Cardiovascular system

• Common features of a transport system

  • a medium to carry materials eg blood
  • form of mass transport to move medium
  • closed system of tubes to reach every part of organism
  • mechanism to move the medium
• Open circularity system is found in molluscs and arthropods
• Closed circularity system vertebrates and earthworms
• In open circularity vessels are open ended
• Closed circularity system blood is fully enclosed within blood vessels at all times. Substances diffuse in and out of the blood into cells.
• Closed circularity system vessels are closed
• Single circularity system are found in fish
• Double circularity system found in mammals
• Arteries have small lumen and thick elastic fibres and smooth muscle to transport high pressure oxygenated blood away from the heart
• Veins have a large lumen and thin elastic and smooth muscle and have semi lunar valves to stop blood back flow. They transport deoxygenated blood back to the heart.
• Capillaries have single cell walls and distribute oxygenated blood from the arteries to tissues around the body and transport deoxygenated blood out of tissues back to the heart
• Tricupsid valve is on the Right of the heart
• Bicuspid valve is on the Left of the heart
• Atrioventricular valves prevent back flow from the ventricles into the atria
• Semi lunar valves prevent back flow from arteries into the ventricles
• Atrial systole. Atria contract pressure increases and volume decreases. Semi lunar valves are shut and atrioventricular valves are open. Blood moves from atria of high pressure to ventricles of low pressure.
• Ventricle systole. Ventricles fill with blood and pressure increases. Ventricles contract and volume decreases. Atrioventricular valves shut and semi lunar valves open. Blood moves from ventricles up into arteries.
• Diastole. Atria and ventricles relax. Volume of atria no ventricles increases. High pressure blood in the arteries closes semilunar valves. Blood enters the atria which increases pressure in atria to open atrioventricular valves. This causes blood to passively move into atria from ventricles.
• Blood moves from an area of high to low pressure.
• As chambers fill with blood pressure increases.
• When chamber contracts pressure increases
• Small volume = high pressure
• High volume = low pressure
• increase in pressure opens valves
• Stroke volume is the volume of blood pumped by the left ventricle in each heart beat
• Heart rate is the number of times the heart beats per minute
• Cardiac output = stroke volume X heart rate
• Aortic pressure increases slightly during diastole due to elastic recoil. This decreases lumen size which increases pressure
• Pressure in veins and capillaries is low and constant
• Blood pressure is highest in the aorta. In systole elastic fibre stretch and allow more blood through. In diastole elastic fibres recoil which forces blood through.
• The left ventricle has thicker muscle than the right
• adaptations of arteries to withstand high blood pressure

  • have lots of smooth muscle to withstand high pressure blood
  • have lost of elastic tissue that stretches and re coils to maintain blood pressure
  • smooth endothelium reduces friction of moving blood
  • protein coat prevents artery walls splitting under high pressure
• haemoglobin contains 4 nitrogen atoms which helps oxygen bind to red blood cells