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Chapter 14 Lecture Slides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiratory System Anatomy Body cells require Constant supply of oxygen Constant removal of carbon dioxide Both respiratory and cardiovascular systems contribute to fulfilling this requirement Respiration is the overall process of gas exchange between atmosphere and body cells Respiration involves four events 1. 2. Movement of air in and out of the lungs, which is call ventilation External respiration Gas exchange between air and blood in lungs by diffusion 3. Transport of gases between lungs and body cells Cardiovascular system 4. Internal respiration Gas exchange between blood and body cells by diffusion 14.1 Organs of the Respiratory System Subdivisions Upper respiratory system Portion not located in the thorax Lower respiratory system Portion located in the thorax Nose Nasal bones support the nose bridge, remaining is supported by cartilage Nostrils allow air to enter and leave nose Has hairs to filter large particles and insects Nasal cavity is the interior nose chamber Palate (roof of mouth) separates it from oral cavity Hard palate Soft palate Nasal septum divides cavity into R and L sides Three nasal conchae project from lateral walls Increase surface area of nasal cavity Lined with pseudostratified ciliated columnar epithelium Goblet cells in epithelium produce mucus Moistens incoming air and traps particles Air is warmed by blood vessels in mucus membrane Cilia move trapped particles to pharynx where they can be swallowed Destroyed by gastric juice in stomach Paranasal sinuses are air filled cavities in the bones around the nasal cavity In the ethmoid, frontal, maxillary, sphenoid bones Functions Lighten the skull Sound resonating chambers during speech Open into nasal cavity Lined with ciliated mucus membranes Pharynx Also called the throat Passageway posterior to nasal and oral cavities, extending to larynx and esophagus Muscular wall covered in a mucus membrane Consists of three parts Nasopharynx Oropharynx Laryngopharynx Auditory tubes Equalize air pressure on each side of tympanic membrane Tonsils Clumps of lymphatic tissues at openings to pharynx Sites of immune responses Three sets of tonsils Palatine tonsils Pharyngeal tonsil Lingual tonsils Larynx Cartilagenous, boxlike structure Passageway for air between pharynx and trachea Thyroid cartilage Adam’s apple Cricoid cartilage Connects to trachea Epiglottis Flap that prevents food from entering larynx Supported by ligaments that extend from hyoid bone Vocal cords Folds of mucus membranes Relaxed during breathing Contract and vibrate to produce sound Glottis is the opening between the cords Changes that occur during swallowing Goal is to prevent food from entering pharynx and direct food to esophagus Muscles lift larynx upward Epiglottis folds over to cover glottis Food is directed into esophagus If food or drink enters larynx, coughing occurs Trachea Tube that extends from larynx into thoracic cavity Branches to form primary bronchi C-shaped cartilagenous rings support trachea Hold airway open during breathing Open portion allows esophagus to expand during swallowing Lined by ciliated mucus membrane Mucus traps particles Cilia move particles upward to pharynx Bronchial Tree Trachea divides into R and L primary bronchi Enter R and L lungs Primary bronchi branch into secondary bronchi One for each lung lobe Secondary bronchi continue to branch into smaller tubules Establishes a bronchial trees Bronchi possess cartilagenous rings Bronchioles Very small tubes lacking cartilage Possess smooth muscle Lined with simple cuboidal epithelium Cannot remove foreign particles effectively Terminal bronchioles form alveolar ducts Alveolar ducts terminate in alveoli Alveoli ~300 million per lung Surface area ~75m2, holding ~6,000ml of air Site of respiratory gas exchange Filled with watery fluid to aid diffusion Surfactant prevents alveolar collapse during exhalation Reduces attraction between water molecules Lungs Cone-shaped and separated by heart and mediastinum Consist of alveoli, air passageways, blood and lymphatic vessels, and connective tissues Lungs are divided into lobes L lung has two lobes R lung has three lobes Lobes are supplied with a secondary bronchus, blood and lymphatic vessels, and nerves Lungs are surrounded by serous membranes Visceral pleura Attached to lung surface Parietal pleura Lines thorax wall and mediastinum Pleural cavity Potential space between the two pleurae Filled with serous fluid to reduce friction Helps keep the pleurae pressed together Respiratory System Physiology 14.2 Breathing Process that exchanges air between atmosphere and alveoli Air moves along a pressure gradient Air moves from high pressure region to low pressure region Three important breathing pressures 1. Atmospheric pressure 2. Intra-alveolar (intrapulmonary) pressure 3. Intrapleural pressure Pressure of air surrounding earth 760 mmHg at sea level Decreases at higher elevations Air pressure within the lungs Fluctuates during breathing Pressure within the pleural cavity Normally 756 mmHg Called “negative pressure” Keeps lungs pressed against thorax walls during breathing If it equals atmosphere pressure, lungs would collapse More info about dealing with higher altitudes: anthro.palomar.edu/adapt/adapt_3.htm Inspiration Process of breathing air into lungs Air pressure in lungs must be reduced to less then atmospheric air pressure Begins with muscle contraction Diaphragm Contraction pulls the diaphragm downward and flattens it External intercostal muscles Contraction lifts the ribs upward and outward Contractions increase volume of thoracic cavity Lungs are pulled outward with the thoracic cavity Increases lung volume and decreases intra-alveolar pressure Higher atmospheric pressure pushes air towards the lower intra-alveolar pressure in lungs Continues until pressures are equal Expiration Diaphragm and external intercostal muscles relax Thoracic cavity and lungs to return to normal size Decreases volume of thoracic cavity and lungs High intra-alveolar pressure pushes air out of lungs Continues until pressures are equal Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). 