Chapter 23: The Respiratory System Cardiovascular system is link between interstitial fluids and exchange surfaces of the lungs Respiratory system is composed of structures involved in ventilation and gas exchange Respiratory system has 5 functions: Providing surface area for gas exchange between air and circulating blood Moving air to and from exchange surfaces of lungs along respiratory passageways Protect respiratory surfaces from dehydration, temp changes, variation and defend respiratory system and other tissues from invasive pathogens Produce sounds for speaking and communication Facilitate detection of odors by olfactory receptors in superior portion of nasal cavity Upper respiratory system = nose, nasal cavity, paranasal sinuses, pharynx (throat) Filter, warm, humidify incoming air, protect more delicate surfaces of lower respiratory system Lower respiratory system = larynx (voicebox), trachea (windpipe), bronchi, bronchioles, alveoli of lungs Respiratory tract = passageways that carry air to and from exchange surfaces of lungs Conducting portion = nasal cavity to pharynx, larynx, trachea, bronchi and larger bronchioles Houses respiratory mucosa Respiratory portion = smallest, thinnest bronchioles and associated alveoli Alveoli = air-filled pockets within lungs where all gas exchange takes place Gas exchange is so quick because of short distance between blood in capillary and air in alveolus Surface area has so be very large for metabolic requirements to be met for the body SA of lungs is 35x SA of body Respiratory mucosa lines conducting portion of respiratory system Consists of epithelium and underlying layer of areolar tissue Lamina propria is underlying layer of areolar tissue that supports resp. epithelium Contains mucous glands in upper resp. system Contains bundles of smooth muscles in conducting portion of resp. system Smooth muscles form thick bands that encircle lumen at bronchioles Epithelium is pseudostratified ciliated columnar in nasal cavity and superior portion of pharynx Stratified squamous at inferior to pharynx Pharyngeal epithelium must protect against abrasion and chemical attack because of air conduction and food processing Pseudostratified ciliated columnar lines superior potion of lower resp. system Exchange surfaces are simple squamous, small bronchioles are cuboidal Respiratory defense system = series of filtration mechanisms Mucous cells in epithelium and mucous glands in lamina propria produce sticky mucus Cilia sweep mucus and trapped debris toward pharynx where it is swallowed Mucus escalator = lower resp. system, cilia beat toward pharynx, moving mucus and cleaning resp. surfaces Particles greater than 10 um are removed by filtration in nasal cavity 1-5 um are trapped in mucus Smaller than 0.5 um remain suspended in air Airborne irritant promote development of lung cancer Pathogens like TB can overwhelm resp. defenses infect lungs Coughing and chest pain, known as consumption CF (cystic fibrosis) mucus created is dense and cannot be transported by defense system Mucus elevator breaks down, breathing is difficult Common in European descent, survival is mid-30s Upper resp. system = nose, nasal cavity, paranasal sinuses, pharynx Nose = primary passageway for air entering resp. system Air enters through external nares (nostrils), open to nasal cavity Nasal vestibule = space contained within flexible tissue of nose Epithelium contains hair that traps large particles Nasal septum = divides nasal cavity into left and right Bony portion formed by ethmoid and vomer plate Anterior portion formed by hyaline cartilage Supports tip of nose Olfactory region = superior portion of nasal cavity (areas lined by olfactory epithelium) Inferior surface of cribiform plate Superior portion of nasal septum Superior nasal conchae Receptors here provide sense of smell Nasal conchae project towards nasal septum Air flows through vestibule to internal nares through meatuses = narrow grooves Turbulence caused by narrow grooves and conchae causes mucus to trap small particles, warms and humidifies and stimulate olfactory receptors Hard palate made up of maxillary and palatine bones Floor of nasal cavity, separates from oral cavity Soft palate extends posterior, boundary marking superior nasopharynx Nasal cavity open into nasopharynx by internal nares Nasal mucosa prepare air for arrival at lower resp. system Lamina propria contains veins that warm and humidify air Protect delicate