Cardiovascular system

apex 顶，上部

myocardium 心肌

epicardium 心外膜

Cardiovascular system

The cardiovascular system is made up of the heart and blood vessels. The heart

is situated between the lungs with its apex directed toward the left. The muscular

walls of the heart consist of three major "layers." The bulk of the walls is made up of

心血管系统由心脏和血管组成。心脏位于双肺之间，其顶部朝向左侧。心脏的肌性壁结构主要有三层。endocardium 心内膜

sac 囊

pericardium 心包

atrium 心房 atria (pl)

ventricle 心室

septum 膈

coat 层

tunic 膜

endothelium 内皮

aorta 主动脉

arteriole 微动脉，小动脉

epithelial 上皮的

a layer of cardiac muscle and is called the myocardium. The muscle is enclosed on

the outside by the epicardium and on the inside by the endocardium. The heart is also

covered completely by a fibrous sac called the pericardium.

The upper receiving chambers of the heart are the atria. The lower pumping

chambers are the ventricles. The interventricular septum separates the two ventricles;

the interatrial septum divides the two atria.

There are three major types of blood vessels, i.e., arteries, veins, and capillaries.

Arteries lead blood away from the heart. These blood vessels have the thickest walls

because they receive the pumping drive from the ventricles of the heart. There are

three coats (tunics) which resemble the three tissue layers of the heart. These are: 1)

the innermost membrane of endothelium, which forms a smooth surface over which

the blood may easily move; 2) the second, more bulky layer, which is made of

involuntary muscle combined with elastic connective tissue; and 3) and outer tunic,

which is made of a supporting connective tissue. The largest artery, the aorta, is about

1 inch in diameter and has the thickest wall. The smallest subdivisions of arteries, the

arterioles, have thinner walls in which there are very little connective tissues but

relatively more muscle. These smaller branches of the arteries carry blood to the

tiniest of blood vessels, the capillaries.

Capillaries have walls that are only one epithelial cell thick. The capillary walls

are transparent and are made of smooth plate like cells that continue from the lining

of the arteries. The walls are so thin that they can allow passage of oxygen and

nutrients out of the bloodstream and into the tissue fluid surrounding the cells. At the

心壁的主体由心肌构成，称为心肌（组织）。心肌外衬5

心外膜，内衬心内膜。心脏被称为心包的纤维囊性结

构包被。

心脏上部受血小室是心房，下部泵血小室为心室。10

室间隔将两心室分开，房间隔将两心房分开。

血管主要有三种类型，即动脉、静脉和毛细胞血

管。动脉从心脏移出血液。因要承受心室泵血压力，15

动脉血管壁最厚。类似于心脏的三层结构，动脉壁具

有三层，它们是①内部的内皮层，形成血液易于流动

的光滑表面；②较厚的第二层由非随意肌和弹性结缔20

组织构成；③外层由支持结缔组织构成。最大的动脉，

主动脉，直径约１英寸且管壁最厚。动脉的最小分枝

称为微动脉，其管壁相对较薄，含极少结缔组织但相25

对较多肌细胞。动脉的小分枝（小动脉）携血液至最

lining 内层

same time, waste products such as carbon dioxide and water pass out of the cells and

into the thin - walled capillaries. The capillary boundaries are the most important

center of activity of the entire circulatory system.

小的血管，毛细血管。

毛细血管壁只有单层上皮细胞厚，其透明并由延续动脉内层的光滑片状细胞构成。管壁极薄，允许氧及营养物质离开血流，进入（胞外）组织液。同时，Veins are thinner-walled than arteries. They conduct waste-filled blood toward

the heart from the tissues. Veins have little elastic tissue and less connective tissue 30

than arteries, and blood pressure in veins is extremely low compared with pressure in

venule 微静脉

valve 瓣膜

mass 肿块

oxygenate 氧合

pulmonary 肺的

pulmonary circuit 肺循环

replenish 补充

systemic circuit 体循环

arteries. The smallest veins, called venule, are formed by the union of capillaries.

Their walls are only slightly thicker than those of the capillaries. As the veins become

larger, the walls become thicker. However, veins have much thinner walls than those

of comparable arteries. Although there are three layer of material in the walls of the

larger veins, as in the artery walls, the middle tunic is relatively thin in vein walls.

