Respiratory System.pdf

The Respiratory System The respiratory system ensures that oxygen is brought to each cell in the body, and that carbon dioxide can leave the cell and be removed from the body. Respiration requires : adequate surface area for the exchange of O2 and CO2 exchange to be ab...

The Respiratory System The respiratory system ensures that oxygen is brought to each cell in the body, and that carbon dioxide can leave the cell and be removed from the body. Respiration requires : adequate surface area for the exchange of O2 and CO2 exchange to be able to occur fast enough to meet the needs of the body A moist environment, so that the O2 and CO2 are dissolved in water Stages in Respiration Breathing 2 stages: Inspiration (breathing in/ inhaling) Expiration (breathing out/ exhaling) External Respiration The exchange of O2 and CO2 between the air and the blood Internal Respiration Exchange of O2 and CO2 between the body’s tissue cells and the blood Cellular Respiration Energy-releasing reactions that take place in the cells which use O2 and produce CO2 The structures of the respiratory tract provide a passageway for air to move from the external environment to deep within the lungs, where external respiration (gas exchange) occurs The Upper Respiratory Tract Air enters through the nostrils (or the mouth, especially if breathing rapidly) The nasal passages are lined with ciliated cells which warm, moisten, and clean the incoming air, as well as cells which secrete mucus, which cleans the air by trapping foreign particles, which are then moved up the respiratory tract by the cilia, and then expelled by coughing or sneezing. Turbinate bones project into the nasal cavity, and serve to increase the surface area of the nasal passages, and to catch and remove foreign particles via mucus and cillia, as well as to warm and moisten the air. Pharynx – “throat” – passageway for air and food Epiglottis - flap of cartilage that lies behind the tongue and in front of the larynx – closes over the glottis when you swallow to prevent food from entering the respiratory system Glottis - The opening of the trachea Larynx – “voice box” – made from cartilage, contains vocal cords, which are lengthened and shortened by muscles to cause them to vibrate and make sounds. Longer cords = lower sounds Trachea – “Windpipe” strengthened by semicircular cartilaginous arches to prevent The Lower Respiratory Tract The trachea branches into smaller passageways called bronchi , which then continue to subdivide several times into smaller and finer tubes called bronchioles Bronchi have C-shaped cartilaginous rings for support, bronchioles do not. Both bronchi and bronchioles are lined with cilia and mucus-producing cells to capture foreign particles and move them up the respiratory tract Lower respiratory tract cont’d Each lung is divided into lobes: 3 on the right and 2 on the left. Each lobe is made up of many lobules that extend from each bronchiole Lungs are surrounded by a thin, double-layered pleural membrane – the outer layer attaches to the inside of the chest wall; the inner layer attaches to the lung. Fluid fills the space between so that they adhere to each other. This ‘sticks’ the lungs to the thoracic cavity, allowing them to expand and contract with the movement of the chest. Each bronchiole ends in a cluster of tiny sacs called alveoli, where gas exchange occurs. Alveolar walls are one cell thick and are surrounded by a network of tiny capillaries, which are blood vessels whose walls are also one cell thick which link arteries and veins. Bronchioles and alveoli are held in place by elastic connective tissue that fills the space between them, and the alveoli are lined with a lubricating film to help them function Section 7.2 Breathing and Respiration The Mechanics of Breathing Two muscular structures – the diaphragm and the rib, or intercostal muscles control the air pressure in the lungs, causing air to move into or out of the lungs accordingly. The Diaphragm is a dome-shaped layer of muscle that separates the thoracic cavity (lung area) from the abdominal cavity (region of the stomace and liver) Intercostal muscles are found between the ribs, and on the inside surface of the ribs extending to the Inhalation When the diaphragm and rib muscles contract, moving the diaphragm downwards and the ribcage upwards and outwards, the volume of the thoracic cavity increases and the air pressure in the cavity decreases. The walls of the lungs are drawn outwards, and air is drawn into the lungs. Exhalation The diaphragm and rib muscles relax , reducing the volume of the thoracic cavity and increasing the pressure inside the lungs, causing air to rush out of the lungs. **Air always moves from areas of higher pressure to areas of lower pressure** Spirograph A spirograph represents the amount of air that moves into or out of the lungs with each breath: Terms: Tidal Volume : The amount of air that is inhaled and exhaled in normal breathing when an individual is at rest. Inspiratory reserve volume: Additional air that can be taken into the lungs beyond a tidal inhalation Expiratory reserve volume : Additional volume of air that can be forced out of the lungs beyond a tidal exhalation Vital Capacity : Also called total lung volume capacity. This is the total amount of gas that can be moved into or out of the lungs. (Tidal volume + inspiratory reserve volume + expiratory reserve volume) Residual Volume: The amount of gas that remains in the lungs and passageways of the respiratory system after a full exhalation – stops the lungs and passageways from collapsing. External Respiration Takes place in the lungs Gasses are exchanged between the alveoli and the blood in the capillaries (recall that the walls of both are one cell thick to allow for easy gas exchange by diffusion through cell membranes). Some gas exchange (about 30%) also takes place via facilitated diffusion , in which proteins in the walls of the alveoli ‘help’ or ‘facilitate’ diffusion by carrying O2 across cell membrane, speeding up the movement of gasses from an area of high concentration to an area of low concentration  After the newly-oxygenated blood leaves the capillary, it travels to the heart, then outward to body tissue cells, where internal respiration occurs Almost all oxygen that reaches cells (99%) is carried in the blood by hemoglobin, a special oxygen-transporting