heart

• Pulmonary artery:

  The heart pumps out deoxygenated blood to the lungs through this artery.
• Coronary arteries:

  The heart muscle is supplied with oxygenated blood through these arteries.
• Aorta:

  The heart pumps out oxygenated blood to the body through this artery.
• Pulmonary vein:

  The heart receives oxygenated blood from the lungs through this vein.
• Vena cava:

  The heart receives deoxygenated blood from the body through this vein.
• the heart has 4 chambers
• top chambers of the heart: atriums
• bottom chambers of the heart: ventricles
• Double circulatory system

  -blood flows into the heart via the vena cava and pulmonary vein

  -blood then flows into the right atrium and the left atrium

  -blood from pulmonary vein is oxygenated

  -blood from vena cava is returning from the body and is deoxygenated

  -as the 2 atria contract, they push blood into the ventricles

  -2 ventricles contract

  -pushes blood out into the pulmonary artery which travels to the lungs

  -pushes out blood into the aorta which goes to the rest of the body
• process of heart beating happens 70 times a minute:

  group of cells in the right atrium act as a pacemaker
• pacemaker cells generate small electrical impulses which spread though the muscular walls of the heart causing it to contract
• faulty pacemaker:

  -doctors can implant an artificial pacemaker, a small device under the skin, has wire tat can carry electrical impulses to the heart causing it to contract
• artery:carries blood away from the heart, thick muscular wall, high pressure
• vein: carries blood to the heart
• coronary arteries supply the heart with oxygenated blood.
• pulmonary artery: carries deoxygenated blood away from the heart to the lungs
• pulmonary vein: carries oxygenated blood from the lungs to the left atrium
• The journey of blood around the body

  Body tissues ➔ vena cava ➔ right atrium ➔ right ventricle ➔ pulmonary artery ➔ lungs ➔ pulmonary vein ➔ left atrium ➔ left ventricle ➔ aorta ➔ body tissues
• Which blood vessel carries oxygenated blood from the heart to the body?

  aorta
• The movement of blood between the ventricles and atria: 

  1. The walls of the atria contract, pushing blood into the relaxed ventricles.
  2. The walls of the ventricles contract, pushing blood out of the heart. At the same time, more blood will enter the now-relaxed atria.
  3. The cycle repeats.
• capillaries: exchange nutrients and oxygen with tissues
• arteries:

  -blood will be at high pressure

  -need to be strong and elastic

  -have thick layer of muscle and elastic tissue

  -the wall of the artery is thick compared to its lumen
• capillaries:

  -really small vessels and come into contact with all the cells in our body

  -to exchange substances with cells, supplying them with nutrients and oxygen

  -take away waste products such as carbon dioxide

  -walls are a single cell thick and permeable so substances can easily diffuse through them

  -as they are so tiny, the lumen is also tiny but total cross sectional area is huge

  -lower blood pressure giving time to exchange things with tissues
• capillaries join to form larger vessels called veins
• veins:

  -large, with biggest lumens

  -thin walls with a small layer of elastic fibres and smooth muscle

  -blood travels at low pressures so dont need to be strong

  -have valves to prevent backflow of blood, ensuring it alwys flows towards the heart
• right atrium receives deoxygenated blood from the body through the vena cava
• oxygenated blood moves through the left ventricle which pumps it around the body through the aorta