The lungs are the main organs of the respiratory system. There are two lungs in the human body located in the lateral cavities of the chest. The lungs are separated from each other by the

The Lungs

The lungs are the main organs of the respiratory system. There are two lungs in the human body located in the lateral cavities of the chest. The lungs are separated from each other by the mediastinum. The lungs are covered with the pleura. They are conical in shape. Each lung has the base, apex, two borders and three surfaces.

The lung has the apex extending upward 3-4 centimetres above the level of the first rib.

The base of the lung is located in the convex surface of the diaphragm. The posterior borders of the lungs are on each side of the spinal column. The anterior border is thin and overlaps the pericardium.

The weight of the lungs varies according to many conditions. In the adult male the weight of the lungs is about 1,350 gr. The right lung is about 15% heavier than the left one. The vital capacity of the lungs is 3.5-4 liters in the male and it is 3-3.5 liters in the female.

The right lung consisting of three lobes is heavier than the left one because the latter consists only of two lobes. The lower lobe of the left lung is larger than the upper one.

In infants the lungs are of a pale rose colour, but latter they become darker.

The lung is covered with an external serous coat, i.e. with visceral layer of the pleura. The parenchyma or proper substance of the lungs consists of the bronchial tree with elastic tissue and vessels.

Pulmonary ventilation is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation). Under normal conditions, the average adult takes 12 to 15 breaths a minute. A breath is one complete respiratory cycle that consists of one inspiration and one expiration.

Factors such as age, sex, body build, and physical conditioning have an influence on lung volumes and capacities. Lungs usually reach their maximum in capacity in early adulthood and decline with age after that.

The respiratory conducting passages are divided into the upper respiratory tract and the lower respiratory tract. The upper respiratory tract includes the nose, pharynx, and larynx. The lower respiratory tract consists of the trachea, bronchial tree, and lungs. These tracts open to the outside and are lined with mucous membranes. In some regions, the membrane has hairs that help filter the air. Other regions may have cilia to propel mucus.

VOCABULARY

1. respiratory system 2. lateral cavities 3. mediastinum 4. pleura 5. extending upward 6. convex surface 7. posterior borders 8. to overlap 9. vital capacity 10. in infants 11. of a pale rose colour 12. external serous coat 13. visceral 14. parenchyma 15. breathing (breath, to breathe) 16. inspiration (inhalation) 17. expiration (exhalation) 18. complete respiratory cycle

19. lung volumes and capacities 20. decline with age 21. respiratory conducting passages 22. are lined with mucous membranes 23. cilia 24. in early adulthood 25. oxygen 26. to oxidize 27. under normal conditions 28. to cough (up) 29. sputum (phlegm) 30. loose (dry) cough 31. mucoid 32. due to the presence of pus (purulent) 33. blood-stained 34. to give up smoking 35. haemoptysis 36. dispnoea 37. c/o complains of

Cough

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