シャドーイング練習: The Composition and Function of Blood - 動画で英語スピーキングを学ぶ

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Professor Dave here, let's learn about blood.

Of all the substances within the human body, blood is one of the more familiar ones, as we've all had an injury that involves bleeding.

For a long time, it was not well understood exactly what blood is,

or what it does, we just knew that if you lose enough of it, you die.

But we now have an intimate understanding of this fluid, as well as the circulatory system,

whose function it is to continuously pump blood around the body.

We will get to this system in a moment.

First let's examine blood itself, what it's made of, and why it is so critical for human life.

First, let's mention that blood is technically considered a connective tissue, and as such, it is the only fluid tissue in the body,

full of fibrous proteins.

It is comprised of formed elements, which are blood cells suspended in a fluid called plasma.

If we place blood in a centrifuge, it will separate into its components.

The densest section is comprised of erythrocytes, or red blood cells, and the least dense section will be the yellowish plasma.

They are separated by the buffy coat, a white layer containing platelets, as well as leukocytes, otherwise known as white blood cells.

As a whole, blood is responsible for distributing various substances around the body,

most notably oxygen, which we can't survive very long without up, but it also carries nutrients absorbed from the digestive tract,

and hormones secreted by endocrine organs.

Blood also delivers waste products to the organs that will dispose of them, like the carbon dioxide that we exhale.

Beyond this, blood serves to regulate pH in various tissues, maintain body temperature, and prevent infection.

Let's discuss each component of blood now, beginning with plasma.

This is a sticky fluid made mostly of water, but also containing a variety of proteins, nutrients, ions, gases, and hormones.

The most abundant plasma protein is called albumin, which contributes significantly to plasma's osmotic pressure,

and this is followed by a variety of globulins which bind to certain molecules for transport.

Moving to the formed elements, these are erythrocytes, or red blood cells, leukocytes, or white blood cells, and platelets.

Red blood cells and platelets are interesting in that they don't possess all the typical organelles, and they don't divide.

They are replaced by stem cells in the bone marrow.

Red blood cells are very numerous in the bloodstream, and they are shaped like flattened discs with depressed centers.

There is no nucleus, not much of anything inside other than lots of hemoglobin.

This is the protein that allows for the transport of oxygen throughout the bloodstream, which is picked up in the lungs,

and then released for tissue cells throughout the body.

There are other proteins as well that have structural or protective functions, but hemoglobin will be the focus here.

This is the structure of hemoglobin.

It is made of a protein called globin, consisting of four polypeptides, two identical alpha chains, and two identical beta chains,

each of which is bound to a heme group with iron at the center.

The iron in this heme is able to bind to an oxygen molecule in reversible fashion, so that it can bind and then release when necessary,

so each hemoglobin can bind four oxygen molecules.

And there are around 250 million hemoglobins per red blood cell,

so one red blood cell can transport one billion oxygen molecules cells.

Blood cells are produced through a process called hematopoiesis, and this occurs in the red bone marrow,

which is a soft network of connective tissue found on certain blood capillaries, and which contains hematopoietic stem cells.

For erythrocytes, this is more specifically called erythropoiesis,

and billions of new red blood cells are made every day to maintain a nearly constant number,

given that red blood cells function properly for only about three months, only to be destroyed by macrophages,

which are a phagocytic type of white blood cell.

Next, let's look at leukocytes, or white blood cells, which unlike the far more abundant red blood cells,

are complete cells with nuclei and organelles.

These are part of the immune system, which we will discuss in greater detail later,

but for now we will just understand that these help us defend against pathogens and other harmful things tissues.

These use the circulatory system to get around the body, but they can also slip out into other connective tissues to do their work.

There are two types of white blood cells,

granulocytes and agranulocytes, which differ in the presence or absence of granules.

The three types of granulocytes are neutrophils, which kill bacteria, eosinophils, which kill parasitic worms,

and basophils, which contain histamine that attracts other white blood cells to a site of inflammation.

Agranulocytes, on the other hand, can be lymphocytes, which fight viruses and tumors, and also give rise to plasma cells,

which produce antibodies, which we will discuss later, or they can be monocytes, which become macrophages that can eat up intruders.

Leukocytes are produced by leukopoiesis, which is stimulated by certain chemical messengers.

Lastly we get to the platelets.

These are fragments of large cells, called megakaryocytes.

These fragments are essential during blood clotting, which happens when blood vessels are damaged,

as platelets can plug up any holes or tears to seal things off.

They flow through the bloodstream in an inactive state unless needed, dying every ten days or so, and constantly regenerated.

Megakaryocytes form due to repeated mitotic cycles that do not perform cytokinesis,

so So the result is one huge cell with a multi -lobed nucleus.

This then presses against a sinusoid, and its extensions burst to release the platelets.

These platelets are important during hemostasis, which is the process by which the body will stop bleeding through vascular spasm,

platelet plug formation, and then coagulation, or blood clotting.

This essentially means that where there is damage to a vessel,

smooth muscle will contract, platelets will plug the tear,

and a protein called fibrin will form a mesh to patch everything up.

