Respiratory System PDF

THE RESPIRATORY SYSTEM FUNCTIONS Surface area for gaseous exchange Moving air between gas exchange surfaces and environment Sound production Facilitates detection of olfactory stimuli http://www.medical-exam-essentials.com/images/Respiratory_system2.jpg  SUB-DIVISIONS OF THE RESPIRATORY...

THE RESPIRATORY SYSTEM FUNCTIONS Surface area for gaseous exchange Moving air between gas exchange surfaces and environment Sound production Facilitates detection of olfactory stimuli http://www.medical-exam-essentials.com/images/Respiratory_system2.jpg  SUB-DIVISIONS OF THE RESPIRATORY SYSTEM Upper Lower Nose Larynx Nasal cavity Trachea Paranasal sinuses Bronchi Pharynx Bronchioles Alveoli THE RESPIRATORY MUCOSA Consists of a mucous membrane of epithelium and supporting lamina propria (areolar tissue) THE TYPE OF EPITHELIUM VARIES ALONG THE RESPIRATORY TRACT ❖Upper tract, trachea & bronchi – pseudostratified ciliated columnar ❖Oropharynx and laryngopharynx – stratified squamous ❖Small Bronchioles – simple cuboidal with scattered cilia ❖Alveoli – simple squamous UPPER TRACT , TRACHEA & BRONCHI FUNCTIONS OF THE RESPIRATORY MUCOSA OF THE UPPER TRACT, TRACHEA AND BRONCHI Cleans inhaled air Mucus traps particles in air & cilia moves the mucus Humidifies inhaled air Water evaporates from mucus & moistens air Warms inhaled air Blood in vessels of lamina propia EFFECTS OF SMOKING ON THE RESPIRATORY EPITHELIUM  THE RESPIRATORY MUCOSA OF SMALL BRONCHIOLES Simple Cuboidal epithelium with scattered cilia. Lamina propria underlies the epithelium Function Mucus traps particles in the inhaled air and the cilia moves the mucus up toward the pharynx THE RESPIRATORY MUCOSA – ALVEOLI Simple Squamous Function Epithelial Cells Gaseous exchange UPPER RESPIRATORY TRACT (NOSE – PHARYNX) THE NOSE The primary passageway for air entering the respiratory system Air enters through paired External nares (nostrils) THE NASAL VESTIBULE The Nasal Vestibule is the space contained within the flexible tissues of the nose. The epithelium of the vestibule contains coarse hairs that extend across the external nares. The hairs trap large airborne particles such as sand, sawdust and even insects  NASAL SEPTUM Divides the nasal cavity into left and right portions Formed by  hyaline cartilage (anterior) and  fusion of the perpendicular plate of the ethmoid bone and the vomer bone BONES OF THE NASAL CAVITY Lateral and Superior walls made up of the: Maxillary Nasal Frontal Ethmoid & Sphenoid Bones The hard palate (floor of nasal cavity) is made up of: Portions of the maxillary and palatine bones THE SOFT PALATE Extends posteriorly from the hard palate Marks the boundary between the nasopharynx and the oropharynx HARD AND SOFT PALATE OLFACTORY REGION OF THE NASAL CAVITY Areas lined by olfactory epithelium Receptors in the Olfactory epithelium provide your sense of smell Includes:  Inferior surface of the cribriform plate  Superior portion of the nasal septum  Superior nasal conchae  NASAL CONCHAE (TURBINATES) The superior, middle and inferior conchae are bony projections that extend toward the nasal septum from the lateral walls of the nasal cavity SWOLLEN TURBINATE MEATUSES Air passes between adjacent conchae, through the superior, middle and inferior meatuses FUNCTION OF THE CONCHAE & MEATUSES Creates turbulence of incoming air Allows for efficient cleaning of air Allows for sufficient warming and humidifying of air Creates eddy currents that bring olfactory stimuli to the olfactory receptors PARANASAL SINUSES - FUNCTIONS Make skull lighter Resonance chambers Lined by mucous membrane Mucus keeps nasal cavity clean and moist Osteomeatal ducts lead into nasal cavity NASOLACRIMAL DUCT Delivers tears to nasal cavity into inferior nasal concha Keeps nasal cavity moist and clean THE PHARYNX  THE PHARYNX Nasopharynx  superior portion of pharynx;  separated from oral cavity by the soft palate  Lined by pseudostratified ciliated columnar epithelium  