Respiratory Physiology 2024 PDF

Respiratory Physiology Lecturer: Abdullah Hassan  Introduction and Definitions Respiration is the process in which human being exchange gases between their body cells and the environment. Respiratory System is very important for human being live, outside the womb, as it allo...

Respiratory Physiology Lecturer: Abdullah Hassan  Introduction and Definitions Respiration is the process in which human being exchange gases between their body cells and the environment. Respiratory System is very important for human being live, outside the womb, as it allows the exchange of oxygen and carbon dioxide gases between the environment and body tissues and cells. Dysfunction of the respiratory system ultimately leads to hypoxia, because of hypoventilation. During inhalation or exhalation air is pulled towards or away from the lungs, by several cavities, tubes, and openings. The organs of the respiratory system make sure that oxygen enters, and carbon dioxide leaves the body. Organs or Parts of Respiratory System Respiratory system is made up of nose and mouth, throat, voice box, airways (trachea, bronchi and bronchioles), lungs and diaphragm, The main function of the respiratory system is to breathe in oxygen and breathe out carbon dioxide. Respiratory system helps in smell and speak and also in protecting the body from harmful particles and germs.  Organs or Parts of Respiratory System Nose and Mouth: Air enters the respiratory system through the nose or the mouth. Pharynx (throat): The nasal cavity and the mouth openings meet at the pharynx at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air. The Larynx (voice box): Top part of Trachea. This short tube contains a pair of vocal cords, which vibrate to make sounds. Tracheobronchial tree: Network of trachea, bronchi, bronchioles and alveoli. Trachea: The walls of the trachea are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airways. Carina: The angle made between the two primary bronchi when they diverge at the tracheal bifurcation.  Organs or Parts of Respiratory System Bronchi: At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles. Lungs: The functional units of respiration and are key to survival. The structure of the lung is well suited for efficient exchange of respiratory gases. Lungs are affected by a wide range of pathology that results in a diverse range of illnesses. Alveoli: Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide takes place. Each lungs contain hundreds of millions of alveoli. The Thorax houses: The bronchial tree, lungs, heart, and other structures. The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by the diaphragm. The chest walls form a protective cage around the lungs and other contents of the chest cavity. What are the main functions of the respiratory system? Gas exchange. Respiratory system pulls in oxygen for the body’s cells and get rid of carbon dioxide, a waste product. This is happened by breathing in and out and through gas exchange between the small air sacs of the lungs (alveoli) and the blood vessels running nearby. Warms and adds moisture to the inhaled air8. Respiratory system warms the air to match the body temperature. It moisturizes the air to bring it to the humidity level the body needs. Protects the body from breath in particles. Parts of respiratory system can block harmful germs and irritants from getting in or push them out if they do get in. Talk. Air vibrates the vocal cords, which makes sounds. Helps in smell. Breathing in air moves its molecules past the olfactory nerve, which sends messages to the brain about the way something smells. Balances level of acidity in the body. Too much carbon dioxide lowers the blood’s pH, making it acidic. By removing carbon dioxide, the respiratory system helps maintain the acid-base balance in the body.  The Respiratory System  There are three types of Respiration External respiration involves inhalation and exhalation of gases. In the human body, oxygen is taken into the lungs by inhalation and carbon dioxide is expelled from the lungs by exhalation. External respiration encompasses the mechanical processes related to breathing. This includes contraction and relaxation of the diaphragm and accessory muscles, as well as breathing rate. Internal respiration involves the transportation of gases between the lungs and body tissues. Oxygen within the lungs diffuses across the thin epithelium of lung alveoli (air sacs) into surrounding capillaries containing oxygen depleted blood. At the same time, carbon dioxide diffuses in the opposite direction (from the blood to lung alveoli) and is expelled. Oxygen rich blood is transported by the circulatory system from lung capillaries to body cells and tissues. While oxygen is being dropped off at cells, carbon dioxide is being picked up and transported from tissue cells to the lungs. Cellular respiration involves the conversion of food and oxygen to energy. As blood is circulated throughout the body, nutrients are transported to body cells. In cellular respiration, glucose obtained from digestion is split into its constituent parts for the production of energy. Through a series of steps, glucose and oxygen are converted to carbon dioxide (CO2), water (H2O), and the high energy molecule adenosine triphosphate (ATP).  