Respiratory System PDF

WEEK 14: THE RESPIRATORY SYSTEM The amount of oxygen and carbon dioxide in the blood must be maintained within a limited range for What is Respira on? the survival of the organism....

WEEK 14: THE RESPIRATORY SYSTEM The amount of oxygen and carbon dioxide in the blood must be maintained within a limited range for What is Respira on? the survival of the organism. Respiration is the life-sustaining process in which Cells cannot survive for long without oxygen, and if gases are exchanged between the body and the there is too much carbon dioxide in the blood, the outside atmosphere. blood becomes dangerously acidic (pH is too low). Specifically, oxygen moves from the outside air into Conversely, it there is too little carbon dioxide in the the body; and water vapor, carbon dioxide, and blood, the blood becomes too basic (pH is too high). other waste gases move from inside the body into The respiratory system works hand-in-hand with the the outside air. nervous and cardiovascular systems to maintain Respiration is carried out mainly by the respiratory homeostasis in blood gases and pH. system. It is the level of carbon dioxide rather than the level It is important to note that respiration by the of oxygen that is most closely monitored to maintain respiratory system is not the same process as cellular blood gas and pH homeostasis. respiration that occurs inside cells, although the two The level of carbon dioxide in the blood is detected processes are closely connected. by cells in the brain, which speed up or slow down Cellular respiration is the metabolic process in which the rate of breathing through the autonomic nervous cells obtain energy, usually by “burning” glucose in system as needed to bring the carbon dioxide level the presence of oxygen. within the normal range. When cellular respiration is aerobic, it uses oxygen Faster breathing lowers the carbon dioxide level and releases carbon dioxide as a waste product. (and raises the oxygen level and pH); slower Respiration by the respiratory system supplies the breathing has the opposite effects. oxygen needed by cells for aerobic cellular In this way, the levels of carbon dioxide and oxygen, respiration and removes the carbon dioxide as well as pH, are maintained within normal limits. produced by cells during cellular respiration. The respiratory system also works closely with the Respiration by the respiratory system actually cardiovascular system to maintain homeostasis. involves two subsidiary processes. The respiratory system exchanges gases between One process is ventilation or breathing. This is the the blood and the outside air, but it needs the physical process of conducting air to and from the cardiovascular system to carry them to and from lungs. body cells. The other process is gas exchange. This is the Oxygen is absorbed by the blood in the lungs and biochemical process in which oxygen diffuses out of then transported through a vast network of blood the air and into the blood while carbon dioxide and vessels to cells throughout the body where it is other waste gases diffuse out of the blood and into needed for aerobic cellular respiration. the air. The same system absorbs carbon dioxide from cells All of the organs of the respiratory system are and carries it to the respiratory system for removal involved in breathing, but only the lungs are involved from the body. in gas exchange. Respiratory Structure How the Respiratory System Works with Other Respiratory Organs Organ Systems The organs of the respiratory system form a continuous system of passages, called the respiratory tract, through which air flows into Upper respiratory tract organs provide a route for air and out of the body. to move between the outside atmosphere and the lungs. The respiratory tract has two major divisions: They also clean, humidity, and warm the incoming the upper respiratory tract and the lower respiratory air. tract. The organs in each division are shown in the figure below. However, no gas exchange occurs in these organs. In addition to these organs, certain muscles of the Nasal Cavity thorax (the body cavity that fills the chest) are also involved in respiration by enabling breathing. The nasal cavity is a large, air-filled space in the skull above and behind the nose in the middle of the face. Most important is a large muscle called the diaphragm, which lies below the lungs and separates It is a continuation of the two nostrils. the thorax from the abdomen. As inhaled air flows through the nasal cavity, it is Smaller muscles between the ribs also play a role in warmed and humidified. breathing. You can learn more about breathing Hairs in the nose help trap larger foreign particles in muscles in the concept of Breathing. the air before they go deeper into the respiratory tract. In addition to its respiratory functions, the nasal cavity also contains chemoreceptors that are needed for the sense of smell and that contribute importantly to the sense of taste. Pharynx The pharynx is a tube-like structure that connects the nasal cavity and the back of the mouth to other structures lower in the throat including the