Structure and Function of the Respiratory System Essay Paper

The five primary functions of the respiratory system, in order of significance, are:

1. The inhalation and exhalation of air or Breathing. This involves the nasal and oral cavities, the pharynx, the larynx, the trachea and the lungs. Also involved are the diaphragm, the intercostal muscles, and the rib cage to pull in air for inhalation and push it out for exhalation.Structure and Function of the Respiratory System Essay Paper
2. Gas exchange between the lungs and the bloodstream (External Respiration). This involves the passage of oxygen from the air in the alveoli (tiny sacs at the end of the bronchioles in the lungs) through the alveolar and capillary walls to the blood in the capillaries, as well as the passage of carbon dioxide from the bloodstream to the alveoli.
3. Gas exchange between the bloodstream and the body tissues (Internal Respiration). This involves the transport of oxygenated blood from the heart to all parts of the body, where the oxygen is delivered to tissues and cells for energy and metabolism, while carbon dioxide, as a waste product, is absorbed by the blood.
4. Vibration of the vocal cords in the larynx to produce Sound. This is a more specialised function in which air passing over the vocal cords is modulated by laryngeal muscles pushing the vocal cords together so that they vibrate when air passes over them, creating sound.Structure and Function of the Respiratory System Essay Paper
5. The sense of Smell. Olfaction, or the sense of smell, occurs when air passes over olfactory fibres in the nasal cavities that sense certain chemicals in the inhaled air that bind to them and transmit a signal to the brain which is then identified.

The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary history. In land animals the respiratory surface is internalized as linings of the lungs.^[1] Gas exchange in the lungs occurs in millions of small air sacs called alveoli in mammals and reptiles, but atria in birds. These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood.^[2] These air sacs communicate with the external environment via a system of airways, or hollow tubes, of which the largest is the trachea, which branches in the middle of the chest into the two main bronchi. These enter the lungs where they branch into progressively narrower secondary and tertiary bronchi that branch into numerous smaller tubes, the bronchi oles. In birds the bronchi oles are termed para bronchi. It is the bronchi oles, or para bronchi that generally open into the microscopic alveoli in mammals and atria in birds. Air has to be pumped from the environment into the alveoli or atria by the process of breathing which involves the muscles of respiration.Structure and Function of the Respiratory System Essay Paper

In most fish, and a number of other aquatic animals (both vertebrates and invertebrates) the respiratory system consists of gills, which are either partially or completely external organs, bathed in the watery environment. This water flows over the gills by a variety of active or passive means. Gas exchange takes place in the gills which consist of thin or very flat filaments and lammelae which expose a very large surface area of highly vascularized tissue to the water.

Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants includes anatomical features such as stomata, that are found in various parts of the plant.^{[3]Structure and Function of the Respiratory System Essay Paper}

Taking more than 6 million breaths per year, the lungs affect every aspect of our bodies and health.

This article looks at the form and function of the lungs, diseases that affect the lungs, and how to maintain healthy lungs.

Structure

The lungs not only enable us to breathe and talk, but they also support the cardiovascular system and help maintain pH in the body, among others.

The lungs are located in the chest, behind the rib cage on either side of the heart. They are roughly conical in shape with a rounded point at their apex and a flatter base where they meet the diaphragm.

Although they are a pair, the lungs are not equal in size and shape.

The left lung has an indentation bordering where the heart resides, called the cardiac notch. The right lung is shorter to allow space for the liver below.Structure and Function of the Respiratory System Essay Paper

Overall, the left lung has a slightly smaller weight and capacity than the right.

The lungs are surrounded by two membranes, known as the pulmonary pleurae. The inner layer directly lines the outer surface of the lungs, and the outer layer is attached to the inner wall of the rib cage.

The space between the two membranes is filled with pleural fluid.

Function

The lungs’ main role is to bring in air from the atmosphere and pass oxygen into the bloodstream. From there, it circulates to the rest of the body.

Help is required from structures outside of the lungs in order to breathe properly. To breathe, we use the muscle of the diaphragm, the intercostal muscles (between the ribs), the muscles of the abdomen, and sometimes even muscles in the neck.

The diaphragm is a muscle that is domed at the top and sits below the lungs. It powers most of the work involved in breathing.

As it contracts, it moves down, allowing more space in the chest cavity and increasing the lungs’ capacity to expand. As the chest cavity volume increases, the pressure inside goes down, and air is sucked in through the nose or mouth and down into the lungs.

As the diaphragm relaxes and returns to its resting position, the lung volume decreases because the pressure inside the chest cavity goes up, and the lungs expel the air.Structure and Function of the Respiratory System Essay Paper

The lungs are like bellows. As they expand, air is sucked in for oxygen. As they compress, the exchanged carbon dioxide waste is pushed back out during exhalation.

When air enters the nose or mouth, it travels down the trachea, also called the windpipe. After this, it reaches a section called the carina. At the carina, the windpipe splits into two, creating two main stem bronchi. One leads to the left lung and the other to the right lung.

From there, like branches on a tree, the pipe-like bronchi split again into smaller bronchi and then even smaller bronchi oles. This ever-decreasing pipework eventually terminates in the alveoli, which are little air sac endings.Structure and Function of the Respiratory System Essay Paper

Here, gas exchange occurs.The alveoli

The alveoli are the end point of the oxygen’s journey from the outside world to the depths of the lungs.

Alveoli are minute sacs that are microscopic in size, each wrapped in a fine mesh of capillaries.

Each human has around 700 million individual alveoli. The total surface area of membrane that the alveoli provide is 70 meters squared. This is often said to be around the size of half a tennis court.

After the lungs, the body takes oxygen out of the bloodstream to its other tissues as it travels around the circulatory system.

The blood that has given up its oxygen in exchange for carbon dioxide from the tissues then passes through the heart and travels to the lungs to reach the capillaries surrounding the alveoli.

The alveoli now contain a new supply of oxygen that the person has breathed in. This oxygen passes across a membrane, called the alveolar-capillary membrane, into the bloodstream.

