Respiratory System PDF

Respiratory System Ariette Acevedo, O.D. BMS 2 1 – Discussion of the Anatomy and Histology of the Respiratory System Objectives – Discussion of the Physiology of Respiration – Discussion of Respiratory Pathology – Obstructive and Restrictive Disease – Infectious Disease – Neoplasms 2 Anatomy...

Respiratory System Ariette Acevedo, O.D. BMS 2 1 – Discussion of the Anatomy and Histology of the Respiratory System Objectives – Discussion of the Physiology of Respiration – Discussion of Respiratory Pathology – Obstructive and Restrictive Disease – Infectious Disease – Neoplasms 2 Anatomy/Histology 3 – The respiratory system contributes to homeostasis by providing for the exchange of gases (oxygen and carbon dioxide) between the atmospheric air, blood and tissue cells. – It also helps adjust the pH of body fluids – Blood pH: 7.35-7.45, avg. 7.40 – Above 7.45: Alkalemia – Below 7.35: Acidemia – Body's cells continually use O2 for metabolic reactions that release energy from nutrient molecules and produce ATP. – These reaction release CO2 – Large amounts of CO2 produce acidity – CO2 must be eliminated quickly and efficiently – The cardiovascular and respiratory systems cooperate to supply O2 and eliminate CO2. – Respiratory system: gas exchange – Cardiovascular system: transports blood containing gases between the lungs and body cells. 4 – Respiratory system consists of: – – – – – – Nose Pharynx Larynx Trachea Bronchi Lungs – Can be classified according to function and structure: – Structurally – Upper Respiratory System – Lower Respiratory System – Functionally – Conducting Zone – Respiratory Zone 5 Respiratory System Anatomy 6 – Structurally (Anatomically) – Upper Respiratory System – Nose, pharynx and associated structures – Lower Respiratory System – Larynx, trachea, bronchi, and lungs – Functionally Classification – Conducting Zone: series of interconnecting cavities and tubes both outside and within the lungs. – Nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. – Function: filter, warm, and moisten air and conduct it into the lungs. – Respiratory Zone: tissues within the lungs where gas exchange occurs. – Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. – These are the main sites of gas exchange between air and blood. 7 Lateral Nasal Cartilage External Nose Septal Cartilage Alar Cartilage External Nares 8 Internal Nose 9 Nasal Meatuses Internal Nose 10 – Funnel-shaped tube, ~13cm (5 in.) long. – Starts at the internal nares and extends to the level of the cricoid cartilage. Pharynx – Lies just posterior to the nasal and oral cavities, superior to the larynx and just anterior to the cervical vertebrae. – Its walls are composed of skeletal muscle and lined with mucous membranes. – Contraction of the muscles helps in deglutition – Functions as a passageway for air and food, provides a resonating chamber for speech sounds and houses the tonsils, which aid in immunological reactions. 11 Pharynx 12 – AKA Voice box – Is a short passageway that connects the laryngopharynx with the trachea. – Lies in the midline of the neck, anterior to the esophagus and the fourth-sixth cervical vertebrae (C4-C6) Larynx – Composed of nine pieces of cartilage: – – – – – – 2 Arytenoid Cartilage 2 Cuneiform Cartilage 2 Corniculate Cartilage Thyroid Cartilage (Adam’s Apple) Cricoid Cartilage Epiglottis 13 Larynx 14 – Large, leaf-shaped piece of elastic cartilage, covered in epithelium. Epiglottis – The “stem” of the epiglottis is the tapered inferior portion attached to the anterior rim of the thyroid cartilage and hyoid bone. – The ”leaf” portion is unattached and free to move up and down, like a trap door. – During swallowing the pharynx and larynx rise, widening the pharynx to receive food and the larynx elevates causing the epiglottis to move down and form a lid over the glottis, preventing food from entering the larynx. 15 16 – AKA “windpipe” – Tubular passageway for air ~12cm (5in.) long and 2.5cm (1 in.) in diameter. Trachea – Located anterior to the esophagus and extends from the larynx to the superior border of T5 , when it divides into the right and left primary bronchi. – Has 16-20 incomplete “C”, staked one above the other, connected by dense connective tissue. – The open part of the “C” faces posteriorly the esophagus – The semi-solid cartilages provide support to prevent the tracheal wall from collapsing inward and obstructing the passage of air. 17 Cartilage of Trachea Anterior Trachea Esophagus Posterior Trachea 18 – The trachea divides at the level of T5 into the primary bronchus Bronchi – Right Primary Bronchus -> into the right lung – Shorter, wider and more vertical – Left Primary Bronchus -> into the left lung – At the point where the trachea divides into the right and left primary bronchi an internal ridge is formed called the carina. 