The Respiratory System: Tracing the Vital Life Sustaining Process

Sep 17 11:00 2006 Nilutpal Gogoi Print This Article

Intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system. The respiratory system carries out these life-sustaining acts in close coordination with the circulatory system. Most of the time, we remain blissfully unaware of these automatic functions.


Intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system. The respiratory system carries out these life-sustaining acts in close coordination with the circulatory system. Most of the time,Guest Posting we remain blissfully unaware of these automatic functions. The respiratory organs deliver oxygen to the circulatory system. The circulatory system transports the oxygen to all body cells. Oxygen is used by cells to liberate the energy needed for cellular activities. The respiratory system also removes carbon dioxide. Thus, the circulatory system prevents the buildup of this lethal waste byproduct in the body tissues. Irreversible damage to tissues can occur if the respiratory system is halted even for a few minutes. This can cause failure of all the other body systems. The consequence is death!


The respiratory system begins from the nose. It ends in the lungs. The respiratory system is broadly divided into two parts, viz., the upper and the lower respiratory tracts. The upper respirator tract is made up of the nose and the throat (pharynx). The lower respiratory tract includes five organs. They are the voice box (larynx), and the windpipe (trachea), bronchi, bronchioles and the lungs. The trachea splits into the two branches called bronchi. The bronchi further gets divided into further smaller branches called bronchioles. The lungs are a pair of spongy saclike organs. The bronchioles, bronchi, trachea, larynx, pharynx and the nose transport air to and from the lungs. It is the lungs that interact with the circulatory system for delivering oxygen and removing carbon dioxide from the lungs.


Respiration is a two-pronged process. It involves the respiratory and the circulatory systems. Respiration connotes the coordinated functioning whereby the cells are delivered oxygen and the lethal carbon dioxide is removed.

The first phase: The nose begins the first phase of respiration. This is done with inhaling or inhalation (breathing in). The process brings in air along with oxygen from outside the body into the lungs. From the lungs, oxygen goes via the blood vessels to the heart. The heart pumps the oxygen-rich blood to all parts of the body. The first phase of respiration ends with the oxygen moving into the cells from the bloodstream. The second phase: The second phase commences after the oxygen gets into the cells. The cells use the oxygen to produce energy. This independent process is called cellular respiration. It produces the byproduct -- carbon dioxide. The accumulated carbon dioxide now moves from the cells to the bloodstream. Next, the bloodstream transports the carbon dioxide to the heart. Then, the carbon dioxide-laden blood is pumped back to the lungs. The third phase: Again the nose comes into picture during this stage. The lungs push the byproduct to the nose from where it is exhaled or breathed out. This is the final or the third stage when the body gets rid of the carbon dioxide. At the end of the third stage or the entire respiratory cycle another one starts automatically.


The respiratory system further regulates the balance of acid and base in tissues. This balancing act is crucial for the normal functioning of cells. It protects the body against disease-causing organisms and toxic substances inhaled with air. The respiratory system also houses the cells that detect smell. Moreover, the respiratory system assists in the production of sounds for speech.


The brownish olfactory nerve is also called olfactory receptors. The olfactory nerve inside the nose is the main nerve of smell. The olfactory region is made up of thick nasal soft mucous membrane. Its brownish color is because of a pigment. The olfactory nerve ends in minute varicose fibers (several small branches). These fibers ultimately conclude in the epithelial cells. Mentionably, the epithelial cells project into the nasal free surface.

The olfactory nerve is the first to know of any chemicals that may enter the nasal passages. The receptors immediately trigger off a signal to the brain. This creates the smell perception.


Esophagus is a muscular tube. The esophagus carries food from the throat to the stomach. The esophagus and the pharynx situated behind the mouth swallow the food and move it to the stomach. The stomach temporarily stores the food, mixes it with digestive juices, and carries out some digestion. The esophagus also holds the stomach contents in place. Actually, this function is carried out by the lower esophageal sphincter. This sphincter is a muscle. It is located at the lower end of the esophagus.


