b4

• what makes up the human circulatory system?

  the blood, blood vessels, and heart makes up the human circulatory system which transports substances to and from the body cells
• what is plasma?


  plasma is a watery fluid which holds all the components of blood flow
• what does plasma transport abround the body?

  plasma has blood cells suspended in it and transports proteins and other chemicals around the body
• what do red blood cells contain?

  red blood cells contain haemoglobin that binds to oxygen to transport it from the lungs to the tissues
• what do white blood cells help with?

  they help to protect the body against infection
• what are platelets?


  they are cell fragments that start the clotting process at wound sites
• what are blood vessels? what are the main types?

  blood flows around the body in the blood vessels. the main types are: arteries, veins, and capillaries
• what do substances do in the capillaries?

  substances diffuse in and out of the blood in the capillaries
• what do valves prevent?

  the valves prevent backflow, ensuring that blood flows in the right direction
• human beings have a double circulatory system
• characteristics of an artery

  thick walls, thick layer of muscles and elastic fibres, small lumen
• characteristics of veins


  relatively thin walls, large lumen, often have valves
• characteristcs of capillaries


  walls a single cell thick, tiny vessel with narrow lumen
• what is the heart?

  an organ that pumps blood around the body
• what do heart valves do?

  keep the blood flowing in the right direction
• what do stnets do?

  stents can be used to keep narrowed or blocked arteries open
• what do statins do?

  statins reduce chlorestrol levels in the blood, reducing risk of coronary heart disease
• the pathway of blood

  R - starts at the right

  V - vena cava

  A - right atrium

  V - right ventricle

  A - pulmonary artery(makes deoxygenated blood oxygenated)

  V - pulmonary vein

  A - left atrium

  V - left ventricle

  A - aorta(blood goes to the rest of the body)

  L - left
• how are damaged heart valves replaced?

  biological or mechanical valves
• how is the resting heaart rate controlled?

  by a group of cells in the right atrium that form a natural pacemaker
• what are artificial pacemakers?

  electrical devices used to correct irregularities in the heart rhythm
• when are artifical hearts used?

  occasionally used to keep patients alive while they wait for a transplant, or for their heart to rest as an aid to recovery
• where are the lungs?

  the lungs are in your chest cavity, portected by your ribcage and seperated from your abdomen by the disphragm
• what does alveoli provide?

  they provide a very large surface area and a rich spply of blood capillaries. this means gases can diffuse into and and of the blood as efficiently as possible
• what happens when you breathe in?

  -as ribs move up and out and diaphragm flattens, the volume of the chest increases

  -increased volume means lower pressure in the chest

  -atmospheric air at higher pressure than chest - so air is drawn into the lungs
• what happens when you breathe out?

  -as ribs fall and diaphragm moves up, the volume of the hcest gets smaller

  -decreased volume means increased pressure in the chest

  -pressure in chest higher than outside - so air is forced out of the lungs
• what is are plant tissues?

  plant tisues are a collecton of cells specialised to carry out specific functions
• the structure of the tissue in plant organs is related to their functions
• what forms the plant organ system? what do they do?


  the roots, stem, and leaves

  they transport substances around the plant
• what are epidermal tissues?

  they cover the surface and protect them. these cells often secrete a waxy sustance that waterproofs the surface of the leaf
• what are palisade mesophyll tissues?

  a tissue that contains lots of chloroplasts, which carry out photosynthesis
• what are spongy mesophyll tissues?

  a tissue that contains some chloroplasts for photosynthesis but also has big air spaces and a large surface area to make diffusion of gases easier
• what do xylem do?

  xylem carry water and dissolved mineral ions from the roots up to the leaves
• what do phloem do?

  phloem carry dissolved food from the leaves around the plant
• what is transpiration?

  the loss of water vapour from the surface of plant leaves
• where is water lost in plant? why?

  water is lost through the stomata which open to let in carbon dioxide for photosynthesis
• what does the stomata and guard cells do?

  they control gas exchange and water loss
• what are the factors that increase the rate of photosynthesis/increase the rate of transpiration?

  -temperature

  -humidity

  -air flow

  -light intensity
• when is transpiration more rapid?

  it is more rapid in hot, dry, windy, or bright conditions