Section 3 Medical Literature 第三部分 医学文献
Part 1.
Arteriosclerosis is a generic term for a number of diseases in which the arterial wall becomes thicker and loses elasticity.Atherosclerosis is the most important；others include monckeberg’s arteriosclerosis and arteriosclerosis.
Major risk factors for atherosclerosis are(1)hypertension，(2)elevated serum lipid-elevated low density lipoprotein1) and reduced levels of high density lipoprotein，(3)cigarette smoking，(4)diabetes mellitus，(5)obesity，(6)male sex，and(7)family history of premature atherosclerosis.Presumed risk factors include physical inactivity and increasing age.Hypertriglyceridemia2) is commonly associated with obesity.The prevalence of clinical manifestations of atherosclerosis increases in postmenopausal3) women and begins to approach that in age-matched men.Although personality type has been proposed as a risk factor，its role is controversial.
Arteriosclerosis is generalized.Hypertrophy of the media and subintimal fibrosis with hyaline degeneration develop in small muscular arteries or arterioles(arteriolosclerosis)as well as in large vessels.During the age process，fibrosis and some intimal thickening develop，with weakening and disruption of the elastic lamellae4) in the walls of the great arteries.The media atrophies to a certain extent，and the lumen of aorta or ＞1of its branches widens，and may lead to aneurysm5).The process may have a genetic basis.
注释：
1）low density lipoprotein［ˌlipəˈprəuti：n］低密度脂蛋白
2）hypertriglyceridemia［ˌhaipətraiˌglisəraiˈdi：miə］血甘油三酯过多，高甘油三酯血症
3）postmenopausal［ˌpəustmenəˈpɔ：zəl］绝经后的
4）elastic lamellae［ləˈmelə］弹性层
5）aneurysm［ˈænjuərizəm］动脉瘤
Part 2.
The heart lies in the lower part of the left side of the chest and consists of four muscular chambers:two atria and two ventricles.The muscle of the heart is called the myocardium.the anterior surface of the heart is formed mainly by the right ventricle and is in contact with the ribs and sternum1)(Fig.4.1).The inferior surface of the heart is formed mainly by the left ventricle and is in contact with the diaphragm2).The posterior surface of the heart is formed mainly by the left atrium.This surface is also known as the base of the heart.The apex which is anterior to the rest of the heart consists only of the left ventricle and forms an important clinical landmark when assessing the size of the heart.In an adult，the heart is about the size of a clenched fist.The atria are thin-walled chambers that receive blood from the large veins and deliver it to the ventricles.The walls of the ventricles are much thicker than those of the atria—the wall of the left ventricle being thickest.The two ventricles are separated by a muscular sheet known as the interventricular septum3).The contraction of the ventricles provides the force required to pump the blood round the pulmonary and systemic circulations.
Fig.4.1 External anatomy of the heart
The aorta and the pulmonary trunk arise from the left and right ventricles respectively at the superior pole of the heart(Fig.4.1).The superior and inferior vena cava open into the upper and lower parts of the right atrium.There are four pulmonary veins which opern into the back of the left atrium.The junction between the atria and the ventricles is marked by the atrioventricular groove and the junction between the ventricles both posteriorly and anteriorly is marked by the interventricular grooves4).The atria are separated from the ventricles by a fibrous skeleton on which the four heart valves are located.These serve to ensure the unidirectional flow of blood from the atria to the ventricles and from the ventricles into the pulmonary artery and aorta.Back flow of blood from the ventricles into the atria is prevented by the atrio-ventricular valves5).On the right side of the heart,the atrio-ventricular valve(the tricuspid valve)consists of the roughly triangular flaps of fibrous connective tissue.On the left side，the atrio-ventricular valve consists of two such flaps and is known as the mitral(or bicuspid)valve.Back flow of blood from the pulmonary valve，while back flow of blood from the aorta into the left ventricle is prevented by the aortic valve.The pulmonary and aortic valves are also known as the semilunar valves6).The valves and chambers of the heart are lined by a cellular layer known as the endocardium.(https://www.daowen.com)
注释：
1）sternum 胸骨
2）diaphragm 膈肌
3）interventricular septum 室间隔，心室间隔
4）interventricular grooves 室间沟
5）atrio-ventricular valves 房室瓣
6）semilunar valves 半月瓣
Part 3.
Valvular heart disease1) can be congenital(i.e.the patient is born with the problem)or acquired(the pathology occurs as a result of illness after birth).The spectrum of valvular heart disease，particularly in the developed world，is changing as some diseases such as rheumatic heart disease become much rarer.From a pathologist’s viewpoint，disease of a valve can lead to an incompetent valve that allows blood back into the chamber from which it was expelled or a stenotic2) valve that impedes blood flow from one chamber to the next.A stenotic valve can of course also be incompetent.The common congenital valve diseases are described below.
Bicuspid aortic valve About 1% of the adult population has a congenital bicuspid aortic valve compared to the tricuspid valve found in the rest of the population.The two cusps may be of the same or different sizes and there may be a median raphe(a fibrous bar)that extends from one cusp to the wall of the aorta.The bicuspid valve is much more prone to calcification than a normal valve and young patients may present with the symptoms and signs of a heavily calcified valve3)(aortic stenosis/incompetence)that is then found to be bicuspid.
Aortic valve stenosis A complete fibrous tissue membrane may be found instead of a normal valve.Occasionally，a uni-commissural valve is found—effectively a complete fibrous sheet with a tear towards one side.Subvalvular and supravalvar congenital stenosis can also occur.
Aortic valve incompetence Aortic valve incompetence may occur because of an intrinsic abnormality of the valve itself or because of dilatation of the aortic root.Aortic root dilatation may be idiopathic，but can be seen in Marfan’s syndrome and osteogenesis imperfecta.In both the idiopathic and Marfan’s cases，accumulation of mucin occurs in the wall of the aorta.
Mitral valve incompetence In the condition “floppy mitral valve” the valve cusps are larger than normal，dome-or parachute-shaped and look rather myxoid/mucoid.The chordae tendineae often also have this appearance and are elongated.Congenital pulmonary valve stenosis(or sub-or supravalvar stenosis)also occurs.
注释：
1）valvular heart disease 心脏瓣膜病
2）stenotic 狭窄的
3）a heavily calcified valve 瓣膜严重钙化