Respiratory System Anatomy PDF

The Respiratory System Learning Objectives Structure and Functions of the Respiratory System Describe the major functions of the respiratory system. List, in order, the respiratory structures that air passes through during breathing, from the mouth and nose to the exchange surface of the l...

The Respiratory System Learning Objectives Structure and Functions of the Respiratory System Describe the major functions of the respiratory system. List, in order, the respiratory structures that air passes through during breathing, from the mouth and nose to the exchange surface of the lungs. Differentiate between structure and function of the conducting zone versus the respiratory zone. Respiratory System Primary functions is to supply oxygen and remove carbon dioxide Secondary functions is for sound production and maintenance of homeostasis by regulating pH of blood/body fluids Main Components: Nose Nasal cavity Pharynx Larynx Trachea Bronchi Lungs Alveoli Respiratory System Respiration involves four processes 1. Pulmonary ventilation (breathing): movement of air into and out of lungs Respiratory 2. External respiration: exchange system of O2 and CO2 between lungs and blood 3. Transport of O2 and CO2 in blood 4. Internal respiration: exchange of O2 and CO2 between systemic Circulatory blood vessels and tissues system © 2016 Pearson Education, Ltd. 6 Anatomy of Respiratory System nose & nasal cavity pharynx Conducting Zone larynx – gas conduits – cleanse, warm & trachea humidify air bronchi bronchioles respiratory bronchioles alveolar ducts alveoli Respiratory Zone – gas exchange Respiratory System Anatomy: Nose The Nose is the only external visible part of the respiratory system Functions: Provides an airway for respiration Moistens & warms entering air Nasal cavity Filters & cleanses air Soft palate Hard Serves as resonating chamber for speech palate Houses smell receptors Oral cavity Nasal cavity is divided by nasal septum Respiratory System Anatomy: Nose Two types of mucous membranes line the large portion of nasal cavity: Olfactory mucosa: contains receptors for the sense of smell Respiratory mucosa: pseudostratified ciliated columnar epithelium → create a gentle current that moves mucus to pharynx Containing mucous & serous glands: Mucous glands: secrete mucus, traps inspired dust, bacteria & other debris Serous gland: secrete lysozyme (enzymes that damage bacterial cell walls), antibacterial enzymes Respiratory System Anatomy: Pharynx Pharynx: Nasopharynx, Oropharynx, Laryngopharynx Connects nasal cavity & mouth to larynx & esophagus Funnel-shaped (about 13 cm long) Commonly called throat Respiratory System Anatomy: Pharynx Nasopharynx: is continuous with the nasal cavity Serves only as an air passageway Pseudostratified ciliated columnar epithelium -Pharyngeal tonsil (adenoids) on its posterior wall traps & destroys pathogens Oropharynx: lies posterior to oral cavity Serves as both food and air pass passageway Stratified squamous epithelium: protection against friction & chemical trauma Two kinds of tonsils in mucosa: Palatine tonsils (paired) Lingual tonsil Laryngopharynx: Extends anteriorly to the larynx and posteriorly to the esophagus Common passageway for both food and air Stratified squamous epithelium Respiratory System Anatomy: Larynx Larynx: voice box (about 5 cm) Functions as an open airway A switching mechanism to route air & food into proper channels Voice production (vocal cords) Thyroid cartilage: formed by fusion of 2 cartilage plates (midline = Adam’s apple) Respiratory System Anatomy: Trachea Windpipe: flexible tube running from larynx 10-12 cm long & 2.5 cm wide, 16-20 C-shaped cartilages (rings) → prevents it from collapsing Internal surface lined with Pseudostratified ciliated columnar epithelium → remove debris Bronchi & Subdivisions 2 primary bronchi formed by the division of the trachea The right pulmonary bronchus is wider, shorter & more vertical than left one In the lungs the primary bronchi divides into secondary bronchi (3 in right & 2 in left), each supplies one lung lobe Secondary bronchi divide into tertiary bronchi Bronchioles: air passages under 1 mm in diameter Terminal bronchioles: tiniest bronchioles, < 0.5 mm (diameter) Respiratory Zone Actual site of gas exchange, composed of: Respiratory bronchioles: branched from terminal bronchioles Alveolar ducts: branches of respiratory bronchioles Alveolar sacs: clusters of alveoli formed by alveolar ducts Alveoli: actual sites of gas exchange 300 millions alveoli account for most of lung volume & provide large surface area for gas exchange Gas exchange occurs by simple diffusion across the respiratory membrane Respiratory zone respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli Alveoli Alveolar duct Respiratory Alveolar duct bronchioles Terminal Alveolar bronchiole sac (a) Respiratory System Anatomy: Alveoli Two types of cells in alveolar wall: Type I cells: form major part of alveolar walls single layer of squamous epithelial cells Type II cells: surfactant secreting cells Cuboidal