in chapter 22 we will discuss the respiratory system the respiratory system is important because during respiration we exchange gases most notably oxygen and carbon dioxide between the atmosphere lungs blood and tissue we have to maintain a certain amount of o2 and co2 content oxygen and carbon dioxide content within our body in order for homeostasis to be maintained there is many factors that can contribute to alterations in our respiratory rate such as being at a high elevation like when you are climbing a mountain as shown in the diagram the functions of the respiratory system are shown here the respiratory system provides an extensive surface area for gas exchange between the air and the circulating blood it also moves air to and from the exchange surfaces of the lungs along the respiratory passageways the respiratory system protects respiratory surfaces from dehydration temperature changes or other environmental variations and defends the respiratory system and others tissues from invasion by pathogens the respiratory system produces sounds involved in speaking singing and other forms of communication and the respiratory system facilitates the detection of olfactory stimuli by olfactory receptors in the superior portions of the nasal cavity let's begin our study of the respiratory system by examining some of the organs structures of the respiratory tract here we can see the major respiratory structures and we will examine the respiratory system by looking at the upper respiratory tract and then the lower respiratory tract let's examine the upper respiratory tract first this includes the nose nasal cavity paranasal sinuses and pharynx the nose is the primary passageway for air entering the respiratory system when you are resting and breathing quietly the nose consists of several structures in respiration like the bridge of the nose the nasal septum the nasal cartilages and the external nares other structures of the nose consist of the apex dorsum neighs eye and root the upper airway structures are shown here and the upper airway structures consist of a multitude of structures that are important in respiration such as the paranasal sinuses which include the maxilla frontal ethmoid and sphenoid bones which contain hollow membrane line cavities called sinuses the mucous secretions produced in these sinuses keep the surfaces of the nasal cavity moist and clean the pharynx which is also shown here is a chamber that's more commonly called the throat and is shared by the digestive and respiratory tracts the curving and superior and posterior walls of the pharynx are closely bound to the axial skeleton the lateral walls are flexible and muscular the pharynx is divided into three regions the nasopharynx which is the superior portion of the Farex located between the soft palate and the internal nares the oral pharynx which extends between the soft palate and the base of the tongue at the level of the hyoid bone and the laryngeal Paris which includes portions of the Farex between the hyoid bone and the entrance to the larynx called the glottis and the esophagus other nasal structures are found or respiratory structures are found within the nasal cavity and the nasal cavity is the space between the external nares and the internal nares at the back of the nasal cavity here we have the nasal vestibule which is the space contained within the flexible tissues of the nose the cribriform plate of the ethmoid bone which forms the roof of the nasal cavity the hard palate which forms the anterior portion of the floor of the nasal cavity the soft palate which is a membranous and muscular flap with attached reticular tissue called the uvula the Conca which is bony ridges that project towards nasal septum from the lateral walls of the nasal cavity and there are three Conca superior inferior and middle nasal conchae the me anuses which allows air that passes from the external nares to the internal nares when it flows between the Conca it goes through the superior middle and inferior me a das's and the internal nares which actually distinguished the end of the nasal cavity and the beginning of the Ference here we can see the respiratory epithelium which is composed of pseudo stratified ciliated columnar epithelium here you can see the divisions of the pharynx that I mentioned the nasal pharynx oropharynx and Lorenzo pharynx now the other respiratory tract consists of the larix trachea bronchial tree lungs alveolar epithelium and the respiratory membrane let's first examine the larynx the larynx is a cartilaginous structure that surrounds and protects the glottis and is more commonly called the voice box it consists of the glottis and this is where this is a structure when inhaled air leaves the pharynx and enters the larynx through the narrow opening the glottis we also have the epiglottis which is the only piece of formed of elastic cartilage forming a flexible flap that covers the glottis during swallowing so that food cannot enter the respiratory passageways the larynx also contains another cartilage called the thyroid cartilage and the thyroid cartilage is a large single piece of hyaline cartilage forming the anterior and lateral walls of the larynx the prominent anterior surface is more commonly called