surfaces from chilling or drying out Breathing through mouth eliminates this, respirators warm and humidify air for patients Warm air moves out, breathing through nose prevents heat and water loss Nosebleed = epitaxis common because of extensive vascularization Bleeding involves vessels of mucosa covering cartilaginous septum Causes = trauma, drying, allergies, clotting, hypertension Pharynx = throat that is a chamber shared by digestive and respiratory systems Extends between internal nares and entrances to larynx and esophagus Superior and posterior bound to axial walls, lateral walls are flexible and muscular Nasopharynx = superior portion of pharynx Connected to posterior portion of nasal cavity through internal nares Lined with pseudostratified ciliated columnar Each auditory tube open into nasopharynx at nasopharyngeal meatus on each side of pharyngeal tonsil Oropharynx = extends between soft palate and base of tongue at level of hyoid bone Posterior portion of oral cavity communicates with oropharynx Lined with stratified squamous Laryngopharynx = narrow inferior part of pharynx Includes portion between hyoid bone and entrance of larynx and esophagus Stratified squamous to resist abrasion, chemicals and pathogens Larynx is cartilaginous tube that surrounds and protects glottis (voicebox) Begins at C4 or C5 and ends at C6 Three large unpaired cartilage form larynx Thyroid cartilage Largest laryngeal cartilage Forms anterior and lateral walls Adams apple Cricoid cartilage Inferior to thyroids Both cricoid and thyroid protect glottis and entrance to trachea Attached to tracheal cartilage by ligaments Composed of hyaline cartilage (so is thyroid) Epiglottis Shoe-horned shaped Superior to glottis and forms lid over it Closed when swallowing, larynx is elevated here Composed of elastic cartilage Larynx contains three smaller pairs of hyaline cartilage Arytenoid cartilage Articulates superior border of cricoid cartilage Corniculate cartilage Articulate with arytenoid cartilage, function to close glottis and produce sound Cuneiform cartilage Extends between lateral surface of arytenoid and epiglottis within folds of tissues Median cricothyroid ligament is easily identifiable and where emergency tracheostomy usually takes place Vestibular ligaments and vocal ligaments extend between thyroid cartilage and arytenoid cartilage Covered by folds of laryngeal epithelium Vestibular ligaments lie within vestibular folds Inelastic and lateral to glottis Glottis is made up of vocal folds and space between them rima glottidis Vestibular folds help prevent foreign objects from entering open glottis and more delicate inferior folds Vocal folds are highly elastic and involved in production of sound and known as vocal cords Sound is produced when air passes through open glottis, vibrates vocal folds and produces sound waves Pitch depends on diameter, length and tension in folds Diameter and length determined by size of larynx, we control tension Increased distance = pitch rises Children and woman have smaller larynx = higher voices Sound production = phonation Clear speech also requires articulation (modification of sound with other structures) like teeth, tongue and lips Amplification and resonance occurs when walls vibrate and sound echoes in pharynx, oral cavity, nasal cavity and paranasal sinuses Voice sounds different when paranasal sinuses are filled with mucus rather than air Inflammation of larynx = laryngitis, causes hoarseness Acute epiglottis = swelling of epiglottis, may cause suffocation, common in children Larynx is made up of two sets of muscles: Muscles of neck and pharynx Position and stabilize larynx Smaller intrinsic muscles that control tension in glottal vocal folds or open and close glottis Rotational movements When swallowing, both sets of muscles work together to prevent objects from entering glottis Food is chewed into pasty mass = bolus Food that touches vestibular folds or glottis rings causes coughing reflex, air ejects mass that blocks glottis Trachea is tough, flexible windpipe that begins at C6 and ends in T5, branches to right and left primary bronchi Submucosa of trachea surrounds mucosa Submucosa contains mucous glands Contains 15-20 tracheal cartilages stiffen tracheal walls and protect airway from collapsing or overextending C-shaped Trachealis muscle band of smooth muscle connects ends of each tracheal cartilage Contraction reduces diameter of trachea Airflow resistance increases