Biology 3 Unit 2

To transport blood around the body

• Blood vessels
• The heart
• Blood

The heart is a muscular organ that pumps blood around the body

• Right - forces deoxygenated blood to the lungs where it picks up oxygen and loses carbon dioxide
• Left - pumps oxygenated blood around the body

• Upper chambers - Atria: right receives blood from the vena cava, left from the pulmonary vein. They contract and force blood into the ventricles
• Lower chambers - Ventricles: they contract and force blood out of the heart, into the pulmonary artery from the right, into the aorta on the left

Valves in the heart ensure that blood flows in the correct direction

• Arteries have thick walls containing muscle and elastic tissue
• They carry blood away from the heart

• Veins have thinner walls that arteries
• Often have valves to prevent back-flow of blood

• Capillaries have narrow thin-walled vessels
• The carry the blood through the organs and allow the exchange of substances with all the living cells in the body

If blood vessels are too narrow the blood will not flow efficiently. This means organs will be deprived of nutrients and oxygen

• Leaky valves means that blood could flow into the wrong direction
• Artificial or animal valves can be inserted to replace damaged valves

If arteries begin to narrow and restrict blood flow, stents are used to keep blood vessels open

Blood is a tissue and consists of a fluid calls plasma. Plasma contains red blood cells white blood cells and platelets

• Blood plasma transports:
• Carbon dioxide from the organs to the lungs
• Soluble products of digestion from the small intestine to other organs
• Urea from the liver to the kidney

• Red blood cells:
• Are biconcave discs which do not have a nucleus
• Contain the red pigment haemoglobin
• Use their haemoglobin which combines with oxygen to form oxyhaemoglobin in the lungs
• Carry the oxygen to all organs where the oxyhaemoglobin splits into haemoglobin and oxygen

• They have a nucleus
• Form part if the body's defence system against microorganism

• Platelets:
• Are small fragments of cells
• Do not have a nucleus
• Help blood to clot at the site of a wound

Xylem tissues transports water and mineral ions from the roots to the stem and leaves

Transpiration stream is the movement of water from the roots through the xylem and out of the leaves

Phloem tissue carries dissolved sugars from the leaves to the rest of the ant including the growing regions and the storage organs