B7: Blood and the Circulatory System

B7: Blood and the Circulatory System

1. Blood - Cells, Platelets and Plasma

   • Red Blood Cells
     • Transports oxygen from the lungs to the rest of the body.
       • There is no nucleus so that they can be filled with haemoglobin, the substance that binds with oxygen.
       • They have a biconcave shape, giving them a large surface area for the exchange of oxygen.
   • Plasma
     • The liquid that carries nutrients (e.g. glucose and amino acids), antibodies, hormones and waste (e.g. carbon dioxide and urea).
   • Platelets
     • Small fragments of cells that help the blood to clot at the site of a wound
   • White Blood Cells
     • Help to fight infection by protecting the body against attack from microorganisms

2. The Circulatory System

   • Humans have a double circulatory system - two circuits joined together.
     • The first circuit pumps deoxygenated blood to the lungs, to take in oxygen. The blood then returns to the heart.
     • The second circuit pumps oxygenated blood around the body. The blood gives up it's oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped around the first circuit.