epithelial cells scattered amid type I cells Secrete fluid containing surfactant: complex of lipid & protein, helps to keep lungs inflated by reducing surface tension Respiratory System Anatomy: Lungs 2 lungs are separated by mediastinum Right lung, bigger, has 3 lobes: upper, middle & lower Left lung smaller, has 2 lobes: upper & lower Each lobe is divided into a number of broncho- pulmonary segments & then into lobules Respiratory System Anatomy: Pleural Cavity In the thoracic cavity: Two cavities are separated by central mediastinum (houses the heart) Pleurae: parietal pleura + visceral pleura Parietal pleura: thin membrane lining Visceral pleura: covers the external surface of lung Pleural fluid fills the slit-like pleural cavity between 2 layers of pleurae → lubrication  Clinical – Homeostatic Imbalance 22.6 Pleurisy: inflammation of pleurae that often results from pneumonia Inflamed pleurae become rough, resulting in friction and stabbing pain with each breath Pleurae may produce excessive amounts of fluid, which may exert pressure on lungs, hindering breathing © 2016 Pearson Education, Ltd.  Blood Supply and Innervation of Lungs Lungs are perfused by two circulations 1. Pulmonary circulation Pulmonary arteries deliver systemic venous blood from heart to lungs for oxygenation – Branch profusely to feed into pulmonary capillary networks Pulmonary veins carry oxygenated blood from respiratory zones back to heart Low-pressure, high-volume system Lung capillary endothelium contains many enzymes that act on different substances in blood – Example: angiotensin-converting enzyme activates blood pressure hormone © 2016 Pearson Education, Ltd.  Blood Supply and Innervation of Lungs (cont.) 2. Bronchial circulation Bronchial arteries provide oxygenated blood to lung tissue – Arise from aorta and enter lungs at hilum – Part of systemic circulation, so are high pressure, low volume – Supply all lung tissue except alveoli – Bronchial veins anastomose with pulmonary veins » Pulmonary veins carry most venous blood back to heart © 2016 Pearson Education, Ltd.  Blood Supply and Innervation of Lungs (cont.) Innervation of the lungs – Lungs are innervated by parasympathetic and sympathetic motor fibers, as well as visceral sensory fibers – Nerves enter through pulmonary plexus on lung root Run along bronchial tubes and blood vessels – Parasympathetic fibers cause bronchoconstriction, whereas sympathetic fibers cause bronchodilation © 2016 Pearson Education, Ltd. Summary- Path of air flow Air enters the lungs primarily through the nose ◊ warmed, filtered and humidified Next, air enters the pharynx ◊ epiglottis remains up while breathing, but closes over the larynx while swallowing Passing the larynx, air enters the trachea → branches into two bronchi which enter separate lungs → lining of the bronchi is highly ciliated and secretes mucous → mucous and cilia clean particulate matter from air Bronchi further branch into bronchioles which eventually terminate at alveoli ◊ site of gas exchange 2 5 Summary 2 6 Summary Learning Objectives Mechanisms of pulmonary ventilation Define pulmonary ventilation, inspiration (inhalation), and expiration (exhalation). Define and explain the relationship of intrapleural pressure, transpulmonary pressure, and intrapulmonary pressure relative to atmospheric pressure during ventilation. Describe how changing the volume of a gas affects its pressure [Boyle’s Law]. Apply understanding of the inverse relationship between gas pressure and volume of the gas to explain how changes in volume create airflow during inspiration and expiration. List several physical factors that influence pulmonary ventilation. Pressure Relationships in the Thoracic Cavity Respiratory pressure are described relative to atmospheric pressure Atmospheric pressure: pressure exerted by air (gases surrounding the body) Sea level atmospheric (atm) pressure = 760 mm Hg pressure less than atm. pressure → -4 mm Hg pressure equal to atm. pressure = 0 mm Hg Intrapulmonary Pressure: pressure within alveoli of lungs Rises & falls with the phases of breathing but eventually equalizes Itself with atmospheric pressure Intrapleural Pressure: pressure within pleural cavity Fluctuates with breathing phases Always 4 mm Hg less than pressure in alveoli, so negative relative to atmospheric & intrapulmonary pressures The difference between intrapulmonary & intrapleural pressure keeps the lungs from collapsing Figure 22.13 Intrapulmonary and intrapleural pressure relationships. Atmospheric pressure (Patm) 0 mm Hg (760 mm Hg) Parietal pleura Thoracic Visceral pleura wall Pleural cavity Transpulmonary pressure 4 mm Hg (the difference between 0 mm Hg and −4 mm Hg) −4 0 Intrapleural pressure (Pip) −4 mm Hg (756 mm Hg) Lung Diaphragm Intrapulmonary pressure (Ppul) 0 mm Hg (760 mm Hg) © 2016 Pearson Education, Ltd. 3 0 Pressure Relationships Two forces act to pull the lungs away from the thoracic wall, promoting lung collapse Elasticity of lungs causes them to assume smallest possible size Surface tension of alveolar fluid draws alveoli to their smallest