At the same time, the carbon dioxide that has collected in the bloodstream during its travels around the body enters the alveoli. From there, it is breathed back out into the atmosphere during exhalation.Structure and Function of the Respiratory System Essay Paper

Put simply, as the oxygen goes in, carbon dioxide comes out. This is gas exchange.

Diseases of the Respiratory System

When you have a cold, your nasal passages may become so congested that it’s hard to breathe through your nose. Many other diseases also affect the respiratory system, most of them more serious than the common cold. Some lung diseases, such as lung cancer, can be especially dangerous. The following list includes just a sample of respiratory system diseases.

• Asthma is a disease in which the air passages of the lungs periodically become too narrow, often with excessive mucus production. This causes difficulty breathing, coughing, and chest tightness. An asthma attack may be triggered by allergens, strenuous exercise, stress, or other factors.Structure and Function of the Respiratory System Essay Paper
• Pneumonia is a disease in which some of the alveoli of the lungs fill with fluid so gas exchange cannot occur. Symptoms usually include coughing, chest pain, and difficulty breathing. Pneumonia may be caused by an infection or injury of the lungs.
• Emphysema is a lung disease in which walls of the alveoli break down so less gas can be exchanged in the lungs (see Figure below). This causes shortness of breath. The damage to the alveoli is usually caused by smoking and is irreversible.

• Causes of Respiratory Diseases

  Many respiratory diseases are caused by pathogens. Certain bacteria, viruses, and fungi are pathogens of the respiratory system. The common cold and flu are caused by viruses. Tuberculosis, whooping cough, and acute bronchitis are caused by bacteria. The pathogens that cause colds, flu, and TB can be passed from person to person by coughing and sneezing.Structure and Function of the Respiratory System Essay Paper

  Air pollution is another significant cause of respiratory disease. The quality of the air you breathe can affect the health of your lungs. Asthma, heart and lung diseases, allergies, and several types of cancers are all linked to air quality. Air pollution is not just found outdoors; indoor air pollution can also be responsible for health problems.

  Smoking is the most significant cause of respiratory disease as well as cardiovascular disease and cancer. Exposure to tobacco smoke by smoking or by breathing air that contains tobacco smoke is the leading cause of preventable death in the United States. Regular smokers die about 10 years earlier than nonsmokers. The Centers for Disease Control and Prevention (CDC) describes tobacco use as “the single most important preventable risk to human health in developed countries and an important cause of [early] death worldwide.”

  Whether you’re wide awake and getting ready for a big date or asleep during your most snooze-worthy afternoon class, you don’t have to think about breathing. It’s so important to life that it happens automatically. If you didn’t breathe, you couldn’t live.Structure and Function of the Respiratory System Essay Paper

  Lungs & Respiratory System Basics

  Each day we breathe about 20,000 times. All of this breathing couldn’t happen without help from the respiratory system, which includes the nose, throat, voice box, windpipe, and lungs. With each breath, you take in air through your nostrils and mouth, and your lungs fill up and empty out. As air is inhaled, the mucous membranes of the nose and mouth warm and humidify the air.

  Although we can’t see it, the air we breathe is made up of several gases. Oxygen is the most important for keeping us alive because body cells need it for energy and growth. Without oxygen, the body’s cells would die.Structure and Function of the Respiratory System Essay Paper

  Carbon dioxide is the waste gas that is produced when carbon is combined with oxygen as part of the body’s energy-making processes. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out.

  Respiration is the term for the exchange of oxygen from the environment for carbon dioxide from the body’s cells. The process of taking air into the lungs is called inhalation or inspiration, and the process of breathing it out is called exhalation or expiration.Structure and Function of the Respiratory System Essay Paper

  Even if the air you breathe is dirty or polluted, your respiratory system filters out foreign matter and organisms that enter through the nose and mouth. Pollutants are breathed or coughed out, destroyed by digestive juices, or eaten by macrophages, a type of blood cell that patrols the body looking for germs to destroy.

  Tiny hairs called cilia (pronounced: SIL-ee-uh) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose with the breathed air. As air is inhaled, the cilia move back and forth, pushing any foreign matter (like dust) either toward the nostrils, where it is blown out, or toward the pharynx, where it travels through the digestive system and out with the rest of the body’s waste.Structure and Function of the Respiratory System Essay Paper

  What They Do

  The two openings of the airway (the nasal cavity and the mouth) meet at the pharynx (pronounced: FAR-inks), or throat, 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. At the bottom of the pharynx, the pathway for both food and air divides in two. One passageway is for food (the esophagus, pronounced: ih-SAH-fuh-gus, which leads to the stomach) and the other for air. The epiglottis (pronounced: eh-pih-GLAH-tus), a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into our lungs.Structure and Function of the Respiratory  System Essay Paper

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  The larynx (pronounced: LAR-inks), or voice box, is the uppermost part of the air-only passage. This short tube contains a pair of vocal cords, which vibrate to make sounds. The trachea (pronounced: TRAY–kee-uh), or windpipe, extends downward from the base of the larynx. It lies partly in the neck and partly in the chest cavity. The walls of the trachea are strengthened by stiff rings of cartilage to keep it open so air can flow through on its way to the lungs. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs.

  At its bottom end, the trachea divides into left and right air tubes called bronchi (pronounced: BRAHN-kye), which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchi oles (pronounced: BRAHN-kee-olz). Bronchi oles, which are as thin as a strand of hair, end in tiny air sacs called alveoli (pronounced: al-VEE-oh-lye). Each of us has hundreds of millions of alveoli in our lungs — enough to cover a tennis court if they were spread out on the ground. The alveoli are where the exchange of oxygen and carbon dioxide takes place.Structure and Function of the Respiratory System Essay Paper

  With each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion (pronounced: dih-FYOO-zhun), oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels, pronounced: KAP-uh-lair-eez) that line the alveolar walls. Once in the bloodstream, oxygen gets picked up by a molecule called hemoglobin (pronounced: HEE-muh-glo-bun) in the red blood cells. This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body.Structure and Function of the Respiratory System Essay Paper

  In the tiny capillaries of the body tissues, oxygen is freed from the hemoglobin and moves into the cells. Carbon dioxide, which is made by cells as they do their work, moves out of the cells into the capillaries, where most of it then dissolves into the plasma of the blood. Blood rich in carbon dioxide then returns to the heart via the veins. From the heart, this blood is pumped to the lungs, where carbon dioxide passes into the alveoli to be exhaled.

