The main function of the respiratory system is to provide oxygen to body cells for energy metabolism and to eliminate carbon dioxide, a byproduct of metabolism. Because these gases must be carried to and from the cells in the blood, the respiratory system works closely with the cardiovascular system to accomplish gas exchange. Exchange of gases between the atmosphere and the blood takes place in the lungs. A double membrane, the pleura, covers the lungs and lines the thoracic cavity. The outer layer that is attached to the wall of the thoracic cavity is the parietal pleura; the inner layer that is attached to the surface of the lungs is the visceral pleura.
The very thin, fluid-filled space between the two layers of the pleura is the pleural space.
Upper Respiratory Passageways: Air is carried to and from the lungs in a series of tubes in which no gas exchange occurs. Air enters through the nose, where it is warmed, filtered, and moistened as it passes over the hair-covered mucous membranes of the nasal cavity. Cilia, microscopic hair-like projections from the cells that line the nose, sweep dirt and foreign material toward the throat for elimination. Material that is eliminated from the respiratory tract by coughing or clearing the throat is called sputum.
In the bones of the skull and face near the nose are air-filled cavities lined with mucous membranes that drain into the nasal cavity. These chambers lighten the bones and provide resonance for speech production. Each of these cavities is called a sinus, and they are named specifically for the bones in which they are located, such as the sphenoid, ethmoid, and maxillary sinuses. Together, because they are near the nose, these cavities are referred to as the paranasal sinuses.
Receptors for the sense of smell are located within bony side projections of the nasal cavity called turbinate bones or conchae. Inhaled air passes into the throat, or pharynx, where it mixes with air that enters through the mouth and also with food destined for the digestive tract.
The pharynx is divided into three regions:
(1) an upper portion, the nasopharynx, behind the nasal cavity;
(2) a middle portion, the oropharynx, behind the mouth; and
(3) a lower portion, the laryngeal pharynx, behind the larynx. The palatine tonsils are on either side of the soft palate in the oropharynx; the pharyngeal tonsils, or adenoids, are in the nasopharynx.
Lower Respiratory Passageways: and Lungs The pharynx conducts air into the trachea, a tube reinforced with C-shaped rings of cartilage to prevent its collapse (you can feel these rings if you press your fingers gently against the front of your throat). Cilia in the lining of the trachea move impurities up toward the throat, where they can be eliminated by swallowing or by expectoration. At the top of the trachea is the larynx. The larynx is shaped by nine cartilages, the most prominent of which is the thyroid cartilage at the front that forms the “Adam’s apple.” The opening between the vocal cords is the glottis. The small leaf-shaped cartilage at the top of the larynx is called the epiglottis. When one swallows, the epiglottis covers the opening of the larynx and helps to prevent food from entering the respiratory tract.
The larynx contains the vocal cords, folds of tissue that are important in speech production. Vibrations produced by air passing over the vocal cords form the basis for voice production, although portions of the throat and mouth are needed for proper articulation of speech.
The trachea is contained in a region known as the mediastinum, which consists of the space between the lungs together with the organs contained in this space. In addition to the trachea, the mediastinum contains the heart, esophagus, large vessels, and other tissues. At its lower end, the trachea divides into a right and a left main stem bronchus that enter the lungs. The right bronchus is shorter and wider; it divides into three secondary bronchi that enter the three lobes of the right lung. The left bronchus divides into two branches that supply the two lobes of the left lung. Further divisions produce an increasing number of smaller tubes that supply air to smaller subdivisions of lung tissue. As the air passageways progress through the lungs, the cartilage in the walls gradually disappears and is replaced by smooth (involuntary) muscle. The smallest of the conducting tubes, the bronchioles, carry air into the microscopic air sacs, the alveoli, through which gases are exchanged between the lungs and the blood. It is through the ultrathin walls of the alveoli and their surrounding capillaries that oxygen diffuses into the blood and carbon dioxide diffuses out of the blood for elimination.
► BREATHING
Air is moved into and out of the lungs by the process of breathing, technically called ventilation. This consists of a steady cycle of inspiration (inhalation) and expiration (exhalation), separated by a period of rest. The cycle begins when the phrenic nerve stimulates the diaphragm to contract and flatten, thus enlarging the chest cavity. The resulting decrease in pressure within the thorax causes air to be pulled into the lungs. The intercostal muscles between the ribs aid in inspiration by pulling the ribs up and out. Muscles of the neck and thorax are used in addition for forceful inhalation. The measure of how easily the lungs expand under pressure is called compliance. Fluid produced within the lung, known as surfactant, aids in compliance by reducing surface tension within the alveoli. Expiration occurs as the breathing muscles relax, the lungs spring back to their original size, and air is forced out. Muscles of the rib cage and abdomen can be called on for forceful exhalation. Breathing is normally regulated unconsciously by centers in the brainstem. These centers adjust the rate and rhythm of breathing according to changes in the composition of the blood, especially the concentration of carbon dioxide.
