Transport in Animals
IGCSE Biology Topic 9 8:21 English narration · English + 中文 subtitles burned in
Chapters
Transcript
Your heart beats about a hundred thousand times a day, and it has never once stopped to rest.
你的心脏每天大约跳动十万次，而且从来没有停下来休息过。
It is not really one pump — it is two, side by side, sharing a wall.
它其实不是一个泵——它是两个泵并排在一起，共用一堵墙。
One side sends blood to your lungs.
一侧把血送到你的肺。
The other sends it to everywhere else.
另一侧把血送到其他所有地方。
Understand why there are two, and most of this topic falls into place.
理解为什么有两个，这个专题的大部分内容就都通了。
Welcome to transport in animals.
欢迎来到动物的运输。
The heart, the blood vessels, and the blood itself.
心脏、血管，还有血液本身。
Let's begin.
让我们开始吧。
Follow one drop of blood.
跟着一滴血。
It goes to the lungs, comes back to the heart, then goes to the body, and comes back again.
它去肺，回到心脏，然后去身体，再回来。
Two loops, one heart.
两个回路，一个心脏。
The circulatory system has three parts: a pump, which is the heart; a network of blood vessels; and valves that keep blood flowing one way only.
循环系统有三个部分：一个泵，也就是心脏；一个血管网络； 还有让血液只朝一个方向流动的瓣膜。
Now the supplement comparison.
现在是补充部分的比较。
A fish has a single circulation — its blood passes through the heart once on each trip round the body.
鱼是单循环——它的血液每绕身体一圈只经过心脏一次。
A mammal has a double circulation: the blood passes through the heart twice, once on the way to the lungs and once on the way to the rest of the body.
哺乳动物是双循环：血液经过心脏两次，一次是去肺的路上，一次是去身体其余部分的路上。
And here is the advantage, which is the mark: the blood can be pumped again at high pressure before it goes to the body, so it travels faster and delivers oxygen quickly.
这就是它的优点，也是得分点：血液在送往身体之前可以再次被高压泵出， 所以流得更快，能迅速输送氧气。
The heart is made of muscle, and a wall called the septum divides it into a left side and a right side.
心脏由肌肉构成，一堵叫做隔膜的墙把它分成左侧和右侧。
On each side there is an upper chamber, the atrium, and a lower chamber, the ventricle.
每一侧都有一个上腔室，叫心房，和一个下腔室，叫心室。
Valves between them stop blood flowing backwards.
它们之间的瓣膜防止血液倒流。
The septum does one crucial job: it keeps oxygenated blood on the left apart from deoxygenated blood on the right, so the two never mix.
隔膜做了一件关键的事： 它把左侧的含氧血和右侧的缺氧血分开，让两者永不混合。 经典的问题是：为什么左心室的壁比右心室厚？
And the classic question: why is the wall of the left ventricle thicker than the right?
因为左侧必须把血泵到全身各处，而右侧只把血泵到附近的肺。
Because the left must pump blood all the way around the body, while the right only pumps it to the nearby lungs.
心房的壁很薄，因为它们只是把血推到正下方的心室里。
The atria have thin walls.
心房的壁很薄。
They only push blood into the ventricles just below them, so they do not need a thick muscle.
它们只是把血推到正下方的心室里，所以不需要厚的肌肉。
The left ventricle is the opposite: its wall is the thickest in the heart, because it must drive blood all the way around the body.
左心室正好相反：它的壁是心脏里最厚的，因为它必须把血送到全身。
The right ventricle only has to reach the nearby lungs, so its wall is thinner.
右心室只要到达附近的肺，所以壁更薄。
Name the wall, and you have named the job.
说出这堵墙，你就说出了它的工作。
Watch one beat.
看一次心跳。
The upper chambers squeeze, then the lower chambers squeeze, then everything relaxes and fills again.
上面的腔室收缩，然后下面的腔室收缩，然后一切放松，重新充满。
In words, for the supplement paper, there are three stages.
用文字说，补充部分有三个阶段。
One: the atria contract and push blood down into the ventricles.
第一：心房收缩，把血推入心室。
Two: the ventricles contract and force blood out into the arteries, and the valves snap shut so blood cannot flow back.
