Lesson slides

• What is the circulatory system?

  An organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilise temperature and pH, and maintain homeostasis
• What do arteries divide into?

  Narrow capillaries
• How are are they well adapted?

  Narrow lumin, very thin one-cell thick walls to allow faster diffusion of substances into and out of the capillary and they form a fine network running through the tissues
• Where do capillaries carry blood?

  All over the body, mainly running through tissues
• Where does blood flow in arteries?

  Away from the heart
• Why can you feel your pulse?

  Your pulse is due to a wave of stretching that passes along the walls of arteries which you can feel
• What does the circulatory system help stabilise?

  Temperature, pH and homeostasis
• How are arteries structured?

  They have narrow lumen but have a thick layer of elastic and muscle fibres
• Why do arteries have thick walls?

  The heart pumps high pressure blood into arteries with each beat. The walls are thick to withstand the sudden increases in pressure
• How do arteries maintain blood pressure?

  After stretching, muscles contract making the blood flow much more smoothly and the elastic fibred in the artery walls recoil maintaining the blood pressure
• Where do veins carry blood to?

  The heart
• How are veins structured?

  They have wide lumen but thin flexible walls with vein valves
• How are veins suitably adapted?

  Blood flows under low pressure in veins so they only need thin walls. As you move, muscles in your skeleton help to push blood along the veins
• What do valves do?

  Valves prevent blood from flowing the wrong way
• How much blood is in the human body?

  5 litres
• What is plasma?


  a straw-coloured liquid in which all the cells are suspended and carries dissolved substances such as glucose, carbon dioxide and urea
• What are red blood cells?

  Called erythrocytes
• How many erythrocytes are in the body?

  5,000,000 per ml³ of blood
• How many white blood cells are in the body?

  7,000 per ml³ of blood
• How many platelets are in the body

  250,000 per ml³ of blood
• What makes up blood?

  • Plasma- 55%
  • Erythrocytes- 41%
  • White blood cells- 4%
  • Platelets- 0.01%
• What is the function of erythrocytes?

  Haemoglobin in the erythrocytes absorb oxygen and transport it around the body. They also remove carbon dioxide from the body
• How are erythrocytes well adapted to their function

  They have no nucleus so there is more space for haemoglobin. Their 'biconcave' shape allows for a large SA:V ratio for oxygen to diffuse in and out
• What are the two types of white blood cells?

  Phagocytes and lymphocytes
• How are lymphocytes and phagocytes different?

  Lymphocytes produce proteins called antibodies that stick to foreign cells and help to destroy them. Phagocytes surround foreign cells and digest them.
• What are platelets?


  Platelets are tiny fragments of cells that have no nucleus and produce substances needed to clot the blood at the site of an injury which helps to create scabs