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I/GCSE Biology - Circulatory System

Circulatory System

· IGCSE,biology,Circulatory system,Heart,Blood cells

The Heart

Do you remember the previous post regarding blood vessels and double circulation in I/GCSE Biology?

If yes, let's move on talking about the structure of heart!

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As you can see the diagram of the heart shown above, it is important to memorize the following points in I/GCSE Biology.

  • 2 pumps side by side:
  1. RIGHT SIDE -> deoxygenated blood
  2. LEFT SIDE -> oxygenated blood
  • Important blood vessels in the circulation:
    • The aorta – takes blood from the heart to the body
    • The pulmonary artery – takes blood from the heart to the lungs
    • The vena cava – brings blood back to the heart from the body
    • The pulmonary vein – brings blood back to the heart from the lungs
  • Ventricles have muscular walls to pump the blood
  • The valves prevent blood flowing back into the atrium
  • Left ventricle is stronger as it has to pump the blood further
  • When the muscle contracts, the chamber gets smaller and squeezes the blood out
  • Diastole -> when the muscles are relaxed
  • Systole -> when the muscles contract
  • The right ventricle pumps blood to the lungs in the pulmonary artery
  • The left ventricle pumps blood to the rest of the body in the aorta
  • Deoxygenated blood returns to the right atrium in the vena cava
  • Oxygenated blood returns to the left atrium in the pulmonary vein

Control of the heart beat

  • Controlled by the pacemaker.
  • Group of cells in the right atrium
  • Sends electrical messages to the heart muscle which stimulates it to contract
  • During exercise, your heart beats faster and the arteries supplying the muscles dilate.

The heart’s blood supply

  • Coronary arteries carry oxygenated blood to the heart muscle
  • They supply the heart with glucose and oxygen for respiration
  • Causes of heart disease (caused by...
  1. Eating fatty foods
  2. Being over-weight
  3. Smoking
  4. Doing little or no exercise
  • If one becomes blocked, oxygen supply cuts off -> heart attack

In I/GCSE Biology, don't forget about the prevention of heart disease too!

  • Take care of your diet (less red meat, more poultry + fish, cut down on fried food, eat more fruit and veg), don’t smoke, exercise regularly.

Blood

In I/GCSE Biology, it is important to understand each blood cell.

If you leave a sample of blood to stand it separates into 2 parts:

  1. Plasma – mainly water with chemicals dissolved in it:
    • Food (sugars, amino acids, vitamins and minerals)
    • Chemical waste like urea
    • Blood proteins like antibodies
    • Hormones
  2. 3 types of blood cells:
    • Red blood cells
    • White blood cells
    • Platelets

Red Blood Cells

  • No nucleus
  • Hollow disc shape allows them to absorb a lot of oxygen
  • Haemoglobin is a protein containing iron (makes blood red)
  • Combines with oxygen to produce -> oxyhaemoglobin
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White Blood Cells

  • Fight disease
  • A lot fewer than red blood cells
  • No nucleus
  • Made in the bone marrow
  • Protect the body from pathogens
  • 2 types of white blood cells
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Lymphocytes

  • Make chemicals called antibodies
  • They attack pathogens in different ways; make them stick together, dissolve them, destroy the toxins the pathogens make.
  • After you have a disease the antibodies stay in your blood and make you immune to that disease.

Phagocytes

  • 'cell-eaters'
  • They ‘engulf’ or swallow up the pathogens and take them into the cell
  • They digest and kill them
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Platelets

  • Platelets are small fragments of cells made of bone marrow
  • Platelets change fibrinogen into fibrin
  • Fibrin forms a meshwork of threads that traps red cells to make a clot.
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Blood Clotting

The process of blood clotting is crucial in I/GCSE Biology too!

  1. The skin is cut and starts bleeding.
  2. The platelets turn fibrinogen into threads of fibrin. The threads make a net over the cut.
  3. Red blood cells get caught in the net and make a blood clot, sealing the cut.
  4. New skin grows under the scab.

    References:

    1. "The Heart Function And Structure", https://1.bp.blogspot.com/-a_oHjSfFiAM/XSYXXYFEZMI/AAAAAAAAANM/4__3Efs0E9QHX8b_lLyIoqR4KngfVPAowCLcBGAs/s1600/Screenshot%2B2019-07-11%2Bat%2B12.49.55%2BAM.png
    2. "Red Blood Cells Diagram", https://i.pinimg.com/originals/7a/12/d7/7a12d7c31355759ec5d97daf84343fed.png
    3. "Endocytosis", https://microbenotes.com/wp-content/uploads/2020/03/Phagocytosis-1024x512.jpeg
    4. "Unit 5 – Anatomy & Physiology Circulatory System", https://images.slideplayer.com/34/10197787/slides/slide_5.jpg
    5. "Biology 3 - Blood and Circulation", https://getrevising.co.uk/resources/biology_3_blood_and_circulation

    And we're done with this topic! Well Done!

    CLICK HERE TO LEARN MORE ABOUT OUR I/GCSE BIOLOGY COURSES

    SIGN UP FOR AN I/GCSE BIOLOGY TRIAL NOW

    Drafted by Alyssa (Biology)

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