The pharynx is a passageway for both air and food. The pharynx connects the nose and mouth with the windpipe (trachea) and the food pipe (esophagus). The pharynx is a muscular tube. The pharynx is located within the neck. The pharynx is lined with a mucous membrane. The pharynx is approximately five inches (13 cm) in length. The pharynx lies in the front of the spinal column. The upper portion of the pharynx is known as nasopharynx. The name arises as it begins in the back of the nasal cavity.. The lower part is oropharynx. It points to that area in the back of the mouth. The pharynx ends at the epiglottis. Epiglottis is a flap of cartilage. Epiglottis prevents food from entering the trachea. However, the epiglottis allows the food to enter the esophagus. Two eustachian tubes connect the pharynx to the middle ear. These eustachian equalizes the eardrums air pressure.

The pharynx can be infected via the mouth as well as the nose. Sore throat involves pharynx infection (pharyngitis) or throat inflammation. Pharyngitis can be due to infectious mononucleosis, herpes, and viral infections. The viral infections are German measles (rubella), influenza, and common cold. It can also be caused by bacteria like staphylococcal, streptococcal, chlamydial, and diphtherial. These bacteria multiply cause sore throat by multiplying rapidly within the pharynx.

Tonsils and AdenoidsAmong the adults the pharynx contains the tonsils, while among the children the pharynx contains the adenoids. Tonsils: Tonsils are lymphoid tissues at the back of the throat. Tonsils form a tissue ring around the pharynx or the throat. Tonsils are cells. Tonsils are similar to the bloodstream lymphocytes. Tonsils are embedded in fibrous connective tissues. Tonsils are covered by a single epithelium layer. The lymphoid cells are phagocytic. The cells protect the pharynx from bacteria that can cause diseases. Tonsils may become inflamed and chronically or acutely infected. This condition is called tonsillitis. It is generally caused by streptococcus infection. During tonsillitis and streptococcal, the tissues surrounding the tonsils form pus. Then a whitish coat forms over the tonsils which can appear as white specks. This state is called quinsy. When the pharyngeal tonsils become inflamed they become abnormally large. They are called adenoids. Acute cases of tonsillitis are often treated by antibiotics like penicillin. Chronic recurrent tonsillitis may be treated by tonsillectomy (surgical removal of the tonsils). Adenoids: Adenoids are lymphoid tissue at the back of the throat. Adenoids usually shrink and disappear by adolescence. Enlargement of this tissue is common among children. Such a state can interfere with breathing. Symptoms of enlarged adenoids include restless sleep, snoring, breathing via mouth, and a nasal voice. Earlier, these tissues were removed in children. It was thought that inflamed adenoids led to recurrent colds and infections. Nowadays, this condition is recognized as benign. As a result, there are lesser adenoidectomies.


From the pharynx, the inhaled air moves to the larynx. The larynx is about five inches (13 cm) in length. The larynx is located in the central part of the neck. The larynx is made up of several layers of flexible but tough cartilage, a tissue. Mentionably, during puberty the males experience a protrusion of the cartilage. This enlarged prominent extension at the neck is called the Adam’s apple.


The larynx primarily transports air to the wind pipe (trachea). Besides, the larynx also helps in producing the sounds. The epiglottis -- a leaflike thin tissue portion of the larynx -- further prevents the food from entering the trachea (thus obviating the possibility of choking). Moreover, the cilia cells as well as the mucous membrane of the larynx also filter air. The cilia cells take the airborne substances towards the pharynx where they are swallowed.