Pharyngeal tonsil on posterior wall  Opening to the pharyngotympanic (auditory) tube on lateral walls  THE PHARYNX Oropharynx Extends between the soft palate and the base of the tongue at the level of the hyoid bone Posterior to oral cavity Stratified squamous epithelium  THE PHARYNX Laryngopharynx Inferior part of the pharynx Lies between the hyoid bone and the entrance to the larynx and oesophagus Stratified squamous epithelium  THE LARYNX A cartilaginous structure that surrounds and protects the glottis Begins at veretbra C4 or C5 and ends at C6 Has incomplete cartilaginous walls stabilized by ligaments and muscles THE LARYNX CARTILAGES OF THE LARYNX Three large, unpaired cartilages form the larynx: Thyroid cartilage Cricoid cartilage Epiglottis  CARTILAGES OF THE LARYNX Thyroid Cartilage  Largest  Hyaline cartilage  Forms most of the anterior and lateral walls of the larynx  Incomplete posteriorly  Anterior surface forms the Laryngeal Prominence (Adam’s Apple)  Protects the glottis and entrance to the trachea  CARTILAGES OF THE LARYNX Cricoid Cartilage Hyaline cartilage Inferior to thyroid cartilage Posterior greatly expanded Supports thyroid cartilage Protects glottis and opening to the trachea  CRICOID CARTILAGE Important laryngeal muscles and ligaments are attached to the cricoid cartilage Articulates superiorly with the arytenoid cartilages Attached inferiorly to the first tracheal cartilage via ligaments IDENTIFY STRUCTURES A AND B A B  CARTILAGES OF THE LARYNX The Epiglottis  Projects superiorly and forms a lid over the glottis  Elastic cartilage  Attached to the hyoid bone and thyroid cartilage by ligaments  During swallowing the larynx is elevated while the epiglottis folds back over the glottis  THE EPIGLOTTIS Black arrow shows the direction the epiglottis moves during swallowing White arrows show the direction that air flows SMALL PAIRED CARTILAGES OF THE LARYNX  VOCAL CORDS (Vestibular fold) Vestibular Folds (False Vocal Cords) Vocal Cords Glottis THE TRACHEA  THE TRACHEA ❖12.5 cm long; 2.5 cm diameter ❖Anterior to esophagus ❖Begins at vertebra C6 and ends in the mediastinum at vertebra T5 where it branches to form the left and right primary bronchi ❖Lined by15 -20 C-shaped cartilage rings ❖An elastic ligament & the trachealis muscle (smooth muscle) connect the ends of the cartilage rings The primary function of the trachealis muscle is to constrict the trachea, allowing air to be expelled with more force, e.g., during coughing. Bifurcation of the trachea occurs at vertebra T5 to form the left and right primary bronchi. THE BRONCHIAL TREE  THE PRIMARY BRONCHI Right and left primary bronchi are separated by an internal ridge called the carina Supported by c-shaped cartilage rings Right primary bronchus has a larger diameter and enters the right lung at a steeper gradient than the left Primary bronchi branch into secondary bronchi  THE BRONCHI & LUNGS Each bronchus travels to the Hilum, along the medial surface of the lung The hilum also provides access to pulmonary vessels, nerves and lymphatics All are anchored in a mesh of connective tissue collectively called the ROOT of the lung  THE LUNGS The right lung has three lobes and is shorter and broader than the left lung. The left lung has two lobes. PLEURAL MEMBRANE Each lung is surrounded by a serous membrane called the Pleural Membrane. The Pleural Membrane consists of an internal Visceral Pleura and an external Parietal Pleura.  PLEURAL MEMBRANE The Visceral Pleura is the outer layer of the lungs while the Parietal Pleura lines the Pleural Cavity. The Visceral and Parietal Pleura are held together by serous fluid (pleural fluid). Therefore as the rib cage and diaphragm move during breathing the lungs move along with them. The serous fluid also reduces friction between the two layers.  