  The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape and are encased by a thin lining called the pleura (pronounced: PLUR-uh). This network of alveoli, bronchi oles, and bronchi is known as the bronchial tree.Structure and Function of the Respiratory System Essay Paper

  The chest cavity, or thorax (pronounced: THOR-aks), is the airtight box that 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 by a large muscle called the diaphragm. The chest walls form a protective cage around the lungs and other contents of the chest cavity.

  The diaphragm (pronounced: DYE-uh-fram), which separates the chest from the abdomen, plays a lead role in breathing. When we breathe out, the diaphragm moves upward, forcing the chest cavity to get smaller and pushing the gases in the lungs up and out of the nose and mouth.

  When we breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward, enlarging the chest cavity and pulling air in through the nose or mouth. Air pressure in the chest cavity and lungs is reduced, and because gas flows from high pressure to low, air from the environment flows through the nose or mouth into the lungs.Structure and Function of the Respiratory System Essay Paper

  As we exhale, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to contract. Air pressure in the lungs rises, so air flows from the lungs and up and out of respiratory system through the nose or mouth.

  The respiratory system is usually considered in two parts: the upper respiratory tract and the lower respiratory tract.

  The Respiratory System

  Upper Respiratory Tract

  The major passages and structures of the upper respiratory tract include the nostrils, the nasal cavity, the pharynx, the epiglottis, and the larynx. The upper respiratory tract is lined a mucous membrane. Mucus helps to trap smoke, dust and other small particles. The membrane is lined with cilia (hair-like structures that move the mucous upwards only the upper respiratory tract). The lining of the tract and the close laying blood vessels (especially in the nose) help to warm and moisten air as it passes.Structure and Function of the Respiratory System Essay Paper

  The pharynx, commonly called the throat, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra. It serves both the respiratory and digestive systems by receiving air from the nasal cavity and air, food, and water from the oral cavity. Inferiority, it opens into the larynx and esophagus.

  The larynx, commonly called the voice box or glottis, is the passageway for air between the pharynx above and the trachea below. It extends from the fourth to the sixth vertebral levels. The larynx plays an essential role in human speech. During sound production, the vocal cords close together and vibrate as air expelled from the lungs passes between them.

  The epiglottis acts like a trap door to keep food and other particles from entering the larynx.

  Apnoea is the absence of breathing

  Wheeze whistling noise

  Agonal breathing gasping breaths

  Lower Respiratory Tract

  The major passages and structures of the lower respiratory tract include the trachea, the right & left bronchus, the bronchi oles, and the lungs containing the alveoli. Deep in the lungs, each bronchus divides into secondary and tertiary bronchi, which continue to branch to smaller airways called the bronchi oles. The bronchi oles end in air sacs called the alveoli. Alveoli are bunched together into clusters to form alveolar sacs. Gas exchange occurs on the surface of each alveolus by a network of capillaries carrying blood that has come through veins from other parts of the body.Structure and Function of the Respiratory System Essay Paper

  The trachea, commonly called the windpipe, is the main airway to the lungs. It divides into the right and left bronchi at the level of the fifth thoracic vertebra, channeling air to the right or left lung. The cartilage in the tracheal wall provides support and keeps the trachea from collapsing. The mucous membrane that lines the trachea is similar to that in the nasal cavity. Mucus traps airborne particles and microorganisms, and the cilia propel the mucus upward, where it is either swallowed or expelled.

  The alveoli are grouped together like a lot of interlinked caves, rather than existing as separate individual sacs. The alveoli have a structure specialized for efficient gaseous exchange: the alveoli walls are extremely thin; they have a large surface area in relation to volume, they are fluid lined enabling gases to dissolve; and they are surrounded by numerous capillaries.Structure and Function of the Respiratory System Essay Paper

  Aveoli showing capillary network

   

  Breathing

  During inspiration the dome-shaped muscle of the diaphragm flattens, and the inter-coastal muscles pull the rib cage upwards and outwards. This increases the volume of the chest cavity and air is drawn into the lungs.

  During expiration the diaphragm relaxes and resumes it’s dome shape. The inter-coastal muscles also relax and the rib cage falls inwards and downwards. This reduces the volume of the chest cavity and air is forced out of the lungs.

   

  Inspiration and Expiration

  In a normal average adult male, the lungs have a combined capacity of about 6 litres, with about 500 mls of air inspired at each breath. Breathing is normally very quiet, and without much effort.

  During exertion the respiratory rate will increase, and so might the respiratory effort so that more air is pulled into the lungs and, therefore, more oxygen is made available to the cells in the body. This also allows the increasing amount of CO2 to be exhaled. It is easier to breathe when you are sitting or standing, as the diaphragm can more easily ‘push’ the contents of the abdomen downwards. Your age, size, gender, and general health can all affect your respiratory performance.Structure and Function of the Respiratory System Essay Paper

  Gaseous Exchange

  Once the inspired air reaches the smallest part of the lungs, the alveoli, gaseous exchange can take place. This refers to the process of Oxygen and Carbon Dioxide moving between the lungs and blood.

  

  Diffusion occurs when molecules move from an area of high concentration (of that molecule) to an area of low concentration. This occurs during gaseous exchange as the blood in the capillaries surrounding the alveoli has a lower oxygen concentration of Oxygen than the air in the alveoli which has just been inhaled. Both alveoli and capillaries have walls which are only one cell thick and allow gases to diffuse across them. The same happens with Carbon Dioxide (CO2). The blood in the surrounding capillaries has a higher concentration of CO2 than the inspired air due to it being a waste product of energy production. Therefore CO2 diffuses the other way, from the capillaries, into the alveoli where it can then be exhaled. When Oxygen diffuses into the blood it attaches to hemoglobin in red blood cells to be transported via the circulatory system.