The Respiratory Pathways When one breathes air in at sea level, the inhalation is composed of different gases. These gases and their quantities are Oxygen which makes up 21%, Nitrogen which is 78%, Carbon Dioxide with 0.04% and others with significantly smaller portions. In the process of breathing, air enters into the nasal cavity through the nostrils and is filtered by coarse hairs (vibrissae) and mucous that are found there. The vibrissae filter macro-particles, which are particles of large size. Dust, pollen, smoke, and fine particles are trapped in the mucous that lines the nasal cavities (hollow spaces within the bones of the skull that warm, moisten, and filter the air). There are three bony projections inside the nasal cavity. The superior, middle, and inferior nasal conchae. Air passes between these conchae via the nasal meatuses. Respiration And Gas Exchange  Divisions and Mechanism of Respiration Respiration in Physiology is a process by which oxygen is transport from the atmosphere to the tissue and carbon dioxide from the tissue to atmosphere. Ventilation is the exchange of air between the external environment and the alveoli. Air moves by bulk flow from an area of high pressure to low pressure. All pressures in the respiratory system are relative to atmospheric pressure (760 mmHg at sea level). Air will move in or out of the lungs depending on the pressure in the alveoli. The body changes the pressure in the alveoli by changing the volume of the lungs. As volume increases pressure decreases and as volume decreases pressure increases.  Divisions and Mechanism of Respiration Pulmonary ventilation: inflow and outflow between atmosphere and lungs. Mechanism: Air enters the body through the mouth or nose and quickly moves to the pharynx, or throat. Air then, passes through the larynx, or voice box, and enters the trachea. The trachea is a strong tube that contains rings of cartilage that prevent it from collapsing. Within the lungs, the trachea branches into a left and right bronchus. These further divide into smaller and smaller branches called bronchioles. The smallest bronchioles end in tiny air sacs. These are called alveoli. They inflate when a person inhales and deflate when a person exhales.  Mechanism of Respiration In the human body respiratory system, oxygen is taken into the lungs by inhalation and carbon dioxide is expelled from the lungs by exhalation.  Mechanism of Respiration There are two phases of ventilation; inspiration and expiration. During each phase the body changes the lung dimensions to produce a flow of air either in or out of the lungs. The body is able to stay at the dimensions of the lungs because of the relationship of the lungs to the thoracic wall. Each lung is completely enclosed in a sac called the pleural sac. Two structures contribute to the formation of this sac. The parietal pleura is attached to the thoracic wall whereas the visceral pleura is attached to the lung itself. In-between these two membranes is a thin layer of intra-pleural fluid. The intra-pleural fluid completely surrounds the lungs and lubricates the two surfaces so that they can slide across each other.  Mechanism of Respiration Changing the pressure of The intra-pleural fluid also allows the lungs and the thoracic wall to move together during normal breathing. The rhythm of ventilation is also controlled by the "Respiratory Centre" which is located largely in the medulla oblongata of the brain stem. This is part of the autonomic system and as such is not controlled voluntarily (breathing rate is voluntarily, but that involves a different part of the brain). While resting, the respiratory centre sends out action potentials that travel along the phrenic nerves into the diaphragm and the external intercostal muscles of the rib cage, causing inhalation. Relaxed exhalation occurs between impulses when the muscles relax. Normal adults have a breathing rate of 12-20 respirations per minute.  Divisions and Mechanism of Respiration Gas exchange between alveoli and blood. Mechanism By simple diffusion. O2 to the blood an CO2 to the lung. During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli. Red blood cells traveling through the capillaries. The walls of the alveoli share a membrane with the capillaries. That's how close they are. This lets oxygen and carbon dioxide diffuse, or move freely, between the respiratory system and the bloodstream. Oxygen molecules attach to red blood cells, which travel back to the heart. At the same time, the carbon dioxide molecules in the alveoli are blown out of the body the next time a person exhales. Transport of Oxygen and Carbon Dioxide from the Lungs  Transport of Gases by the Blood Oxygen is primarily transported through the blood by erythrocytes. These cells contain a metalloprotein called haemoglobin, which is composed of four subunits with a ring- like structure. Each subunit contains one atom of iron bound to a molecule of heme. Heme binds oxygen so that each haemoglobin molecule can bind up to four oxygen molecules. When all of the heme units in the blood are bound to oxygen, haemoglobin is considered to be saturated. Haemoglobin is partially saturated when only some heme units are bound to oxygen. An oxygen–haemoglobin saturation/dissociation curve is a common way to depict the relationship of how easily oxygen binds to or dissociates from haemoglobin as a function of the partial pressure of oxygen. As the partial pressure of oxygen increases, the more readily haemoglobin binds to oxygen. At the same time, once one molecule of oxygen is bound by haemoglobin, additional oxygen molecules more readily bind to haemoglobin. Other factors such as temperature, pH, the partial pressure of carbon dioxide, and the concentration of 2,3-bisphosphoglycerate can enhance or inhibit the binding of haemoglobin and oxygen as well. Foetal haemoglobin has a different structure than adult haemoglobin, which results in foetal haemoglobin having a greater affinity for oxygen than adult haemoglobin. Transport of Oxygen and Carbon dioxide to the tissue  Transport of Gases by the Blood Carbon dioxide is transported in blood by three different mechanisms: as dissolved carbon dioxide, as bicarbonate, or as carbaminohaemoglobin. A small portion of carbon dioxide remains. The largest amount of transported carbon