BRONCHIOLES Tertiary bronchi branch into bronchioles Bronchioles into terminal bronchioles Terminal bronchioles into respiratory bronchioles Respiratory bronchioles into alveolar ducts BRONCHIOLES Terminal bronchioles – smooth muscle; simple cuboidal epithelium; no goblet cells Respiratory Bronchioles – simple cuboidal epithelium with scattered cilia; no goblet cells; elastic fibres; some smooth muscle fibres STRUCTURAL FEATURES OF THE BRONCHIAL TREE  THE ALVEOLI The Alveolus is the basic unit of gaseous exchange. Lung alveoli are the ends of the respiratory tree, branching from either alveolar sacs or alveolar ducts, sites of gas exchange with the blood. A typical pair of human lungs contain about 700 million alveoli, producing 70m2 of surface area. Each alveolus is wrapped in a fine network of capillaries covering about 70% of its area. An adult alveolus has an average diameter of 200 micrometres, with an increase in diameter during inhalation ALVEOLAR EPITHELIUM ALVEOLAR EPITHELIUM Consists of: Pneumocytes type I  simple squamous cells that facilitate gaseous exchange Alveolar Macrophages “dust cells”; phagocytic cells that engulf particles that may have eluded other respiratory defenses Pneumocytes type II septal cells; produce surfactant that reduces the surface tension of water lining the lungs preventing lung collapse RESPIRATORY MEMBRANE ❖The Respiratory membrane consists of the alveolar epithelium, the capillary endothelium & the fused basal laminae between the epithelial layers. ❖Average distance between alveolar air and blood is about 0.5 µm Notice the pressure gradient of oxygen and carbon dioxide across the membrane. THE DIAPHRAMATIC MUSCLE The diaphragm is the dome-shaped, skeletal muscular partition that separates the abdominopelvic and thoracic cavities. THE DIAPHRAMATIC MUSCLE – ORIGIN & INSERTION THE DIAPHRAMATIC MUSCLE The diaphragm has two surfaces: thoracic and abdominal. The thoracic diaphragm is in contact with the serous membranes of the heart and lungs; namely, the pericardium and pleura. The abdominal diaphragm is in direct contact with the liver, stomach, and spleen. THE DIAPHRAMATIC MUSCLE Contraction of the diaphragmatic muscle facilitates expansion of the thoracic cavity. This increases volume of the cavity, which in turn decreases the intrathoracic pressure allowing the lungs to expand and inspiration to occur. HOW MANY STRUCTURES CAN YOU IDENTIFY? PULMONARY VENTILATION - BREATHING Physical movement of air into and out of the respiratory tract PULMONARY VENTILATION - BREATHING There are four important factors to remember as we study pulmonary ventilation FACTOR 1 Atmospheric pressure is exerted on all objects on the earth’s surface. It is 760mmHg at sea level. ATMOSPHERIC PRESSURE DECREASES AS ALTITUDE INCREASES FACTOR 1 (CONT’D) Atmospheric pressure represents the combined effects of collisions involving each type of molecule in air. Each of the gases in air contributes to the total pressure in proportion to its relative abundance – Dalton’s Law FACTOR 1 (CONT’D) The partial pressure of a gas is the pressure contributed by a single gas in a mixture of gases. All the partial pressures added together equal the total pressure exerted by the gas mixture. For the atmosphere, this relationship can be summarized as follows: P N2 + PO2 + PH2O + PCO2 = 760 mm Hg FACTOR 1 (CONT’D) The direction of airflow is determined by the relationship (the difference) between the atmospheric pressure and intrapulmonary pressure Intrapulmonary pressure is the pressure inside the alveoli. FACTOR 2 Boyle’s Law ( P = 1/V): The pressure (P) of a gas is inversely proportional to its volume (V) FACTOR 2 (CONT’D) As the volume of the lungs change during breathing, the intrapulmonary pressure changes relative to atmospheric pressure. When lung volume decreases intrapulmonary pressure increases above atmospheric pressure causing air to move out of the lungs. FACTOR 3 – HENRY’S LAW At a given temperature, the amount of a particular gas in solution is directly proportional to the partial pressure of that gas. FACTOR 3 – HENRY’S LAW The actual amount of a gas in