► GAS TANSPORT :
Oxygen is carried in the blood bound to hemoglobin in red blood cells. The oxygen is released to the cells as needed. Carbon dioxide is carried in several ways but is mostly converted to an acid called carbonic acid. The amount of carbon dioxide that is exhaled is important in regulating the acidity or alkalinity of the blood, based on the amount of carbonic acid that is formed. Dangerous shifts in blood pH can result from too much or too little carbon dioxide being exhaled.to help this system works properly Regular exercise and deep breath is very important.if you like to read this turtorial in hausa, visit my alternated website,at
Www.kimiyyadahausa.blogspot.com.for any question or corrections leave your comment in below box.
Than to all of us.
(1) an upper portion, the nasopharynx, behind the nasal cavity;
(2) a middle portion, the oropharynx, behind the mouth; and
(3) a lower portion, the laryngeal pharynx, behind the larynx. The palatine tonsils are on either side of the soft palate in the oropharynx; the pharyngeal tonsils, or adenoids, are in the nasopharynx.
Lower Respiratory Passageways: and Lungs The pharynx conducts air into the trachea, a tube reinforced with C-shaped rings of cartilage to prevent its collapse (you can feel these rings if you press your fingers gently against the front of your throat). Cilia in the lining of the trachea move impurities up toward the throat, where they can be eliminated by swallowing or by expectoration. At the top of the trachea is the larynx. The larynx is shaped by nine cartilages, the most prominent of which is the thyroid cartilage at the front that forms the “Adam’s apple.” The opening between the vocal cords is the glottis. The small leaf-shaped cartilage at the top of the larynx is called the epiglottis. When one swallows, the epiglottis covers the opening of the larynx and helps to prevent food from entering the respiratory tract.
The larynx contains the vocal cords, folds of tissue that are important in speech production. Vibrations produced by air passing over the vocal cords form the basis for voice production, although portions of the throat and mouth are needed for proper articulation of speech.
The trachea is contained in a region known as the mediastinum, which consists of the space between the lungs together with the organs contained in this space. In addition to the trachea, the mediastinum contains the heart, esophagus, large vessels, and other tissues. At its lower end, the trachea divides into a right and a left main stem bronchus that enter the lungs. The right bronchus is shorter and wider; it divides into three secondary bronchi that enter the three lobes of the right lung. The left bronchus divides into two branches that supply the two lobes of the left lung. Further divisions produce an increasing number of smaller tubes that supply air to smaller subdivisions of lung tissue. As the air passageways progress through the lungs, the cartilage in the walls gradually disappears and is replaced by smooth (involuntary) muscle. The smallest of the conducting tubes, the bronchioles, carry air into the microscopic air sacs, the alveoli, through which gases are exchanged between the lungs and the blood. It is through the ultrathin walls of the alveoli and their surrounding capillaries that oxygen diffuses into the blood and carbon dioxide diffuses out of the blood for elimination.
► BREATHING
Air is moved into and out of the lungs by the process of breathing, technically called ventilation. This consists of a steady cycle of inspiration (inhalation) and expiration (exhalation), separated by a period of rest. The cycle begins when the phrenic nerve stimulates the diaphragm to contract and flatten, thus enlarging the chest cavity. The resulting decrease in pressure within the thorax causes air to be pulled into the lungs. The intercostal muscles between the ribs aid in inspiration by pulling the ribs up and out. Muscles of the neck and thorax are used in addition for forceful inhalation. The measure of how easily the lungs expand under pressure is called compliance. Fluid produced within the lung, known as surfactant, aids in compliance by reducing surface tension within the alveoli. Expiration occurs as the breathing muscles relax, the lungs spring back to their original size, and air is forced out. Muscles of the rib cage and abdomen can be called on for forceful exhalation. Breathing is normally regulated unconsciously by centers in the brainstem. These centers adjust the rate and rhythm of breathing according to changes in the composition of the blood, especially the concentration of carbon dioxide.
► GAS TANSPORT :
Oxygen is carried in the blood bound to hemoglobin in red blood cells. The oxygen is released to the cells as needed. Carbon dioxide is carried in several ways but is mostly converted to an acid called carbonic acid. The amount of carbon dioxide that is exhaled is important in regulating the acidity or alkalinity of the blood, based on the amount of carbonic acid that is formed. Dangerous shifts in blood pH can result from too much or too little carbon dioxide being exhaled.to help this system works properly Regular exercise and deep breath is very important.if you like to read this turtorial in hausa, visit my alternated website,at
Www.kimiyyadahausa.blogspot.com.for any question or corrections leave your comment in below box.
Than to all of us.
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