1、Respiratory System,The respiratory system can be divided into two parts: The upper respiratory tracts:mouth, nose it divides into two main bronchi, each of which ends in a lung, and allows air to pass. The inner membrane of the trachea is covered in tiny hairs called cilia, which catch particles of

2、dust which we can then remove through coughing. Bronchi The trachea divides into two tubes called bronchi, one entering the left and one entering the right lung. Bronchi branch into smaller and smaller tubes known as bronchioles. Bronchioles terminate in grape-like sac clusters known as alveoli. Alv

3、eoli are surrounded by a network of thin-walled capillaries. Bronchioles: Tertiary bronchi continue to divide and become bronchioles, very narrow tubes. There is no cartilage within the bronchioles and they lead to alveolar sacs. Alveoli: Individual hollow cavities contained within alveolar sacs (or

4、 ducts). Alveoli have very thin walls which permit the exchange of gases oxygen and carbon dioxide. They are surrounded by a network of capillaries, into which the inspired gases pass. There are approximately 3 million alveoli within an average adult lung.,The Lower Respiratory Tracts,The lungs take

5、 in oxygen, which all cells throughout the body need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the bodys cells. The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the ch

6、est, or the thorax (the part of the body between the base of the neck and diaphragm). The lungs are separated from each other by the mediastinum, an area that contains the following: heart and its large vessels trachea (windpipe) esophagus thymus lymph nodes The right lung has three sections, called

7、 lobes. The left lung has two lobes.,When you breathe, the air: enters the body through the nose or the mouth travels down the throat through the larynx (voice box) and trachea (windpipe) goes into the lungs through tubes called main-stem bronchi one main-stem bronchus leads to the right lung and on

8、e to the left lung in the lungs, the main-stem bronchi divide into smaller bronchi and then into even smaller tubes called bronchioles bronchioles end in tiny air sacs called alveoli,Diaphragm located below the lungs, attaching to the lower ribs, sternum and lumbar spine and forming the base of the

9、thoracic cavity, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continually, and most of the time, involuntarily. Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls

10、 air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its domelike shape, and air is forced out of the lungs.,The tube which carries the air from the mouth is called the Trachea or Windpipe, this later divides into two at which point it becomes the Bronchi and divides the air equally to each lung. Once the air enters the lungs it passes through a fine spongy structure which con