the Adam's apple and is known as the laryngeal prominence the cricoid cartilage is a single piece of hyaline cartilage which has a greatly expanded posterior portion to provide support together the cricoid and thyroid cartilage protect the glottis and entrance to the trachea in addition their broad surfaces provide sites for the attachment of important muscles and ligaments the arachnoid cartilages are two small pieces of hyaline cartilage which articulate with the superior surface of the cricoid cartilage and also help to anchor the vocal chords cuneiform cartilage is too long curved pieces of hyaline cartilage and these lie within the folds of tissue that extend between the lateral surface of each ear at anoint cartilage and the epiglottis core niculae cartilage consists of two small pieces of hyaline cartilage that articulate with the arachnoid cartilage to function in the opening and closing of the glottis and the production of sound the vocal cords are shown here the vestibular and vocal ligaments are bands of connective tissue that extend between the thyroid cartilage and arachnoid cartilage the vocal folds housed the vocal ligaments and lie inferior to the vestibular folds the vocal folds vibrate as air passes over them and are therefore involved with the production of sound and are also known as the vocal cords or true vocal cords the vestibular folds housed a relatively inelastic pair of a Stig Euler ligaments that are not associated with sound production instead these folds help prevent foreign objects from entering the glottis and matching the more delicate vocal folds the vestibular folds are also known as the false vocal cords the trachea is shown here and the trachea or windpipe as it is more commonly known is a tough flexible tube that conducts air towards the lungs it is composed of three distinct layers the mucosa submucosa and adventitia it also contains tracheal cartilages these are 15 to 20 C shaped rings of hyaline cartilage which stiffen the trachea walls and protect the airway they also prevent its collapse or over expansion as pressure changes within the respiratory system the trachea Allis muscle is a muscle that when contraction of the smooth muscle helps to reduce the diameter of the trachea and can thereby increase resistance to air flow for example sympathetic stimulation relaxes the trachea Allis muscle increasing the diameter of the trachea and making it easier to move air along the respiratory passageways such as during exercise on the side of the Carina which is at the bottom of the trachea and is a triangular piece of cartilage that helps to support the branching of the trachea to form the primary bronchi we can also begin to see some of the bronchial tree which we will discuss further in another upcoming slide now the lungs are the next part of the respiratory system that we will examine first let's look at the gross anatomy of the lungs the lungs are paired organs of the thoracic cavity composed of approximately a hundred and fifty million alveoli each giving the lungs a spongy appearance and texture the lungs has an apex and a base the apex of the lungs is the narrow pointed region at the top while the base is the wide region at the bottom in contact with the diaphragm the right long as you can see here is composed of three lobes a superior middle and inferior lobe / to fissures a horizontal fissure divides the superior from the middle lobe and the oblique fissure divides the middle lobe from the inferior lobe the left lung is composed of only two lobes a superior and inferior lobe divided by a single fissure the oblique fissure the left lung also possesses the cardiac notch which is a curvature that allows for the heart to tilt to the left of the midline here you can see the respiratory zone and you can see how the bronchioles lead to alveolar sacs in the respiratory zone where gas exchange occurs as noted on the previous slide the bronchial tree divides into the primary bronchi secondary bronchi and tertiary bronchi each tertiary bronchus delivers air to microscopic passageways called bronchioles the terminal bronchioles are shown here and are the last branch of the conducting zone and supply a single pulmonary lobule while the respiratory bronchioles are the first branch of the respiratory zone that extend within the pulmonary lobule and terminate and many tiny alveoli respiratory bronchioles open into regions called alveolar ducts which connect many individual alveoli forming an alveolar sac as the cartilage progressively disappears in the bronchioles smooth muscle increases and changes in the contraction of this thick muscle layer causes bronchodilation and bronchoconstriction here you can see the structures of the respiratory zone including the alveoli which is responsible for gas exchange and you can also see the alveolar ducts the lumen of the bronchial leading into the alveolar ducts the alveolar sac and the individual alveoli now the respiratory membranes are also shown here of the alveolar epithelium the pleura of the lungs are noted here and the pleural membranes consists of a serous membrane forming two distinct layers you have the parietal pleura which is a serous membrane that lines the interior of the thoracic cavity and extends