Once the vessel has healed, the clot is removed through a process called fibrinolysis, so that there is no blockage in the vessel.

So those are the components of blood.

We can look at a diagram like this one to see how these arise during hematopoiesis.

We can also briefly mention the different blood types that humans can exhibit.

These are A, B, AB, and O.

These have to do with glycoproteins and glycolipids found in the plasma membranes of red blood cells.

A and B refer to two different agglutinogens that can be found in these membranes, so blood group A has one of them,

B has the other, AB has both, and O has neither.

This is important for blood transfusions, because if someone's body only recognizes A and gets blood with B,

the new blood cells will be recognized by antibodies as foreign and destroyed, which can be fatal.

So someone with AB blood can receive any blood, since both A and B will be recognized, hence they are universal recipients.

And someone with O blood can give blood to anyone, since there are no markers to be recognized, hence they are universal donors.

There are also RH blood groups which refer to agglutinogens called RH factors, and for For these, a person is either positive or negative.

This is reported along with the ABO blood group by tacking on positive or negative to the end, giving us groups like O positive,

A negative, and so on.

And with that, we are familiar enough with the structure

and function of blood that we can begin to examine the circulatory system as a whole, so let's move forward and do just that.

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このレッスンの語彙とスピーキングのポイント

このスピーキングレッスンは、動画「The Composition and Function of Blood」を教材にしています。繰り返し出てくる語は次のとおりです：blood, cell, platelet, protein, plasma。この動画には、シャドーイング用の文が53文、単語が1298語あります。音声の長さは9:57です。話す速さは1分あたり約130語で安定しており、シャドーイングしやすいペースです。英語の頻出3,000語に含まれる単語は76%だけなので、語彙は難しめです。

この動画の重要語彙

動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
tissue 名詞	/ˈtɪʃ.(j)u/	織物
plasma 名詞	/ˈplæzmə/	プラズマ
oxygen 名詞	/ˈɑksɪd͡ʒən/	酸素
vessel 名詞	/ˈvɛsəl/	船舶
fluid 名詞	/ˈflu.ɪd/	流体, 液体
molecule 名詞	/ˈmɑ.lɪ.kjul/	分子
component 名詞	/kəmˈpoʊ.nənt/	部分
plug 名詞	/plʌɡ/	プラグ
nucleus 名詞	/ˈnuː.kli.əs/	核, 核心
universal 形容詞	/ˌjunəˈvɜɹs(ə)l/	宇宙の
bone 名詞	/boʊn/	骨
refer 動詞	/ɹɪˈfɜː/	問い合わせる
hence 副詞	/ˈhɛns/	ここから
tear 動詞	/tɛɹ/	破る, 引き裂く
substance 名詞	/ˈsʌbstəns/	物質

動画に出てくる句動詞

単語	意味
eat up 動詞	平らげる

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	is technically considered · is comprised · are separated
関係詞節 who / which + 節 — 人や物について情報を加える	elements, which are · bloodstream, which is · leukopoiesis, which is

注意したい発音

話し手はdon't, can't, we'veなど、短縮形や弱形を4回使っています。聞こえたとおりの短い形で発音しましょう。

「th」の音: smooth /smuːð/, erythrocyte /əˈɹɪθɹəˌsaɪt/, pathogen /ˈpæθəd͡ʒn̩/
「sh」と「zh」の音: tissue /ˈtɪʃ.(j)u/, extension /ɪkˈstɛnʃən/, essentially /ɪˈsɛnʃəli/, infection /ɪnˈfɛkʃən/, structural /ˈstɹʌk(t͡)ʃəɹəl/
長い単語（アクセントの位置に注意）: universal /ˌjunəˈvɜɹs(ə)l/, essentially /ɪˈsɛnʃəli/, technically /ˈtɛk.nɪˌkəl.i/, continuously /kənˈtɪnjuəsli/, recipient /ɹəˈsɪp.i.ənt/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: universal /ˌjunəˈvɜɹs(ə)l/, briefly /ˈbɹiːfli/, structural /ˈstɹʌk(t͡)ʃəɹəl/, harmful /ˈhɑɹmfl̩/, regulate /ˈɹɛɡ.jə.leɪt/
/v/ — /b/ にならないように、上の歯を下唇に当てる: vessel /ˈvɛsəl/, universal /ˌjunəˈvɜɹs(ə)l/, virus /ˈvaɪ.ɹəs/, involve /ɪnˈvɑlv/, protective /pɹəˈtɛk.tɪv/
/f/ — 「フ」ではなく、上の歯と下唇で出す: fluid /ˈflu.ɪd/, refer /ɹɪˈfɜː/, fragment /ˈfɹæɡmənt/, defend /dɪˈfɪnd/, infection /ɪnˈfɛkʃən/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
通常の速度で一文ずつシャドーイングし、話し手のリズムに合うまで繰り返します。
自分の声を録音して元の音声と比べます。tissue, plasma, oxygenなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: The Composition and Function of Blood - 動画で英語スピーキングを学ぶ

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