  If the circulatory system is inadequate, or there is a reduced amount of hemoglobin or red blood cells (anemia or blood loss, for example), then the respiratory rate and effort might increase to try and compensate.Structure and Function of the Respiratory System Essay Paper

  Measuring Respiration

  Respiratory rate can be counted by observing the rise and fall of a person’s chest over a minute. You might need to place your hand on their chest to feel the movement if it is not obvious.

  Respiratory effort can be observed, especially if the person is having to use their accessory muscles of respiration rather than only the diaphragm. You might see retractions or recessions – sucking in of the skin, around the ribs and the top of the sternum, and nasal flaring.

  Respiratory sounds might include grunting with increased respiratory effort or a stridor if there is a blockage in the airway.

  Oxygen Saturation measurement is done by using a monitor. The oxygen saturation of hemoglobin (sO2) is defined as the percentage of oxygenated hemoglobin in relation to the amount of hemoglobin capable of carrying oxygen. Normal sO2 will be between 95%-100%.

  In humans, the respiratory tract is the part of the anatomy of the respiratory system involved with the process of respiration. Air is breathed in through the nose or the mouth. In the nasal cavity, a layer of mucous membrane acts as a filter and traps pollutants and other harmful substances found in the air. Next, air moves into the pharynx, a passage that contains the intersection between the esophagus and the larynx. The opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway.

  From the larynx, air moves into the trachea and down to the intersection that branches to form the right and left primary (main) bronchi. Each of these bronchi branch into secondary (lobar) bronchi that branch into tertiary (segmental) bronchi that branch into smaller airways called bronchi oles that eventually connect with tiny specialized structures called alveoli that function in gas exchange.Structure and Function of the Respiratory System Essay Paper

  The lungs which are located in the thoracic cavity, are protected from physical damage by the rib cage. At the base of the lungs is a sheet of skeletal muscle called the diaphragm. The diaphragm separates the lungs from the stomach and intestines. The diaphragm is also the main muscle of respiration involved in breathing, and is controlled by the sympathetic nervous system.

  The lungs are encased in a serous membrane that folds in on itself to form the pleurae – a two-layered protective barrier. The inner visceral pleura covers the surface of the lungs, and the outer parietal pleura is attached to the inner surface of the thoracic cavity. The pleurae enclose a cavity called the pleural cavity that contains pleural fluid. This fluid is used to decrease the amount of friction that lungs experience during breathing Structure and Function of the Respiratory System Essay Paper

  Lower respiratory tract

  The lower respiratory tract consists of the trachea, bronchi and lungs. The air passages are lined with mucous membrane composed mainly of cilia ted epithelium. Cilia constantly clean the tract and carry foreign matter upwards for swallowing or expectoration.

  Trachea

  The trachea (windpipe) extends from the laryngopharynx at the level of the cricoid cartilage at the top to the carina (also called the tracheal bifurcation). C-shaped cartilage rings reinforce and protect the trachea to prevent it from collapsing. The carina is a ridge-shaped structure at the level of T6 or T7. The carina possesses sensory nerve endings which cause coughing if food or water is inhaled accidently.

  Bronchi

  The primary bronchi begin at the carina. The right primary bronchus – shorter, wider and more vertical than the left – supplies air to the right lung. The left primary bronchus delivers air to the left lung. Along with blood vessels, nerves, and lymphatics, the primary bronchi enter the lungs at the hilum. Located behind the heart, the hilum is a slit on the lung’s medial surface.Structure and Function of the Respiratory System Essay Paper

  Secondary bronchi

  Each primary bronchus divides to form secondary bronchi. In each lung, one secondary bronchus goes into each lobe which means that the right lung has three secondary bronchi and the left lung has two.

  Branching out

  Each lobar bronchus enters a lobe in each lung. Within its lobe, each of the lobar bronchi branches into segment al bronchi (tertiary bronchi). The segments continue to branch into smaller and smaller bronchi, finally branching into bronchi oles. The larger bronchi consist of cartilage, smooth muscle and epithelium. As the bronchi become smaller, they lose cartilage and then smooth muscle. Ultimately, the smallest bronchi oles consist of just a single layer of epithelial cells.

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  Respiratory bronchi oles

  Each bronchi ole includes terminal bronchi oles and the alveolar sac – the chief respiratory unit for gas exchange. Within the acinus, terminal bronchi oles branch into yet smaller respiratory bronchi oles. The respiratory bronchi oles feed directly into alveoli at sites along their walls.

  Alveoli

  The respiratory bronchi oles eventually become alveolar ducts, which terminate in clusters of alveoli surrounded by capillaries (alveolar sacs). Gas exchange takes place through the alveoli.

  Alveolar walls contain two basic epithelial cell types:

  • Type I cells are the most abundant. It is across these thin, flat, squamous cells that gas exchange occurs.
  • Type II cells secrete surfactant, a substance that coats the alveolus and reduces surface tension. This allows the alveoli to remain inflated so that gas exchange can occur by diffusion. Surfactant is formed relatively late in foetal life; thus premature infants born without adequate amounts experience respiratory distress and may die.Structure and Function of the Respiratory System Essay Paper

  Lungs

  The cone-shaped lungs are located in the thoracic cavity and are surrounded by pleura. The right lung is shorter, broader and larger than the left. It has three lobes and handles 55% of gas exchange. The left lung has two lobes and contains a space for the heart (cardiac notch). Each lung’s concave base rests on the diaphragm; the apex extends about 1.5 cm above the first rib.