19 – After entering the lungs, the primary bronchi divide to form smaller bronchi – Secondary (lobar) Bronchi: one for each lobe of the lungs Bronchi – Right lung has 3 lobes – Left lung has 2 lobes – Tertiary (segmental) Bronchi – Bronchioles – Terminal Bronchioles 20 Bronchi 21 – As the branching becomes more extensive several structural changes can be noted: 1. Mucous membrane changes from pseudostratified ciliated columnar epithelium (primary, secondary and tertiary bronchi) to ciliated simple columnar epithelium with goblet cells (larger bronchioles) to ciliated simple cuboidal epithelium with no goblet cells (smaller bronchioles) to nonciliated simple cuboidal epithelium (terminal bronchioles) 2. Plates of cartilage gradually replace the incomplete rings of cartilage in primary bronchi and finally disappear in the distal bronchioles. 3. As the amount of cartilage decreases, the amount of smooth muscle increases. – Since there is no supporting cartilage, muscle spasms can close of the airways. (asthma) 22 Lungs – Paired, cone-shaped organs in the thoracic cavity – Each lung is enclosed and protected by a doublelayered serous membrane, known as the pleural membrane – Parietal Pleura: superficial layer, lines the walls of the thoracic cavity – Visceral Pleura: covers the lungs 23 Lobes/Fissures 24 Terminal Bronchiole Respiratory Bronchiole Alveolar Ducts Alveoli Alveolar Sac 25 – The walls of the alveoli consist of 2 types of alveolar epithelial cells: – Type I Alveolar Cells: simple squamous epithelial cells that form a nearly continuous lining of the alveolar wall. – Considered the main site for gas exchange – Type II Alveolar Cells: rounded cuboidal epithelial cells with free surface microvilli. Alveoli – Secrete alveolar fluid, keep surface between cells and air moist. . – Associated with alveolar walls there are also alveolar macrophages: phagocytes that remove fine dust particles and other debris from the alveolar space. – The exchange of O2 and CO2 between the air spaces in the lungs and the blood takes place by diffusion across the alveolar and capillary walls – Which together form the respiratory membrane. 26 Alveoli 27 – Very thin, only 0.5µm thick – Consist of 4 layers: Respiratory Membrane – Alveolar Wall: a layer of type I and type II alveolar cells and associated alveolar macrophages. – Epithelial Basement Membrane: underlying the alveolar wall. – Capillary Basement Membrane: fused to the epithelial basement membrane – Capillary Endothelium – The lungs contain ~300 million alveoli (70m2) for gas exchange 28 – Arteries: – Pulmonary Arteries: deoxygenated blood enters the pulmonary trunk, which divides into the left and right pulmonary arteries (2). – The only arteries in the body to carry deoxygenated blood Blood Supply – Bronchial Arteries: branch from the aorta and deliver oxygenated blood to the lungs. – Mainly used to perfuse the muscular walls of the bronchi and bronchioles – Veins: return of the oxygenated blood to the heart. – 4 pulmonary veins which drain into the left atrium. 29 Pulmonary Ventilation 30 – The process of gas exchange is called respiration. – 3 basic steps: Respiration – Pulmonary ventilation (breathing): the inhalation (inflow) and exhalation (outflow) of air and involves the exchange of air between the atmosphere and the alveoli of the lungs. – External (pulmonary) respiration: the exchange if gasses between the alveoli of the lungs and the blood in pulmonary capillaries across the respiratory membrane. – Process in which capillaries gain O2 and lose CO2. – Internal (tissue) respiration: the exchange of gases between blood in systemic capillaries and tissue cells. – Blood loses O2 and gains CO2 – Which cellular process is known to consume O2 and produce CO2? 31 Pressure Changes during Pulmonary Ventilation – Air moves into the lungs when the air pressure inside the lungs is less than the air pressure in the atmosphere. – Air moves out of the lungs when the air pressure inside the lungs is greater than the air pressure in the atmosphere. 32 – Just before inhalation, the air pressure inside the lungs is equal to the air pressure of the atmosphere. Inhalation – For air to flow into the lungs, the pressure inside the alveoli must become lower than the atmospheric pressure. – Atmospheric pressure is 760 mmHg at sea level or 1 atmosphere (atm) • The difference in pressure in respiration case is caused by changes in lung volume. • The lungs expand to increase in volume and decrease air pressure 33 Inhalation • Lung Expansion • Contraction of the main muscles of inhalation, the diaphragm and the external intercostals • Inhalation is considered an active process-there is muscle contraction involved. 