Respiratory System Notes.docx

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Biological Sciences Program
BSCI 201
Justicia Opoku

Respiratory System Function and structures of the respiratory System: Functions and structures of the respiratory System Gas exchange between the blood and external environment: occurs in the alveoli of the lungs Passageways to the lungs purify, humidify and warm the incoming air Maintain blood plasma pH Structures of the respiratory System Nose Pharynx Larynx Trachea Bronchi Lungs Alveolar ducts Alveolar sacs Alveoli Anatomy of the respiratory system: Upper airways:Air passage of the head and neck Respiratory Tract: From the larynx throughout the lung: Composed of the: Conducting zone: conducts air from larynx through lungs Respiratory zone: sit of gas exchange: respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli Alot of branching to increase the surface area so we reduce the resistance.Allows us to increase air flow. Functions of the conducting zone: Air passageway, 150mL volume = dead space volume Increase air temperature to body temperature HumidifyAir Remove some particles Contains: Goblet cells  secret mucus Particles get stuck in the mucus. Ciliated cells  move particles toward mouth to be expelled Anatomy of the Nasal Cavity Olfactory receptors are located in the mucosa on the superior surface The rest of the cavity is lined with respiratory mucosa that MoistenAir Too little moisture: needed in order to use the right amount of moisture. Trap incoming foreign particles. Lateral walls have projections called conchae Increase surface area Increase air turbulence within the nasal cavity The nasal cavity is separated from the oral cavity by the palate Anterior hard palate (bone) Posterior soft palate (muscle) Sense of taste is usually pretty reliant off the sense of smell. People smell if before you taste it. Paranasal Sinus Cavities within bones surrounding the nasal cavity are called sinuses Functions of the sinuses Lighten the skull Provides structural integrity Act as resonance chambers for speech produce mucus that drains into the nasal cavity Allow us to hear ourselves when we speak Sinuses are located in the following bones Frontal bone Sphenoid bone Ethmoid bone Maxillary bone Pharynx (throat) Muscular Passage from the nasal cavity to larynx Three regions of the pharynx Nasopharynx – superior region behind nasal cavity Oropharynx – middle region behind mouth Laryngopharynx – inferior region attached to larynx The oropharynx and laryngopharynx are common passageways from air and good Larynx (voice Box) Routes air and food into proper channels Plays a role in speech Made of eight rigid hyaline and a spoon-shaped flap of elastic cartilage (epiglottis) Structures of the Larynx Thyroid Cartilage Largest of the hyaline cartilages ProtrudeAnteriorly (Adam’s Apple) Epiglottis Protects the superior opening of the larynx Routes food to the esophagus and air toward the trachea When Swallowing, the epiglottis forms a lid over the opening of the larynx Vocal Folds (true vocal cords): Vibrate with expelled air to create sound (speech) Glottis: opening between vocal cords Trachea Four inch long tube that connects larynx with bronchi Walls are reinforce with C shaped hyaline cartilage Protection Structural Integrity: keeps it open for air flow Line with ciliated mucosa Beat continuously in the opposite direction of incoming air Expel mucus loaded with dust and other debris away from lungs Structures of the Thoracic Cavity Chest Wall is air right, protects lungs Rub cage, sternum Thoracic Vertebrae Muscles – internal/external intercostal diaphragm Pleura is a membrane lining of lungs and chest wall Pleural sac around each lung This is so that the lungs and move freely in a frictionless environment Intrapleural space filled with intra pleural fluid, volume = 15mL Lungs: Occupy most of the thoracic cavity Heart occupies central portion called mediastinum Apex is near the clavicle (superior portion) Based rests on the diaphragm (inferior portion) Each lung is divided into lobes by fissures Left lung, two lobes Right lung, three lobes Coverings of the lungs Serosa covers the outer surface of the lungs Pulmonary (visceral) pleura covers the lung surface Parietal pleura lines the walls of the thoracic Cavity Pleural fluid fills the area between layers of pleura to allow gliding Those two pleural layers resist being pulled apart Bronchial (respiratory) tree divisions All but the smallest of these passageways have reinforcing cartilage in their walls Primary bronchi Secondary bronchi Tertiary Bronchi Bronchioles Terminal Bronchioles Feed into Alveoli Respiratory Zones Structures Respiratory bronchioles Alveolar ducts Alveolar sacs