Human Systems - Respiration - Article Example

Human Systems – Respiration The human body is an intricate combination of an array of chemicals, compounds and various components which work simultaneously and co-operatively with each other so as to ensure health and survival of the being. The basic structural and functional units of a living being are the cells, which are arranged in groups called tissues. Groups of tissues combined form organs, and organs working towards a specific purpose together are called a system. One of the most important systems of the human body is the Respiratory System. The respiratory system is the biological system of any organism that engages in gaseous exchange. It provides the energy needed by cells of the body. The following diagram shows the structure of the human respiratory system. www.health.uab.edu/default.aspx?pid=65823 Each of the above labelled parts performs an important task specific to only that organ during the process of respiration. The following are the various components of the Respiratory Tract: Parts of the Respiratory System Primary Parts: Air is breathed in through the nostrils where it encounters the Nose Hairs, located at the entrance of the nose which filter out large dust and other unwanted foreign particles from it. The air then passes onto the interior of the nose called the Nasal Cavity/ Passage. It is lined with a sticky mucous membrane and contains tiny, surface hairs called cilia. The mucus and cilia collect dust, bacteria, and other particles in the air.  The mucus also helps in moistening the air.  Under the mucous membrane there are a large number of capillaries.  The blood within these capillaries helps to warm the air as it passes through the nose. Thus, the nasal cavity serves as a moistener, a filter, and to warm up the air before it reaches the lungs. Then comes the Pharynx, or the throat, which is followed by the Larynx, which is the voice-box. There are two pairs of membranes that are stretched across the inside of the larynx called the vocal cords. When air is expired, these cords vibrate and by controlling these vibrations, one is able to produce different sounds. Also, epiglottis, a cartilaginous flap prevents food from entering the wind-pipe during swallowing. Both the pharynx and larynx form part of the respiratory tract. The larynx opens up into the Trachea, or the wind pipe. The trachea is a tube approximately 12 cm in length and 2.5 cm wide.  Rings of cartilage within its walls prevent it from collapsing during expiration. It is also covered with a ciliated mucous membrane, which keeps foreign particles and mucus out. The trachea divides into two cartilage-ringed tubes called Bronchi. Also lined with ciliated cells, they form the two main passages for entry of air into the lungs. After entering the lungs, the bronchi divide and spread in a tree-like manner into smaller tubes called Bronchial Tubes. The bronchial tubes divide and then subdivide, becoming thinner and having less and less cartilage in their walls.  Eventually, they become a tiny group of tubes called Bronchioles. Each bronchiole ends in a tiny air chamber which contains many air-bags called Alveoli. At about one cell thick, the walls of these alveoli serve as the respiratory surface. They are thin, moist, and are surrounded by several numbers of capillaries.  The exchange of oxygen and carbon dioxide between blood and air occurs through these walls. A pair of human lungs is estimated to contain an average of 300 million alveoli. Auxiliary Parts: Apart from the main respiratory tract through which the air flows, the system has other parts which support breathing and respiration: The Diaphragm is the muscle separating the chest cavity from the abdominal cavity. Its up-and-down movement aids in breathing. The Pleural Membrane, consisting of two thin layers covering the lungs, is a form of protection. The Ribs support the chest wall and protect the heart, lungs, and other organs in the chest. The Intercostal Muscles are thin sheets of muscle between each rib that expand during inhaling, and contract during exhaling. The Respiratory Centre (in the Medulla Oblongata) is the area of the brain that controls breathing. Together, all the parts mentioned above form the respiratory system of an organism. Breathing The respiratory system is involved in two distinct activities called Breathing and Respiration. Breathing is the mechanical process of taking in and expelling of air through the nose and respiratory tract with the aid of muscles. Respiration is the chemical process in which gaseous exchange takes place at a cellular level from the blood stream. Breathing consists of two phases- Inspiration and Expiration. During Inhalation, or breathing in, the diaphragm and the intercostal muscles contract. The contraction of the diaphragm causes it to shorten and lower, increasing the volume of the thoracic cavity. Contraction of the intercostal muscles lifts the ribs up and out, further increasing the volume of the thoracic cavity. This increased volume of the thoracic cavity results in a decreased pressure within the lungs. Air in the environment is at higher pressure than in the lungs and moves in to equalize the pressure. Thus, oxygen rich air is brought into the body. During Exhalation, or breathing out, the diaphragm and intercostal muscles relax. Their relaxation causes the volume of the thoracic cavity to decrease. This results in an increased pressure within the lungs and air is forced out into the environment to equalize pressure. Thus, air containing carbon-dioxide and water vapour is expelled out of the lungs. A normal human breathes about 18-20 times a minute. http://www.biology.eku.edu/RITCHISO/breathingmuscles.jpg Role of the Respiratory Centre Like all functions of the body, each and every step involved in breathing and respiration is controlled by the Brain. The part of the brain responsible for controlling the working of the respiratory system is called the Respiratory Centre and it is located in the Medulla Oblongata. When air is exhaled, there starts an accumulation of carbon-dioxide and hydrogen ions in the blood stream, which are the products from cellular respiration. These increased levels are detected by the respiratory centre which then sends nervous signals that cause the muscles of the diaphragm and the intercostal muscles of the rib cage to contract. After air fills up the alveoli, stretch receptors in the alveoli signal the respiratory center in the medulla oblongata to stop signals to the diaphragm and intercostal muscles. Thus, the diaphragm and intercostal muscles relax resulting in exhalation. Respiration The second activity of the respiratory system is Cellular Respiration. This too consists of two phases namely External Respiration and Internal Respiration. It is the process by which the chemical energy contained in food molecules is released and captured in the form of ATP. External Respiration is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs.   