Human cardio

• Cardiovascular system


  Main transport system for nutrients and the disposal of bodily by-products
• Cells of the body

  • Act like individual engines that are able to cooperate collectively
  • Require nutrients from food to supply energy
  • Require oxygen (O2) from the air to combine with nutrients in energy release
  • Require a way to dispose of the by-products, like carbon dioxide (CO2), water (H2O), and heat
• The body has cells numbering in the billions, so an elaborate transportation system is needed to deliver fuel and O2 to the cells and remove the by-products
• Blood


  • Performs the important body function of the cardiovascular system
  • Represents about 7% of the body mass or about 4.5 kg (~4.4 liters) in a 64 kg person
  • Has a density of 1.04 x 103 kg/m3, a little bit more than the density of water

  
• Components of blood


  • Blood plasma
  • Red blood cells (erythrocytes)
  • White blood cells (leukocytes)
  • Platelets (thrombocytes)

  
• Blood plasma


  • Whitish liquid that composes about 55% of the total volume
  • Approximately 900g of H2O per liter and about 70 g of protein per liter

  
• Red blood cells (erythrocytes)

  • Compose about 44% of the volume
  • Disk-shaped with a 7 μm diameter and about 2 μm thickness
  • Determine the fluid characteristics of blood

  
• White blood cells (leukocytes)


  • Spherically shaped and are about 10 – 20 μm in diameter
  • Important in the immune system as they increase in number during an infection
• Platelets (thrombocytes)


  • Flat-shaped with a length of about 2.5 m and a thickness of 0.6 m
  • Important in blood clotting
• Functions of blood


  • Red blood cells carry O2 from the lungs to the tissues and CO2 from the tissues to the lungs
  • Blood plasma transports antibodies, food substances, waste products, and hormones
  • Clotting factors circulate in the plasma to prevent blood loss
  • Regulates the water content of tissue cells
  • Blood buffers maintain the correct acidity of body fluids
  • Enzymes may be transported by blood plasma, which also distributes the heat produced by metabolism

  
• Arteries


  Transport blood away from the heart
• Veins


  Transport blood towards the heart
• Heart


  Provides the force needed to circulate the blood through the pulmonary circulation in the lungs and the systemic circulation in the rest of the body

  
• Heart valves


  • If functioning properly, permit the blood to flow only in the correct direction
  • If diseased and do not open or close properly, the pumping of the blood becomes inefficient

  
• The blood volume is not uniformly divided between the pulmonary and systemic circulation

  
• Calculating the mass of blood in circulation

  1. Multiply body mass by 7% to get total blood mass

  2. Multiply total blood mass by 80% to get mass of blood in systemic circulation

  3. Multiply total blood mass by 20% to get mass of blood in pulmonary system

  4. Multiply mass of blood in systemic circulation by 15% to get mass of arteries

  5. Multiply mass of blood in systemic circulation by 10% to get mass of capillaries

  6. Multiply mass of blood in systemic circulation by 75% to get mass of veins

  7. Multiply mass of blood in pulmonary system by 46.5% to get mass of arteries

  8. Multiply mass of blood in pulmonary system by 7% to get mass of capillaries

  9. Multiply mass of blood in pulmonary system by 46.5% to get mass of veins

  
• Calculating the mass of a person from pulmonary blood mass

  1. Compute total blood mass by dividing pulmonary blood mass by 20%

  2. Compute body mass by dividing total blood mass by 7%

  
• Left ventricle


  Compressed by heart muscle at a pressure of 17kPa (125 mmHg) to pump blood through the aorta into the large systemic cycle

  
• Right ventricle


  Compressed with 3.5kPa (25 mmHg) to pump blood through the pulmonary arteries into the small pulmonary cycle

  
• Diastole


  When the heart relaxes after contraction
• Systole


  When the heart contracts to pump blood out

  
• The muscle driving the left ventricle is about three times thicker than that of the right ventricle, and the circular shape of the left ventricle is more efficient for producing high pressure than the elliptical shape of the right ventricle

  
• Each contraction pumps about 75 – 80 ml of blood, which is about 1.82% of total blood mass per contraction

  
• Calculating the time for total blood mass to circulate

  1. Assume flow rate is about 80 ml/s and total blood mass is 4,400 ml

  2. Time = volume / flow rate = 4,400 ml / 80 ml/s = 55 s

  
• Calculating the action time and resting time of the heart muscle

  1. Assume pulse rate is 120 bpm

  2. Time per beat = 1 beat / (120 beats/60 seconds) = 0.5 s

  3. Action time = 0.5 s x 1/3 = 0.17 s

  4. Resting time = 0.5 s x 2/3 = 0.33 s
• There are drastic differences in pressure in the blood vessel system, with peak pressure conditions reached in the left ventricle during contractions of the heart

  
• 80 ml/s


  It will take about a minute for the total blood mass to flow through the whole CVS
• Cardiac cycle


  The pumping action of the heart takes place in one-third of the cycle, the heart muscle rests for about two-thirds of the cycle
• Computing action time and resting time of the heart muscle

  1. Time per beat = 1 beat / 120 beats/60 seconds = 0.5 s

  2. Action time = 0.5 s x 1/3 = 0.17 s

  3. Resting time = 0.5 s x 2/3 = 0.33 s
• Action time


  When the heart muscle is contracted
• Resting time


  When the heart muscle is relaxed
• There are drastic differences in pressure in the blood vessel system

  
• Peak pressure conditions are reached in the left ventricle during contractions of the heart muscle

  
• Pressure drops with increasing distance to the heart
• Gravity influences the pressure conditions in the cardiovascular system
• Static pressure is height dependent: P = ρgh
• The pressure across the blood vessel wall is called the transmural pressure

  
• Blood vessels have elastic walls which have the tendency to contract, which means vessels may collapse due to wall tension
• When a pressure pulse travels along the blood vessel, the blood vessel may burst due to the rapid pressure increase

  
• The greatest pressure changes occur in the region of the arterioles and capillaries