Bunches of Alveoli Alveoli (air sac) AsingleAlveolus. Primary site of exchange is only the alveoli Linings allows for uniform air flow Large amount of capillaries to allow for gas exchange very easily. Alveoli = site of gas exchange 300 million alveoli/lung (tennis court size) Rich blood supply – capillaries from sheet over alveoli Type I alveolar cells make up wall of alveoli single layer epithelial cells Type II alveoli cells secrete surfactant Soap Alveolar macrophages Rate of Diffusion in Lungs Diffusion betweenAlveoli and blood Rapid Small diffusion barrier Large SurfaceArea Membrane must be moist Respiratory membrane (Air blood Barrier) Thin squamous epithelial layer lines alveolar walls Alveolar pores connecting neighboring air sacs Pulmonary capillaries cover external surface of alveoli One side of the membrane is air and on the other side is blood flowing part. Barrier for diffusion Type 1 cells & basement membrane Capillary endothelial cells and basement membrane 0.2 microns thick (very thin) Surfactant Reduces the surface tension of a liquid. Amphipathic Breaks Hydrogen Bonds Needs to break Hydrogen bonds so we have effective air flow Factors Affecting pulmonary Ventilation Compliance: Ease with which lungs can be stretched Lung compliance: Elasticity of the lung (how easy it is to stretch the lungs) Exhaling is mainly due to the elasticity pushing air out of the lungs at that point Normal Value: 0.1 L /cm H20 Too elastic because of scar tissue = decreased compliance (hard to stretch lung) = tuberculosis (hard to inspire, easy to expire) Not elastic enough before os tissue breaking down = increased compliance (and less recoil) = emphysema (easy to inspire, hard to expire) Recoil doesn’t happen as efficiently Surface tension of lungs: greater tension  less compliant Depends on humidity Less compliant Respiratory Volumes and Capacities Normal breathing moves about 500 mL of air with each breath, this respiratory volume is tidal volume (TV) Many factors that affect respiratory capacity Aperson’s size Sex Age Physical Condition Inspiratory Reserve Volume (irV) amount of air that can be taken in, forcibly, over the tidal volume Usually between 2100 and 3200 mL Expiratory reserve volume (ERC) amount of air that can be forcibly exhaled Approximately 1200mL Residual Volume This happens because cannot completely squish out all of the air in the alveoli because that would crush the alveoli Air remaining in the lung after expiration About 1200 mL Respiratory Volumes Vital Captivity The total of exchangeable air Vital Capacity = TV + IRV + ERV Dead Space Volume (not the same as residual volume) Air that remains in the conducting zone and never reaches alveoli About 150mL  old air that mixed with the new air Functional Volume Air that actually reaches the respiratory Zone Usually about 350mL Respiratory capacities are measured with a spirometer Anatomical Dead Space Volume Air in conducting zone does not participate in gas exchange Thus, conducting zone = anatomical dead space Dead Space  approximately 150mL Mechanics of Breathing (pulmonary ventilation) Completely mechanical process that depends on volume changes in the thoracic cavity Open System Volume changes lead to pressure changes which lead to the flow of gases to equalize pressure Two phases Inspiration = inhalation = flow air into lungs Expiration = exhalation = air leaving the lungs Changing Lung Volume will change the pressure Inspiration Diaphragm and external intercostal muscles contract The size of the thoracic cavity increases External air is pulled into the lungs due to increase in intrapulmonary volume, which causes a decrease in gas pressure. Pressure decreases (negative pressure) Goes to negative 1 pressure 1 mm Hg is able to move pressure. Cardiovascular system has higher pressure difference than lung Any pressure below 0 , air flows into the lungs Any pressure above 1, air flows out of the lungs Expiration: Largely a passive process which depends on natural lung elasticity, recoil As the muscles relax, air is pushed out of the lungs due to Decrease in intrapulmonary volume Increase in gas pressure Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage Contraction of expiratory muscles creates greater and faster decrease in volume of thoracic cavity Pressure is greater than 0 so air flow is out of the lungs. Role of Pressure in Pulmonary Ventilation Air flow moves in and out of lungs by bulk flow Pressure Gradient drives flow Air moves from high to low pressure Inspiration: pressure in lungs less than atmosphere Expiration: pressure in lungs greater than atmosphere Pleural Sac pulls the lungs open Decreases the pressure which pull the alveoli open and inflated Pushing would create more