[JOAN CARTAN-HANSEN] BLOOD IS MADE UP OF RED BLOOD CELLS WHICH CARRY OXYGEN… WHITE BLOOD CELLS WHICH FIGHT INFECTIONS… PLATELETS WHICH CAUSES BLOOD TO CLOT AND HELPS STOP BLEEDING… AND PLASMA. MORE THAN HALF OF YOUR BLOOD IS MADE UP OF THIS YELLOWISH WATERY LIQUID.

BLOOD MOVES AROUND YOUR BODY BRINGING OXYGEN AND NUTRIENTS TO THE CELLS, AND THEN TAKING AWAY WASTE PRODUCTS AND CARBON DIOXIDE.

THE HEART, THE MUSCLE ABOUT THE SIZE OF YOUR FIST, PUMPS OR PUSHES YOUR BLOOD THROUGH YOUR BODY’S BLOOD VESSELS.

ARTERIES TAKE OXYGENATED RED BLOOD AWAY FROM THE HEART, VEINS RETURNED THE BLUE OR PURPLISH-TINTED BLOOD BACK TO THE HEART, AND CAPILLARIES ARE THE TINY THIN WALLED TUBES THAT CONNECT SMALL ARTERIES AND VEINS TOGETHER.

BLOOD PRESSURE IS THE MEASURE OF HOW HARD BLOOD IS PUSHING AGAINST THE WALLS OF YOUR ARTERIES.

TOGETHER, THE HEART, BLOOD, AND BLOOD VESSELS MAKE UP THE CIRCULATORY SYSTEM.

MOST BLOOD CELLS ARE MADE IN THE VERY CENTER OF YOUR BONES IN A PLACE CALLED THE BONE MARROW.

A SINGLE DROP OF BLOOD CAN CONTAIN MILLIONS OF RED BLOOD CELLS. OTHER BLOOD CELLS ARE MADE IN YOUR SPLEEN, AND LYMPH GLANDS.

BLOOD CELLS CIRCULATE IN YOUR BODY FOR ABOUT 120 DAYS AND THEN ARE REPLACED. THAT’S WHY ADULTS CAN GIVE BLOOD.

DOCTORS STARTED SERIOUSLY COLLECTING BLOOD DURING WORLD WAR I AND WORLD WAR II. THEY KNEW IF A SOLDIER LOST TOO MUCH BLOOD, HE DIED.

SCIENTISTS LEARNED THAT YOU CAN TRANSFUSE, OR GIVE ONE PERSON’S BLOOD TO SOMEONE ELSE. A TRANSFUSION OF BLOOD CAN SAVE A LIFE. BUT NOT ALL BLOOD IS EXACTLY THE SAME.

HUMANS HAVE FOUR BASIC BLOOD TYPES – A, B, AB, AND O.

BLOOD GIVEN IN A TRANSFUSION MUST MATCH OR BE THE SAME AS THE BLOOD TYPE OF THE PERSON WHO’S RECEIVING IT. IF YOU’RE GIVEN A TRANSFUSION OF THE WRONG BLOOD TYPE, YOU CAN GET SICK OR DIE.

WHEN YOU GIVE BLOOD, SCIENTISTS DETERMINE WHAT YOUR BLOOD TYPE IS, TEST YOUR BLOOD FOR ANY DISEASES IT MAY CARRY, AND THEN THEY STORE IT. LATER IT’S USED IN HOSPITALS AND TO MAKE MEDICINE.

DOCTORS STUDY BLOOD AND DISEASES OF THE BLOOD. HEMATOLOGY IS WHAT THEY CALL, THE STUDY OF BLOOD.

AND WHY IS BLOOD RED? WELL YOUR BLOOD HAS A PROTEIN CALLED HEMOGLOBIN THAT CARRIES IRON. IRON HELPS BLOOD HOLD ONTO OXYGEN, AND WHEN IRON AND OXYGEN MIX, THE HEMOGLOBIN TURNS RED.