possible size Opposing force – elasticity of the chest wall pulls the thorax outward to enlarge the lungs Lung Collapse- Caused by equalization of the intrapleural pressure with the intrapulmonary pressure Transpulmonary pressure keeps the airways open, ie keeps lungs from collapsing Transpulmonary pressure – difference between the intrapulmonary and intrapleural pressures (Ppul – Pip)  Clinical – Homeostatic Imbalance 22.7 Atelectasis: lung collapse due to – Plugged bronchioles, which cause collapse of alveoli, or – Pneumothorax, air in pleural cavity Can occur from either wound in parietal pleura or rupture of visceral pleura Treated by removing air with chest tubes When pleurae heal, lung reinflates © 2016 Pearson Education, Ltd. Figure 22.14 Pneumothorax. Punctured parietal pleura Ruptured visceral pleura (e.g., knife wound) (often spontaneous) Parietal pleura Visceral pleura Pleural cavity (Intrapleural pressure = −4 mm Hg) 0 0 0 0 −4 Intrapulmonary −4 −4 pressure (0 mm Hg) −4 Atmospheric pressure 0 mm Hg (760 mm Hg) Pneumothorax (air in pleural cavity): Intrapleural intrapleural pressure pressure becomes equal to 0 ( −4 mm Hg) 0 atmospheric pressure 0 Intrapulmonary Collapsed lung −4 pressure (0 mm Hg) (atelectasis) © 2016 Pearson Education, Ltd. Mechanics of Breathing Pulmonary Ventilation: is a mechanical process that depends on volume changes Breathing consists of two phases: Inspiration: flowing of air into lungs Expiration: flowing of gases out of lungs Volume changes lead to pressure changes which lead to flow of gases to equalize the pressure Relationship between pressure & volume of gases is given by Boyles’ law  How/why does air flow into and out of the lungs? Gas Laws Boyle’s Law pressure is inversely proportional to volume *Needs constant temperature Gases will fill their container Large container, molecules will be far apart and pressure low Small container, molecules will be forced together and pressure rise Law of Gases Boyle’s law: “at constant temperature, pressure of gas varies inversely with its volume” ↑volume → ↓ pressure ↓volume → ↑ pressure Inspiratory muscles = diaphragm & external intercostal muscles Charles’ law:“Volume of a gas is directly proportional to its absolute temperature (at constant pressure)” Gases are warmed on entering lungs & therefore expand Learning Objectives Mechanisms of gas exchange in the lungs and tissues Explain the relationship between the total pressure of gasses in a mixture and the partial pressure of an individual gas [Dalton’s Law]. Basic Properties of Gases: Dalton’s Law The pressure exerted by an individual gas in a mixture is known as its partial pressure. Dalton’s law: Dalton's law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases: Each gas in a mixture exerts its own pressure called its partial pressure (Px), in proportion to its relative concentration in a mixture of gases, e.g PTotal​=Pgas 1​+Pgas 2​+Pgas 3​... Partial pressure of O2 in atmosphere (21%) Po2 = 0.21 X 760 mm Hg = 159 mm Hg Partial pressure of N2 in atmosphere (78.6%) PN2 = 0.786 X 760 = 597 mm Hg Basic Properties of Gases: Henry’s Law Henry’s law: when a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure. Thus: ↑concentration of gas → ↑partial pressure → dissolve in liquid fast Henry’s law also states: a gas will flow from high pressure to low pressure (diffusion) until the partial pressures are the same (equilibrium) Carbon dioxide is the most soluble Oxygen is 1/20th as soluble as carbon dioxide Nitrogen is practically insoluble in plasma  Composition of Alveolar Gas The atmosphere is mostly oxygen and nitrogen, while alveoli contain more carbon dioxide and water vapor These differences result from: Gas exchanges in the lungs – oxygen diffuses from the alveoli and carbon dioxide diffuses into the alveoli Humidification of air by conducting passages The mixing of alveolar gas that occurs with each breath  Processes of Gas exchange External respiration: exchange of gases between alveoli & capillaries O2 from alveoli → blood CO2 from blood→ alveoli Internal respiration: exchange of gases in body tissues O2 from blood → body tissue CO2 from body tissue → blood Partial pressure gradients promote gas movements in the body Same mechanism → diffusion in both processes External Respiration: Pulmonary Gas Exchange Factors influencing the movement of oxygen and carbon dioxide across the respiratory membrane Partial pressure gradients and gas solubilities Matching of alveolar ventilation and pulmonary blood perfusion Structural characteristics of the respiratory membrane – Thickness and surface area  Summary- Factors Affecting Gas Exchange Concentration gradients of gases PO2 = 104 in alveolar air versus 40 in blood PCO2 = 46 in blood arriving versus 40 in alveolar air Gas solubility CO2 is 20 times as soluble as O2 O2 has ↑ conc. gradient, CO2 has ↑ solubility Membrane thickness - only 0.5 µm thick Membrane surface area - 100 ml blood in alveolar capillaries, spread over 70 m2 Ventilation-perfusion coupling - areas of good ventilation need good perfusion (vasodilation)