over the diaphragm and mediastinum and the visceral pleura which is a serous membrane that lines the external surface of the lung in addition pleural cavity the pleural cavity and pleural fluid is also shown here the pleural cavity is the space between the parietal and visceral pleura the pleural cavity contains a small volume of pleural fluid that coats the pleural surfaces and reduces here we can see the difference in Normal and asthmatic tissue normal tissue does not have the characteristics of lung tissue an asthma attack which includes thickened mucosa increased mucus producing goblet cells and asano fill intra infiltrates is also shown asthmatic tissue because of these additional structures and glandular secretions as well as cells can cause a narrowing of the passageways which makes it difficult for a person to breathe now let's examine the process of breeding pulmonary ventilation is defined as the moving of air into and out of the respiratory tract basically inhalation and exhalation it's the exchange of air between the atmosphere and the lungs and is more simply referred to as breathing there are several different pressures that must be considered when discussing pulmonary ventilation atmospheric pressure is the force exerted by the mixture of air surrounding the body normal atmospheric pressure at sea level is 760 millimeters of mercury alveolar pressure which is also known as inter pulmonary pressure is the force exerted by the air within the alveoli of the lungs this pressure rises and falls as the phases of breathing progress intrapleural pressure is the pressure within the pleural cavity it is always four millimeters of mercury lower than the alveolar pressure so the alveoli will be able to inflate if the pressure in the pleural cavity rises it causes a pneumothorax here we can see the inter pulmonary and intrapleural pressure relationship alveolar pressure changes during the different phases of the cycle and you can see the intrapleural pressure the transpulmonary pressure and the intra alveolar pressure another factor that is important in pulmonary ventilation is Boyle's law and Boyle's law refers to volume and states that volume is inversely proportional to pressure that is as volume increases pressure decreases and you can see that demonstrated in the slide and as volume decreases pressure increases if you reduce the volume of the thoracic cavity by half the pressure when the thoracic cavity will double if you double the volume of the thoracic cavity the pressure within will decline by half now the changes that occur in alveolar pressure that occur with breathing are created by variations in lung and thoracic volume and there are some muscles that are you there are several units of measurement listed here for gas pressures and other units are also used in clinical practice you can review the definitions of the units of measurement demonstrated here now there's many factors that can affect pulmonary ventilation surface-tension compliance and resistance surface tension is the liquid that's keeping the respiratory membranes moist primarily composed of water molecules and as such has the tendency to form hydrogen bonds surfactant helps reduce the surface tension so that the lungs do not collapse on themselves compliance is an indicator of expandability or stretch the greater the compliance the lower the tension in the walls of the lungs at a given volume and therefore air flows more easily along the conducting passages the lower the compliance the greater tension in the walls of the lungs at a given volume and the less air flows as readily or easily along the conducting passageways resistance is an indication of how much force is required to inflate and deflate the lungs at rest the muscular activity involved in pulmonary ventilation accounts for about 3 to 5 percent of the resting energy demand the higher the resistance the harder it is to force air along the conducting passageways the lower the resistance the more easily air flows along the conducting passageways and this is regulated by bronchodilation and bronchoconstriction here we can see some of the pulmonary volumes and capacities tidal volume is the amount of air moved into the lungs during inhalation and out of the lungs during exhalation it is approximately 500 milliliters inspiratory reserve volume is the amount of air that can be forcibly inhaled after a normal tidal volume inhalation I RV or inspiratory reserve volume ranges from 1900 to 3,300 milliliters expiratory reserve volume or ERV is the amount of air that can be forcibly exhaled after a normal tidal volume exhalation and it ranges from 700 to a thousand milliliters residual volume or RV is the amount of air that remains in your lungs even after a forcible exhalation this volume range is from 1,100 to 1,200 milliliters other respiratory capacities and pulmonary volumes are shown here inspiratory capacity or IC is the maximum amount of air that can be inspired after a normal expiration inspiratory capacity is equal to IR V Plus tidal volume functional residual capacity or FR v FR c sorry is the amount of air remaining in your lungs after you have completed a quiet respiratory cycle FR c is equal to e RB plus RV vital capacity is the maximum amount