  Pleura and pleural cavities

  The pleura – the membrane that totally encloses the lung – is composed of a visceral layer and a parietal layer. The visceral pleura covers the entire lung surface, including the areas between the lobes. The parietal pleura lines the inner surface of the chest wall and upper surface of the diaphragm.Structure and Function of the Respiratory System Essay Paper

  Serous fluid has serious functions

  The pleural cavity – a potential space between the visceral and parietal pleural layers – contains a thin film of serous fluid. This fluid has two functions:

  • It lubricates the pleural surfaces, which allows them to slide smoothly against each other as the lungs expand and contract.
  • It creates a bond between the layers that causes the lungs to move with the chest wall during the mechanical breathing process.

  Pulmonary Fibrosis

  Reverse Lung Degeneration from Pulmonary Fibrosis Using Natural Solutions

  • Have you just been diagnosed with Pulmonary Fibrosis and suffering from shortness of breath, dry cough, and low energy?Structure and Function of the Respiratory System Essay Paper
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  The relationship between structure and function of the pulmonary gas-exchange apparatus and its comparative aspects is demonstrated in four sections: (1) the lung as gas exchanger, (2) the gas-exchange structures of the human lung, (3) comparative aspects of structure-function correlation, and (4) analysis of structure-function discordancy. Physical activity and body size are described to influence the structural dimensions of the pulmonary gas exchange apparatus in different ways. As far as the inhalation of toxic substances is concerned, different kinds of effects must therefore be taken into consideration, depending on an animal’s size and metabolism; hence, experiments of comparative anatomy and physiology are desirable in order to find an appropriate animal model that permits extrapolation to humans.Structure and Function of the Respiratory System Essay Paper

  Respiratory

  The respiratory system, which includes air passages, pulmonary vessels, the lungs, and breathing muscles, aids the body in the exchange of gases between the air and blood, and between the blood and the body’s billions of cells. Most of the organs of the respiratory system help to distribute air, but only the tiny, grape-like alveoli and the alveolar ducts are responsible for actual gas exchange.Structure and Function of the Respiratory System Essay Paper

  In addition to air distribution and gas exchange, the respiratory system filters, warms, and humidifies the air you breathe. Organs in the respiratory system also play a role in speech and the sense of smell.

  The respiratory system also helps the body maintain homeostasis, or balance among the many elements of the body’s internal environment.

  The respiratory system is divided into two main components:

  Upper respiratory tract: Composed of the nose, the pharynx, and the larynx, the organs of the upper respiratory tract are located outside the chest cavity.

  • Nasal cavity: Inside the nose, the sticky mucous membrane lining the nasal cavity traps dust particles, and tiny hairs called cilia help move them to the nose to be sneezed or blown out.
  • Sinuses: These air-filled spaces along side the nose help make the skull lighter.
  • Pharynx: Both food and air pass through the pharynx before reaching their appropriate destinations. The pharynx also plays a role in speech.
  • Larynx: The larynx is essential to human speech.Structure and Function of the Respiratory System Essay Paper

  Lower respiratory tract: Composed of the trachea, the lungs, and all segments of the bronchial tree (including the alveoli), the organs of the lower respiratory tract are located inside the chest cavity.

  • Trachea: Located just below the larynx, the trachea is the main airway to the lungs.
  • Lungs: Together the lungs form one of the body’s largest organs. They’re responsible for providing oxygen to capillaries and exhaling carbon dioxide.
  • Bronchi: The bronchi branch from the trachea into each lung and create the network of intricate passages that supply the lungs with air.
  • Diaphragm: The diaphragm is the main respiratory muscle that contracts and relaxes to allow air into the lungs.

  What are the lungs?

  

  The lungs are a pair of organs in the chest that are primarily responsible for the exchange of oxygen and carbon dioxide between the air we breathe and the blood.

  What are the symptoms of carbon dioxide poisoning?

  • The cells in the body constantly need a new supply of oxygen to produce energy.
  • With lack of oxygen, cellular function is impaired and damage or cell death may occur.Structure and Function of the Respiratory System Essay Paper
  • As energy is utilized, waste products are created, one of which is the gas carbon dioxide.
  • Eliminating carbon dioxide from the body is just as important as breathing in oxygen from the air.
  • If carbon dioxide builds up in the blood it will lead to headaches, drowsiness, coma, and eventually even death.

    

    Pneumonia and emphysema are caused by damage to the alveoli of the lungs.Structure and Function of the Respiratory System Essay Paper

  What is the structure of the respiratory system?

  Air enters the body via the nose (preferably) or the mouth. The air enters the main windpipe, called the trachea, and continues en route to each lung via either the right or left bronchus (plural=bronchi). The lungs are separated into sections called lobes, two on the left and three on the right. The air passages continue to divide into ever smaller tubes, which finally connect with tiny air sacs called alveoli. This gradually branching array of tubes is referred to as the tracheobronchial “tree” because of the remarkable similarity to the branching pattern of a tree.

  The other half of the respiratory system involves blood circulation. Venous blood from the body is returned to the right side of the heart and then pumped out via the pulmonary artery. This artery splits in two for the left and right lungs and then continues to branch much like the tracheobronchial tree. These vessels branch into a fine network of very tiny tubes called capillaries. The capillaries are situated adjacent to the alveoli and are so small that only one red blood cell at a time can pass through their openings. It is during this passage that gases are exchanged between the blood and the air in the nearby alveoli. After passing the alveoli, capillaries then join together to begin forming the pulmonary veins, which carry the blood back to the left side of the heart.Structure and Function of the Respiratory System Essay Paper

  

  Human Respiratory System

  The respiratory system consists of all the organs involved in breathing. These include the nose, pharynx, larynx, trachea, bronchi and 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. There, 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.Structure and Function of the Respiratory System Essay Paper

  

  The Upper Airway and Trachea

  When you breathe in, air enters your body through your nose or mouth. From there, it travels down your throat through the larynx (or voicebox) and into the trachea (or windpipe) before entering your lungs. All these structures act to funnel fresh air down from the outside world into your body. The upper airway is important because it must always stay open for you to be able to breathe. It also helps to moisten and warm the air before it reaches your lungs.Structure and Function of the Respiratory System Essay Paper

