Shadowing Practice: The Composition and Function of Blood - Learn English Speaking with Video
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Professor Dave here, let's learn about blood.
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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.
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For a long time, it was not well understood exactly what blood is,
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or what it does, we just knew that if you lose enough of it, you die.
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But we now have an intimate understanding of this fluid, as well as the circulatory system,
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whose function it is to continuously pump blood around the body.
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We will get to this system in a moment.
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First let's examine blood itself, what it's made of, and why it is so critical for human life.
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First, let's mention that blood is technically considered a connective tissue, and as such, it is the only fluid tissue in the body,
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full of fibrous proteins.
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It is comprised of formed elements, which are blood cells suspended in a fluid called plasma.
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If we place blood in a centrifuge, it will separate into its components.
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The densest section is comprised of erythrocytes, or red blood cells, and the least dense section will be the yellowish plasma.
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They are separated by the buffy coat, a white layer containing platelets, as well as leukocytes, otherwise known as white blood cells.
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As a whole, blood is responsible for distributing various substances around the body,
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most notably oxygen, which we can't survive very long without up, but it also carries nutrients absorbed from the digestive tract,
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and hormones secreted by endocrine organs.
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Blood also delivers waste products to the organs that will dispose of them, like the carbon dioxide that we exhale.
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Beyond this, blood serves to regulate pH in various tissues, maintain body temperature, and prevent infection.
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Let's discuss each component of blood now, beginning with plasma.
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This is a sticky fluid made mostly of water, but also containing a variety of proteins, nutrients, ions, gases, and hormones.
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The most abundant plasma protein is called albumin, which contributes significantly to plasma's osmotic pressure,
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and this is followed by a variety of globulins which bind to certain molecules for transport.
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Moving to the formed elements, these are erythrocytes, or red blood cells, leukocytes, or white blood cells, and platelets.
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Red blood cells and platelets are interesting in that they don't possess all the typical organelles, and they don't divide.
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They are replaced by stem cells in the bone marrow.
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Red blood cells are very numerous in the bloodstream, and they are shaped like flattened discs with depressed centers.
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There is no nucleus, not much of anything inside other than lots of hemoglobin.
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This is the protein that allows for the transport of oxygen throughout the bloodstream, which is picked up in the lungs,
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and then released for tissue cells throughout the body.
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There are other proteins as well that have structural or protective functions, but hemoglobin will be the focus here.
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This is the structure of hemoglobin.
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It is made of a protein called globin, consisting of four polypeptides, two identical alpha chains, and two identical beta chains,
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each of which is bound to a heme group with iron at the center.
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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,
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so each hemoglobin can bind four oxygen molecules.
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And there are around 250 million hemoglobins per red blood cell,
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so one red blood cell can transport one billion oxygen molecules cells.
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Blood cells are produced through a process called hematopoiesis, and this occurs in the red bone marrow,
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which is a soft network of connective tissue found on certain blood capillaries, and which contains hematopoietic stem cells.
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For erythrocytes, this is more specifically called erythropoiesis,
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and billions of new red blood cells are made every day to maintain a nearly constant number,
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given that red blood cells function properly for only about three months, only to be destroyed by macrophages,
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which are a phagocytic type of white blood cell.
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Next, let's look at leukocytes, or white blood cells, which unlike the far more abundant red blood cells,
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are complete cells with nuclei and organelles.
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These are part of the immune system, which we will discuss in greater detail later,
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but for now we will just understand that these help us defend against pathogens and other harmful things tissues.
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These use the circulatory system to get around the body, but they can also slip out into other connective tissues to do their work.
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There are two types of white blood cells,
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granulocytes and agranulocytes, which differ in the presence or absence of granules.
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The three types of granulocytes are neutrophils, which kill bacteria, eosinophils, which kill parasitic worms,
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and basophils, which contain histamine that attracts other white blood cells to a site of inflammation.
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Agranulocytes, on the other hand, can be lymphocytes, which fight viruses and tumors, and also give rise to plasma cells,
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which produce antibodies, which we will discuss later, or they can be monocytes, which become macrophages that can eat up intruders.
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Leukocytes are produced by leukopoiesis, which is stimulated by certain chemical messengers.
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Lastly we get to the platelets.
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These are fragments of large cells, called megakaryocytes.
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These fragments are essential during blood clotting, which happens when blood vessels are damaged,
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as platelets can plug up any holes or tears to seal things off.
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They flow through the bloodstream in an inactive state unless needed, dying every ten days or so, and constantly regenerated.
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Megakaryocytes form due to repeated mitotic cycles that do not perform cytokinesis,
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so So the result is one huge cell with a multi -lobed nucleus.
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This then presses against a sinusoid, and its extensions burst to release the platelets.
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These platelets are important during hemostasis, which is the process by which the body will stop bleeding through vascular spasm,
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platelet plug formation, and then coagulation, or blood clotting.
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This essentially means that where there is damage to a vessel,
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smooth muscle will contract, platelets will plug the tear,
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and a protein called fibrin will form a mesh to patch everything up.