pressure which would squish the alveoli Atmospheric Pressure 760 mm Hg at sea level Decreases as altitude increases Pressure decreases, less air molecules. Increases number of blood cells. Increases under water Other lung pressure given relative to atmospheric (set Patm = 0 mm Hg) Nitrogen Narcosis: At high pressure, Nitrogen will flow into the lungs and make people act loopier Partial Pressure of Gases: Ideal Gas Low Pressure of Gas depends on temperature, number of fas molecules, and volume PV = nRT Pressure = P n = number of air molecules R = It’s a made up constant number T = Constant Temperature (because in the body it’s 37 C) V = Volume. Changes P = nRT/V Effectively, the equation is P = n/V Pressure is inversely related to Volume Important Pulmonary Pressure Atmospheric Pressure = Patm Intra-alveolar pressure = Palv = pressure of air in alveoli Intrapleural Pressure = Pip= pressure inside pleural sac Less thanAlveolar Pressure (Needs at least 4 mm Hg) Intra-alveolar Pressure Pressure of air in alveoli Given relative to atmospheric pressure Varies with phase of respiration During inspiration – negative (less than atmospheric) During expiration – positive (more than atmospheric) Difference between P alv and P atm drives ventilation Differences in lungs and pleural space pressure keeps lungs from collapsing. Intrapleural Pressure Pressure inside pleural sac Always negative under normal conditions (-4 mmHG, really 756 mm HG) Always less than P alv Varies with phase of respiration at rest, -4 mm Hg Intrapleural Pressure The Diaphragm pulls open the lungs for inhalation. Exhalation pushes Pneumothorax-air in the pleural cavity When a lung is punctured, it goes to atmospheric pressure. If we add air, it increases pressure which crush the alveoli So we decide to take away air that reinflates the lung due to less pressure that will reexpand the lungs. Determinants of Intra-Alveolar Pressure Factors determining Intra-alveolar pressure Quantity of air in Alveoli (number of air molecules) Volume of alveoli (due to side of chest cavity) Lungs expand causing alveolar volume to increase Palv decreases Pressure gradient drives air into lungs As lungs recoil the alveolar volume decreases Palv increases Pressure gradient drives air out of the lungs Forces for air flow Flow = (P atm – P alv) / R Force for flow = pressure gradient Atmospheric pressure constant (during breathing cycle) Therefore changes in alveolar pressure creates/changes gradients Movement of air in and out of lungs due to pressure gradients Mechanics of breathing describes mechanisms for creating pressure gradients Bronchoconstriction Forces for Air Flow Boyle’s Law: pressure inversely related to volume Therefore, can change alveolar pressure by changing its volume R = resistant to air flow. Resistance related to radius of airways and mucus Gas Mixtures Many gases are mixtures of different molevules Partial pressure of a gas = proportion of pressure of entire gas that is due to presence of the individual gas P total = P1 + P2 + P3 … Pn Partial pressure of a gas depends on fractional concentration of the gas Fresh air mixes with Old Air Water is in air because it humidifies air High levels of Co2 compared to InspiredAir Cell cultures need to be frown in CO2 (40 mm Hg) because it gives them the proper pH to live in Gas Composition ofAir Composition of Iar ~ 79% Nitriogen, ~21% Oxygen Trace amoungs of carobn Cioxde, helium, argon, etc. Water can be a factor depending on the humidity 760 mm Hg = Pn2 + Po2 Pn2 = 0.79 x 760 mm HG = 600 mm Hg Po2 = 0.21 x 760 mm Hg = 160 mm Hg Air is only 0.03% carbon dioxide PCO2 = 0.0003 x750 mm HG = 0.23 Hg The partial pressure of a gas affects the amount of gas that goes into solution External Respiration, Gas Transport, and Internal respiration Summary Cellular Respiration: Generating ATP Free Radicals are formed from cellular respiration Anti-oxidants are used to counter the free radicals Digestive and respiratory systems are related because they generateATP. Diffusion of Gases NEED TO KNOW NUMBERS FROM FIGURES Gases diffuse down pressure gradients, high pressure  low pressure In gas mixture, gases diffuse down partial pressure gradients, high partial pressure  low partial pressure Aparticular gas diffuses down its own partial pressure gradient, presence of other gases irrelevant O2 and CO2 levels are measured in oxygenated blood Not measured in veins because veins have all the waste products Not looking at waste to see what we need Numbers refer to arteriole levels Gas Transport in the Blood Oxygen Oxygen not very soluble in plasms Thus only 3.0 mL/200 mL arterial bood oxygen dissolved in plasma (1.5%) Other 197 mL
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