 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. When the partial pressure of oxygen is higher in the alveolar air than it is in the capillary blood, oxygen will diffuse into the blood. When the partial pressure of carbon dioxide is greater in the blood than in the alveolar air, carbon dioxide will diffuse out of the blood and into the alveolus. A number of factors favor increased diffusion; more surface area, shorter distance, greater solubility of gases, and a steeper partial pressure gradient 72 73 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gases are transported in association with molecules in the blood or dissolved in the plasma. 74 Over 98% of oxygen is carried in the blood bound to hemoglobin of red blood cells, producing oxyhemoglobin. Oxyhemoglobin is unstable in areas where the concentration of oxygen is low, and gives up its oxygen molecules in those areas. More oxygen is released as the blood concentration of carbon dioxide increases, as the blood becomes more acidic, and as blood temperature increases. A deficiency of oxygen reaching the tissues is called hypoxia and has a variety of causes. 76 CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon dioxide may be transported dissolved in blood plasma, as carbaminohemoglobin, or as bicarbonate ions. Most carbon dioxide is transported in the form of bicarbonate. 77