  The Lungs

  Structure
  The lungs are paired, cone-shaped organs which take up most of the space in our chests, along with the heart. Their role is to take oxygen into the body, which we need for our cells to live and function properly, and to help us get rid of carbon dioxide, which is a waste product. We each have two lungs, a left lung and a right lung. These are divided up into ‘lobes’, or big sections of tissue separated by ‘fissures’ or dividers. The right lung has three lobes but the left lung has only two, because the heart takes up some of the space in the left side of our chest. The lungs can also be divided up into even smaller portions, called ‘bronchopulmonary segments’.Structure and Function of the Respiratory System Essay Paper
  These are pyramidal-shaped areas which are also separated from each other by membranes. There are about 10 of them in each lung. Each segment receives its own blood supply and air supply.
  How they work
  Air enters your lungs through a system of pipes called the bronchi. These pipes start from the bottom of the trachea as the left and right bronchi and branch many times throughout the lungs, until they eventually form little thin-walled air sacs or bubbles, known as the alveoli. The alveoli are where the important work of gas exchange takes place between the air and your blood. Covering each alveolus is a whole network of little blood vessel called capillaries, which are very small branches of the pulmonary arteries. It is important that the air in the alveoli and the blood in the capillaries are very close together, so that oxygen and carbon dioxide can move (or diffuse) between them. So, when you breathe in, air comes down the trachea and through the bronchi into the alveoli. This fresh air has lots of oxygen in it, and some of this oxygen will travel across the walls of the alveoli into your bloodstream. Travelling in the opposite direction is carbon dioxide, which crosses from the blood in the capillaries into the air in the alveoli and is then breathed out. In this way, you bring in to your body the oxygen that you need to live, and get rid of the waste product carbon dioxide.Structure and Function of the Respiratory System Essay Paper

  
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  Blood Supply
  The lungs are very vascular organs, meaning they receive a very large blood supply. This is because the pulmonary arteries, which supply the lungs, come directly from the right side of your heart. They carry blood which is low in oxygen and high in carbon dioxide into your lungs so that the carbon dioxide can be blown off, and more oxygen can be absorbed into the bloodstream. The newly oxygen-rich blood then travels back through the paired pulmonary veins into the left side of your heart. From there, it is pumped all around your body to supply oxygen to cells and organs.

  How Does the Respiratory System Work?

  Organs specialized for breathing usually contain moist structures with large surface areas to allow the diffusion of gases. They are also adapted to protect the organism from the invasion of pathogens along those surfaces.

  In fish, this gas exchange occurs through gills. Some invertebrates, like cockroaches, have simple respiratory systems made of interconnecting tubules directly delivering oxygen to tissues. In humans and other mammals, there is an extensive, highly vascularized organ system specialized for gas exchange.Structure and Function of the Respiratory System Essay Paper

  The respiratory system begins in the nose, continues into the pharynx and larynx, leads to the trachea which branch to create bronchi, and finally down the bronchi oles into the lungs. This respiratory tree ends in puffy structures called alveoli that are made of a single layer of squamous cells, surrounded by a network of capillaries. Gas exchange occurs within alveoli. Since external respiration in many vertebrates involves lungs, it is also called pulmonary ventilation. Changes to the volume and pressure in the lungs are the primary driving forces for breathing.

  Respiratory System Function

  Primary Function

  The primary function of the respiratory system is gas exchange. Animal cells use oxygen and produce carbon dioxide as a byproduct. Not only do animals need a way to get more oxygen into the cells, but they also need a way to remove carbon dioxide. The respiratory system provides this functionality. The lungs or gills of an animal remove carbon dioxide while delivering oxygen to the blood. This oxygen is carried to the tissues. The tissues deposit their carbon dioxide waste, which is then carried back to the lungs for release.Structure and Function of the Respiratory System Essay Paper

  Creating Sounds

  While the primary function of the respiratory system is gas exchange, this extensive organ system also has some other roles. In humans and other mammals, the respiratory system is integral creating sounds such as those used for speech. Structures of the upper respiratory tract, especially the larynx, are involved in the production of sound and can modulate pitch, volume, and clarity. Making noises is called phonation.

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  Olfactory Senses

  The nose plays an important role in respiration, but the olfactory nerves and their associated structures are also involved in sensing smell. This has functions ranging from digestion (the cephalic phase of digestion) to hunting, recognition, and mating. Most animals have some sort of olfactory senses, usually in the form of nerves within the respiratory system. Sharks, for instance, can smell blood in the water up to several miles away. Terrestrial predators, like wolves, also use their olfactory senses to detect prey.Structure and Function of the Respiratory System Essay Paper

  Immunity

  The cells of the respiratory tract also protect the body from the invasion of pathogens through the nasal passages. They have an important role in the immune system since the respiratory tract is one of the organ systems with intensive and repeated interaction with the environment (the other is the digestive system). Epithelial cells in the airway can secrete antibodies, defensins and various enzymes and peptides, as well as small oxidative molecules that hamper pathogenic colonization.

  In addition, some of these epithelial cells also secrete mucus to trap larger dust particles. The respiratory system plays host to a specialized lymphoid tissue that can produce lymphocytes as a first-line of defense. Coughing and sneezing are other important mechanisms used to fight infections, by removing large quantities of bacteria or viruses trapped in mucus.Structure and Function of the Respiratory System Essay Paper

  Other Functions

  The cells of the respiratory tract can help in removing clots in pulmonary blood vessels. They also activate hormones and either remove or add to the substances circulating in the blood. They can make incoming air warm and moist, in order to protect the delicate cells of the inner respiratory passages.

  Finally, epithelial cells of the lung also produce surfactant that makes the process of inhalation and exhalation easier. In fact, adequate production of surfactant by fetal lung cells is an important prerequisite for viability in pre-term births.

