The circulatory system

• Circulatory System


  Carries food and oxygen to every cell in the body, as well as removing waste products
• Heart


  • Acts as a waste collection service - carries waste products to where they can be removed
• Circulatory System


  • A DOUBLE Circulatory System
  • Made up of the heart, blood vessels and blood
• Double Circulatory System


  1. Right ventricle pumps deoxygenated blood to the lungs

  2. Left ventricle pumps oxygenated blood to the body
• The blood gives its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again
• Heart


  • Contracts to pump blood around the body
  • Walls are mostly made of muscle tissue
  • Has valves to make sure blood flows in the right direction
• How the heart pumps blood

  1. Blood flows into the two atria

  2. The atria contract, pushing the blood into the ventricles

  3. The ventricles contract, forcing the blood into the pulmonary artery and aorta

  4. The blood then flows to the organs through arteries and capillaries
• Arteries


  • Carry blood away from the heart
  • Have thick, elastic walls to withstand the high pressure
  • Contain thick layers of muscle to control the lumen size
• Capillaries


  • Extremely thin-walled, only one cell thick
  • Allow exchange of substances between blood and body cells
• Veins


  • Carry blood back to the heart
  • Have larger lumen and thinner walls than arteries
  • Have valves to prevent backflow of blood
• The heart also needs its own supply of oxygenated blood through coronary arteries
• Pacemaker


  Group of cells in the right atrium wall that produce an electrical impulse to control the heart rate
• An artificial pacemaker can be used to control the heartbeat if the natural pacemaker cells don't work properly
• You can calculate the rate of blood flow by dividing the volume of blood by the time taken
• Calculating blood flow rate

  • 2.175 litres of blood passed through a vein in 8.7 minutes
  • Rate of blood flow = 2.175 / 8.7 = 0.25 litres/min
• Blood


  Part of a huge transport system
• Main things in blood

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


  • Carry oxygen from the lungs to all the cells in the body
  • Biconave disc shape with large surface area for absorbing oxygen
  • No nucleus to allow more room to carry oxygen
  • Contain haemoglobin
• Haemoglobin in red blood cells

  1. In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin

  2. In body tissues, oxyhaemoglobin splits up into haemoglobin and oxygen
• White blood cells


  • Defend against infection
  • Some can change shape to engulf microorganisms (phagocytosis)
  • Others produce antibodies and antitoxins to fight microorganisms
  • Have a nucleus
• Platelets


  • Help the blood to clot at a wound to stop bleeding and prevent microorganisms getting in
  • Lack of platelets can cause excessive bleeding and bruising
• Plasma


  Pale straw-coloured liquid that carries red and white blood cells, platelets, nutrients, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
• Blood tests can be used to diagnose loads of things, not just disorders of the blood, because the blood transports so many chemicals produced by so many organs
• Diastolic pressure - when the ventricles relax between contractions (lower)
• Systolic pressure - when the ventricles contract and pump blood into the arteries (higher)
• Blood pressure is measured using a sphygmomanometer, which consists of a cuff around the upper arm and a gauge to measure pressure.
• Red Blood Cells (RBCs)

  Type of blood cell responsible for carrying oxygen throughout the body; bright red in color due to hemoglobin protein
• White Blood Cells (WBCs)


  Type of blood cell that is part of the immune system and helps fight infections and diseases; colorless and come in several different types
• Platelets


  Tiny cell fragments that play a crucial role in blood clotting; when a blood vessel is damaged, platelets clump together to form a plug and prevent further blood loss
• Plasma


  Liquid component of blood that suspends all other components; about 90% water and 10% dissolved substances, including nutrients, hormones, waste products, gases, and proteins