Essay --

The respiratory system is an ingeniously constructed system to carry out it’s cardinal function, oxygenation of blood and exhalation of carbon dioxide, with minimal energy cost (McCance et al., 2014). Situated in the thorax, respiration is efficiently carries out the processes of inhalation and exhalation air - also known as ventilation, in which lung is central unit. The whole respiratory system is divided into distinct zones: the upper and lower respiratory zones, also known as conducting and respiration portions respectively. The conducting portion comprises a series of open, unobstructed tubes for the movement of gases in and out of the lungs. The air conducting part begins as a system of cavities comprising of the nasal cavity, para-nasal sinuses and nasophyrnx - which begin the cleaning, warming, and moistening of the air entering the anterior nares. These cavities are lined by respiratory epithelium with two cell types, which line nearly all the airways pathways. Goblet cells are the one which secretes mucus that traps particulate matter, and the pseudostratified columnar ciliated cells that bear surface cilia that beats in a unidirectional rhythm only i.e. towards the mouth – known as the epithelial ciliated cells. The finger-like projections, cilia, move the debris and mucus full of pathogenic material to the oral region, where it coughed out or swallowed. The abundant blood vessels beneath the epithelium layer warm the inhaled air. The serous glands in the submucosa layer and the mucous secretions of the goblet cells aid in the entrapment of the particulate matter and in the absorption of harmful gases such as SO2 and bacteria. It also moistens the inhaled air. The air then enters a single tube - the trachea - that div... ... allows the lung to carry out its function efficiently. The thin-walled alveoli allow gaseous exchange to take place efficiently, and the small area allows increased surface area for diffusion to take place rapidly. The blood vessels and capillaries enable the lungs to have a good blood supply which transport oxygen around the body. There is a major structure of the lung referred to as the pleural sac that protects the lungs structure, prevent any damage its morphology. The lung is soft, it’s a delicate tissue that is easily damaged by its surroundings such as; bones, muscles and even connective tissues. Each lung is protected with this pleural sac which is a double layer or moist tissue. Between the two layers of tissue there is a microscopically thin layer of water that acts as a lubricate which makes the two tissues adhere to each other (Brooker et.al 2011).