2023 HUB105 Lecture 19 Functions Of The Respiratory System PDF

Lecture 19 Functions of the Respiratory system BChD I HUB 105 2023 Dept. Medical Biosciences University of the Western Cape Introduction Cells within the body produce energy for maintenance, growth, defense, and division. Cells obtain this energy through aerobic me...

Lecture 19 Functions of the Respiratory system BChD I HUB 105 2023 Dept. Medical Biosciences University of the Western Cape Introduction Cells within the body produce energy for maintenance, growth, defense, and division. Cells obtain this energy through aerobic mechanisms that requires oxygen (O2)and produce carbon dioxide(CO2) as by-products. Respiratory exchanges surfaces within the lungs, provide a warm, moist and protected environment for the diffusion of gases between the air and blood. CVS provides the circulating blood which carries both O2 to and CO2 away from tissues. Functions of Respiratory System 1. Gas exchange – provides a large enough area for gas exchange between air and blood – allows O2 from the air to enter the blood & CO2 to leave the blood and enter the air 2. Regulation of blood pH – changes to the blood pH can be made by altering the CO2 levels in the blood 3. Protection – protects the respiratory surfaces from dehydration & changes in temperature – preventing microorganisms, dust & debris to the enter the body by removing them from the respiratory surfaces 4. Voice production – sounds are produced as air flows past the vocal cords in the larynx 5. Olfaction – the sensation of smell occurs when chemical substances in the air (odorants) are drawn into the nasal cavity Organization of the Respiratory System Anatomically the respiratory system consists of: nose nasal cavity pharynx larynx trachea bronchi lungs (including bronchioles & alveoli) Functionally the respiratory system consists of: conducting portion = from nose to terminal bronchioles respiratory portion = from terminal bronchioles to alveoli (air-filled sacs , where all gas exchange takes place betwn air and blood) Organization of the Respiratory System Upper respiratory system is a single large conductive tube Lower respiratory system starts after the larynx and continually divides to the smallest regions which form the exchange membranes Nasal cavity Paranasal sinuses Pharynx Larynx Conductive portion Trachea Bronchi Bronchioles Terminal Bronchioles Respiratory Bronchioles Alveoli of lungs Respiratory portion Organization of the Respiratory System Tracheo- = all the respiratory passageways, including all the bronchial tree branches from the trachea to the alveoli, and consists of a conducting zone and a respiratory zone 1. Conducting zone 2. Respiratory zone Extends from the trachea to Extends from the terminal the terminal bronchioles bronchioles to the alveoli Conduction Portion Conduction is the movement of air between the external and the internal environment through the structures of the conducting portion of the respiratory tract. Conduction portion begins at: nasal cavity and moves through conduction passages to end at terminal bronchioles. Functioning to filter, warm and humidify inhaled air at the entrance of the upper respi. tract and continues throughout the conducting portion. By the time air reaches the alveoli, this conditioning process of the air allows for optimal gases exchange at the alveoli. Conduction Portion Process of conditioning inhaled air is primarily determined by the respiratory mucosa. Raises incoming air – Warming (cooling) air to 37 Celsius – Humidifying Raises incoming air Forms mucociliary – Filtering air to 100% humidity escalator Respiratory mucosa contains specialized cells lining the conducting portion and is composed of a mucous membrane (consist of epithelium and underlying basement membrane). Structure of the epithelium changes along the tract, depending on the functional needs within the tract. Respiratory mucosa with mucous secreting glands; trap particles send to throat for expulsion. Conduction Portion Conditioning Process: Mucosa is composed of psuedostratified ciliated columnar epithelium containing mucous secreting glands. Basement membrane has blood vessels which provide nutrients and water to the secretory cells. But this vascularization provides a mechanism to warm and humidify inspired air. (as well as cool and dehumidify expired air) As cool air passes over the mucosa, the warm epithelium radiates heat and water from the mucus evaporates into the inhaled air. Air is heated to almost body temp. and it is saturated with water vapour. This process protects delicate respiratory surfaces from cooling down or drying out to maintain optimal gas exchange. Filters and cleans: – Mucus secreted to trap particles/pathogens in the inspired air. – Mucus moved by cilia with trapped particles to pharynx, where it is swallowed and exposed to acids in the stomach: Mucus escalator. Respiratory Portion Located in the lower respiratory system; consists of the respiratory bronchioles and the alveoli Functions Exchange of gases as it has: - ~300 million alveoli , huge surface area - 80-90% of the space between alveoli is filled with blood in pulmonary capillary networks. - Alveolar and capillary walls with their fused basement membranes form the respiratory membrane. - Creates exchange distance of approx 1 um thin from alveoli to blood Protection through - Free alveolar macrophages (dust cells) that destroy pathogen/foreign particles - Surfactant produced by type II pneumocytes (septal), is an oily secretion that helps reduce surface tension and keep alveoli open. Respiratory Portion Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries (a) Diagrammatic view of pulmonary capillary-alveoli relationships Figure 22.9a Respiratory Portion Respiratory Membrane The process of gas exchange occurs between blood and alveolar