Circulatory System

• Main functions of the circulatory system

  • Transports gases from the respiratory system
  • Transports nutrients from the digestive system
  • Regulates internal temperature
  • Transports chemical substances that are vital to health from one part of the body to another
  • Protects against blood loss from injury or toxic substances introduced into the body
• Simple celled organisms

  • Don't have a circulatory system
  • Water pulled into organisms brings oxygen and nutrients
  • Water and waste expelled through an opening
• Complex multicellular animals


  • Have a circulatory system
  • Have 3 layers of cells
  • Cells in mesoderm need a circulatory system to deliver needed substances
• Open Circulatory System

  • Blood flows freely within the body cavity
  • No distinction between the blood and the interstitial fluid
• Closed Circulatory System


  • Blood is kept in the blood vessels
  • Separate from body tissues
  • Blood is separate from interstitial fluid
• How the heart works


  1. Heart has 2 parallel pumps separated from the septum

  2. Left and right pumping action synchronised

  3. Pump on right receives deoxygenated blood from the body tissue and pumps it to lungs

  4. Pump of the left receives oxygenated blood from lungs and pumps it to body tissues
• Pulmonary circulation


  The path that blood from the heart to the lungs and back to the heart
• Systemic circulation


  The path that blood follows from the heart to the body and back to the heart
• Atherosclerosis is the hardening of the arteries, plaque buildup that results in heart failure or a heart attack and death
• Arteries

  • Carries blood away from the heart, inner and outer layers are composed of connective tissue while middle layer is made of elastic connective tissue
• Capillaries


  • Single layers of cells, very small (<0.0005), great for diffusion but bruise easy
• Veins


  • Carries blood to the heart
• Vasodilation


  The widening of the blood vessels, happens when someone exercises
• Vasoconstriction


  The narrowing of the blood vessels, happens when cold, stressed
• Components of blood


  • 5L of blood
  • Erythrocytes (different types of blood A, B, AB, O with + or - antigens)
  • Red blood cells which contains haemoglobin which contains iron
  • White blood cells help fight off infections/invaders
  • Platelets form clots
  • Plasma helps maintain blood pressure and circulation
• Role of circulatory system and regulation of temperature

  1. Thermoregulation by vasodilation and vasoconstriction

  2. Vasodilation is the process of blood vessels close to the surface of the skin enlarging, allowing more heat to be lost from the blood

  3. Controlling the flow of blood to the skin is an important way to control the rate of heat loss to—or gain from—the surroundings

  4. The cardiovascular system works with thermoregulation to keep the body at a healthy temperature
• How heartbeat works


  1. SA nodes controls the hearts tempo, small mass of tissue in the right atrium that stimulates the heartbeat

  2. Contractions travel to the AV nodes, small mass of tissue in the right atrioventricular where SA nodes are passed to ventricles
• Heart sounds


  • Lub is the closing of the atrioventricular valve (AV)
  • DUB is the closing of the semilunar valves (SA)
• ECG - electrocardiogram


  1. P = SA nodes fire and the atria contracts

  2. QRS = begins when the AV nodes stimulates the ventricles and the AV nodes close creating "Lub"

  3. T =When the SA nodes close that creates the "DUB"
• Blood pressure


  • The pressure that acts upon the vessel walls as it travels through the body
  • Measured by a blood pressure cuff
  • Written/recorded in millimetres of mercury
  • Systolic is written over diastolic in the form of a fraction
  • Normal BP is 120/80 or less
• Cardiac output


  The amount of blood being pumped into the heart, measured in mL/min, an indication of O2 delivered to the body
• Stroke volume


  The amount of blood forced out of the heart with every heartbeat, determined by how easily the heart fills with blood and how readily the blood is emptied from the heart, average person has a stroke volume of ~70mL and resting heart rate of ~70 bpm
• Cardiac output = heart rate x stroke volume
• Aneurysm


  A bulge in an artery or chamber caused by a weakened area of heart muscle, if left untreated can burst which leads to internal bleeding and death, they are surgically removed
• Arrhythmia


  The irregular of the heartbeat, if left untreated it's not too harmful but can lead to less blood flow to vital organs like the brain, people with an arrhythmia usually get a pacemaker that helps regulate their heart rate
• Haemophilia


  Lacking of proteins used to help clot blood in the body, hemophilic people (like Alfano) result in needing clotting medications when they get hurt, they don't stop bleeding as their body doesn't clot for them
• What is Atheroscleroisis?


  Hardening of the arteries