2021/7/241The respiratory system can be divided into two parts:The upper respiratory tracts:mouth, nose & nasal cavity,pharynx and larynx The lower respiratory tracts:trachea,bronchi,bronchioles,alveoli,diaphragm and lungsFunctionTransports air into the lungs and facilitates the diffusion of oxygen into the blood stream. It also receives waste carbon dioxide from the blood and exhales it. 2021/7/242Mouth, nose & nasal cavity: The function of this part of the system is to warm, filter and moisten the incoming air.Pharynx: Here the throat divides into the trachea (wind pipe) and esophagus (food pipe). There is also a small flap of cartilage called the epiglottis which prevents food from entering the trachea. Larynx: This is also known as the voice box as it is where sound is generated.It contains the vocal cords. It also helps protect the trachea by producing a strong cough reflex if any solid objects pass the epiglottis. The Upper Respiratory Tracts2021/7/243Trachea Muscular cartilaginous tract that is a continuation of the larynx; 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 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. Alveoli 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 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 Tracts2021/7/244The lungs take 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 chest, 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 lobes. The left lung has two lobes. 2021/7/245When you breathe, the air:enters the body through the nose or the mouthtravels 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 one to the left lungin the lungs, the main-stem bronchi divide into smaller bronchiand then into even smaller tubes called bronchioles bronchioles end in tiny air sacs called alveoli 2021/7/246Diaphragm located below the lungs, attaching to the lower ribs, sternum and lumbar spine and forming the base of the 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 air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its domelike shape, and air is forced out of the lungs. 2021/7/247The 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 contains an extensive network of blood vessels, these vessels bring carbon dioxide into the lungs for removal, and take oxygen from the lungs to the body.2021/7/2482021/7/249个人观点供参考，欢迎讨论