circulatory system in animals

• Circulatory system


  A mass transport system that connects exchange surfaces in larger organisms
• Cells of all living organisms need a constant supply of reactants for metabolism, e.g. oxygen and glucose
• Single celled organisms can gain oxygen and glucose directly from their surroundings, and the molecules can diffuse to all parts of the cell quickly due to short diffusion distances
• Larger organisms are made up of many layers of cells, meaning that the time taken for substances such as glucose and oxygen to diffuse to every cell in the body would be far too long.The diffusion distances involved are too great
• Mass transport


  Bulk movement of gases or liquids in one direction, usually via a system of vessels and tubes
• The digestive system


  Is connected to the circulatory system
• The lungs

  Are connected to the circulatory system
• • In a closed circulatory system, blood is pumped around the body and is always contained within a network of blood vessels
  • All vertebrates and many invertebrates have closed circulatory systems
  • In an open circulatory system, blood is not contained within blood vessels but is pumped directly into body cavities
  • Organisms such as arthropods and molluscs have open circulatory systems.
• • Humans have a closed double circulatory system: in one complete circuit of the body, blood passes through the heart (the pump) twice
  • The right side of the heart pumps blood deoxygenated blood to the lungs for gas exchange; this is the pulmonary circulatory system
  • Blood then returns to the left side of the heart, so that oxygenated blood can be pumped efficiently (at high pressure) around the body; this is the systemic circulatory system
• The main blood vessels

  • Pulmonary artery - carries deoxygenated blood away from the heart, towards the lungs
  • Pulmonary vein - carries oxygenated blood away from the lungs, towards the heart
  • Coronary arteries - supply the heart with oxygenated blood
  • Aorta - carries oxygenated blood out of the heart and to the rest of the body
  • Vena cava - carries deoxygenated blood into the heart
  • Renal artery - supplies the kidneys with oxygenated blood
  • Renal vein - carries deoxygenated blood away from the kidneys, towards the heart
• arteries

  • thick muscular walls
  • elastic tissue to stretch and recoil as heart beats
  • can withstand high pressure
  • inner lining- endothelium is folded, allow artery to stretch, helps maintain high pressure
  • carry blood from heart to rest of the body
  • divided into arterioles
• capillaries


  • vessels which link arterioles to veins
  • has thin walls for short diffusion pathways
  • many of them to provide large SA
  • narrow diameter and narrow lumen so that on red blood cell can fit at one time for efficient diffusion
• vein

  • takes blood back to heart under low pressure
  • thin muscle layer: so low blood pressure, easily constrict and dilate to control blood flow
  • wide lumen
  • have valves to prevent backflow of blood
• arterioles

  • lower pressure than in arteries
  • thicker muscle layer than arteries allow constriction of lumen in arteriole, restrict blood flow and controls movement to capillaries
  • thinner elastic layer than arteries since blood pressure is lower
• the human heart

  the right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood the the whole body

  A) pulmonary artery

  B) aorta

  C) pulmonary veins

  D) left atrium

  E) vena cava

  F) right atrium

  G) tendons

  H) right ventricle

  I) left ventricle

  
• label the heart

  A) superior vena cava

  B) pulmonary artery

  C) aorta

  D) pulmonary veins

  E) right atrium

  F) right atrioventricular valve

  G) left atrium

  H) semi-lunar valves

  I) left atrioventricular valve

  J) septum

  K) right ventricle

  L) left ventricle

  M) inferior vena cava

  
• Left ventricle

  • Thicker, more muscular wall than right ventricle
  • Needs to contract more powerfully to pump blood all the way around the body
• Right ventricle


  • Needs to get blood all around the body
• Ventricles

  • Thicker walls than atria
  • Push blood out of the body
• Atria


  • Push blood a short distance into ventricle
• Atrioventricular (AV) valves


  Link atria to ventricles and stop backflow of blood back into atria when ventricles contract
• Semilunar (SL) valves

  Link ventricles to pulmonary artery and aorta, and stops backflow of blood back into the heart after ventricles contract
• Valves in the heart

  • Open when the pressure of blood behind them is greater than the pressure in front of them
  • Close when the pressure of blood in front of them is greater than the pressure behind them
  • Important for keeping blood flowing forward in the right direction and stopping it flowing backwards
  • Important for maintaining the correct pressure in the chambers of the heart
• Atrioventricular valve


  • Also known as the tricuspid valve
  • Separates the right atrium and right ventricle
• Pulmonary valve


  Separates the right ventricle and the pulmonary artery
• Mitral valve


  • Also known as the bicuspid valve
  • Separates the left atrium and left ventricle
• Aortic valve


  Separates the left ventricle and aorta
• Blood vessels bringing blood to the heart

  • Vena cava
  • Pulmonary vein
• Blood vessels taking blood away from the heart

  • Pulmonary artery
  • Aorta
• Coronary arteries

  • The heart is a muscle and so requires its own blood supply for aerobic respiration
  • The heart receives blood through arteries on its surface, called coronary arteries
  • It’s important that these arteries remain clear of plaques, as this could lead to angina or a heart attack (myocardial infarction)
• Left ventricle

  Thicker
• Right ventricle


  Thinner
• Blood leaving the right ventricle

  Travels less distance than blood leaving the left ventricle
• The blood pumped out from the right ventricle travels to the lungs
• Blood leaving the left ventricle has to travel to the rest of the body to deliver oxygen for respiration
• Blood leaving the left ventricle

  Must be under high pressure
• High pressure of blood leaving the left ventricle

  Generated by the contraction of the muscular walls of the left ventricle
• Blood leaving the right ventricle


  Generates less pressure from the contraction of its thinner walls
• Blood only has to reach the lungs from the right ventricle
• The Cardiac Cycle

  • The cardiac cycle is the series of events that take place in one heart beat, including muscle contraction and relaxation
  • The contraction of the heart is called systole, while the relaxation of the heart is called diastole
  • One cardiac cycle is followed by another in a continuous process
  • There is no gap between cycles where blood stops flowing