Respiratory tract

The respiratory system consists of the nose, pharynx, larynx, trachea, and lungs. Respiration is a process that takes in oxygen from the air and removes carbon dioxide from the blood. The respiratory tract also contributes to the production of sound, smell, and taste, but its most important function is to perform respiration. Because respiration is a very necessary process for life.

The nose is an organ made of bone and cartilage, covered with muscle and skin. The lower part of the nose is made of cartilage and the upper part is made of bone. There are two nasal cavities inside the nose, separated by the sling bone. During respiration, air passes through these cavities and reaches the pharynx. The olfactory organ is located at the top of the nasal cavity. During respiration, air first touches this olfactory organ and therefore the presence of harmful gases in the air can be determined. On the outer side walls of the nasal cavity, there are three inward-extending bone protrusions, coiled like a snail, and these protrusions are called horn bones. The nasal cavity is divided into many paths by these bones. The surface of the nasal cavity is covered with a hairy epithelium-covered mucous membrane. The secretion of this membrane always keeps the inside of the nose moist. As the air passes through here during respiration, it is warmed and moistened at the same time. The pharynx not only takes food to the esophagus, but also transmits the air taken from outside to the trachea and delivers the air coming out of the lungs to the nose or mouth. During the swallowing movement, breathing stops. At the same time, while the food is being swallowed, the part of the throat that opens to the pharynx is closed by the soft palate. During each swallow, the larynx, which is the passageway of the trachea, lifts upwards. The valve on the larynx is pushed forward by the root of the tongue and closes the laryngeal passage leading to the trachea.

The larynx is a vocal organ located in the upper part of the trachea and is made up of a number of cartilage pieces. One of these pieces is called the sphenoid cartilage and is slightly more prominent than the others. This protrusion is more prominent in men and moves upwards and then downwards during each swallow. The larynx is suspended from the hyoid bone at the base of the tongue by a special muscle. The inner surface of the larynx is covered with multi-layered, ciliated epithelial tissue. There are two pairs of folds facing each other towards the inside of the laryngeal cavity. Only the lower folds play a role in the formation of the voice. These are called the lower vocal cords. The upper folds are called the upper vocal cords. The lower vocal cords are stretched by the muscles related to them, they vibrate with the air exhaled from the lungs and thus the sound is produced. The larynx has a laryngeal valve as mentioned above and this valve prevents the food eaten from escaping into the trachea.

The trachea is a tube consisting of 16-20 horseshoe-shaped cartilages, 9-15 centimeters long and 1.5-2.7 centimeters in diameter. Since the trachea is made of horseshoe-shaped cartilages, its front and side parts are hard and its back parts are made of flexible skin. The inside of the trachea is covered with a mucous membrane covered with multilayered epithelium. The outer rows of epithelial cells have cilia. The mucous membrane has glands that secrete mucus. There are also glands between the epithelial cells that secrete mucus. These secretions of the glands and cells always keep the trachea moist. The cilia of the epithelial cells set these fluids into motion and provide a flow towards the larynx. Dust that comes to these areas during respiration is expelled with the help of this flow. The thyroid endocrine glands are located outside the larynx, in the front part and below. The trachea, which starts from the 7th thoracic vertebra and extends to the 4th small thoracic vertebra, divides into two branches at the lower part, one of which enters the left lung and the other the right lung, and then divides into thinner branches like tree branches. 

Thus, the branches gradually become thinner. These tubes, which are formed in different diameters inside the lungs, form an air tube system. The slightly thicker air tubes, including the two branches that branch off from the trachea, are called bronchi. The thinner tubes are called bronchioles. The bronchioles end in the lung cells, which contain many alveoli (sacs). The inner surfaces of the air tubes are covered with a mucous membrane, as in the larynx and trachea. On this membrane, there are epithelial cells with trembling hairs. The function of these hairs is to move the mucous discharge and expel dust that enters the lungs.