She's tripped and scraped her knee. Like most kids, Lisa gets cuts and scrapes. At times they bleed. After she put a bandage on her scrape, Lisa began to wonder about blood. Blood is an important part of our body.
Newborn babies have about one third of a litre of blood.
Grownups have between four and five litres. Each part has its own job. Red blood cells carry oxygen and food to all the parts of our body. They also give blood its color. White blood cells fight infections.