Blood enters the lungs via the pulmonary artery.  It then proceeds through arterioles and into the alveolar capillaries. In the alveoli, carbon-dioxide is given out and oxygen is absorbed into the blood. This blood then flows out of the alveolar capillaries, through venuoles, and back to the heart via the pulmonary vein, from where it is pumped to the whole body. Haemoglobin in humans is the respiratory pigment in the blood which carries the oxygen molecules to the various tissues throughout the body.  Internal Respiration is the exchange of gasses between the blood in the capillaries and the bodys cells. Once the oxygenated blood reaches the other cells in the body, exchange of gases between the tissues and the blood in the capillaries takes place. Carbon-dioxide is absorbed into the blood stream, and oxygen is given out to the cells. This deoxygenated blood is carried back through veins to the heart, from where it is pumped to the lungs through the pulmonary artery. The whole process then repeats. Importance of Oxygen The oxygen supplied by the cells is highly important for is used to obtain chemical energy from the fats and carbohydrates in our food. These fats and sugars undergo chemical reactions whereby they are oxidized to water, carbon dioxide and energy. The energy produced is trapped in the form of ATP (Adenosine Tri-Phosphate) molecules. These energy molecules are then used to do any work in or by the body like protein synthesis, locomotion, movement, etc. All activities of the body require energy which is supplied in the form of ATP, and these ATP molecules can only be released during cellular respiration when oxidation of food-stuffs takes place. A small amount is also used up for the synthesis and breakdown of other metabolically important molecules (like steroid hormones). Thus, the biological importance of oxygen can be clearly noticed. An average human cannot survive without oxygen for more than four minutes. Effects of Smoking Smoking harms the respiratory system as much as it harms the rest of the body leading to disease like tuberculosis, lung cancer, asthma, and chronic bronchitis to name a few. The respiratory system cannot deal with tobacco smoke very keenly.  Smoking stops the cilia from moving.  Just one cigarette slows their motion for about 20 minutes.  The tobacco smoke increases the amount of mucus in the air passages. In fact, when smokers cough, their body is attempting to dispose of the extra mucus.  Smoking makes it difficult for oxygen to be taken through the alveoli.  When cigarette smoke is inhaled, about one-third of the particles remain within the alveoli.  There are too many particles from smoking or from other sources of air pollution which can damage the walls of the alveoli.  This causes a certain tissue to form.  This tissue reduces the working area of the respiratory surface and leads to the disease called emphysema. Smoking can shorten a person’s life by as much as fourteen years. Addictive smoking can lead to a lot many diseases and disorders like coronary artery disease, heart disease, heart attack and stroke, ulcers of the digestive system, lung diseases such as chronic obstructive pulmonary disease, osteoporosis and hip fracture, poor blood circulation in feet and hands, which can lead to pain and, in severe cases, gangrene and even amputation. Specific to the respiratory system, cigarette smoking results in irritation of the trachea and larynx, reduced lung function and breathlessness due to swelling and narrowing of the lung airways and excess mucus in the lung passages, impairment of the lungs’ clearance system, leading to the build-up of poisonous substances, which results in lung irritation and damage, increased risk of lung infection and symptoms such as coughing and wheezing, and permanent damage to the air sacs of the lungs. It should be realized that the respiratory system is highly essential for a person’s survival and it is very hard to replace it once it is damaged. In fact, a few years ago, when stem cell therapy and organ transplants were not discovered, even replacing seemed impossible. Moreover, it is still very difficult to do transplants due to organ rejection, lack of donors, lack of resources and information, etc. Smoking causes immense harm to the entire body and once started, the process cannot be reversed. Therefore, abstinence from smoking is a key step in taking care of one’s health and ensuring survival. References UAB Health System (2006). Respiratory Changes. Retrieved June 17, 2007, from www.health.uab.edu/default.aspx?pid=65823 American Medical Association. Respiratory System -- Structure Detail. Retrieved June 17, 2007, from http://www.ama-assn.org/ama/pub/category/7166.html Rice, D., Harnett, A., Inkpen, P. Biology 2201. Structure of the Human Respiratory System. Retrieved June 18, 2007, from http://www.cdli.ca/~dpower/resp/struct~1.htm The Breathing Process. (n.d.). Retrieved June 17, 2007, from http://www.coolschool.ca/lor/BI12/unit11/U11L04.htm Rice, D., Harnett, A., Inkpen, P. Biology 2201. Gas Exchange In Humans. Retrieved June 18, 2007, from http://www.cdli.ca/~dpower/resp/exchange.htm#Cellular Better Health Channel (May, 2007). Smoking - effects on your body. Retrieved June 18, 2007 from http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Smoking_effects_on_your_body?OpenDocument Read More