Therefore, veins are easily collapsed, and slight pressure by a tumor or some other

mass may interfere with the return blood flow. Most veins are equipped with one-way

valves that permit the blood to flow in only one direction. They are most numerous in

the veins of the extremities.

The heart pumps blood through two circuits. The right side of the heart pumps

blood to the lungs to be oxygenated through the pulmonary circuit. Pulmonary

vessels include the pulmonary artery and its branches, and the veins that drain the

lung capillaries. The pulmonary arteries carry blood low in oxygen from the right

ventricle, while the pulmonary veins carry blood high in oxygen from the lungs into

the left atrium. This circuit concerns itself with eliminating carbon dioxide from the

blood and replenishing its supply of oxygen. The left side of the heart pumps blood to

the remainder of the body through the systemic circuit. This circuit is concerned with

supplying food and oxygen to all the tissues of the body and carrying away waste

materials from the tissues for disposal.

Blood returning from tissues other than the lungs enters the heart by way of the

venae cavae; the superior vena cava and the inferior vena cava. The venae cavae

empty into the right atrium. When the atria contracts, blood in the right atrium is

像二氧化碳及水等代谢产物离开细胞进入薄壁的毛细

血管。毛细血管网为整个循环细胞最重要的活动中心。

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静脉壁薄于动脉壁。它们引导来源于组织含代谢

废物的血液至心脏。静脉比动脉含更少弹性玫结缔组40

织。与动脉相比，静脉血压极低。最小的静脉（微静

脉）由毛细血管汇集而成。微静脉壁略厚于毛细血管

壁。随着静脉变大，管壁变厚。但静脉壁薄于同等级

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动脉。像动脉壁一样，大静脉也具有三层结构，但静

脉壁的中层相对较薄。因此，静脉易于塌陷，肿瘤或

其它肿块的轻微压力可干扰血液回流。许多静脉具有

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单向瓣膜，使血液单向流动。四肢静脉瓣膜更多。

心脏经双循环泵血，右心将血液泵入肺，经肺循

vena cava 腔静脉

semilunar 半月形的

forced through the tricuspid valve into the right ventricle. When the ventricles

contract, blood in the right ventricle is forced through the pulmonary semilunar valve 55

into the pulmonary artery; at the same time, the tricuspid valve closes to prevent the

backward flow of blood into the atrium. Blood that enters the pulmonary artery is

carried to the lungs. There it undergoes oxygenation, a process in which carbon

环氧合，肺血管包括肺动脉及其分枝，和毛细血管流入的静脉。肺动脉运送来自于右心低氧的血液，而肺静脉将来自于肺的富氧血液运至左心房。肺循环负责从血中排除二氧化碳并补充氧气。左心将血液经体循dioxide (a waste product of cellular metabolism) is exchanged for oxygen from the

tricuspid valve 三尖瓣

mitral valve 二尖瓣

bicuspid valve 二尖瓣

ascending aorta 升主动脉

aortic arch 主动脉弓

thoracic 胸的

thoracic aorta 胸主动脉

vertebral 脊骨的，脊椎的

vertebral column 脊柱

pleura 胸膜

abdominal 腹部的

abdominal aorta 腹主动脉

cavity 腔

environment.

Oxygenated blood returns to the heart by way of pulmonary veins, which empty

into the left atrium. Atrial contractions force blood from the left atrium through the

mitral valve, also called bicuspid valve, into the left ventricle. When the ventricles

contract, blood in the left ventricle is force through the aortic semilunar valve into the

aorta, the body’s largest artery, for distribution to the tissues. The aorta is one

continuous tube divided into the following regions: 1). the ascending aorta, which is

near the heart and inside the pericardial sac; 2). the aortic arch, which curves from the

right to the left, and also extends backward; 3). the thoracic aorta, which lies just in

front of the vertebral column behind the heart and in the space behind the pleura; and

4). the abdominal aorta, which is the longest section of the aorta, spanning the

abdominal cavity.

There are two phases of the heartbeat: diastole (relaxation) and systole

(contraction). This diastole-systole cardiac cycle (relaxation-filling, then contraction-

pumping) lasts about 0.9 second and occurs between 70 and 80 times per minute.

