I/GCSE Biology - Circulatory System

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!

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

• 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.

• 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.

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

• 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

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

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

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.

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!

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Drafted by Alyssa (Biology)