Science

• Blood


  A tissue that transports substances around the body
• Components of blood


  • Platelets
  • Red blood cells
  • White blood cells
  • Plasma
• Red blood cells


  • Contain a red pigment called haemoglobin (rich in iron) that carries oxygen
  • Do not have a nucleus to make room for carrying oxygen
  • Have a large surface area to take up oxygen quickly
• White blood cells


  • Fight pathogens to prevent disease
  • Produce antibodies
  • Carry out phagocytosis to engulf and destroy pathogens
• Antibodies are special proteins that can directly kill pathogens
• Phagocytosis is a process which involves engulfing and destroying a pathogen
• Blood smear


  • Red blood cells - smaller, oval, no nucleus
  • White blood cells - larger, lobed nucleus, fewer in number than red blood cells
  • Platelets
• Red blood cells are larger in number than white blood cells because red blood cells carry oxygen so there has to be more to help more oxygen flow
• Types of blood vessels

  • Arteries
  • Capillaries
  • Veins
• Arteries


  • Carry blood away from the heart
  • Have thick, elastic walls to withstand the high pressure of the blood
  • The blood pulsing from the heart makes the walls stretch and recoil, which can be felt as a pulse
• Veins


  • Carry blood to the heart
  • Have thinner walls and valves to stop the blood flowing back the wrong way
• Capillaries


  • Carry nutrients and oxygen to cells and remove carbon dioxide and waste from cells
  • Have walls that are just one cell thick to allow these substances to pass in and out of the blood easily
• Heart


  • A pump made of cardiac muscle
  • Divided into left and right sides
  • Each side has an atrium (upper chamber) and a ventricle (lower chamber)
  • The atria receive blood and the ventricles pump blood
• Flow of blood through the circulatory system

  1. Deoxygenated blood flows from the body to the right atrium

  2. Blood flows from the right atrium to the right ventricle

  3. Blood is pumped from the right ventricle to the lungs

  4. In the lungs, blood becomes oxygenated

  5. Oxygenated blood flows from the lungs to the left atrium

  6. Blood flows from the left atrium to the left ventricle

  7. Blood is pumped from the left ventricle to the body
• Double circulatory system


  Blood passes through the heart twice in one complete circuit around the body
• Heart disease

  Occurs when coronary arteries become blocked with deposits of cholesterol, cutting off blood supply to the heart muscle
• What happens when heart disease occurs


  1. Coronary arteries become blocked

  2. Blood supply to heart muscle is cut off

  3. Heart muscle cells do not receive oxygen or glucose

  4. Heart muscle cells cannot respire aerobically

  5. No energy is released

  6. Heart muscle cannot contract

  7. Heart stops beating

  8. Muscle cells respire anaerobically for a short time

  9. This produces lactic acid and the muscle cramps

  10. This is what causes the pain in a heart attack
• Risk factors for heart disease

  • High Cholesterol Diet
  • Family History (genetics)
  • Stress
  • Smoking
  • Lack of Exercise
  • High Blood Pressure
• Day and Night

  The Earth rotates (spins) on its axis
• Day and Night

  1. The side facing the Sun is in daytime

  2. The side facing away from the Sun is in night time
• Earth's rotation


  Takes 24 hours to complete one rotation
• Day and night lasts 24 hours
• Direction of Earth's rotation

  • Rotates anticlockwise
• Sunlight


  Determines time of day or night
• A satellite is any object which orbits a planet
• Natural satellites are called Moons
• Moon's orbit


  Takes a lunar month (28 days) to orbit the Earth
• The Earth spins around the Sun and the Moon orbits the Earth
• The Earth also rotates on its axis
• As the Earth spins on its axis, the side facing the Sun is in daytime
• A day lasts 24 hours
• The Moon takes 29 days to orbit the Earth
• Earth's rotation


  When the Earth spins on its own axis
• Earth's orbit

  When the Earth travels round the Sun
• The seasons are caused by the tilt of the Earth
• When the Earth is tilted towards the Sun, it is summer
• When the Earth is tilted away from the Sun, it is winter
• The Earth's tilt causes the seasons
• The Earth's orbit around the Sun determines the length of the year
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