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The Structure and function of the respiratory tract
Man can survive without food and water for about three days or more , but if he stops breathing for 3 to 5 minutes he will immediately die . From this point the importance of the respiratory tract in our bodies comes. All organs in the human body need oxygen in their metabolism and carbon dioxide to be removed from their tissues as a waste product and the respiratory tract is responsible to perform this function. In this essay we will look at the structure and function of the respiratory tract. The respiratory tract is divided into two main parts: the upper
respiratory tract and the lower respiratory tract. The upper respiratory
tract consists of the nose, the nasal cavity and the pharynx. The lower tract consists of
the larynx, the trachea , the bronchi and the
lungs. In addition, there are some muscles helping in the respiratory
movements which are the intercostal muscles and the diaphragm (4).
1- The nose and the nasal cavity : The nose forms the visible part of the upper tract which has two exteranl openings ( the nostrils) (4). The nasal cavity forms the internal part which is divided by the nasal septum into right and left halves (3). The nasal cavity is lined with mucus membranes. Air enters the body through the nose and then it is moistened , wormed and filtered by the respiratory mucosa of the nasal cavity. Moreover , the nasal cavity includes paranasal sinuses which produce mucus, maintain sound and lighten the skull (1). 2- The pharynx : The pharynx is a muscular tube serving to connect the nasal cavity and the mouth with the lower respiratory tract and the esophagus. It is divided into three parts: the nasopharynx, the oropharynx and the laryngopharynx (2).
1- The larynx : The larynx , also known as voice box, lies between the phraynx and the trachea. The larynx is made up mainly of cartigles. It includes the vocal cords which are responsible for speech (3). The larynx allows air to pass from the glottis which closes during swallowing (5). 2- The trachea : The trachea is a tube begining from the edge of the larynx and divides into two bronchi which continue into the lungs. The trachea allows air to pass from the larynx to the bronchi and then to the lungs (2). The trachea is lined with mucus membranes and with ciliated cells which are responsible for removing dirt particles from air befor it enters the lungs (1). 3- The bronchi : The bronchi divide into smaller bronchioles which branch in the lungs forming passageways for air. The terminal parts of the bronchi are the alveoli (2).The alveoli are the functional units of the lungs and they form the site of gasous exchange (1). 4- The lungs : The lungs are located in the thoracic cavity and they are covered with the pleural membranes. The right lung has three lobes, while the left lung has two lobes only (2). The lungs include the bronchi, the alveoli, connective tissues, blood vessels, lymph vessels and nerves (5). The lungs are the part of the respiratory tract responsible for respiration, since the exchange of gases takes place in them (3). The lungs supply the heart with oxygenated blood through the pulmonary veins and take off the deoxygenated blood through the pulmonary arteries (2). Moreover, the elastic properties of the lungs enable it to inhale and exhale the air (1). In addition, the respiratory tract has very important role in maintaing
the pH of the body fluids (4). There are also other functions of the
respiratory tract which include coughing, sneezing, crying, laughing, hiccuping
and snoring (1).
In conclusion, the respiratory tract is a very important system in our
bodies. It is divided into two parts : the lower respiratory tract and the
upper respiratory tract and the these two parts have specialized structures
which asisst in the respiratory functions. The respiratory tract enables
us to breath and supply the heart with oxygenated blood which is pumped out to
all parts of our bodies. It has also other functions such as :
helping in maintaing the pH of the body fluids, sneezing and coughing.
(1) Carola, Rebert, et al. Human Anatomy & Physiology. 2nd ed. NewYork :
Mc Graw-Hill ,lnc , 1992, p. 719-720 ,p.750-751.
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Introduction.