biology

• Transport in animals

  Our blood and circulatory system
• Main job of the human circulatory system

  Deliver oxygen and remove wastes like carbon dioxide from the body before they build up to poisonous levels
• Blood


  Red liquid kept moving by a pump called the heart which pumps it through a series of tube-like blood vessels
• Components of blood

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

  Do NOT contain a nucleus so that they can be packed with the red pigment haemoglobin which combines easily with oxygen
• White blood cells

  Form part of the body's immune system, including phagocytes that engulf and digest microbes and lymphocytes that make and send out antibodies
• Platelets


  Small fragments of cells that produce substances to help the blood clot
• Plasma


  Pale yellow liquid which carries the blood cells and many dissolved substances
• Arteries


  Carry blood away from the heart, have a thick layer of smooth and elastic fibres and a narrow lumen to withstand the high pressure of blood flow
• Veins


  Carry blood towards the heart, have a wider lumen and valves to prevent backflow of blood
• Capillaries


  Extremely small vessels that deliver oxygen and glucose to cells and collect waste products
• There are 60,000 miles of blood vessels in the average adult
• At the lungs, oxygen moves into red blood cells and carbon dioxide moves out of the plasma and into the lungs
• At the body cells, oxygen and glucose are delivered and carbon dioxide and urea are collected
• Exchange of substances at the capillary

  Glucose and oxygen pass from blood into body cells, carbon dioxide, urea and other wastes pass from cells into blood
• At the lungs, carbon dioxide is released out of the plasma and exhaled, oxygen moves into red blood cells
• Function of the heart


  Muscular pump that forces blood through the blood vessels of the body
• Heart structure


  Divided into two halves by a thick wall of muscle, left side deals with oxygenated blood, right side deals with deoxygenated blood, each half further divided into atria and ventricles by valves
• Left side of the heart has thicker muscle wall to pump blood with greater force around the whole body, right side only has to pump blood to the lungs
• Both sides of the heart work simultaneously
• Atria


  The top chambers of the heart
• Ventricles


  The lower chambers of the heart
• The left side of the heart is stronger than the right, which means that the left side has a thicker muscle wall
• Reason for left side being stronger

  The left side needs to pump blood with greater force so that it will travel the greater distance around the whole body. The right side only has to pump blood a shorter distance to the lungs
• Blood flow through the heart


  1. Blood always enters the atria (top chambers) first

  2. Blood then pushes the valves open and flows into the ventricles (lower chambers)

  3. The muscle wall of the ventricles then contracts which forces the blood upwards into the blood vessels

  4. Blood from the right ventricle goes to the lungs

  5. Blood from the left ventricle goes to the rest of the body
• A heart attack occurs when the coronary artery becomes blocked, reducing the supply of oxygen and glucose to the heart muscle cells, causing them to stop contracting (beating) and the heart to stop
• How coronary arteries become blocked


  • Fatty deposits being laid down on their inside surface
  • When the artery gets narrower it is more likely that red blood cells will form a clot
• Factors that contribute to coronary artery blockage

  • Eating an excess of foods high in saturated fat and cholesterol
  • Smoking
  • High blood pressure
  • High salt diet
  • Obesity
  • Lack of exercise
• Ways to prevent coronary heart disease/heart attacks

  • Eating a diet low in saturated fat
  • Eating a diet low in salt
  • Exercising regularly
  • Reducing stress
  • Reducing smoking
• Xylem


  Cells that carry water in plants
• Transpiration


  The mechanism of moving water in a plant
• External factors affecting transpiration

  • Wind speed
  • Temperature
  • Humidity
• Phloem


  Tubes that carry sugars in plants
• Translocation


  The process of moving sugar (food) molecules from one place to another in a plant
• Roots absorb water and dissolved minerals, which move through the roots and stem to the leaves
• Leaves are covered in stomata (pores) to allow gases to enter and leave
• If a plant loses more water than it can absorb, it will start to wilt
• Plants also take in dissolved minerals with the water they absorb
• Water is carried through xylem cells in plants
• The process by which water moves through a plant is called transpiration