what is lungs?

lungs are two in number having length of 25 to 35 cm and width of 10 to 15 cm and having the weight of 0.8 to 1.2 kg and are the organs where the gaseous exchange takes place. Protection Lungs is usually protected by a double membranous structure called pleura. The outer layer of pleura is attached to thoracic cavity while the inner is attached to lungs. In between these membrane fluid is present called interpleural fluid which is secreted by the inner layer of pleura. These membrane along with fluid protect and nourish the lungs. Ribs also provide protection to it. Location Apex of lungs is extended beyond first rib up to clavicle having its lower end on diaphragm and is located in the thoracic cavity. Blood supply Lungs recieves upto 9 percent of the stroke volume or 450ml per min. Asymmetric volume Lungs have asymmetric volume the right being 56 while 44 to 46 percent is of the left one. Right lung is quite smaller and has larger diameter while the left being narrow and longer. Lung volume during breathing Lungs have a total volume or capacity of about 5.5 litres in which 0.5 litres volume is exchange during normal breathing while upto 3.5 litres of lung volume is exhaled or inhaled during forceful breathing. About 1.5 litre of lung volume is always retained known as residual volume. Control of lung volume Lung volume during inhalation or exhalation is controlled by intercoastal muscle through intercoastal nerves and muscle of diaphragm through phrenic nerves. lobes of lungs... the right lung has three lobes called superior lobe inferior lobe and middle lobe while the left lung has only two lobes called superior lobe and inferior lobe. bronchi and bronchioles... the bronchi leading to right lung is short and wide as compare to left lung bronchi which is long and thin. bronchi divide to form primary bronchi. primary bronchi approaching to right lung 3 while towards the left lung are 2.bronchi divides and re divides to form small diameter structure called bronchioles which control the distribution of air in to the lungs. they are about 1 mm in diameter. alveoli...bronchioles leading to sacs like structure inside the lungs called alveoli which are spongy in nature. alveoli are about 0.1 micrometer in diameter and are made of squamous epithelium cells. alveoli are also called respiratory surfaces because they are the site where The actual gaseous exchange between the body and the external environment takes place. alveoli also contain immune substances called surfactants which reduce surface tension inside the alveoli to make it flexible and also provide protection against foreign harmful particles. artery and vein...the artery that takes the blood to the lung is called pulmonary artery having de oxygenated blood which surrounds the alveoli where gaseous exchange takes place and the blood become oxygenated. The oxygenated blood is then carry away from the lungs by the pulmonary vein.. some common related diseases... emphysema.. the type of lung disease in which the walls of bronchi and bronchioles become constricted and thin and alveoli swollen or burst is called emphysema. Usually smoking and air pollution are its causes. pneumonia.. pneumonia is the lung disease in which air sacs or alveoli are filled with fluid like substances.. they are usually caused by bacteria and virus line streptococcus pneumonia. lung cancer.. it is one of the most common type of cancer in the world. it main cause is constant smoking other factors while air pollution or exposure to toxin can also cause it. These are some general information about hope it enhances your knowledge.