air across the respiratory membrane. Respiratory membrane structural composed of: 1) Type I pneumocytes; a squamous epithelial cells lining the alveolus 2) Endothelial cells lining an adjacent capillary 3) Fused basal membrane between alveolar and capillary Permit gas exchange by simple diffusion across this relatively short distance. O2 and CO2 are lipid soluble and easily move between blood and alveolar air space across the thin respiratory membrane. Respiratory Portion Red blood cell Nucleus of type I (squamous epithelial) cell Alveolar pores Capillary O2 Capillary Type I cell CO2 of alveolar wall Alveolus Macrophage Alveolus Endothelial cell nucleus Alveolar epithelium Fused basement membranes of the Respiratory alveolar epithelium Red blood cell membrane and the capillary Alveoli (gas-filled in capillary Type II (surfactant- endothelium air spaces) secreting) cell Capillary endothelium (c) Detailed anatomy of the respiratory membrane Figure 22.9c Gas Laws Characteristics of respiratory membrane allows for the fast circulation of blood through the lungs for gas exchange. – Pulmonary circulation = 5L/min through lungs – Systemic circulation = 5L/min through entire body Various gas laws are applied to the diffusion of O2 and CO2 into and out of the body and blood. Gases exchanged between the alveolar air and blood through diffusion occurs in response to concentration [] gradients. Rate of diffusion of gas depends on the size of the [] gradient, temp and volume. Basic Atmospheric conditions – Pressure is typically measured in mmHg, Atmospheric pressure is 760 mmHg at sealevel A few laws to remember – Dalton’s law – Boyle’s Law – Henry’s Law Gas Laws Dalton’s Law: Law of Partial Pressures “each gas in a mixture of gases will exert a pressure independent of other gases present” OR The total pressure of a mixture of gases is equal to the sum of the individual gas pressures. This means in practical application: If we know the total atmospheric pressure (760 mm Hg) and the percentage of each gas in the air. – We can calculate individual gas pressure (partial pressure = P) – Patm x % of gas in atmospheric air = Partial pressure of any atmospheric gas the partial pressures differences will allow the diffusion of gases across the respiratory membrane and within tissues. 159mmHg 595mmHg 6mmHg 760mmHg Gas Laws Henry’s law: Diffusion of liquids and gases At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. OR the solubility of a gas in a liquid at a particular temperature is proportional to the pressure of that gas above the liquid. Gas under pressure is forced into liquids until equilibrium is reach Incr. partial pressure = incr. gas diffusion into solution Decr. partial pressure = gas easily diffuses out of solution Gas Laws Boyle’s Law: Describes the relationship between gas pressure and volume “the pressure and volume of a gas in a system are inversely related” In a contained gas: – External pressure forces molecules closer together – Movement of gas molecules exerts pressure on container If you incr. the vol., If you decr. the vol. in fewer collisions occur, the container, collisions because it takes occur more frequently, longer for a gas molecule elevating/ incr. to travel from one wall to the pressure of the gas. another. As a result, the gas pressure inside the container declines/decr. Gas Exchange Respiration External Respiration Internal Respiration Pulmonary ventilation O2 transport Tissues Gas Gas diffusion diffusion Lungs Gas Gas diffusion diffusion CO2 transport Includes all processes involved in Involves the uptake of exchanging O2 and CO2 within the O2 and production of environment CO2 within individual cells Gas Exchange External respiration in alveoli. Physical movement of air in and out of respiratory tract (pulmonary ventilation); provides alveolar ventilation External air changes with inhalation: heats up, water vapour increases. Direction and rate of diffusion of gases across the respiratory membrane determine by different partial pressures and solubilities. Blood arriving in pulmonary arteries has a Low PO and High PCO than 2 2 alveolar air. Diffusion betw alveolar air and pulmonary capillaries caused by the [ ] gradient results in O2 uptake into blood and CO2 released from blood. Rapid exchange allows blood and alveolar air to reach equilibrium when it enters pulmonary vein. Blood leaving alveoli = PO2 of 100mm Hg and PCO2 of 40 mm Hg Gas exchange in alveoli External Respiration Systemic Pulmonary PO2 = 40 Alveolus circuit circuit PCO2 = 45 Respiratory membrane PO2 = 100 PCO2 = 40 Pulmonary PO2 = 100 capillary PCO2 = 40 Systemic circuit Gas Exchange Internal respiration within the tissues Partial Pressures of gases in the systemic circuit change as oxygenated blood mixes with deoxygenated blood from conducting passageways. This lowers the PO of blood entering systemic circuit (drops to about 2 95 mm Hg) Interstitial Fluid: PO 40 mm Hg and PCO 45 mm Hg 2 2 [ ] gradient in peripheral capillaries is different to that of the lungs as CO2 diffuses into blood and O2 diffuses out of blood Systemic gas exchange Systemic Pulmonary circuit circuit Internal Respiration Interstitial fluid PO2 = 95 PCO2 = 40 PO2 = 40 PCO2 = 45 Systemic circuit PO2 = 40 Systemic PCO2 = 45 capillary Revision Questions: 1. Define the following: conduction, conduction process, external and internal respiration, Boyle’s law, Dalton’s Law, Henry’s law 2. Explain the organisation of the respiratory system and the respiratory tract. 3. Fully explain the conduction process and its importance. 4. Structurally describe the respiratory mucosa and lamina propria. 5. Explain the function of the respiratory mucosa. 6. Describe the structural features of the respiratory membrane. 7. Explain the movement of oxygen and carbon dioxide during external respiration within the alveoli.