Sympathetic nervous system increases diameter Internal ridge, carina separates left and right primary bronchi C-shaped rings, like trachea, ends of Cs overlap, however Right primary bronchus larger than left in diameter, descends towards lung at steeper angle Foreign objects enter right then Bronchi branch to groove, hilum, provides access for entry to pulmonary vessels, nerves, lymphs Known as root of lung Lungs are surrounded by pleural cavities Lungs have distinct lobes, separated by deep fissures Right lungs has superior, middle and inferior lobes, separated by horizontal and oblique fissures Left lung has superior and inferior separated by oblique fissure Right lung broader, left lung longer Cardiac notch = vertical line of right lung Primary bronchi and branches form bronchial tree Extrapulmonary bronchi are primary, and outside lungs Intrapulmonary bronchi are branches within lungs Primary bronchi divide to form secondary bronchi (lobar) Each secondary bronchi goes to an individual lobe Secondary branch to form tertiary bronchi (segmental) Supplies air to bronchopulmonary segment Right = 10 left = 8/9 Walls of bronchi progressively contain less cartilage As amount of cartilage decreases, amount of smooth muscles increase, amount of tension is muscles has greater effect of bronchial diameter and resistance to airflow Bronchitis infection of bronchi and bronchioles, individual has difficulty breathing Tertiary bronchi branches into bronchioles then into terminal bronchioles 6500 terminal bronchioles from each tertiary bronchus, lumen = .3-.5 mm Changes in diameter of bronchioles control resistance to airflow and distribution of air in lungs Sympathetic = bronchodilation Parasymphateic = bronchoconstriction Allergic reactions These are ways of adjusting airflow Tension in smooth muscles can cause bronchiole mucosa to form series of folds that limits airflow Asthma causes excessive stimulation Can almost completely prevent airflow along terminal bronchioles Interlobular septa divide lungs into pulmonary lobules Each terminal bronchiole delivers air to single pulmonary lobule Terminal bronchiole branches to form several respiratory bronchioles Thinnest and most delicate branches of bronchial tree Deliver air to gas exchange surfaces of lungs Pathogens or particulates will damage if reach here Respiratory bronchioles are connected to individual alveoli and multiple alveoli along regions called alveolar ducts End at alveolar sacs, common chambers connected to multiple individual alveoli Each lung contains 150 million alveoli Each alveolus is associated with network of capillaries Network of elastic fibers surround capillaries When fibers recoil during exhalation, size of alveoli is reduces and air is pushed out of lungs Alveolar epithelium is simple squamous Type I pneumocytes = squamous epithelial cells that are unusually thin and sites of gas diffusion Alveolar macrophages = dust cells, patrol epithelial surfaces and phagocytize particles Large type II pneumocytes = produce surfactant, oily secretion containing phospholipids and proteins Plays roles in keeping alveoli open, reduces surface tension If inadequate amount produce alveoli collapse after each exhale, inhale must be forceful to open them, person soon exhausted = respiratory distress disorder Gas exchange occurs at respiratory membrane 3 layers Squamous epithelial cells lining alveolus Endothelial cells lining adjacent capillary Fused basement membrane between alveolar and endothelial cells Diffusion occurs very rapidly across respiratory membrane because distances are short and O2 and CO2 are lipid-soluble molecules Pneumonia develops from infection that cause inflammation of lobules of lungs Fluids leak into alveoli, respiratory bronchioles swell, restricts passage of air Disease more likely when respiratory defenses already compromised b/c of AIDS, smoking, etc. Blood supply to lungs Two circuits nourish lung tissue Respiratory exchange Receive blood from arteries of pulmonary circuit, enter lungs at hilum Endothelial cells of alveolar capillaries are primary source of ACE (converts circulating angiotensin I to angiotensin II) Conducting exchange Receive oxygen and nutrients from capillaries supplied by bronchial capillaries Pulmonary embolism = blockage of a branch of a pulmonary artery that stops blood flow to a group of lobules or alveoli Can result in congestive heart failure If pulmonary embolism is in place for several