Cardiovascular System

• Systole

  • Period of the cardiac cycle when the heart muscle contracts and blood is pumped out of the chambers. 
• Diastole 

  • Period of the cardiac cycle when the heart muscle relaxes and blood fills the chambers. 
• Pulmonary circulation

  • Deoxygenated blood returns to the right atrium of the heart from the systemic circulation. From here, it empties into the right ventricle and is pumped through the lungs. Within the lungs, blood picks up oxygen (O2) and releases carbon dioxide (CO2). The pulmonary veins deliver the newly oxygenated blood to the left atrium of the heart, where it enters the systemic circulation.
• Systemic circulation

  • Oxygenated blood in the left atrium empties into the left ventricle. From here, it is pumped throughout the body. As blood flows through the body, active tissues extract O2 and release CO2 so that blood becomes increasingly deoxygenated. Systemic veins deliver the deoxygenated blood to the right atrium of the heart, where it enters the pulmonary circulation.
• What causes the heart valves to close?

  • Due to Pressure Gradient
• • Pressure gradient is also the primary determinant of blood flow
• Flow of blood goes from high pressure to low pressure
• Coronary Ostia

  • Two holes located in the aorta next to the aortic valve
  • One ostia opens to the right coronary artery
  • Other opens to the left of coronary artery
  • On this part = drains oxygenated blood
• Coronary Sinus

  • Located at the right atrium
  • Between opening of inferior vena cava and tricuspid valve
  • On this part = drains deoxygenated blood into the right atrium through through the coronary sinus
• BASIC PRINCIPLES OF HEMODYNAMICS

  • Closed circuit of distensible tubes (one pathway)
  • Circuit: 
  • Systemic
  • Pulmonary 
  • Arrangement: 
  • Parallel
  • Series 
  • Unidirectional blood flow propelled along a PRESSURE GRADIENT. 
  • Flow changes in one area will lead to changes in other areas.
• Skeletal Muscle Pump

  Blood pressure within a vein increases as the skeletal muscles surrounding the vessel contract. The increased pressure causes valves within the vein to open and pushes blood toward the heart. 
• When the skeletal muscle is relaxed, the valves are closed, preventing backward flow of the blood.
• Contract muscles = open valve = allow transport of blood (Systemic circulation back to the heart)
• Clinical Application: Varicose Veins

  • Distended veins at the back of leg
  • Pregnancy/ prolonged standing
  • Lower leg muscles are contracted = valves open = but blood from lower part of the valve cannot enter (or flow back to the heart) therefore blood will just stay inside the valve = distention
  • Management: Position legs upwards (facilitate gravity to pull again the distended vein to go back to normal)
• Intercalated discs - this is where transmission of action potential happens which allows the heart to contract
• Intercalated discs

  • It contains gap junctions and desmosomes that allow transmission of different ions for effective contraction. It also contains actin, myosin, z-line, mitochondrion, etc
• Gap junctions - direct path
• Desmosomes - also makes muscle cells more rigid
• As long as there is pressure gradient in your body there will be blood flow
• As long as there is pressure gradient in your heart then there is opening and closing of heart valves