When the blood passes through our two lungs, it absorbs the oxygen present there and at the same time gets rid of its content of carbon dioxide from the metabolism of the cells. This automatically happens when we breathe.
The spongy lung tissue contains so many thin thin-walled air-filled alveoli that the total area over which the exchange of oxygen and carbon dioxide takes place is approximately 80 square metres (860 square feet).
The right lung is divided into three sections called lobes which are separated by a membrane of connective tissue. The left lung is divided into two lobes. Each lung is surrounded by a thin membrane of connective tissue called the pleura which can also be affected by inflammation (pleurisy).
In pneumonia, the lung tissue swells, becomes red, warm, and painful just as in any other kind of inflammation. The symptoms of pneumonia vary a lot. They can be few and light or very severe with high fever - according to the type of infection and how large a part of the lung is affected and the degree of weakening. Pneumonia can affect one or more lobes of the lung and it can affect one or both lungs.
A typical pneumonia is caused by inhaling bacteria, for example pneumococci, which, because of weakening of the immune system or other kind of general weakening has the opportunity of propagating in the alveoli. Another way of infection is through the naturally occuring bacteria in our throat entering the lungs.
When the infection spreads in the alveoli of the lungs, laboured breathing will be the result.
The symptoms begin with shivers and high fever. Stitches in the chest can occur which originate from the infected pleura. The patient affected by pneumonia will have a rapid and shallow breathing, and will develop a dry cough that changes successively with mucus developing.
In some bacterial infections, the expectorate can be bloody. In cases where the supply of oxygen is reduced because of inadequate breathing, the colour of the skin can become bluish because of the low oxygen content of the blood.
Weakened, elderly individuals who are not capable of breathing properly and whose coughing reflex is reduced will not be able to adequately clean their airways of microorganisms. This increases the risk of pneumonia. These fragile, elderly persons will often suffer from confusion during a pneumonia attack.
In some cases, the pneumonia is caused by a spreading bronchitis. This is called bronchopneumonia.
Rare cases of pneumonia can also be caused by infection with bacteria from other infected organs which are transported to the lungs via the bloodstream.
In rare cases, vomit and chemical toxins can also end up in the airways and cause both chemical and bacterial damage to the lung tissue.
Pneumonia caused by vira, e.g. cold vira and mycoplasma, rarely causes a very high fever. For this reason, these diseases are called cold pneumonia even though the expression is somewhat misleading. They are typically accompanied by a dry cough and pronounced tiredness - especially in the middle of the day.
