Sputum in everyday speech is any content that is expelled from the oral cavity. The doctor thinks mainly of the contents that are expelled by expectoration from the deeper parts of the respiratory system, from the airways and lungs. In many diseases of the respiratory system, the amount of sputum expelled per day can be more than one liter per day. It depends on the disease whether the sputum will be mucous, mucopurulent, purulent, bloody, frothy. The color of the sputum can be red, black, brown and green. The coughed contents can be pure blood or a clear clear liquid such as spring water. Most people like to look at their own sputum from time to time, especially if there is a respiratory illness. In the past, doctors diagnosed many lung diseases solely on the basis of the appearance of sputum. Even today, despite numerous diagnostic possibilities, sputum examination is often an irreplaceable test. Sometimes just looking at the sputum can diagnose the disease.

Purulent sputum always indicates the existence of a purulent focus in the respiratory system. These are most often cavities filled with pus, from where it can enter the airways and be expelled by coughing. Fertilization can be caused by many types of bacteria. They come to the lungs by inhalation with the help of blood or from a diseased adjacent organ. Limited purulent foci may develop after pneumonia and inhaled foreign body. From the pus cavity, pus gradually penetrates the airways and is expelled by coughing. One of the most common causes of purulent sputum is dilated airways, the bronchi.

The sight of sputum containing larger or smaller amounts of blood often leads to unnecessary panic. Spit blood is not always coughed up blood. Therefore, blood in the sputum does not mean that it originates from the lungs. Spit blood mixed only with saliva usually comes from the oral cavity, pharynx, tongue, and even from the salivary glands. There is no mucus in that blood that builds up in the airways. Blood mixed with mucus can also originate from the nose, if the mucus of the nasal cavity is drawn into the oral cavity. Prolonged expulsion of bloody or bloody sputum always requires a medical examination. Such sputum can also be one of the first signs of lung cancer, especially if it is about people over forty years of age, men, smokers.

Accumulation of a larger amount of mucus in the airways causes a coughing sensation. By coughing, excess mucus is expelled to maintain complete patency and cleanliness of the airways. Mucous and more or less frothy sputum without odor is a pure product produced by numerous mucous glands in the airways. The formation of mucus in the airways may be intensified. Irritants that can cause increased mucus production are often infections, inflammation, irritating gases, dust, cold, sudden changes in temperature. But all these causes only lead to transient, short-term and excessive mucus production. In rare cases, there may be permanent, continuous and excessive production of mucus in the airways due to the increased ability of the glands to produce mucus and due to the increased number of mucus glands. Then the body tries to maintain airway patency (chronic bronchitis) with frequent coughing.