of air that you can move into or out of your lungs in a single respiratory cycle vital capacity or vc is equal to ir v plus tidal volume plus ERV and total lung capacity or TLC is the volume of your lungs and is the sum of all for respiratory volumes so TLC is equal to IR V Plus tidal volume plus erv plus residual volume and these volumes and capacities are outlined here for you now a pulmonary ventilation must be closely regulated to meet the tissues demand for oxygen and the respiratory system adjusts pulmonary ventilation to meet oxygen demands during changing activities these adjustments involve varying the number of breaths per minute and the amount of air move per breath respiratory minut volume is shown here respiratory - volume is the amount of air moved per minute and is calculated by multiplying the number of breaths per minute times the tidal volume so for example if the number of breaths per minute is 12 and the tidal volume is around 500 milliliters then the respiratory minut volume would be 12 times 500 milliliters or 6,000 milliliters the normal respiratory rate is also shown here and that's the number of breaths you take each minute and in an adult it ranges from 12 to 18 breaths per minute children breathe more rapidly and have a respiratory rate of about 18 to 20 breaths per minute alveolar ventilation is the amount of air reaching the alveoli each minute the alveolar ventilation is less than the respiratory mining volume because some of the air never reaches the alveoli but instead remains in the conducting zone of the lungs and bronchial tree this is known as anatomical dead space and at rest amounts to roughly a hundred and fifty MLS of the 500 MLS of tidal air not reaching the alveoli alveolar ventilation is calculated by the number of breaths per minute times the tidal volume minus the anatomical dead space here we can see the respiratory centers of the brain the control of respiration involves interacting mechanisms of the brainstem higher brain centers baroreceptors chemoreceptors and stretch receptors the respiratory centers are located with the in the medulla oblongata and serve as the pacemaker to establish the basic pace of breathing the dorsal respiratory group or DRG contains the neurons that control lower motor neurons innervating the primary inspiratory muscles this centered functions in every respiratory cycle and is therefore called the pacemaker the ventral respiratory group or vrg has inspired Tory and expiratory centers that function only when the ventilation demands increase and accessory respiratory muscles are needed the Avenue istic and pneumo toxic centers are located within the pons and these are paired nuclei that adjust the output of the respiratory centers the Avenue istic Center promotes inhalation by stimulating the drg during forced breathing the avenue istic center adjusts the degree of stimulation in response to sensory information from the vagus nerve concerning the amount of lung inflation the pneumo toxic Center inhibits the AAP new astok Center and thereby promotes passive or active exhalation higher brain centers are located within the cerebral cortex limbic system and hypothalamus and can alter the activity of the pneumo toxic centers but essentially normal respiratory cycles continue even if the brain stem superior to the pons has been severely damaged in addition chemoreceptors baroreceptors and stretch worship receptors are also shown here and have a function in response to changes in respiration and control of respiration are also noted now let's examine gas exchange gas diffusion depends on the partial pressures and solubility of gases the partial pressure of a gas is the pressure contributed by a single gas in a mixture of gases the principles that govern the movement and diffusion of gas molecules are relatively straightforward these principles are known as the gas laws and include Boyle's law already mentioned dalton's law and Henry's law the definitions of those laws are shown here there is different definitions of respiration although we have been talking about pulmonary ventilation external respiration is the exchange of gases between the lungs and the blood oxygen moves from the lungs into the blood while carbon dioxide moves from the blood into the lungs an internal respiration is the exchange of gases between the blood and the tissues oxygen moves from the blood to the tissues while carbon dioxide moves from the tissues into the blood and here we can see that process of external respiration of internal respiration now let's examine the transport of gases here we conceive the erythrocytes and hemoglobin we're going to first examine oxygen transport approximately 98 to 99 percent of oxygen in the blood is transported bound to hemoglobin within red blood cells as oxyhemoglobin the remaining 1 to 2 percent of oxygen is dissolved in the blood plasma there are several factors that can affect the amount of oxygen bound to hemoglobin or rather the hemoglobin saturation and that is shown here the partial pressure of oxygen can impact the amount of oxygen bound to hemoglobin as the partial pressure of oxygen increases the percent hemoglobin saturation increases the partial pressure of co2 can also impact the amount of oxygen