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Forceful expiration Contraction of internal intercostal muscles Pull ribs down and inward Contraction of abdominal muscles Force abdominal viscera and lungs upward Further decreases volume of lungs Increases air pressure in lungs, causing more air to flow out 14.3 Respiratory Volumes Average adult: 12 to 15 quiet breathing cycles per minute Breathing cycle: one inspiration followed by one expiration Volume of air inhaled during quiet or forceful breathing cycle varies Size, age, sex, physical condition Volumes 80% or less than normal average indicate respiratory disease Spirometers are used to determine respiratory volumes Produces a spirogram, a graphic record of air volumes being exchanged Tidal volume (TV) Volume of air exchanged during quiet breathing ~500ml Inspiratory reserve volume (IRV) Maximum volume of air that can be forcefully inhaled after a tidal inspiration ~3,000ml Expiratory reserve volume (ERV) Maximum volume of air forcefully exhaled after a tidal expiration ~1,100ml Residual volume (RV) Volume of air remaining in lungs are ERV ~1,200ml Keeps alveoli open, preventing lung collapse Vital capacity (VC) Maximum amount of air that an be forcefully exchanged TV + IRV + ERV ~4,600ml Total lung capacity (TLC) VC + RV ~5,800ml 14.4 Control of Breathing Control is through neurons of the respiratory center Located in both the medulla and the pons of the brain stem Medullary Respiratory Centers Controls the rhythmic nature of breathing Consists of two components Ventral respiratory group (VRG)- sets the normal breathing rhythm Dorsal respiratory group (DRG)- changes breathing pattern according to sensory input Pontine respiratory group (PRG) Coordinates the actions of the medullary respiratory centers Alters the rate and depth of breathing Adapts breathing to speech, singing, etc… 14.5 Factors Influencing Breathing • Chemicals – Important chemical factors include • CO2 • H+ ions – Formed when CO2 is carried in blood – Increase in CO2 causes an increase in H + • O2 Control of Respiration Chemoreceptors detect changes in these chemicals Respiratory center Carotid bodies Aortic bodies Control of Respiration Respiratory center is sensitive to changes in CO2 and H+ Increase in CO2 and H+ causes respiratory center to increase rate and depth of breathing Decrease in CO2 and H+ causes brief apnea Carotid and aortic bodies are sensitive to O2 concentration Low oxygen levels causes them to send impulses to respiratory center Control of Respiration Inflation Reflex Visceral pleurae have stretch receptors Inspiration stretches the visceral pleurae Impulses are sent via vagus nerve to respiratory center Inhibits the formation of impulses causing inspiration Promotes expiration and prevents excessively deep inspirations Control of Respirations Higher Brain Centers Voluntarily generated When a person chooses to alter the normal pattern of quiet breathing Limited in their control Control of Respirations Involuntary impulses Emotional experiences and chronic pain increase breathing rate Examples: fear, excitement Sudden emotional experience, sharp pain, or sudden cold stimulus can cause apnea Body Temperature Increase temperature, increase breathing rate Decrease temperature, decrease breathing rate 14.6 Gas Exchange External respiration Gas exchange between air in alveoli and blood in capillaries Diffusion through the respiratory membrane O2 moves from air into blood CO2 moves from blood into air Internal respiration Gas exchange between blood in capillaries and tissue cells Involves diffusion across capillary walls O2 moves from blood and into tissues CO2 moves from tissues and into blood 14.7 Transport of Respiratory Gases Red blood cells play a major role in transport of both O2 and CO2 Oxygen Transport In alveolar capillaries, 97% of O2 enters RBCs and forms oxyhemoglobin Binds to heme of hemoglobin 3% is dissolve in plasma In body tissues, 25% of O2 is released from oxyhemoglobin so it can diffuse out of the capillary Forms deoxyhemoglobin Bond between O2 and hemoglobin is unstable If surrounding O2 levels are high (i.e. lungs), hemoglobin readily binds O2 If surrounding O2 levels are low (i.e. tissues), hemoglobin readily releases O2 Carbon Dioxide Transport When CO2 diffuses from capillary blood, it takes three pathways 1. 7% is dissolved in plasma 2. 23% combines with globin of hemoglobin to form carbaminohemoglobin 3. 70% enter RBC and combines with water to form carbonic acid Reaction catalyzed by carbonic anhydrase Carbonic acid breaks down into H+ and bicarbonate ions The reactions forming bicarbonate ions and H + reverse to allow diffusion of CO2 into alveolar air Inflammatory Disorders Chronic obstructive pulmonary disease (COPD) Long-term obstruction Chronic bronchitis Emphysema Bronchitis Inflammation of bronchi accompanied by excessive mucus production partially obstructing air flow Acute bronchitis: viral or bacterial infection Chronic bronchitis: chronic asthmatics and smokers Emphysema Due to long term exposure to airborne irritants Effects- basically overinflated lungs Large spaces form when alveoli rupture Air blocked in alveoli due to excess mucus production Reduces respiratory surface area and impairs gas exchange Reduced ERV and increased RV result Exhaling requires voluntary effort Asthma Characterized by wheezing and dyspnea Due to contraction of bronchiole smooth muscle Causes Allergic reactions Hypersensitivity to pathogens infecting the bronchial tree Pleurisy Inflammation of pleural membranes Can have two effects Decreases serous fluid production, Causes sharp pains during breathing Increase serous fluid production, Causes increase in pressure on lungs Impairs their expansion Pneumonia Acute inflammation of alveoli caused by virus or bacteria Alveoli become filled with fluid, pathogens, and WBCs Reduces gas exchange space, resulting in low blood oxygen levels