This is to say, the ventricles pump blood into the arteries regularly about 70 to 80

times a minute. The force of ventricular contraction starts a wave of increased

pressure which begins at the heart and travels along the arteries. This wave is called

the pulse. It can be felt in the arteries that are relatively close to the surface,

particularly if the vessel can be pressed down against a bone. At the wrist the radial

artery passes over the bone on the thumb side of the forearm, and the pulse is most

commonly obtained here. Other vessels sometimes used for obtaining the pulse

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环泵入机体其它部位，负责为全身组织提供营养及氧

气，并运走要处理的代谢废物。

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来自于除肺外其它全身组织的血液经腔静脉回流

至心脏。腔静脉将血液运至右心房。当心房收缩时，

右房内血液将三尖瓣进入右室。当心室收缩时，右室

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血液经肺半月瓣进入肺动脉，同时三尖瓣关闭防止血

液回流至心房。进入肺动脉的血液被运至肺，进行氧

合过程，即与周围环境进行氧及二氧化碳的交换。

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氧合血经肺静脉回流至心脏，进入左心房。心房

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收缩驱动左房血液经二尖瓣进入左室。当心室收缩时，

include the carotid artery in the neck and the dorsalis pedis artery of the top of the

diastole 舒张期

systole 收缩期

左室内血液经半月瓣流入主动脉，为全身组织供血。连续管状结构的主动脉分为如下节段：①升主动脉，foot.

Blood pressure is the force exerted by blood on the walls of the arteries. This

pressure varies over the course of the cardiac cycle, increasing when blood is ejected 85

近心且处于心包内。②主埃及弓，由右向左呈弧形前from the heart (during systole), and decreasing as the heart relaxes (during diastole).

行，亦向后延伸。③胸主动脉，位于心后脊柱前胸膜Since the pressure inside the blood vessels varies with the condition of the heart and

radial 桡侧的，桡骨的

carotid artery 颈动脉

dorsalis pedis 足背

systolic pressure 收缩压

diastolic pressure 舒张压

the arteries as well as with other factors, the measurement of blood pressure together

with careful interpretation may prove a valuable guide in the care and evaluation of a

person’s health. The pressure decreases as the blood flows from arteries into

capillaries and finally into veins. Ordinarily, measurements are made of arterial

pressure only. The instrument used is called a sphygmomanometer. The two

measurements made are of: 1) the systolic pressure, which occurs during heart muscle

contraction and averages around 120, expressed in millimeters of mercury; and 2) the

diastolic pressure, which occurs during relaxation of the heart muscle and averages

around 80 millimeters of mercury. A blood pressure recording of 120/80 mmHg,

therefore, indicates a systolic pressure of 120 and a diastolic pressure of 80

millimeters of mercury. Blood pressure is valuable diagnostic measurement that is

easily obtained.

后。④腹主动脉，是主动脉最长的部分，贯穿腹腔。

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心跳有两期：即舒张期和收缩期。这种舒张收缩

心动周期（舒张充盈，然后收缩射血）持续约9秒，95

每分心博介于70－80次之间。这就是说，心室泵血入

动脉通常每分70－80次。心室收缩力启动一个压力上

升波，这一波型起始于心并沿动脉行进，称为脉搏。脉搏可在相对接近表层的动脉感知，尤其是当动脉可被按压于骨上时。因桡动脉越过前臂拇指侧骨，脉搏可在腕部触及。其它用检查脉搏的血管包括颈部的颈动脉和足背部的足背动脉。

血压是血液施加于动脉壁的压力。整个心动周期

血压是变化的，（收缩期）心脏射血时血压升高，而（舒张期）心脏扩张时血压下降。因血管内压力变化与心脏状况、动脉以及其它因素有关，测量血压并认真解读会对个人健康状况评价及监护起重要指导作用。随着血液从动脉流经毛细血管，最终至静脉，血压下降。通常只测动脉血压。所用仪器叫血压计。测得的血压是：①收缩压，心肌收缩时形成，平均值120左右，以毫米汞柱表示；②舒张压，心肌舒张时形成，平均80mmHg左右。因此，记录为120/80 mmHg的血压提示收缩压120，舒张压80 mmHg。血压是较易获得有价值的诊断指标。