34 Pressure Changes 35 – The pressure in the lungs is greater than the pressure in the atmosphere. – Normal quiet exhalation is considered a passive process, since no muscle contraction is involved. Exhalation – It results from elastic recoil of the chest wall and lungs – Natural tendency to spring back after they have been stretched – Exhalation becomes active only during forceful breathing – Playing a wind instrument or exercise – Muscles of exhalation: – Abdominals and internal intercostals 36 Pressure Changes 37 Lung Volumes and Capacities 38 – Tidal Volume (VT): the volume of one breath. The amount of air that moves in and out of the airways during normal quiet breathing. – 70% reaches the respiratory bronchioles – 30% remains in anatomic dead space (nose, larynx, pharynx, ect) – Minute Ventilation (MV): the total volume of air inhaled and exhaled each minute. – 𝑴𝑽 = 𝑹𝒆𝒔𝒑𝒊𝒓𝒂𝒕𝒐𝒓𝒚 𝑹𝒂𝒕𝒆 𝒙 𝑻𝒊𝒅𝒂𝒍 𝑽𝒐𝒍𝒖𝒎𝒆 – 𝑴𝑽 = 𝟏𝟐 𝒙 𝟓𝟎𝟎 = 𝟔𝑳/𝒎𝒊𝒏 – A lower-than-normal MV is usually a sign of pulmonary malfunction. 39 – Alveolar Ventilation Rate: the volume of air per minute that actually reaches the respiratory zone. – Inspiratory Reserve Volume (IRV): the additional amount of air taken by a deep breath. – Avg Adult Male: 3,100mL and Avg Adult Female: 1,900mL – Expiratory Reserve Volume (ERV): the additional amount of air exhaled after a normal inspiration. – Avg Adult Male: 1,200mL and Avg Adult Female: 700mL – FEV1: Forced Expiratory Volume in 1 second, the volume of air that can be exhaled from the lungs in 1 second with maximal effort following a maximal inhalation. – Residual Volume: volume of air remaining in the lungs that cannot be measured. – Avg Adult Male: 1,200mL and Avg Adult Female: 1,100mL 40 – Inspiratory Capacity: the sum of tidal volume and inspiratory reserve volume. – Avg Adult Male: 3600mL and Avg Adult Female: 2400mL – Functional Residual Capacity: the sum of residual volume and expiratory reserve volume. – Avg Adult Male: 2400mL and Avg Adult Female: 1800mL Lung Capacities – Vital Capacity: the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. – Avg Adult Male: 4800mL and Avg Adult Female: 3100mL – Total Lung Capacity: the sum of vital capacity and residual volume. – Avg Adult Male: 6000mL and Avg Adult Female: 4200mL 41 Spirogram 42 – Dalton’s Law: each gas in a mixture of gases exerts its own pressure as if no other gases are present. – Atmospheric Air: 78.6 nitrogen, 20.9% oxygen, 0.04% carbon dioxide, and 0.06% other gases in addition to water vapor (~0.4%) – Compared to inhaled air, alveolar air has less O2 (13.6% vs 20.9%) and more CO2 (5.25% vs. 0.04%) Gas Laws – Henry’s Law: the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility. – In body fluids the ability of a gas to stay in solution is greater when its partial pressure is higher and when it has a high solubility in water. – The higher the partial pressure the more gas will stay in solution. – In comparison to O2, much more CO2 is dissolved in blood plasma since the solubility of CO2 is 24x greater than that of O2. 43 External Respiration – AKA Pulmonary Gas Exchange – The diffusion of O2 from air in the alveoli of the lungs to blood in pulmonary capillaries and diffusion of CO2 in the opposite direction. 44 2 2 1 1 45 – AKA systemic gas exchange Internal Respiration – The exchange of O2 and CO2 between systemic capillaries and tissue cells. – The left ventricle pumps oxygenated blood into the aorta and through the systemic arteries to systemic capillaries. 46 1 47 Factors Affecting Pulmonary and Systemic Gas Exchange – Partial Pressure differences of the gases: the rate of diffusion is faster when the difference between Po2 in alveolar air and pulmonary capillary blood is larger and diffusion is slower when the difference is smaller. – Surface area available for gas exchange: any pulmonary disorder that decreases the functional surface area of the respiratory membranes decreases the rate of external respiration. – Diffusion Distance: increase in diffusion distance can slow the rate of gas exchange. – Molecular weight and solubility of the gases: when diffusion is slower than normal, O2 insufficiency (hypoxia) typically occurs before there is significant retention of CO2 (hypercapnia). 