bound to hemoglobin as the partial pressure carbon dioxide increases the percent hemoglobin saturation decreases pH is another factor that can impact its transport as the pH decreases meaning it's becoming more acidic the percent of hemoglobin saturation decreases the relationship between pH and hemoglobin saturation is known as the Bohr effect and temperature as the temperature increases the percent of hemoglobin saturation decreases carbon dioxide transport is shown here approximately 93 percent of carbon dioxide that enters the blood from the tissues diffuses into the red blood cells of this only 23 or roughly 23 percent of the carbon dioxide binds to the amino acids in the globular proteins of the hemoglobin molecule forming carbon II no hemoglobin the remaining 70% is converted to carbonic acid by the enzyme carbonic anhydrase which immediately disassociates into a hydrogen ion and a bicarb ion and you can see that here the bicarbonate ion then diffuses out of the red blood cell and into the blood plasma with the aid of a counter transport mechanism that exchanges intracellular bicarbonate ions for extracellular chloride ions this exchange is known as the chloride shift approximately seven percent of carbon dioxide is dissolved and transported in blood plasma here we can see a hyperbaric chamber which may be needed in certain instances where the respiratory system or the level of oxygen or co2 has been compromised in the blood now let's examine the embryonic development of the respiratory system here is the oxygen hemoglobin disassociation curve in both the fetus and the adult and you can see that the fetal hemoglobin has a much greater affinity for oxygen then does adult hemoglobin here we can see the development of the lower respiratory system as it occurs during fetal development going from the beginning of the fourth week all the way into eight weeks where we can see some of the lobes of the lungs have begun to emerge now let's examine some of the disorders of the respiratory system there are many diseases or disorders of the respiratory system as shown here we will examine some of these in a little more detail COPD is known as chronic obstructive pulmonary disease and as a general term that indicates a progressive disorder of the Airways that restricts airflow and reduces alveolar ventilation asthma is when the respiratory passageways are extremely sensitive to irritants resulting in constriction of the Airways inflammation and edema within the mucosa of the passageways an accelerated mucous production it can be caused by allergies toxins or even exercise chronic bronchitis is a long-term inflammation and swelling of the bronchial lining leading to over production of mucous secretions the characteristics - frequent coughing with sputum production commonly related to cigarette smoking but also results from other environmental irritants it is often described as a blue bloater because as a result of the edema from heart failure and skin turning blue from lack of oxygenation emphysema is a chronic progressive condition characterized by shortness of breath and an inability to tolerate physical exertion the underlying problem is the destruction of alveolar surfaces an inadequate surface area for oxygen and carbon dioxide exchange to compensate the individual breathe more rapidly to maintain near normal oxygenation laryngitis is inflammation of the vocal cords cystic fibrosis is the most common lethal inherited disorder among Caucasians of Northern European descent and causes an increase in mucus produced by the mucous membranes of the respiratory and digestive tracts within the lungs the excess mucus inhibits gas exchange and clogged respiratory passageways it's frequency is around 1 in 2,500 births infant respiratory distress system syndrome is when there is inadequate surfactant production in newborns or in premature babies this leads to increase surface tension and alveolar collapse a pneumothorax is air within the intramural space resulting in an increased pressure on the outer surface of the lungs which can cause the lung to collapse pleurisy is inflammation of the pleural membrane apnea is a period in which respiration is suspended it can be associated with sleep which is called sleep apnea and it also occurs as a reflex shortly before a sneeze or a cough tuberculosis is an infectious disease caused by the bacteria Mycobacterium tuberculosis and results in fibroid masses in the lungs and an increase in dead space pneumonia is a bacterial or viral infection of the lungs pleural effusion is shown here and lung cancer is the final disorder that we will discuss lung cancer accounts for about 13% of new cancer cases in both men and women and kills quite a number of people each year outside of colon breast and prostate cancer combined over 50% of lung cancer patients will die within a year of diagnosis research has shown that 85 to 90% of all lung cancer cases are the direct result of cigarette smoking life expectancy of a smoker is shorter than that of a nonsmoker although some decrease in respiratory performance is inevitable you can prevent serious respiratory deterioration by stopping smoking or better yet never starting this conclude our overview of the respiratory system