Hepatitis B is a serious viral infection of the liver, sometimes known as serum hepatitis. Although most people recovered without problems, the infection can lead to chronic liver disease and even death. The disease is usually contracted through sexual intercourse, expose to contaminated blood or blood products, or to an infant from its mother’s breast milk. Occasionally it can be transmitted by... 

Why blood is red? As it courses through the circulatory system, propelled by the contractions of the heart, the blood performs any number of vital functions. It picks up oxygen from the lungs and nutrients from the digestive tract and delivers them to the tissues. It carries away carbon dioxide and other waste products, so that they can be eliminated. Blood also provides a means of transport for... 

“A cure-all remedy” in times past was to apply leeches to suck out the blood. Most households kept a supply on hand. In 1837, one London hospital used 96,000 leeches on 50,557 patients. If you have ever been attacked by a blood-sucking leech, you will know that a surprising and possibly disturbing element is that only after the parasite released its hold did you realize you were its victim. Since... 

artery-disease “A heart attack” in the making, seen in a section of a coronary artery. The vessel is almost blocked by plaque (pink) and a hemorrhage (red) that has caused clot Our arteries do the vital job of distributing blood pumped by the heart. Basically, they are pliable tubes, cunningly constructed in three layers to provide  a smooth, lightweight pipeline that will withstand... 

damaged blood vessel If you have normal blood and suffer a cut, tiny cells known as thrombocytes, or platelets, come to your rescue. These disclike cells, the smallest in the blood stream, clump together within seconds to seal off the wound. But first they need something, such as the feel or a damaged blood-vessel wall, to jolt them into action. The first platelets to detect a hole in the blood-vessel... 

For centuries beliefs persisted that some people, according to race or linage, had superior blood. Members of the same families and races had the same blood type, it was said, but for reasons not explained some blood was purer. When transfusions were first tried seriously in the seventeenth century, some succeeded, but others failed inexplicably, killing so many patients that in France, Italy and England... 

high blood pressure We all have blood pressure of a kind. If we didn’t, blood wouldn’t flow from the heart and through the arteries. This pressure has two forms. When heart contacts, blood reaches its highest – systolic – pressure. When the heart relaxes between beats, the pressure falls to its lowest – diastolic – phase. Your doctor measures these pressures in... 

red blood cell The liquid that runs through the body’s 95,000 km (60,000 miles) of blood vessels is an aver-moving supply train carrying a vast and relentless force of workers who labor nonstop. A single drop of blood holds more than 250 million  separate cells, each with a job to do. Blood makes up about 7 percent of an average  adult’s body weight , a volume of between 3.5 and...