protein molecule that is found only in red blood cells. The remainder is transported in the blood plasma Only 23% of CO2 is carried in the blood by hemoglobin, 7% is carried dissolved in plasma, and 70% is dissolved and carried in the blood as bicarbonate ion (HCO3-) Breathing rates are controlled by a part of our brains called the Medulla Oblongata, which monitors blood CO2 levels - increasing respiration rates with high CO2 levels and inhibiting respiration with low CO2 levels. Section 7.3 Respiratory Health Upper Respiratory Tract Infections Tonsillitis : Infection of the tonsils, which are located in the Pharynx. These are most commonly viral, not bacterial infections. Occasionally, tonsils are removed if infections are frequent and/or impairing breathing. Tonsils are useful in preventing pathogens from entering the body, so removing them can mean more infections later in life. Laryngitis : Inflammation of the larynx, which restricts the vocal cords and stops them from vibrating as they normally do. Most commonly a viral infection, but can also be caused by allergies and overstraining the voice. Symptoms include sore throat and hoarseness, and sometimes the inability to speak. **The suffix “itis” indicates inflammation Lower Respiratory Tract Disorders Bronchitis : A disorder characterized by bronchi which become inflamed and filled with mucus. Acute bronchitis is a short-term disorder caused by bacteria that can be treated with antibiotics. Chronic bronchitis is a long-term disorder caused by repeated exposure to irritants and foreign bodies which has caused destruction of the cilia, so that their cleansing action no longer takes place. The most common cause of chronic bronchitis is smoking cigarettes. There is no cure. Treatment aims to reduce symptoms and complications like infection with medication and regular exercise. Pneumonia : The alveoli in the lungs become inflamed and filled with liquids, interfering with gas exchange. Pneumonia may be: lobular (one or more lobes of the lung is affected). This is caused by a bacterium called Streptococcus pneumoniae, which can then spread out from the lungs via the bloodstream, affecting other tissues. There is a vaccine available for S. pneumoniae called pneumococcal vaccine. Bronchial (several patches are affected throughout both lungs). This may be bacterial or viral, with viral being generally less severe. Viral pneumonia is sometimes followed by a bacterial secondary infection More Lower Respiratory Tract Disorders Pleurisy : Swelling and inflammation of the pleura. May be caused by viral or bacterial infections, a blood clot in the lung, or cancer. Symptoms include a sharp stabbing pain in the chest that is usually localized to one area. Treatment involves treating the cause and reducing swelling. Emphysema: An obstructive respiratory disorder where the walls of the alveoli break down and lose their elasticity. This reduces surface area for gas exchange and causes oxygen shortage in tissues. This condition is permanent and incurable. Almost all cases of emphysema are caused by smoking. People often need to use tanked oxygen in order to get sufficient O2. These may be low-flow and vary O2 concentration with an individual’s breathing rate or high-flow which provides constant flows of O2. Lung Volume Reduction Surgery is sometimes attempted as a treatment for empyhsema. More Lower Respiratory Tract Disorders Cystic Fibrosis: This is a genetic condition that affects the lungs and digestive system because of thick, viscous secretions, particularly of mucus in the lungs caused by problems with the balance of salt and water in the cells. Because of the thickness of the mucus, it, along with pathogens or foreign matter that is contained in the mucus cannot easily be expelled, causing repeated infections and reduced lung function. CF is treated with medicines to thin the mucus and antibiotics to treat infections. Lung transplants are very often necessary. Gene therapy is being investigated as a possible treatment. Asthma: A chronic obstructive lung disease that constricts the bronchi and bronchioles and causes increased mucus production when ‘triggers’ such as pollen, dust, or smoke are present, reducing or eliminating air flow. Effects can range from mild reactions to death. Asthma is may be managed but not cured. Usually, management happens in the form of inhalers which deliver medicine to the lungs which reduce inflammation and relax bronchiole muscles. People with severe asthma may monitor their breathing with a peak flow meter to Lung Cancer: Uncontrolled and invasive growth of abnormal cells in the lung. Leading cause of cancer deaths for men and women in Canada. Abnormal cells multiply and form malignant tumours, or carcinomas. These reduce the space available for gas exchange or block air from entering parts of the lung. Tumors may damage tissue or produce toxins which are harmful to the lungs’ cells. Causes: Most, but not all, cases of lung cancer are caused by smoking (whether first or second-hand, making this a preventable cancer, because many substances in tobacco smoke are known carcinogens (cancer-causing agents) Also caused by radon exposure: Radon is a heavy, gaseous, radioactive element which is found in rocks and soil in small quantities, and sometimes accumulates in buildings by entering through cracks in the foundation. Asbestos exposure: breathing in the fine fibres of this mineral can increase the risk of lung cancer. Asbestos was used as a fire proofing and insulating material for many years (and still is in some parts of Technologies for detecting and treating lung cancer: Lung cancer has usually progressed to an untreatable stage before it is diagnosed. CT scans, a type of specialized x-ray, are usually used for detection. A new type fo CT scan called a helical low-dose CT scan is able to detect much smaller tumors than previous CT scans, but these have still usually progressed beyond a treatable stage. The spread of a tumor throughout the body is called metastasis, and cancerous cells that are spreading are called metastatic cells. Researchers are focusing on finding ways to detect lung cancer before tumours have grown too large to treat. Ex – DNA analysis techniques to identify cells that may become cancerous, or cancer-fighting drugs delivered by liposomes to cancerous cells before they can begin to grow in a new location.