hours, alveoli will permanently collapse Pleural cavities are separated mediastinum Each lung surrounded by single pleural cavity Lined by serous membrane known as pleura Two layers: parietal (covers inner surface of thoracic wall and extends over diaphragm and mediastinum Visceral covers outer surface of lungs, extending into fissures between lobes Pleura secrete small amount of pleural fluid Forms moist, slippery coating that provides lubrication, reduces friction between parietal and visceral surfaces as breath Thoracentesis is sampling of pleural fluid with long needle inserted between ribs Pleural inflammation = pleurisy Breathing becomes difficult, medical attention required External respiration is process involved in exchange of oxygen and carbon dioxide between bodys interstitial fluid and external environment. Purpose is to meet respiration demands of cells Three integrated steps; Pulmonary ventilation (breathing) Gas diffusion across respiratory membrane between alveolar spaces and alveolar capillaries and between blood and other tissues Transport of oxygen and carbon dioxide between alveolar capillaries and capillary beds in other tissues Any abnormalities affecting any steps involved in external resp. affect concentration of gases in interstitial fluids and therefore cellular activities Hypoxia = low tissue oxygen levels Anoxia = oxygen supply cut off completely cells die very quickly, stroke and heart attack damage Pulmonary ventilation = physical movement of air into and out of respiratory tract Function = maintain adequate alveolar ventilation (movement of air into and out of alveoli) Atmospheric pressure compresses our bodies and everything around us Boyles Law (gas pressure & volume) = increase volume of container, gas pressure decreases P=1/V Air flows from area of higher pressure to lower pressure Diaphragm contracts = moves inferior and increases volume of thoracic cavity When thoracic cavity enlarges, volume increases, pressure inside lungs is less thus, air rushes in until pressures are the same Compliance of lungs = how easily lungs expand Lower the compliance, greater the force required to fill lungs Connective tissue, level of surfactant and mobility of thoracic cage all affect compliance Direction of airflow is determined by relationship between atmospheric pressure and intrapulmonary pressure Interpulmonary pressure = pressure inside respiratory tract at alveoli Quiet breathing makes difference between interpulmonary pressure and atmospheric pressure pretty small Inhalation interpulmonary pressure = 759 mm Hg Exhalation intrapulmonary pressure = 761 mm Hg Atmospheric pressure = 760 mm Hg More heavily you breathe = greater difference in gradient achieved interpleural pressure = pressure in pleural cavity between parietal and visceral pleurae (avg -4 mm Hg) respiratory cycle = single cycle of inhalation and exhalation tidal volume = amount of air you move into or out of your lungs in a single respiratory cycle Mechanics of breathing Inhalation (always active) = contraction of diaphragm to increase thoracic cavity (75%) Contraction of external intercostal muscles raises ribs (25%) Contraction of accessory muscles Exhalation = internal intercostal and transversus thoracic muscles depress ribs Ab muscles assist in exhalation by compressing abdomen Quiet breathing = eupnea (passive) Deep breathing = diaphragmatic breathing, diaphragm Minimal levels of activity Costal breathing = shallow breathing, rib cage alters shape Elastic rebound = elastic components involved in breathing recoil, retuning diaphragm and rib cages back to original position Forced breathing = hypernea Involves active inspiratory and expiratory movments Respiratory rates and volumes Respiratory rate = number of breaths you take each minute Respiratory minute volume = respiratory rate x tidal volume VE = f x Vt Volume of air in conducting passages = anatomic dead space Alveolar ventilation = Va, amount of air reaching alveoli each minute Va = f x (Vt x Vd) Vd = anatomic dead space Increasing tidal volume (breathing more deeply) increases alveolar ventilation rate Increasing respiratory rate (breathing more quickly) increases alveolar ventilation rate Respiratory performance Total volume of lungs can be divided into series of volumes and capacities Measurements can be obtained by spirometer Tidal volume = 500ml in females and males Expiratory reserve volume = amount of air you can voluntarily expel after you