  Respiratory System Parts

  In humans and most mammals, the anatomy of the respiratory system is divided into three parts. The first is the series of conducting tubes that carry air from the atmosphere towards the lungs. The second part consists of the muscles of respiration – the diaphragm and intercostal muscles in the ribs. The lungs form the third part.

  

  Muscles of the Respiratory System

  The diaphragm is a dome-shaped muscle that curves upwards towards the lungs. When it contracts, it becomes flattened and therefore increases the volume of the thoracic cavity. Similarly, contraction of the external intercostal muscles moves the ribs upwards and outwards. This increase in volume leads to a drop in pressure within the lungs, allowing air to flow passively into the airways. Gas exchange occurs at alveoli till these muscles relax, reversing the process.Structure and Function of the Respiratory System Essay Paper

  But, the diaphragm is not alone. The intercostal muscles, as seen in the picture below, provide expansion and contraction of the rib cage, which furthers the movement of air in and out of the lungs.

  

  Airways of the Respiratory System

  The airways can be divided into the conducting and respiratory zones. The conducting zone begins at the nose and ends at smaller bronchioles, and these passages carry air towards the inner recesses of the lungs. The respiratory zone contains the terminal bronchioles and the alveoli – the sites where gas exchange occurs.

  The nose and the mouth form the main external openings and mark the beginning of the conducting zone of the airway or respiratory tract. The nasal cavity situated behind the nose contains hair and filters and humidifies air. Most large environmental pollutants are trapped in the mucus secreted by the cells of the nose and nasal cavity. The mouth is unable to reproduce all the functions of the nasal cavity and acts as a second opening when the nose is either blocked or when there is an immediate need for large quantities of air.Structure and Function of the Respiratory System Essay Paper

  Air then passes into the pharynx, which is also involved in swallowing. The epiglottis prevents the movement of food into the respiratory tract and the misdirection of air towards the esophagus. When the epiglottis doesn’t function properly, small particles can enter the trachea. These are removed through coughing. If food is lodged or stuck in the airway, it may need to be quickly removed through abdominal thrusts, also known as the Heimlich maneuver.

  The larynx follows the pharynx and its main function is the production of sound. The flow of air through this region can influence pitch and volume. Air then enters the trachea, a long tube that is covered by a series of cartilaginous rings, which help this tubular structure retain its shape during inhalation and exhalation. The trachea is lined by pseudostratified columnar epithelia with goblet cells secreting mucins and helping to form mucus.

  The Lungs

  The trachea splits to form two primary bronchi, called the left and right bronchi. Each of these leads towards a lung and then undergoes repeated branching to produce secondary, tertiary bronchi, and bronchi oles, with successively smaller diameters. When the bronchi oles are less than a millimeter in diameter, they are called terminal bronchi oles, whose purpose is to end in vascularized alveoli. As the bronchi begin to branch, their internal structure changes. Cartilage is more common in the larger airways, and a single epithelial layer is common in the smallest parts of the conducting zone and the respiratory zone. Bronchi and bronchi oles both contain smooth muscles that can constrict in times of rest, or dilate during exercise.Structure and Function of the Respiratory System Essay Paper

  Lungs are made of spongy tissue containing many vascular tissues and much of the airway that appears after the trachea. A pleural membrane allows these paired organs to expand and contract with minimal friction. The left lung is smaller than the right due to the location of the heart on the left side of the thoracic cavity.

  Respiratory System Structure

  The organs described above work as a functional unit within the respiratory system. Air is taken in through the mouth and nose. From here, it makes its way down the trachea. The trachea splits into the bronchi of each lung, where it further divides into a number of smaller tubes that lead to the alveoli. These tiny sacs within the lung are the actual sites of gas exchange.

  The alveoli directly contact tiny capillaries from the circulatory system and are able to pass small gas molecules and some waste products across the cell membranes separating them. Oxygen is added to the blood, while carbon dioxide is taken into the alveoli. When the breath is released, this carbon dioxide is released into the atmosphere. The oxygen will make its way via the circulatory system to the tissues, where it will release its oxygen and pick up more carbon dioxide. Thus, the cycle of respiration repeats itself constantly.Structure and Function of the Respiratory System Essay Paper

  Diseases of the Respiratory System

  Diseases of the respiratory tract can arise due to obstruction to the airway, constriction of the passages, or the loss of the extensive surface area of alveoli for gas exchange. There could also be difficulties with the capillaries surrounding these alveoli, either due to clots or due to altered cardiac function. These illnesses could be chronic conditions or temporary infections. They could also simply be minor changes to the breathing pattern, as seen with hiccups.

  Common Cold

  The common cold, appropriately named for its ubiquitous nature is caused by a large number of different viruses, with rhinoviruses being the most varied and common cause for this complaint. It is usually an infection of the upper respiratory tract, though it can occasionally spread towards the ears, or the lower respiratory structures as well. The infection is transmitted through direct contact with the infected person, especially their nasal discharges.Structure and Function of the Respiratory System Essay Paper

  This is particularly difficult to prevent since a person is infectious before they begin to show symptoms. The viruses usually establish contact with the cells of the nose, which then produce a clear liquid to trap these microorganisms and expel them from the body. This is followed by sneezing and coughing, especially if the virus travels deeper into the airway. Thick, yellow or green sputum being coughed is a sign of these microbes being attacked by the host’s immune system. Antibiotics are useless against viral infections and the symptoms usually subside after a week.