solution at a given temperature depends on the solubility of the gas in that particular liquid. In body fluids, CO2 is highly soluble, O2 is somewhat less soluble and N2 has very limited solubility. In a pulmonary vein, plasma generally contains 2.62 mL/dL of dissolved CO2 (PCO2 = 40 mmHg), 0.29 mL/dL of dissolved O2 (PO2= 100mm Hg), and 1.25 mL/dL of dissolved N2 (PN2 = 573 mmHg). FACTOR 4 Air moves from high to low pressure As intrapulmoanry pressure changes relative to atmospheric pressure, air moves in or out of the lungs. Before Inhalation occurs: The Diaphragm is relaxed and is dome- shaped. The external intercostal muscles are relaxed and the ribcage is lowered Intrapulmonary pressure is equal to atmospheric pressure (760mmHg)  QUIET BREATHING - INHALATION Diaphragm contracts and flattens External intercostal muscles contract. Pulling ribcage upward and outward Thoracic cavity volume increases Lung volume increases Intra-pulmonary pressure decreases to 759 mmHg Air moves into lungs from the atmosphere  QUIET BREATHING - EXHALATION Diaphragm relaxes and becomes dome-shaped External intercostal muscles relax causing the rib cage to move downward and inward Thoracic and lung volumes decrease Intrapulmonary pressure increases to 761 mmHg Air flows out of lungs Quiet Exhalation is a Passive Process No stimulation is received from the respiratory centers of the brain for the respiratory muscles to relax FORCED BREATHING Involves the use of Accessory muscles along with the external intercostal muscles and diaphragm FORCED BREATHING  FORCED BREATHING - INHALATION Sternocleidomastoid and scalene muscles aid the external intercostal muscles to pull the ribcage upward a little further than in quiet breathing Diaphragm contracts and flattens Thoracic and lung volumes increase Intrapulmonary pressure decreases Air rushes into the lungs because of the sharper gradient in air pressure between the lungs and the environment FORCED BREATHING - EXHALATION Internal intercostals, Rectus abdominis and Transversus abdominis contract; and External intercostals relax causing the ribcage to move inward and downward a bit further than in quiet exhalation Diaphragm relaxes and becomes dome- shaped Thoracic and lung volumes decrease Intrapulmonary pressure increases Air rushes out forcefully OXYGEN TRANSPORT 1.5 % in plasma 98.5% attached to Haemoglobin HAEMOGLOBIN SATURATION Percent haem units containing bound O2 HAEMOGLOBIN SATURATION Hb is a protein and changes shape in different environmental conditions: Partial pressure of Oxygen pH of blood Temperature Ongoing metabolic activity of RBCs HAEMOGLOBIN SATURATION Increases when  Partial pressure of oxygen increases  pH increases/CO2 decreases  Temperature decreases  DPG decreases Decreases when  Partial pressure of oxygen decreases  pH decreases/CO2 increases  Temperature increases  DPG increases HAEMOGLOBIN SATURATION CURVE (PH – 7.4, TEMP – 37OC) Percent Hb saturation increases with increasing oxygen levels The plateau of the curve represents no significant increase in Hb saturation as O2 increases because most haem sites have O2 bound to them  HAEMOGLOBIN SATURATION CURVE http://www.as.miami.edu/chemistry/2086/Chap23/The%20Respiratory%20System%20Part%202_files/image004.jpg As pH increases As temperature increases (increased alkalinity) Hb Hb saturation decreases. Saturation increases HAEMOGLOBIN SATURATION CURVE Black curve represents Hb saturation under normal conditions Left curve produced when  temperature decreases,  pH increases and  metabolic activity of RBCs decreases Diphosphoglycerate (Biphosphoglycerate) is produced by metabolically active RBCs. As DPG increases Hb Saturation decreases REVIEW QUESTION Distinguish between haemoglobin saturation at the lungs and at active muscles. CARBON DIOXIDE TRANSPORT Carbon dioxide is transported in three ways in the blood: 1. Dissolved in plasma 2. Bound to the protein portion of Hb 3. As the bicarbonate ion (HCO3-) in plasma