48 – O2 does not dissolve easily in water Oxygen Transport – 1.5% inhaled O2 is dissolved in blood plasma – 98.5% is bound to hemoglobin in RBC – Hemoglobin – 4 chains (2⍺/2β) – 1 heme ring – 1 Fe2+ – O2 and Hemoglobin bind to form oxyhemoglobin – An easily reversible reaction 49 – The most important factor that determine how much O2 binds to hemoglobin is the Partial Pressure of O2 (PO2) Oxygen Transport – Higher PO2 = more O2 combines with Hb – Fully Saturated: when reduced hemoglobin (Hb) is completely converted to oxyhemoglobin (Hb-O2). – Partially Saturated: when hemoglobin consist of a mix of Hb-O2 and Hb. 50 Oxygen Transport -The relationship between the percent saturation of hemoglobin and PO2 is illustrated in the Oxygen-hemoglobin dissociation curve -When PO2 is high, hemoglobin binds with large amounts of O2 and is almost 100% saturated. - When PO2 is low, hemoglobin is only partially saturated. 51 Factors Affecting the Affinity of Hemoglobin for O2 – These factors are going to create a shift in the curve either to the left (higher affinity) or right (lower affinity) 1. Acidity (pH): as acidity increased (decrease in pH) the affinity of hemoglobin for O2 decreases and O2 dissociated more readily from hemoglobin. – This created a shift to the right. Thus, at any given PO2 Hb is less saturated with O2. – This is termed the Bohr effect, the relationship between pH and hemoglobin's affinity for oxygen. – The opposite effect happens when pH is elevated, increasing the affinity of hemoglobin for O2 and shifting the curve to the left. 52 Basic Acidic 53 2. Partial Pressure of Carbon Dioxide (PCO2): – As CO2 enter the blood much of it is temporarily converted to carbonic acid (H2CO3), a reaction catalyzed by carbonic anhydrase (CA) Factors Affecting the Affinity of Hemoglobin for O2 – This reaction produces hydrogen ions (H+) and bicarbonate ions. – As H+ concentration increases the pH decreases (more acidic) – Thus, an increase in PCO2 created an increase in H+, creating a more acidic pH, leading to more O2 being released from hemoglobin. – Shifting the curve to the right – The opposite is true, a decreased PCO2 (elevated pH) shift the saturation curve to the left. 54 55 3. Factors Affecting the Affinity of Hemoglobin for O2 Temperature: heat is a by product of metabolic reactions of all cells and the heat released by contracting muscle fibers tends to raise body temperature. – As temperature increases, the amount of O2 released from hemoglobin also increases. – Shift of the curve to the right. – Metabolically active cells require more O2 and liberate more heat and acids, this in turn promotes the release of O2 from oxyhemoglobin. – In contrast during hypothermia cellular metabolism slows, the need for O2 is reduced and more O2 remains bound to hemoglobin. – Shift of the curve to the left. 56 57 4. Factors Affecting the Affinity of Hemoglobin for O2 3-bisphosphoglycerate (BPG): a substrate found in RBC, previously called diphosphoglycerate (DPG). BPG is formed in RBC during glycolysis. – Decreases the affinity of hemoglobin for O2 and helps unload O2 from hemoglobin. – The greater the level of BPG, the more O2 is unloaded from hemoglobin. – Certain hormones and higher altitudes increase the level of BPG. – Thyroxine, human growth hormone, epinephrine, norepinephrine, and testosterone. 58 – CO2 is transported in blood in 3 main forms: Carbon Dioxide Transport 1. Dissolved CO2: 7% is dissolved in blood plasma. 2. Carbamino compounds: 23% combines with hemoglobin to form carbaminohemoglobin (Hb-CO2). 3. Bicarbonate ions: 70% transported in blood plasma as bicarbonate ions (HCO3-). – Deoxygenated blood returning to the pulmonary capillaries contain: – CO2 dissolved in plasma – Carbaminohemoglobin (Hb-CO2) – CO2 incorporated into HCO3- within RBCs 59 60 Control of Respiration 61 Respiratory Center – The size of the thorax is altered y the action of the respiratory muscles, which contract due to nerve impulses transmitted from the centers in the brain and relax in the absence of nerve impulses. – These impulses are sent from clusters of neurons located bilaterally in the medulla oblongata and pons of the brain stem. 62 – Divided into 3 areas: – Medullary rhythmicity area located in the medulla oblongata Respiratory Center – In control of the basic rhythm of respiration – Inspiratory and expiratory areas – Pneumotaxic area located in the upper pons – Helps in rhythm regulation of the inspiratory area – Apneuristic area located in the pons – Stimulates the inspiratory area to activate and prolong inhalation 63 – Cortical Influences on Respiration – Voluntary control of respiratory pattern Regulation of Respiratory Center – Chemoreceptor Regulation of Respiration – – – – Chemical stimuli to regulate breathing Chemoreceptors monitor levels of CO2, O2 and H+ Central Chemoreceptors: central nervous system Peripheral Chemoreceptors: aortic bodies and carotid bodies – Proprioceptor Stimulation of Respiration – Inflation (Hering-Breuer) Reflex – Protective mechanism 64 65