larynx. The pharynx has dual functions: both air and food (or other swallowed substances) pass through it, so it is part of both the respiratory and the digestive systems. Air passes from the nasal cavity through the pharynx to the larynx (as well as in the opposite direction). During breathing, inhaled air enters the body Food passes from the mouth through the pharynx to through the nose and passes through the respiratory the esophagus. tract to the lungs. Larynx Exhaled air travels from the lungs in the opposite direc on. (Public The larynx connects the pharynx and trachea and domain; h p://cancer.gov via Wikimedia helps to conduct air through the respiratory tract. CommonsLinks to an external site.). The larynx is also called the voice box because it Upper Respiratory Tract contains the vocal cords, which vibrate when air flows over them, thereby producing sound. All of the organs and other structures of the upper respiratory tract are involved in conduction or the You can see the vocal cords in the larynx in the figure movement of air into and out of the body. below. Certain muscles in the larynx move the vocal cords This diagram illustrates the tree-like branching of the apart to allow breathing. Other muscles in the larynx passages of the lower respiratory tract within the move the vocal cords together to allow the lungs. ( Patrick J. LynchLinks to an external site.; CC production of vocal sounds. BY 2.5; via Wikimedia.org; lungs diagram detailed) The latter muscles also control the pitch of sounds The trachea and other passages of the lower and help control their volume. respiratory tract conduct air between the upper respiratory tract and the lungs. These passages form an inverted tree-like shape , with repeated branching as they move deeper into the lungs. All told, there are an astonishing 1,500 miles of airways conducting air through the human respiratory tract! The larynx as It is only in the lungs, however, that gas exchange viewed from the top. (public domain; Alan occurs between the air and the bloodstream. HoofringLinks to an external site. via wikimedia.org). Trachea A very important function of the larynx is protecting the trachea from aspirated food. The trachea, or windpipe, is the widest passageway in the respiratory tract. It is about 2.5 cm (1 in.) wide When swallowing occurs, the backward motion of and 10-15 cm (4-6 in.) long. the tongue forces a flap called the epiglottis to close over the entrance to the larynx. (You can see the It is formed by rings of cartilage, which make it epiglottis in the figure above.) relatively strong and resilient. This prevents swallowed material from entering the The trachea connects the larynx to the lungs for the larynx and moving deeper into the respiratory tract. passage of air through the respiratory tract. If swallowed material does start to enter the larynx, The trachea branches at the bottom to form two it irritates the larynx and stimulates a strong cough bronchial tubes. reflex. Bronchi and Bronchioles This generally expels the material out of the larynx and into the throat. There are two main bronchial tubes, or bronchi (singular, bronchus), called the right and left Lower Respiratory Tract bronchi. The bronchi carry air between the trachea and lungs. Each bronchus branches into smaller, secondary bronchi; and secondary bronchi branch into still smaller tertiary bronchi. The smallest bronchi branch into very small tubules called bronchioles. The tiniest bronchioles end in alveolar ducts, which terminate in clusters of minuscule air sacs, called alveoli (singular, alveolus), in the lungs. Lungs The smaller left lung allows room for the heart, which is just left of the center of the chest. Lung tissue consists mainly of alveoli. These tiny air sacs are the functional units of the lungs where gas exchange takes place. The two lungs may contain as many as 700 million alveoli, providing a huge total surface area for gas exchange to take place. In fact, alveoli in the two lungs provide as much surface area as half a tennis court! Each time you breathe in, the alveoli fill with air, The cross-sec on of lung ssue on the right in this making the lungs expand. diagram shows the alveoli in which gas exchange takes place with the capillary network that surrounds Oxygen in the air inside the alveoli is absorbed by them. the blood in the mesh-like network of tiny capillaries that surrounds each alveolus. Neuroendocrine cells lining the bronchioles control their diameter and the flow of air through them. The blood in these capillaries also releases carbon dioxide into the air inside the alveoli. Surfactant is a liquid that covers the inside of the alveoli and prevents them from collapsing and Each time you breathe out, air leaves the alveoli and s cking together when air emp es out of them rushes into the outside atmosphere, carrying waste during exhala on. (CC BY-NC 3.0; Na onal Heart gases with it. Lung and Blood Ins tuteLinks to an external site.) The lungs receive blood from two major sources. The gaseous exchange between blood and They receive deoxygenated blood from the heart. outside air inside the lung alveoli. (helix84 [CC BY-SA This blood absorbs oxygen in the lungs and carries it 3.0; wikimedia.org). back to the heart to be pumped to cells throughout The lungs are the largest organs of the respiratory the body. tract. The lungs also receive oxygenated blood from the They are suspended within the pleural cavity of the heart that provides oxygen to the cells of the lungs thorax. for cellular respiration. The lungs are surrounded by two thin membranes called pleura, which secrete a fluid that allows the lungs to move freely within the pleural cavity. Smoking : Overview This is necessary so the lungs can expand and contract during breathing.  