第二：心室收缩，把血挤进动脉，瓣膜啪地关上，所以血不能倒流。
Name them for the supplement: the valves between each atrium and ventricle are the atrioventricular valves, and the valves at the exit of each ventricle are the semilunar valves.
补充内容要记住名字：心房和心室之间的瓣膜叫房室瓣，心室出口处的瓣膜叫半月瓣。
Three: the muscle relaxes and the heart fills with blood again.
第三：肌肉放松，心脏重新充满血液。
And remember the simple rule that goes with it — blood is pumped away from the heart in arteries, and returns to the heart in veins.
还要记住配套的简单规则—— 血液通过动脉被泵离心脏，通过静脉回到心脏。
Arteries away, veins back.
动脉离开，静脉回来。
You can check the heart's activity with an E C G, by feeling the pulse in an artery, or by listening to the valves closing.
你可以用心电图检查心脏的活动，或者摸动脉的脉搏，或者听瓣膜关闭的声音。
During exercise the heart rate goes up, so blood reaches the muscles faster, bringing the extra oxygen and glucose they need.
运动时心率会上升，所以血液更快到达肌肉，带来它们需要的额外氧气和葡萄糖。
Now the calculation.
现在是计算。
A student counts eighteen beats in fifteen seconds at rest, and thirty-three beats in fifteen seconds straight after exercise.
一个学生在静息时数到十五秒十八次，运动后立刻数到十五秒三十三次。
A minute holds four lots of fifteen seconds, so multiply by four.
一分钟包含四个十五秒，所以乘以四。
At rest, eighteen times four is seventy-two beats per minute.
静息时，十八乘四等于每分钟七十二次。
After exercise, thirty-three times four is one hundred and thirty-two beats per minute.
运动后，三十三乘四等于每分钟一百三十二次。
Writing the fifteen-second count straight down is the commonest mistake — always scale it up to a full minute.
直接把十五秒的计数写下来是最常见的错误——永远要把它换算成整整一分钟。
The heart muscle has its own blood supply, through the coronary arteries.
心肌有自己的血液供应，通过冠状动脉。
Coronary heart disease happens when those arteries become narrow or blocked, so the heart muscle cannot get enough oxygen.
当这些动脉变窄或被堵塞，心肌就得不到足够的氧气，这就是冠心病。
Learn the risk factors: a diet high in fat, lack of exercise, stress, smoking, family history, older age, and being male.
记住风险因素：高脂肪饮食、缺乏运动、压力、吸烟、家族史、年龄较大，还有是男性。
Notice that some of those you can change and some you cannot.
注意其中有些你能改变，有些不能。
A healthy diet and regular exercise lower the risk — and those are the two the exam wants when it asks how to reduce it.
健康的饮食和规律的运动能降低风险——当题目问如何降低风险时，考试就要这两个。
Three kinds of blood vessel, each built for its job.
三种血管，每一种都为它的工作而生。
The space inside a vessel is the lumen.
任何血管内部的空间叫做管腔。
Arteries carry blood away from the heart at high pressure, so they have thick, muscular, elastic walls and a narrow lumen, and no valves.
动脉把血液从心脏高压送出，所以它们有厚的、肌肉的、有弹性的壁来承受，管腔很窄。 它们没有瓣膜。
Veins carry blood back at low pressure, so they have thin walls and a wide lumen — and they do have valves, because low-pressure blood could otherwise flow backwards.
静脉把血液低压送回心脏，所以它们壁薄、管腔宽—— 而且它们确实有瓣膜，因为低压的血否则可能倒流。 毛细血管是进行交换的地方。
Capillaries are where exchange happens: walls one cell thick and very narrow, giving a large surface area and a short distance.
它们的壁只有一个细胞厚，而且非常窄， 这提供了大表面积和短距离，所以氧气、葡萄糖和废物能在血液和细胞之间快速通过。
Capillaries are where the real work happens.
毛细血管才是真正干活的地方。
Their walls are one cell thick, and the lumen is very narrow.
它们的壁只有一个细胞厚，管腔非常窄。
That gives a large surface area and a short distance, so exchange is fast.
这提供了大表面积和短距离，所以交换很快。
Oxygen and glucose leave the blood and enter the cells.
氧气和葡萄糖离开血液进入细胞。
Wastes, including carbon dioxide, go the other way.
废物，包括二氧化碳，走相反的方向。
That is why every tissue is wrapped in a capillary network.