dioxide is as bicarbonate, formed in erythrocytes. For this conversion, carbon dioxide is combined with water with the aid of an enzyme called carbonic anhydrase. This combination forms carbonic acid, which spontaneously dissociates into bicarbonate and hydrogen ions. As bicarbonate builds up in erythrocytes, it is moved across the membrane into the plasma in exchange for chloride ions by a mechanism called the chloride shift. At the pulmonary capillaries, bicarbonate re-enters erythrocytes in exchange for chloride ions, and the reaction with carbonic anhydrase is reversed, recreating carbon dioxide and water. Carbon dioxide then diffuses out of the erythrocyte and across the respiratory membrane into the air. An intermediate amount of carbon dioxide binds directly to haemoglobin to form carbaminohaemoglobin. The partial pressures of carbon dioxide and oxygen, as well as the oxygen saturation of haemoglobin, influence how readily haemoglobin binds carbon dioxide. The less saturated haemoglobin is and the lower the partial pressure of oxygen in the blood is, the more readily haemoglobin binds to carbon dioxide. This is an example of the Haldane effect.  Cellular Respiration Cellular respiration consists of three stages: glycolysis, citric acid cycle (Krebs Cycle), and electron transport with oxidative phosphorylation. Glycolysis occurs in the cytoplasm and involves the oxidation or splitting of glucose into pyruvate. Two molecules of ATP and two molecules of the high energy NADH are produced in glycolysis. In the presence of oxygen, pyruvate enters the inner matrix of cell mitochondria and undergoes further oxidation in the Krebs cycle. Krebs Cycle: Citric acid cycle, two additional molecules of ATP are produced in this cycle along with CO2, additional protons and electrons, and the high energy molecules NADH and FADH2. Electrons generated in the Krebs cycle move across the folds in the inner membrane (cristae) that separate the mitochondrial matrix (inner compartment) from the intermembrane space (outer compartment). This creates an electrical gradient, which helps the electron transport chain pump hydrogen protons out of the matrix and into the intermembrane space.  Cellular Respiration Citric acid cycle (Krebs Cycle), and electron transport stages of cellular Respiration occur in the mitochondria.  Cellular Respiration The electron transport chain is a series of electron carrier protein complexes within the mitochondrial inner membrane. NADH and FADH2 generated in the Krebs cycle transfer their energy in the electron transport chain to transport protons and electrons to the intermembrane space. The high concentration of hydrogen protons in the intermembrane space is utilized by the protein complex ATP synthase to transport protons back into the matrix. This provides the energy for the phosphorylation of ADP to ATP. Electron transport and oxidative phosphorylation account for the formation of 34 molecules of ATP. ADP Stand for Adenosine Diphosphate). - ATP Stands for (Adenosine triphosphate). NADH Stands for (Nicotinamide Adenine Dinucleotide Hydrogen). FADH2 Stands for (Flavin Adenine Dinucleotide Hydrogen). It is a coenzyme that is involved in energy metabolism in the body.  Homeostatic Control of Respiration Homeostatic control of respiration is the ability of the body to maintain a steady breathing rate, this is termed eupnea. This state should remain constant until the body need for oxygen is increased and the carbon dioxide levels due to increased which, most likely caused by physical activity. When this happens, chemoreceptors will pick up on the increased partial pressure of the oxygen and carbon dioxide and send triggers to the brain. The brain will then signal the respiratory center to make adjustments to the breathing rate and depth in order to face the increased demands.  Homeostasis and Respiration – Acid Base Balance pH is the concentration of hydrogen ions (H+). Normal blood pH is 7.4, which is slightly alkaline or "basic". There are three factors effecting the process of Homeostasis: the Lungs, the Kidneys and the Buffer system. Lungs gas exchange in Respiration as well as the Kidneys contribute in homeostasis. Buffers are molecules which take in or release ions in order to maintain the H+ ion concentration at a certain level. Bicarbonate Buffer System is important for maintaining homeostasis. H2CO3 is Carbonic Acid - HCO3 is Bicarbonate. CO2 + H2O H2CO3 (H+) + HCO3 If pH is too high, carbonic acid will donate hydrogen ions (H+) and pH will drop. If pH is too low, bicarbonate will bond with hydrogen ions (H+) and pH will rise.  Common Respiratory System Diseases Obstructive sleep apnea syndrome, occurs when the throat muscles relax and block the airway and characterised by repeatedly stop and start breathing during sleep. Snoring is a sign of obstructive sleep apnea. Chronic Obstructive Pulmonary Disease (COPD), is a group of illnesses that cause breathlessness, or the inability to exhale normally, such as Chronic Bronchitis, Emphysema. Asthma, is defined as a common, chronic respiratory condition that causes difficulty breathing due to inflammation of the airways. Cystic Fibrosis, is a genetic respiratory disease caused by a defective gene that creates thick and sticky mucus that block tubes and passageways. Pneumonia, is a common lung disease caused by bacterial or viral infection in the air sacs in the lungs. Pleural Effusion, is a collection of fluid between the lung and the chest wall and might be caused by pneumonia, cancer or congestive heart failure. Lung Cancer, which develops in the main part of the lungs near the air sacs. Corona Virus Disease 2019 (COVID-19), is a respiratory illness that belongs to a large family of viruses called corona viruses. The symptoms of (COVID-19) are fever, tiredness, and dry cough.