Human biology

• Types of circulatory system

  • Open circulatory system
  • Closed circulatory system
• Open circulatory system


  • The heart pumps blood into vessels that are open ended
  • The blood leaves these vessels and flows around the body cells and returns back to the heart through blood vessels

  
• Closed circulatory system


  • Blood remains in a continuous system of blood vessels
  • Any substances in the blood are exchanged with the cells by diffusion through the blood vessels thin walls

  
• Why is a closed circulatory system more efficient

  • Animals are much more active as blood can be pumped around the body faster (allows oxygen to be pumped around the body faster)
  • Allows the flow of blood or pressure to be increased or decreased to different organs (more blood to muscles when exercising)
• Types of blood vessels

  • Arteries
  • Veins
  • Capillaries

  
• Arteries


  Carry blood away from the heart
• Veins


  Carry blood to the heart
• Capillaries


  • Small vessels that connects arteries and veins together
  • Capillaries have very thin walls and are permeable (this allows exchange of oxygen, water, carbon dioxide between blood and body cells)

  
• Structure of arteries and veins

  • Inelastic protein (collagen) – prevents the walls from over expansion
  • Involuntary muscles and elastic fibres – can alter the size of the vessel. During exercise the muscles can cause the arteries to dilate (expand) and allow more blood to flow
  • Endothelium – inner layer of cells lining the lumen
• Blood pressure


  The force the blood exerts against the wall of an artery
• Blood pressure is much higher in arteries than veins
• How does blood flow through veins

  1. Physical activity squeeze the vein pushing blood around in the veins as they are under low pressure

  2. Valves prevent the backflow of blood in veins (ensure blood flows in one direction)
• The heart


  • Located between the two lungs and above the diaphragm
  • Situated in the thoracic cavity (chest cavity)
  • Made of cardiac muscle and that is contractile (can shorten)
  • The heart is surrounded by a double membrane called the pericardium (Pericardial fluid reduces friction when the heart moves)
• The pulmonary vein carries very little carbon dioxide and higher levels of oxygen
• The pulmonary artery carries very little oxygen and higher levels of carbon dioxide
• Atria


  • The two upper chambers of the heart
  • Atria have thin walls as they only have to pump blood to the ventricles (short distance)
• Ventricles


  • Right ventricle pumps blood to the lungs (shorter distance so thinner wall)
  • Left ventricle pumps blood to head and lower body (left ventricle has a much thicker wall as it has to pump blood all over the body)
• Valves


  • Ensure blood can only flow in one direction (prevent the back flow in the heart)
  • Tricuspid valve has three flaps and is located between right atrium and right ventricle
  • Bicuspid valve has two flaps and is located between left atrium and left ventricle
  • Semi lunar valves allow blood to flow out of the heart into the aorta and the pulmonary arteries and prevent blood re-entering the heart, located at the base of the aorta and pulmonary artery
• How blood travels through the heart

  1. Deoxygenated blood enters the right atrium from the vena cava, flows into the right ventricle, then into the lungs through the pulmonary artery

  2. Oxygenated blood enters the left atrium from the pulmonary vein, flows into the left ventricle, then out through the aorta to the body

  
• LORD - Left Oxygenated Right Deoxygenated
• Double circulation


  • The heart is separated into two sections by septum
  • The septum allows the separation of the oxygenated and deoxygenated blood
• The two circuits


  • Pulmonary circuit
  • Systemic circuit
• Rich blood


  Oxygenated blood
• Path of oxygenated blood

  1. Left atrium contracts and forces blood into left ventricle

  2. Left ventricle contracts and the bicuspid valve closes which allows blood to be pumped out through the aorta to the rest of the body

  3. Semi lunar valves close so blood cannot flow back into heart
• LORD


  Left Oxygenated Right Deoxygenated
• Double Circulation


  • The heart is separated into two sections by septum
  • The septum allows the separation of the oxygenated and deoxygenated blood
• The two circuits


  • Pulmonary circuit
  • Systemic circuit
• Pulmonary circuit


  1. Right ventricle pumps blood through pulmonary circuit

  2. Blood gains oxygen and removes carbon dioxide in the lungs (by diffusion)
• Pulmonary circuit


  • Circuit is short (muscles of right ventricle are thin for this reason)
• Systemic circuit


  Left ventricle pumps oxygenated blood to head, arms and legs in the systemic circuit
• Systemic circuit


  • Longer circuit so wall on left ventricle is really thick muscle
• Veins that carry blood

  • Renal vein (lowest in metabolic waste)
  • Hepatic portal vein (between intestine and liver)
  • Hepatic vein (carries blood rich in urea out of the liver)
  • Pulmonary vein (carries blood rich in oxygen and has low levels of carbon dioxide)
• Arteries that carry blood

  • Renal artery (carries blood into the kidney)
  • Hepatic artery (carries blood into the liver)
  • Pulmonary artery (carries blood rich in carbon dioxide and has low levels of oxygen)
  • Aorta (artery the hepatic artery and renal artery arise from)

  
• Double circulation system


  • Keeps blood separate that is rich in oxygen and blood poor in oxygen
  • Blood pressure is higher so oxygenated blood can reach every part of the body
• Single circulation system


  • Blood pressure is low which can reduce the organisms metabolism
• How the heart beat is controlled

  1. Heartbeat is controlled by the pace maker (situated in the top of the right atrium)

  2. Pace makers release electrical impulses causing muscle chambers to contract (controlled by the brain)
• Steps of a heartbeat

  1. SA node (pacemaker or sino – atrial) releases electrical impulses causing the atria to contract

  2. SA nodes electrical impulse also stimulates the AV (atrio - ventricular) node

  3. AV node sends an electrical impulse down muscle of the septum causing the ventricles to contract
• SA node


  Located on wall of right atrium
• AV node


  Located on septum between right atrium and right ventricle
• It is the brain who controls the rate of pacemaker by sending heart electrical impulses