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Once the vessel has healed, the clot is removed through a process called fibrinolysis, so that there is no blockage in the vessel.
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So those are the components of blood.
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We can look at a diagram like this one to see how these arise during hematopoiesis.
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We can also briefly mention the different blood types that humans can exhibit.
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These are A, B, AB, and O.
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These have to do with glycoproteins and glycolipids found in the plasma membranes of red blood cells.
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A and B refer to two different agglutinogens that can be found in these membranes, so blood group A has one of them,
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B has the other, AB has both, and O has neither.
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This is important for blood transfusions, because if someone's body only recognizes A and gets blood with B,
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the new blood cells will be recognized by antibodies as foreign and destroyed, which can be fatal.
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So someone with AB blood can receive any blood, since both A and B will be recognized, hence they are universal recipients.
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And someone with O blood can give blood to anyone, since there are no markers to be recognized, hence they are universal donors.
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There are also RH blood groups which refer to agglutinogens called RH factors, and for For these, a person is either positive or negative.
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This is reported along with the ABO blood group by tacking on positive or negative to the end, giving us groups like O positive,
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A negative, and so on.
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And with that, we are familiar enough with the structure
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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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Vocabulary and speaking notes for this lesson
This speaking lesson is built on the video “The Composition and Function of Blood”. The speaker keeps coming back to these words: blood, cell, platelet, protein, plasma. This video has 53 sentences and 1298 words to shadow. The speech runs for 9:57. The speaker talks at a steady 130 words per minute, a comfortable pace for shadowing. Only 76% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
15 words from the video worth learning, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| tissue noun | /ˈtɪʃ.(j)u/ | Thin, woven, gauzelike fabric. |
| plasma noun | /ˈplæzmə/ | A state of matter consisting of partially ionized gas and electrons. |
| oxygen noun | /ˈɑksɪd͡ʒən/ | The chemical element (symbol O) with an atomic number of 8 and relative atomic mass of 15.9994. It is a colorless and odorless gas. Sometimes called elemental… |
| bind verb | /ˈbaɪ̯nd/ | To tie; to confine by any ligature. |
| vessel noun | /ˈvɛsəl/ | Any craft designed for transportation on or in water, such as a ship, boat, or submarine. |
| fluid noun | /ˈflu.ɪd/ | Any substance which can flow with relative ease, tends to assume the shape of its container, and obeys Bernoulli's principle; a liquid, gas or plasma. |
| molecule noun | /ˈmɑ.lɪ.kjul/ | The smallest particle of a specific element or compound that retains the chemical properties of that element or compound; two or more atoms held together by… |
| component noun | /kəmˈpoʊ.nənt/ | A smaller, self-contained part of a larger entity. Often refers to a manufactured object that is part of a larger device. |
| plug noun | /plʌɡ/ | A pronged connecting device which fits into a mating socket, especially an electrical one. |
| nucleus noun | /ˈnuː.kli.əs/ | The core, central part of something, around which other elements are assembled. |
| universal adjective | /ˌjunəˈvɜɹs(ə)l/ | Of or pertaining to the universe. |
| bone noun | /boʊn/ | A composite material consisting largely of calcium phosphate and collagen and making up the skeleton of most vertebrates. |
| refer verb | /ɹɪˈfɜː/ | To direct the attention of (someone toward something). |
| hence adverb | /ˈhɛns/ | In the future from now. |
| tear verb | /tɛɹ/ | To rend (a solid material) by holding or restraining in two places and pulling apart, whether intentionally or not; to destroy or separate. |
Phrasal verbs you will hear
| Word | Meaning |
|---|---|
| eat up verb | To consume completely. |
| get around verb | To move to the other side of (something, such as an obstruction) by deviating from a direct course or following a curved path. |
| move forward verb | To cause to make progress. |
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | is technically considered · is comprised · are separated |
| Relative clauses who / which + clause — extra information about a person or thing | elements, which are · bloodstream, which is · leukopoiesis, which is |
Pronunciation to watch
The speaker uses 4 contractions and reduced forms, such as don't, can't, we've. Say them the short way, as you hear them.
- The “th” sounds: smooth /smuːð/, erythrocyte /əˈɹɪθɹəˌsaɪt/, pathogen /ˈpæθəd͡ʒn̩/
- The “sh” and “zh” sounds: tissue /ˈtɪʃ.(j)u/, extension /ɪkˈstɛnʃən/, essentially /ɪˈsɛnʃəli/, infection /ɪnˈfɛkʃən/, structural /ˈstɹʌk(t͡)ʃəɹəl/
- Long words — get the stress right: universal /ˌjunəˈvɜɹs(ə)l/, essentially /ɪˈsɛnʃəli/, technically /ˈtɛk.nɪˌkəl.i/, continuously /kənˈtɪnjuəsli/, recipient /ɹəˈsɪp.i.ənt/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Shadow it sentence by sentence at normal speed, repeating each one until your rhythm matches the speaker.
- Record yourself and compare with the original, paying attention to words like tissue, plasma, oxygen.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.