blood
a suspension of red blood cells (or corpuscles) called ERYTHROCYTES , white blood cells ( LEUCOCYTES ) and platelets (small disc-shaped cells involved in BLOOD CLOTTING ) in a liquid medium, blood PLASMA . The circulation of blood through the body provides a mechanism for transporting substances. Its functions include: 1. carrying oxygenated blood from the HEART to all tissues via the arteries while the veins return deoxygenated blood to the heart. 2. carrying essential nutrients, e.g. glucose, fats and AMINO ACIDS to all parts of the body. 3. removing the waste products of METABOLISM - ammonia and carbon dioxide - to the liver, where UREA is formed and then transported by the blood to the KIDNEYS for excretion. 4. carrying important molecules, e.g. HORMONES , to their target cells. The red blood cells, produced in the BONE MARROW , are HAEMOGLOBIN -containing discs, while the white varieties vary in shape and are produced in the marrow and lymphoid tissue. The plasma comprises water, proteins and ELECTROLYTES and forms approximately half the blood volume.
Your blood is made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets.
Red blood cells (RBC) deliver oxygen from your lungs to your tissues and organs. White blood cells (WBC) fight infection and are part of your immune system. Platelets help blood to clot when you have a cut or wound. Bone marrow, the spongy material inside your bones, makes new blood cells. Blood cells constantly die and your body makes new ones. Red blood cells live about 120 days, and platelets live about 6 days. Some white blood cells live less than a day, but others live much longer.
There are four blood types: A, B, AB, or O. Also, blood is either Rh-positive or Rh-negative. So if you have type A blood, it's either A positive or A negative. Which type you are is important if you need a blood transfusion. And your Rh factor could be important if you become pregnant - an incompatibility between your type and the baby's could create problems.
Blood tests such as blood count tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working. Problems with your blood may include bleeding disorders, excessive clotting and platelet disorders. If you lose too much blood, you may need a transfusion.
NIH: National Heart, Lung, and Blood Institute
blood