Section 3 Medical Literature 第三部分 医学文献
Part 1.
The respiratory system is made up of many hollow organs(mouth and nose，larynx and pharynx,lungs)and of air canals(trachea,bronchi,bronchioles),which allow the body to constantly perform gaseous exchanges1) with the outside environment.It is divided into:
Air pathways or respiratory tracts:made up of nasal cavities and paranasal sinuses2),of the mouth,the pharynx,the larynx,the trachea and of the bronchial pathways(bronchi and bronchioles)，which branch out and distribute to the lungs:all these structures have a bony or cartilaginous3) skeletal structure，which guarantees the easy passage of air.The mucous，that covers the wall of these hollow organs，has many functions:it warm up the air，thanks to its high vascularization；it wets it，thanks to the secretion of many glands distributed inside；it filter it，thanks to the mucous，which “glues”dust carrying it outside，through a constant movement of ciliate cells4);
The lungs:due to their cavity-filled structure(pulmonary alveoli or respiratory cells)the lungs are very spongy5) looking，and they collect the air，which is inspired through the pulmonary airways.Just like the wall of the blood capillaries of the pulmonary arteries and veins，the alveolar wall is also very thin:this facilitates the passive diffusion of the respiratory gasses(based on the degree of the concentration)
The lungs are very elastic organs,and they are able to easily stretch and contract.Each lung is protected by pleura6),a membrane divided by a visceral leaflet,attached to the external surface of the lung,and a parietal leaflet,stretched out on the wall of the pulmonary recess，closely connected to both the rib cage and the superior surface of the diaphragm.
This way，each lung is surrounded by a space(pleural cavity7))filled with an extremely thin liquid layer(pleural liquid)at a pressure lower than the atmosphere one.Besides wetting the pleural leaflets，facilitating their sliding movement,it guarantees the adherence of the leaflets,and indirectly that between lungs，rib cage and diaphragm:in this way it allows thoracic movements to be transmitted to the lungs.If for any reason，air reaches the pleural cavity(pneumothorax),the elasticity of the pulmonary tissue is completely reduced and there is an almost total loss of the respiratory.
注释：
1）gaseous exchanges气体交换
2）paranasal sinuses鼻旁窦
3）cartilaginous［ka：tiˈlædʒinəs］软骨的
4）ciliate［ˈsiliit］cells纤毛细胞
5）spongy［ˈspʌdʒi］海绵状的，多孔的
6）pleura 胸膜
7）pleural cavity胸膜腔
Part 2.
A gas diffuses from a region of high partial pressure1) to a region of low partial pressure.
Partial pressure In a mixture of gases，each gas exerts a pressure proportional to its fraction in the total mixture.Therefore，the total pressure of mixture is the sum of the pressure of the individual gases.The partial pressure of a particular gas is equal to its percentage concentration times the total pressure of the gases mixture，the force that drives a gas across the membrane.That is much like water running down stream.This process is entirely a passive one brought about by diffusion.
Partial pressures of O2 and CO2 The Partial pressures of O2 and CO2 in alveolar2) air，venous blood，arterial blood and tissue are shown in the following tablet.(https://www.daowen.com)
The Partial pressures of O2 and CO2 in alveolar air,venous blood,arterial blood and tissue
1mmHg=0.133322 kPa.
According to the partial pressure shown in the above tablet，oxygen diffuses from alveoli to venous blood and from arterial blood to tissue.Carbon dioxide diffuses from venous blood to alveoli and from tissue to arterial blood.
注释：
1）partial pressure 分压
2）alveolar 肺泡的，齿槽的
Part 3.Some symptoms of respiratory disease
Cough Cough is probably the commonest symptoms of respiratory disease and is usually a response to irritation of the respiratory tract.Cough is one of the most important features of chronic bronchitis，and also occurs in patients with chest infectious as well as in asthmatics1)，where it may be particularly common at night.
Sputum Sputum is the substance coughed up from the respiratory tract.The color of sputum may give a clue as to its cause：for example,respiratory infection usually results in thick yellow or green sputum，whereas pink，frothy2) sputum may indicate pulmonary oedma3).
Hemoptysis Hemoptysis means coughing up blood.It may indicate a chest infection,but may be a symptom of more serious respiratory disease such as tuberculosis or bronchial carcinoma.
Breathlessness4) Breathlessness is a symptom of a range of respiratory diseases as well as being a symptom of cardiac failure.
Wheezing Wheeze is a characteristic musical sound caused by gas flow through narrowed airways.Patients may complain of wheeze and it may be audible on auscultation of the chest.It is characteristic of pulmonary disease such as asthma，chronic bronchitis and chest infection，all of which can result in airways narrowing.
Chest pain In certain respiratory conditions patients may complain of chest pain.Such conditions include infection，pleuritis，pulmonary infarction and pneumothorax5).
注释：
1）asthmatics气喘的，似气喘的
2）frothy多泡的，起泡的，有泡沫的
3）oedma 水肿
4）breathlessness呼吸急促
5）pneumothorax 气胸