这就是为什么每块组织都被毛细血管网包着。
That exchange is the whole point of a capillary.
交换，就是毛细血管存在的全部理由。
Now the names, and a pattern makes them easy.
现在是你必须记住的名字，有一个规律让它们变得容易。
For the body, blood leaves in the aorta and returns in the vena cava.
去身体的血液从主动脉离开，从腔静脉返回。
For the lungs, it leaves in the pulmonary artery and returns in the pulmonary vein.
去肺的血液从肺动脉离开，从肺静脉返回。
For the kidney, the renal artery in and the renal vein out — the artery and vein share a name for each organ.
去肾脏的是肾动脉进、肾静脉出。 注意每个器官的动脉和静脉共用一个名字。
One odd one for the supplement paper: the hepatic portal vein, which brings blood from the gut to the liver, not from the heart.
补充部分还有一个特别的：肝脏有肝动脉和肝静脉，但还有肝门静脉， 它很特别，因为它把血液从肠道带到肝脏，而不是从心脏来。
The liver has three vessels, not two.
肝脏有三条血管，不是两条。
The hepatic artery brings oxygenated blood from the heart.
肝动脉从心脏带来含氧血。
The hepatic vein takes blood away, back towards the heart.
肝静脉把血带走， 送回心脏方向。
The odd one is the hepatic portal vein: it brings blood from the gut to the liver, carrying the products of digestion, not from the heart.
特别的是肝门静脉：它把血液从肠道带到肝脏，带着消化产物， 而不是从心脏来。
The exam loves that exception.
考试很喜欢这个例外。
Write portal, write gut to liver, and the mark is yours.
写下门静脉，写下从肠道到肝脏，这个分就是你的。
Blood has four parts, and you need one function for each.
血液有四个部分，每一个你都要记住一个功能。
Red blood cells carry oxygen, using the red pigment haemoglobin.
红细胞携带氧气，用的是红色色素血红蛋白。
White blood cells defend the body against disease.
白细胞保护身体不受疾病侵害。
Platelets help the blood to clot.
血小板帮助血液凝固。
And plasma is the liquid that carries everything else — the blood cells themselves, plus ions, nutrients, urea, hormones and carbon dioxide.
血浆是携带其他一切的液体——血细胞本身，还有离子、营养物质、尿素、激素和二氧化碳。
If a question asks what transports a dissolved substance, the answer is almost always plasma.
如果题目问什么运输某种溶解的物质，答案几乎总是血浆。
White blood cells fight pathogens — the microbes that cause disease — in two different ways, and the exam wants both.
白细胞用两种不同的方式对抗病原体——也就是引起疾病的微生物——考试两个都要。
Phagocytes carry out phagocytosis: they surround and digest the pathogens.
吞噬细胞进行吞噬作用：它们包围并消化病原体。
Lymphocytes make antibodies, which stick to the pathogens and destroy them.
淋巴细胞制造抗体，抗体粘住病原体并摧毁它们。
And when you cut yourself, the blood clots to seal the wound, which does two jobs: it stops blood loss and stops pathogens getting in.
吞掉，或者标记——就是这两种。 当你割伤自己时，血液凝固来封住伤口，这做了两件事： 它止住失血，也阻止病原体进入。
For the supplement paper: a soluble protein called fibrinogen is changed into threads of fibrin, which form a net that traps blood cells and makes a solid clot.
补充部分要说清楚怎么做的： 一种叫纤维蛋白原的可溶性蛋白质变成纤维蛋白的细丝， 这些细丝形成一张网，困住血细胞，形成固体的血块。
Three marks to lock in.
锁住三个分。
First: the left ventricle wall is thickest because it pumps to the whole body, while the right only pumps to the lungs.
第一：左心室的壁最厚，因为它要泵到全身，而右侧只泵到肺。
Second: arteries away, veins back — arteries thick and high pressure, veins with valves at low pressure, capillaries one cell thick for exchange.
第二：动脉离开，静脉回来——动脉厚、高压，静脉有瓣膜、低压， 毛细血管一个细胞厚用于交换。
Third: phagocytes engulf pathogens; lymphocytes make antibodies.
第三：吞噬细胞吞掉病原体；淋巴细胞制造抗体。
Master these, and this topic is yours.
掌握这些，这个专题就是你的了。