  Tuberculosis

  On the other end of the spectrum of infectious diseases of the respiratory tract is tuberculosis, or TB. It is a bacterial infection caused by Mycobacterium tuberculosis and until the advent of powerful antibiotics, could often lead to death after a painful illness. The infection spreads by the transmission of live bacteria from the infected person, especially through oral and nasal discharges. Since the bacterium is hardy and can exist in a desiccated form for many months, the illness can quickly reach epidemic proportions in regions where population density is high, or there is a prolonged cold season where people stay indoors and interact closely with one another. Many healthy children and adults can overcome an infection without obvious symptoms, where only a blood test can confirm that an infection has occurred.Structure and Function of the Respiratory System Essay Paper

  The disease is named after the hard nodules that form within the lungs, called tubercles. These tubercles can not only erode respiratory tissue, but they can also attack the blood vessels, leading to the patient coughing up blood. This is a dramatic symptom indicative of an advanced stage of the disease. The advent of HIV and AIDS brought tuberculosis to the forefront, with the original tubercles of a resolved infection breaking down and releasing bacteria into the bloodstream. Immunocompromised individuals, whether infants, the elderly, or those with autoimmune diseases, become susceptible to the recurrence of this ailment. Treatment usually involves multiple antibiotics over an extended period of time. Caregivers need to be vaccinated.

  Lung Cancer

  Lung cancer is the development of a malignant tumor in the lungs, associated with uncontrolled cell growth within the tissues and the metastasis of these cells to other organs within the body. Smoking, especially when begun at an earlier age, is the highest risk factor for developing lung cancer. Passive smoking is often equally dangerous. In recent history, King George VI died of complications relating to lung cancer, brought on by years of heavy smoking. Though tobacco smoking accounts for over 80% of lung cancer cases, any chemical substance that repeatedly irritates the delicate inner linings of the lung can lead to the formation of a tumor. These include asbestos, chromium, nickel, radon gas, uranium dust, coal dust. The most common organ for the metastasis of lung cancer is the bone. Therefore advanced stages of the disease also involve pain in the bones.Structure and Function of the Respiratory System Essay Paper

  Alveoli are an important part of the respiratory system whose function it is to exchange oxygen and carbon dioxide molecules to and from the bloodstream. These tiny, balloon-shaped air sacs sit at the very end of the respiratory tree and are arranged in clusters throughout the lungs.

  Structure

  Alveoli are tiny balloon shaped structures and are the smallest passageway in the respiratory system. The alveoli are only one cell thick, allowing the relatively easy passage of oxygen and carbon dioxide (CO2) between the alveoli and blood vessels called capillaries.

  One cubic millimeter of lung tissue contains around 170 alveoli. While the total number can vary from one person to the next, there are literally millions within the human lungs spanning a surface area of roughly 70 square meters.

  Function

  Alveoli are the endpoint of the respiratory system which starts when we inhale air into the mouth or nose. The oxygen-rich air travels down the trachea and then into one of the two lungs via the right or left bronchus. From there, the air is directed through smaller and smaller passages, called bronchi oles, past the alveolar duct, until it finally enters an individual alveolus.Structure and Function of the Respiratory System Essay Paper

  Alveoli are lined by a fluid layer known as a surfactant which maintains the shape and surface tension of the air sac. By maintaining surface tension, there is more surface area through which oxygen and CO2 molecules can pass.

  It is at this junction that oxygen molecules diffuse through a single cell in an alveolus and then a single cell in a capillary to enter the bloodstream. At the same time, CO2 molecules, a byproduct of cellular respiration, are diffused back into alveolus where they are expelled out of the body through the nose or mouth.

  During inhalation, capillaries expand as the negative pressure in the chest is created by contraction of the diaphragm. During exhalation, the alveoli recoil (spring back) as the diaphragm relaxes.

  Medical Conditions Affecting Alveoli

  There are a number of medical conditions that can directly affect the alveoli (that we refer to as alveolar lung diseases). These diseases can cause the alveoli can become inflamed and scarred or cause them to fill with water, pus, or blood.

  Among the conditions involving the alveoli:

  • Emphysema is a condition in which the inflammation in the lungs causes the dilation and destruction of alveoli. In addition to the loss of alveoli, the cellular walls of air sacs begin to harden and lose their elasticity. This makes it difficult to expel air from the lungs (a condition called air trapping). This explains why exhaling rather than inhaling is usually more difficult in people with emphysema. This inability to expel air leads to further dilatation of the alveoli and the increased loss of function
  • Pneumonia is an infection that inflames the alveoli in one or both lungs and can result in the air sacs filling with pus.Structure and Function of the Respiratory System Essay Paper
  • Tuberculosis is an infectious bacterial disease characterized by the growth of nodules in the tissues of the lungs. The disease primarily infects the alveoli as bacteria are inhaled, causing the formation of pus in the air sacs.
  • Bronchioloalveolar carcinoma (BAC) is a form of lung cancer that is now instead considered a subtype of lung adenocarcinoma. These cancers begin in the alveoli and are often found diffusely in one or both lungs.

  • Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition that prevents oxygen from getting to the lungs as fluids begin to accumulate in the alveoli. ARDS is common in critically ill patients.
  • Respiratory distress syndrome (RDS) is seen in premature babies whose bodies have not yet produced enough surfactant to line the alveoli.
  • Pulmonary edema is a condition caused by excess fluid in the lungs which collect in the alveoli and can lead to respiratory failure.

  Cigarettes and Alveoli

  As a single risk factor for lung disease, tobacco smoke is known to affect the respiratory tract at every level. This includes the alveoli.Structure and Function of the Respiratory System Essay Paper

  Alveoli are made up of collagen and elastin which provide the sacs their elasticity. Smoking damages both of these, causing the sacs to harden and thicken. Smoking also actively dilates blood vessels, impeding the exchange of oxygen and CO2.

  Cigarette smoke also affects how the alveoli work, causing damage right down to the molecular level. It disrupts our body’s ability to repair itself as it might following an infection or trauma. As such, the alveolar damage is allowed to progress unhindered as the lungs are persistently exposed to toxic fumes.

  A Word From Very well

  The alveoli provide one of the most important functions our bodies perform. They’re the gateway through which oxygen enters our bloodstream and the primary way in which some of the waste products of metabolism (carbon dioxide) exit the body.Structure and Function of the Respiratory System Essay Paper

  Diseases which affect the alveoli can result in reduced oxygen being delivered to the tissues of our body, and consequently, may result in damage (due to hypoxia) to every major organ.Structure and Function of the Respiratory System Essay Paper