The epiglottis: The epiglottis stem is attached to the top and the front portions of the larynx. When the epiglottis remains in a vertical position, it acts like a trap door. This happens during the breathing process. But as a person starts swallowing, a reflexive action forces the epiglottis and the larynx to move near each other toward each other. This coming closer of the epiglottis and the larynx forms a protective seal. As a result, the fluids and food are specifically sent towards the food pipe (esophagus). When the reflexive action doesn’t work: What happens when the reflexive action doesn’t function is that the food can enter the larynx. This happens when one eats the meal fats or when one laughs while swallowing. The result is that there will be a recurrent cough impelled choking effect. At times this apparently simple choking effect can even be life-threatening. The cough is the body’s reflexive action to clear the larynx of the impediment. Whenever such choking takes place, someone must thump the back portion between the shoulder blades several times. This will help the person to get over the choking effect. The Heimlich maneuver: The Heimlich maneuver clears the windpipe of obstructions like food or fluid. The first-aid providing person applies thrusts in quick and in upward motion at the patient’s abdomen. The objective is to expel the object stuck at the trachea (windpipe). Standing behind the victim, the person keeps both his arms across the patient’s waist. Then, he places the fist of one hand below the rib cage and a bit above the navel. All the while, he keeps the thumb against the patient’s body. He uses the other hand for holding the fist and for applying pressure. Next, he puts quick pressure on the abdomen. The pressure is put in an inward and an upward motion. This fast recurrent action forces the lung air to get rid of the substance blocking the windpipe. However, in cases where the patient cannot stand still, is overweight, faints following the choking effect, the Heimlich maneuver is done in a different manner. The patient is made to lie face down. The first-aid provider carries on the process with the heel of a hand. Important: Nonetheless, it is important that the person does not put undue pressure on the rib cage. This is especially true when the patient is a child or an elderly person. Too much pressure can break ribs. Pertaining to pregnant woman or overweight people, the first-aid provider must place his hands only on the lower half of the breastbone (sternum) while carrying out the maneuver.

In acute choking, tracheotomy (a surgical procedure) is undertaken to carry out bypass of the larynx. This operation brings in air to the trachea.


The trachea is another tube measuring approximately six inches (15 cm). The trachea is located below the larynx. From the larynx the air passes on to the trachea. About 20 sturdy C-shaped cartilage rings constitute the trachea. These rings help to keep the trachea open. In the process, air gets transported unhindered. While the unfastened cartilage is located at the trachea’s back portion, their ends are linked to each other by muscle tissues. Bronchi & bronchioles: The trachea base is situated at the portion where the neck meets the body trunk. At this juncture, the trachea splits into the right and the left bronchi. These bronchi transport air to the right and left lungs respectively. Inside the lungs, these bronchi again break up into smaller tubes -- the bronchioles. In fact, the respiratory system’s cleansing process is carried out by those bronchioles that are situated at the initial part, bronchi, and the trachea. These organs carry out the cleansing process via the mucous membrane linings as well as the ciliated cells. These cilia and the lining push the mucus upward towards the pharynx.

Alveoli & capillaries: Alveoli are minute sacs inside the lungs. Most of the alveoli are lung tissues. Alveoli are formed by the bronchioles as they divide several times. The alveoli along with the bronchioles resemble a tree. The alveoli are only 0.02 inches (0.5 mm) in diameter. There are about 150 million alveoli in each lung. The alveoli carry out a dual function. While providing oxygen to the circulatory system, they also remove carbon dioxide from the lungs. The thin elastic alveoli walls expand when air moves into them. The walls collapse to exhale the air.

The alveoli remain in clusters like the grapes. Each cluster is surrounded by capillaries. The capillaries are thin-walled and form a dense net of tiny hairs. The alveoli wall air is generally located 0.2 microns away from the blood carried by the capillary. Mentionably, the alveoli have more oxygen concentration then the capillaries. So, oxygen disseminates to capillaries from alveoli. Through the capillaries, oxygen goes to the larger vessels. These vessels then transport the oxygenated blood to the heart. Next, the heart pumps the cleaned blood to the other parts of the body. Macrophages: Among the alveoli are interspersed many macrophages. The macrophages are blood cells. These large white cells act as the last sentinels of the respiratory system among the alveoli. The macrophages segregate the foreign elements which may have passed through the earlier filtration process. This last line of defense ensures that the alveoli are not infected. Carbon dioxide disposal: The cells from across the body dump Carbon dioxide as a waste product. It is dumped in the bloodstream. The blood carries Carbon dioxide into the heart. From the heart, the Carbon dioxide moves to the alveolar capillaries. Notably, the capillaries have more concentration of carbon dioxide than the alveoli. So, carbon dioxide gets diffused into the alveoli from the capillaries. When a person exhales, the Carbon dioxide is forced back via the respiratory routes. The gas is then thrown outside the body.

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Nilutpal Gogoi
Nilutpal Gogoi

Nilutpal Gogoi is a writer and a freelance journalist having more than 18 years of service in several audio-visual and print media reputed organizations in North East India. He has published more than 1000 articles and a popular adventure book for children. For more information log on to

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