Respiratory System 2021 PDF

Respiration sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells External respiration - every 3 to 5 seconds nerve impulses stimulate the breathing process (ventilation) which moves the air in and out of the lungs - exchange...

Respiration sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells External respiration - every 3 to 5 seconds nerve impulses stimulate the breathing process (ventilation) which moves the air in and out of the lungs - exchange of gases between the lungs and the blood Internal respiration - exchange of gases between the blood and tissue cells Cellular respiration - cells utilize the oxygen for their specific activities Air conducting passages Upper respiratory tract - nose - pharynx - larynx Lower respiratory tract - trachea - bronchial tree - lungs (alveoli) Anatomic dead space - total volume of the air channels that conduct inspired air to the alveoli – about 150 ml - it does not take part in the gas exchange - functions as an air conduit in which the air if freed of dust particles, humidified and warmed before it reaches the alveoli - mouth - nose - pharynx - trachea - bronchi Cleansing of the inspired air - dirt particles in the air are caught by the mucus covering the nasal and pharyngeal cavities, the trachea and the bronchial tree - the particles are phagocyted or returned towards the pharynx by the cilia of the epithelium Mechanics of ventilation (breathing) - pulmonary ventilation is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation) - air flows because of pressure difference between the atmosphere and the gases inside the lungs - for the inspiration pressure in the lungs must be below the atmospheric pressure - for the expiration pressure in the lungs must be above the atmospheric pressure These pressure gradients are estabilished when the lung volume is increased on inspiration and decreased on expiration by action of the diaphragm and thorax Inspiration - active process - muscular contraction increases the volume of the chest - the lungs inflate - air pressure in the lungs falls - air flows into the lungs Expiration - quiet expiration is a passive process - at the end of quiet inspiration, the lungs and chest recoil to the position they occupied at the beginning of inspiration - pressure in the lung increases - air flows out of the lungs Respiratory muscles Diaphragm - accounts for 75% of volume change in quiet inspiration - it moves about 7 cm on deep inspiration External intercostal muscles - other respiratory muscles used in quiet inspiration additional inspiratory muscles - used during deep inspiration additional expiratory muscles - used during forced expiration The lungs follow the movements of the thorax Respiratory volumes TV - tidal volume - the air volume that is inspired and expired during quiet breathing - about 500ml IRV - inspiratory reserve volume - after quiet inspiration we can inspire another 2,5 l of air ERV - expiratrory reserve volume - after quiet expiration we can expire another 1,5 l of air VC - vital capacity - the air volume that can be expired in the maximal expiration after maximal inspiration VC = TV + IRV + ERV RV - residual volume - the air remaining in lungs after maximal expiration (1,2 –1,5 l) - can not be removed because the bronchi are collapsing and closing the passage for the air out of the alveoli TLV - total lungs volume TLV = RV + TV + IRV + ERV RV = TLV – VC Oxygen binding and transport in the blood - oxygen binding to hemoglobin = oxygenation. - pressure of oxygen in arterial blood = 95 mmHg in venous blood – about 40 mmHg - oxygen dissociation curve represents the relationship between the oxygen pressure in the blood and hemoglobin saturation. - oxygen binding capacity of hemoglobin increases with temperature decrease, and pH increase (e.g. in the tissues) Carbon dioxide transport in the blood - major part enters red blood cells and undergoes conversion to HCO3- - carbonic anhydrase makes this process 300 times faster - pressure of carbon dioxide in arterial blood = 40 mmHg in venous blood – about 46 mmHg Hypoxia – oxygen deficit in the tissues anoxia - complete oxygen absence - hypoxic hypoxia - reduced oxygen content in the air - anemic hypoxia - not enough oxygen is bound in the blood (reduced oxygen capacity of blood) - histotoxic hypoxia - tissues cannot utilize oxygen - ischemic hypoxia - decreased blood supply to the tissues Most sensitive organ is the brain  Cyanosis - dark (blue) colour of nails, lips, ears and areas where the skin is thin - occurs when the amount of desoxygenated hemoglobin in the capillaries exceeds 50 g/l Respiratory center - pons and medula oblongata of the brain - controls the rate and depht of breathing inspiratory area - phrenic nerve - diaphragm contraction - normal breathing rate in adults averages between 12 and 20 times per minute - the rate is higher in children - 40/min Factors that influence breathing - central and peripheral chemoreceptors detecting oxygen, carbon dioxide and pH levels - mechanoreceptors in the lungs - higher brain centers - pain, emotions - temperature