The amount of blood in the human body depends on size (body mass is more important than height). An average man of 150 lbs or 70 kgs will have around 8 pints or 5.2 litres of blood. A woman of 110 lbs (50 kgs) will have about 3.3 litres of blood ; about 5 pints. (However, 110 lbs is a petite size!). The average woman will have nearer 6-7 pints and with a male having eight, the average is just over 7 pints. Children obviously have less blood. Tiny, premature babies may have as little as the equivalent of half a wine glass ful of blood. As a general rule blood actually constitutes about 7-8 % of body weight. Some people can have as many as 12 pints of blood. In one day blood can travel the equivalent of 12,000 miles and blood vessels laid end to end would reach around 62,000 miles. Sever lack of blood can result in the heart not having enough blood to pump around and it can then go into shock which may result in a heart attack.
In all humans, the blood is one element that connects all the other parts of the body to one another. It is the main component of the circulatory system that has in it different components such as the red blood corpuscles (RBC), white blood corpuscles (WBC), and platelets. The RBC is responsible for transporting oxygen, as it carries haemoglobin with it. The WBC has the responsibility of providing immunity to the body. The platelets help in the clotting of blood. All these components move around in the plasma, the liquid component of blood. As the blood flows through the entire body, it transports oxygen and other essential nutrients and materials that the cells require, and also transports cellular waste out of the cells for excretion.
The human body has at least eight pints of blood in it. In litres, that is about five litres for every adult. The numbers may vary, though, depending on the size of the person. However, an average person would have anywhere between 8 to 10 pints of blood.
Blood is basically a fluid that is responsible for delivery of necessary substances to the cells in the body. This includes nutrients and oxygen as well as waste products.
Around 7 percent of the human body weight is considered as blood. Researchshows that an average adult has 5 liters of blood in his body. Since 1 liter equals 2.1 pints. So an average adult will have 10.55 pints of blood.
4 to 8 hours, usually closer to the 8. But it can be done much faster in emergency situations. The trade off in such situations is a higher risk of infection (from more hasty insertion of possibly multiple cannulas).
Sometimes it's known in advance that certain types of surgery will involve high blood loss. The surgeon will insert suitable and possibly multiple cannulas in advance to make sure that blood can be transfused quickly when necessary.