Text b. The Respiratory System
The respiratory system is the system of the body dealing with breathing. When we breathe, the body takes in the oxygen that it needs and removes the carbon dioxide that it doesn't need.
First the body breathes in the air sucking through the nose or mouth and down through the trachea (windpipe). The trachea is a pipe shaped by rings of cartilage. It divides into two tubes called bronchi. These carry air into each lung. Inside the lung, the tubes divide into smaller and smaller tubes called bronchioles. At the end of each of these tubes are small air balloons called alveoli.
Capillaries, which are small blood vessels with thin walls, are wrapped around these alveoli. The walls are so thin and close to each other that the air easily seeps through. In this way, oxygen seeps through into the bloodstream and carbon dioxide, in the bloodstream, seeps through into the alveoli, and then it is removed from the body when we breathe out.
The diaphragm is the muscle that controls the breathing process. As the diaphragm flattens, it causes the chest to expand and air is sucked into the lungs. When the diaphragm relaxes, the chest collapses and the air in the lungs is forced out.
Ex. 15. Look at picture 3 and complete the sentences with these words:
mediastinum covers is divided are covered
pleural cavities lines is lined are surrounded
Picture 3.
The thorax ….. into three components.
….. is the central compartment.
The mediastinum ….. by the pericardium.
The lateral compartments are known as ….. .
The lungs ….. by the pleura.
Parietal pleura ….. the outer walls of the cavity.
Visceral (pulmonary) pleura ….. the lungs.
All three compartments ….. by the ribs.
Ex. 16. Now add one of these clauses to the sentences (1) to (5) and write them out as a paragraph:
which contains the heart, esophagus, trachea, thymus and various blood vessels and nerves.
which contain the lungs.
which also surround the heart.
which are called the mediastinum and the pleural cavities.
which also lines the pleural cavities.
Ex.17. Translate text C at sight.
Text C. Intricate Construction
Our two lungs are made up of a complex latticework of tubes, which are suspended, on either side of the heart, inside the chest cavity on a framework of elastic fibers. Air is drawn in via the mouth and the nose, the latter acting as an air filter by trapping dust particles on its hairs. The air is warmed up before passing down the windpipe, where it's divided at the bottom between two airways called bronchi that lead to either lung.
Within the lungs, the mucus-lined bronchi split like the branches of a tree into tens of thousands of ever smaller tubes (bronchioles), which connect to tiny sacs called alveoli. The average adult's lungs contain about 600 million of these spongy, air-filled structures. There are enough alveoli in just one lung to cover an area roughly the size of a tennis court.
The alveoli are where the crucial gas exchange takes place. The air sacs are surrounded by a dense network of minute blood vessels, or capillaries, which connect to the heart. Those that link to the pulmonary arteries carry deoxygenated blood that needs to be refreshed. Oxygen passes through the incredibly thin walls of the alveoli into the capillaries and is then carried back to the heart via the pulmonary veins. At the same time, carbon dioxide is removed from the blood through the same process of diffusion. This waste gas is expelled as we breathe out.
The rate at which we breathe is controlled by the brain, which is quick to sense changes in gas concentrations. This is certainly in the brain's interests