Circulatory + Lymphatic

• The cardiovascular system is made up of the heart, blood vessels, and blood.​ The Lymphatic System is made up of lymph vessels and lymph.
• In an open circulatory system, the heart pumps blood to open-ended vessels and cells are surrounded by blood e.g. insects.
• In a closed circulatory system, the heart pumps blood through a continuous system of blood vessels and cells are not surrounded by blood e.g. humans.
• A closed system allows animals to be more active. It allows the flow of blood to be increased or decreased.
• Smoking causes increased heart rate and raised blood pressure causing the heart to work harder.
• Arteries carry blood away from the heart. They have thick walls and carry blood at high pressure. They have a narrow lumen and no valves.
• Veins have valves to prevent the backflow of blood and a thinner wall to allow for a greater volume of blood to pass through. Blood flows slowly and is deoxygenated.
• Capillaries have a narrow lumen and a thin wall to allow for the diffusion of substances. It provides a large surface area.
• Structure of the heart

  
• 1. The Atria: ​

  • Upper chambers of the heart​
  • Right atrium receives blood from the Vena Cava​
  • Left atrium receives blood from Pulmonary Vein​
  • Both atria pump blood to lower chambers of the heart called ventricles
• The Ventricles​

  • Lower chambers of the heart​
  • Right ventricle contracts and pumps blood to the lungs through Pulmonary Artery​
  • Left ventricle contracts and pumps blood to all parts of the body through the Aorta​
• Left ventricle has to pump around the whole body (greater distance). Right ventricle only has to pump blood a short distance to the lungs​.
• Valves: ​

  • Prevent backflow of blood​
  • Tricuspid Valve: Has 3 flaps, separates right atrium and ventricle​
  • Bicuspid Valve: Has 2 flaps, separates left atrium and ventricle​
  • Semi lunar Valves: Half moon shape, located at the base of pulmonary artery and aorta.
• Pacemaker:​

  A bundle of specialised cells (tissue) located in the wall at the top of right atrium​

  Called the Sino Atrical Node
• A pacemaker is used to control the heartbeat​. It sends electrical impulses to the walls of the atria causing them to contract. The electrical impulses stimulate another bundle of tissues in the right atrium called the AV node causing the ventricles to contract.​
• Pulmonary and Systemic circuits

  
• Tissue fluid is fluid that has leaked out of blood plasma through the walls of capillaries into the spaces between body cells.
• Because of the thin walls of capillaries and high pressure of arterioles some plasma leaks out into spaces between our cells, causing tissue fluid.
• Materials entering and leaving the cell must pass through tissue fluid. It prevents edema (swelling)
• About 10% of tissue fluid enters lymph vessels. Lymph vessels will eventually drain the lymph back into the blood via the subclavian vein in the neck.
• Lymph is a watery fluid which flows slowly in lymph vessels
• Lymph nodes are small swellings found along lymph vessels​. They can be found in clusters in areas such as the tonsils, neck, and armpits​. They contain large numbers of lymphocytes (WBC)
• The lymphatic system protects the body from disease.
• The thoracic duct is situated on the left side of the body while the right lymphatic duct is located on the right shoulder. These ducts empty lymph fluid into the bloodstream.
• Lymph nodes contain white blood cells which kill micro-organisms directly.