have completed a normal, quiet respiratory cycle Male = 1000 ml, female = 700 ml Residual volume = amount of air remaining in lungs after maximal exhalation 1200 males, 1100 females Minimal volume = amount of air remaining lungs even if they collapse Inspiratory reserve volume = amount of air you can take in over the tidal volume Male = 3300 ml, female = 1900 ml Inspiratory capacity = amount of air you can draw into lungs after you have completed quiet respiratory cycle Functional residual capacity = amount of air remaining in lungs after completed quiet respiratory cycle Vital capacity = max amount of air you can move into or out of lungs in a single respiratory cycle 4800 males, 3400 females Total lung capacity = total volume of lungs 6000 males, 4200 females Gas laws Daltons law = each gas contributes to total pressure in proportion to its relative abundance Partial pressure = pressure contributed by a single gas in a mix of gases Henrys law = at a given temperature, the amount of a particular gas in solution is directly proportional to its partial pressure Alveolar air contains more CO2 and less O2 than atmospheric air Gas exchange is efficient for five reasons: Differences in partial pressure across the respiratory membrane are substantial Greater difference = faster rate of diffusion Distance involved in gas exchanges are short Gases are lipid soluble Total surface area is large Blood flow and airflow are coordinated Diffusion between alveolar capillaries increases PO2 and decreases PCO2 PO2 = 100 mm Hg PCO2 = 40 mm Hg Pulmonary veins carry blood that is lower in PO2 (95) Interstitial respiration (cellular/tissue respiration) is process that involves absorption of oxygen and release of carbon dioxide by those cells Oxygen is transported bound to hemoglobin Each hemoglobin molecule can bind to four oxygen, forming oxyhemoglobin Hemoglobin saturation = percentage of heme units containing bound oxygen at any given moment Bohr effect = decreased hemoglobin saturation with decrease pH Carbonic anhydrase = catalyzes reaction of CO2 with water molecules As temperature increases, hemoglobin releases more oxygen Higher concentration of BPG, greater release of oxygen by Hb molecules RBCs of fetus contain fetal hemoglobin Much higher affinity for oxygen than adult hemoglobin After entering blood, CO2 molecule is converted carbonic acid or binds to hemoglobin within red blood cells, or dissolves in plasma 70% in transported as carbonic acid 23% as carbaminohemoglobin 7% in plasma Chloride shift = mass movement of chloride ions into RBCs Neurons in medulla oblongata and ponds control respiration and respiratory reflexes Respiratory centers = three pairs of nuclei in reticular formation of medulla oblongata and pons Respiratory rhythmicity centers can be subdivided into dorsal respiratory group and ventral respiratory group DRG = inspiration Every respiratory cycle, quiet or forced Active after 2 seconds, inhalation takes place, next 3 seconds passive exhalation takes place VRG = expiration Only during forced breathing Active exhalation SIDS leading cause of death for babies under a year old Suggested SIDS results from problem in interconnection process that disrupts reflexive respiratory pattern Respiratory reflexes are modified by chemoreceptors, baroreceptors, stretch receptors, irritating stimuli, other sensations Chemoreceptors reflex Glossopharyngeal nerve, vagus nerve Chemoreceptors located in medulla oblongata Hypercapnia = increase in PCO2 of arterial blood Common cause of is hypoventilation = respiratory rate is abnormally low, CO2 accumulates in blood Hyperventilation = rate and depth of respiration exceeds demands for oxygen delivery Leads to hypercapnia = abnormally low CO2 Baroceptor reflexes Hering-Breuer reflexes Inflation reflex = prevents overexpansion of lungs during forced breathing Deflation reflex = inhibits expiratory centers and stimulates inspiratory centers when lungs are deflating Protective reflexes Sneezing, coughing Apnea period where respiration is suspended Respiratory performance declines with age Elastic tissue deteriorates with age, decreased flexibility limits chest movements, emphysema is normal in individuals over 50 Emphysema blocks airflow, limits breathing Respiratory system also provides oxygen and eliminates CO2 from other organ systems Physiological adjustments are made at higher altitudes with lower atmospheric pressures so individuals can function normally