Smoking is the single greatest cause of preventable death worldwide. You can see in the illustration that each of the two lungs is divided into sections. It has adverse effects on just about everybody system and organ. These are called lobes, and they are separated from each other by connective tissues. Tobacco smoke affects not only The right lung is larger and contains three lobes. smokers but also non-smokers who are exposed to secondhand smoke. The left lung is smaller and contains only two lobes.  The nicotine in tobacco is highly Smokeless tobacco may be less of a danger to the addictive, making it very difficult to lungs and heart, but it too has serious health effects. quit smoking. It significantly increases the risk of cancers of the mouth and throat, among other health problems.  Major health risk of smoking is cancer of the lungs. Even non-smokers may not be spared the deadly risks of tobacco smoke. Smoking also increases the risk of many other types of cancer. If you spend time around smokers either at home or on the job, then you are at risk of the dangers of Tobacco smoke contains dozens of secondhand smoke. chemicals that are known carcinogens. Secondhand smoke enters the air directly from burning cigarettes (and cigars and pipes) and  Smoking is the primary cause of the indirectly from the lungs of smokers. chronic obstructive pulmonary disease (COPD). This smoke may linger in indoor air for hours and increase the risk of a wide range of adverse health Chemicals such as carbon monoxide effects. and cyanide in tobacco smoke reduce the elasticity of alveoli so the lungs can For example, non-smokers who are exposed to no longer fully exhale air. secondhand smoke may have as much as a 30 percent increase in their risk of lung cancer and heart disease.  Smoking damages the cardiovascular system and increases the risk of high The 2014 U.S. Surgeon General’s Report concluded blood pressure, blood clots, heart that there is no established risk-free level of attack, and stroke. exposure to secondhand smoke. Smoking also has a negative impact on Tobacco contains nicotine, which is a psychoactive levels of blood lipids. drug. Although nicotine in tobacco smoke does not directly  A wide diversity of additional adverse cause cancer or most of the other health risks of health effects are attributable to smoking, it is a highly addictive drug. smoking, such as erectile dysfunction, female infertility, and slow wound In fact, nicotine is even more addictive than cocaine healing. or heroin. Why Is Smoking Deadly? As shown in Figure below tobacco smoking has The addictive nature of nicotine explains why it is so adverse effects on just about every bodily system difficult for smokers to quit the habit even when and organ. they know the health risks and really want to stop smoking. The detrimental health effects of smoking depend on the number of years that a person smokes and how The good news is that if someone does stop much the person smokes. smoking, his or her risks of smoking-related diseases and death soon start to fall. Contrary to popular belief, all forms of tobacco smoke — including smoke from cigars and tobacco For example, by one year after quitting, the risk of pipes — have similar health risks as those of heart disease drops to only half of that of a cigarette smoke. continuing smoker. Smoking is known to cause many different cancers and chronic diseases. (public domain; CDCLinks to an external site. via wikipedia.org) In addi on to these diseases enumerated above, enumerate addi onal adverse effect of Smoking Wrap-up: The respiratory system consists of all the organs involved in breathing. These include the nose, pharynx, larynx, trachea, bronchi and the lungs. The respiratory system does two very important things: it brings oxygen into our bodies, which we need for our cells to live and function properly; and it helps us get rid of carbon dioxide, which is a waste product of cellular function. The nose, pharynx, larynx, trachea, and bronchi all work like a system of pipes through which the air is funneled down into our lungs. In very small air sacs called alveoli, oxygen is brought into the bloodstream and carbon dioxide is pushed from the blood out into the air. When something goes wrong with part of the respiratory system, such as an infection like pneumonia, it makes it harder for us to get the oxygen we need, and to get rid of the waste product carbon dioxide. Common respiratory symptoms include breathlessness, cough, and chest pain.