Organsation

• A tissue is a group of cells with a similar structure and function.
• An organ is a group of tissues working together for a specific function.
• What three main nutrients does does food contain?

  carbohydrates, proteins and lipids.
• During digestion large food molecules are broken down into smaller molecules by enzymes. Then they can be absorbed into the bloodstream
• In the digestive system firstly food is chewed in the mouth. Enzymes in the saliva begin to digest the starch into smaller sugar molecules. The food then passes down the oesophagus into the stomach. In the stomach, enyzmes begin the digestion of proteins.
• The stomach contains hydrochloric acid which helps the enzymes to digest protein. The churning action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest. The fluid then passes into the small intestine. Chemicals are then released into the small intestine from the liver and the pancreas.
• The pancreas releases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids. The liver releases bile which helps to speed up the digestion of lipids. The walls of the small intestine release enyzmes to continue the digestion of proteins and lipids. Then the fluid makes its way through the large intestine where water is absorbed into the bloodstream. Finally the faeces is released from the body.
• Arteries carry very high blood pressure from the heart to the organs in the body.
• Arteries have very thick muscular walls to withstand the very high pressure of the blood.
• Capillaries contain the smallest branches of arteries and veins.
• Capillaries have very thin walls. This allows substances to diffuse rapidly between the blood and the body cells.
• Many veins contain valves. The job of the valves is to prevent blood flowing backwards.
• Veins have a thin wall because the blood pressure is low.
• Air passes into the lungs through a tube called the tranchea
• The trachea splits into two tubes called bronchi. Bronchi then subdivide into smaller tubes called bronchioles.
• The bronchioles end in tiny air sacks called aveoli
• Oxegyn diffuses into the bloodstream and carbon dioxide diffuses out of the bloodstream
• Breathing increases the rate of diffusion
• An example of a non communicable disease is type 2 diabetes
• A diet high in salt can increase blood pressure and increase the risk of heart disease.
• Smoking can increase the risk of developing a cardiovascular disease and lung cancer.
• The risk of developing cardiovascular diseases can be reduced by excersise and a healthy diet
• Smoking when pregnant increases the risk of miscarridge and premature birth. It also can lead to the baby being born with a low body mass.
• Drinking alochol whilst pregnant can cause fetal alcohol syndrome. Children born with this can have learning difficulties and mental/

  physical problems.
• Adults who drink alcohol excessively increase their risk of liver cancer. Alcohol can also lead to addiction and memory loss
• Xylem tissue transports water and dissolved mineral ions from the roots to the leaves
• Transpiration is the evaporation of water from the surface area of leaves