circulatory system

• the circulatory system is the transport system carrying nutrients and oxygen to cells, carries wastes to where they can be disposed of and distributes heat throughout your body
• the circulatory system consists of the heart, blood vessels and blood
• • the heart is the engine room of the circulatory system, pumping continuously to keep blood moving
  • the blood carries materials needed by the body through blood vessels
  • the blood vessels are a network of tubes that carry blood throughout the body
• the three types of blood vessels are arteries, veins and capillaries
• arteries:

  • carry blood away from heart
  • walls are thick, tough and elastic to withstand high pressure of blood moving along and to bounce back into shape after each heartbeat
  • arteries carry plenty of blood, so if cut, a lot of blood will be lost in a short amount of time
  • the regular expansion + contraction of arteries in response to heartbeat can be felt in your neck and wrist; this is your pulse
  • generally narrower than veins
  • no valves (except in the heart)
  • usually carries oxygenated blood (except pulmonary artery)
  • high pressure due to proximity to heart's pumping
• arteries branch into smaller and smaller blood vessels called capillaries
• capillaries:

  • one cell thick blood vessels, extremely narrow
  • wall thickness allows materials needed by cells to pass out of capillaries into cells, while waste materials from cell pass into capillary (diffusion)
  • connects arteries and veins, allowing exchange of materials between blood+tissues
  • no valves
  • depending on location, carries both oxygenated and deoxygenated blood
  • low pressure to allow for exchange of substances
  • capillaries join together to form larger blood vessels called veins
• veins:

  • carry blood back to heart
  • generally wider than arteries but have thinner walls as pressure of heartbeat is lost as blood flows through capillaries
  • has valves to ensure blood flows in one direction only, valves open when blood is flowing upwards and close if blood flows downwards
  • usually carries deoxygenated blood (except pulmonary vein)
  • low pressure as blood moves further from heart
• dangerous blood clot in veins: thrombosis
• bruises are caused when tiny capillaries near the skin burst and blood leaks out into surrounding tissue
• the heart:

  • about the size of your fist
  • found in middle of your chest behind breastbone
  • made of cardiac muscle
• the human circulatory system is referred to as a double system as there are two separate circuits through which the blood flows, both starting in the heart:

  • first: goes around body, delivering nutrients and oxygen to cells, while collecting wastes like carbon dioxide and travelling back to heart
  • second: takes deoxygenated blood to lungs, dropping off carbon dioxide, picking up oxygen and returning to heart
• passage of blood through body and heart:

  right ventricle > pulmonary arteries > lungs ≥ pulmonary veins ≥ left atrium ≥ left ventricle ≥ aorta ≥ body tissues > vena cava > right atrium > right ventricle

  > deoxygenated blood

  ≥ oxygenated blood
• the left ventricle is larger than the right ventricle, and also has thicker walls due to higher pressures and having to pump blood to the rest of the body, while the right ventricle only needs to pump blood to the lungs
• pulmonary artery: sends blood to the lungs from heart
• pulmonary vein: heart receives blood from lungs
• aorta (main artery): sends blood to body
• vena cava: receives blood from body
• blood flows into the atriums from the veins, down to ventricles through a valve, then out the arteries
• label 1 is the pulmonary artery

  
• label 6 is the right atrium

  
• label 2 is the aorta

  
• label 5 is the right ventricle

  
• label 3 is the left atrium

  
• label 4 is the left ventricle

  
• the heart

  
• the heartbeat have three phases:

  • the two atria contract, pushing blood into the ventricles
  • ventricles contract, forcing blood out of heart to body and lungs
  • heart muscle relaxes and atria fill with blood
• when arteries become completely blocked, the part of heart they supply oxygen to dies and could cause a heart attack. if a large area of the heart is affected, the heart attack could be severe.
• blood is the only organ of the body that exists as a liquid
• the average adult body contains about 5 litres of blood
• blood helps maintain your body temp by spreading heat around
• blood consists of:

  • red blood cells
  • white blood cells
  • platelets
  • plasma
• red blood cells:

  • contains chemical haemoglobin (gives red colour)
  • haemoglobin contains iron > job is to carry oxygen around to body
  • there are about 300 million red blood cells in one drop of blood
• white blood cells:

  • bigger than red blood cells
  • about 400,000 in each drop of blood
  • part of immune system, help fight disease
• platelets:

  • broken up bits of cells produced in bone marrow
  • help blood to clot
  • without these, you are at risk of excessive bleeding if you get cut
• blood clots in the heart can cause angina (chest pain caused by lack of oxygen to heart) or heart attacks
• blood clots in the brain can cause a stroke
• plasma:

  • clear yellowish liquid
  • 90% water
  • red blood cells, white blood cells and platelets are suspended in this