is a place where blood is collected from donors, typed, separated into components, stored, and prepared for transfusion to recipients. A blood bank may be a separate free-standing facility or part of a larger laboratory in a hospital.
Separation of blood
Typically, each donated unit of blood (whole blood) is separated into multiple components, such as red blood cells, plasma and platelets. Each component is generally transfused to a different individual, each with different needs.
An increasingly common blood bank procedure is apheresis, or the process of removing a specific component of the blood, such as platelets, and returning the remaining components, such as red blood cells and plasma, to the donor. This process allows more of one particular part of the blood to be collected than could be separated from a unit of whole blood. Apheresis is also performed to collect plasma (the liquid part of the blood) and granulocytes (white blood cells).
Who receives blood: Accident victims, people undergoing surgery and patients receiving treatment for leukemia, cancer or other diseases, such as sickle cell disease and thalassemia, all utilize blood.
Giving blood to yourself: Patients scheduled for surgery may be eligible to donate blood for themselves, a process known as autologous blood donation. In the weeks before non-emergency surgery, an autologous donor may be able to donate blood that will be stored until the surgical procedure.
Typing and testing blood: After blood is drawn, it is tested for the ABO blood group type and the Rh type (positive or negative), as well as for any unexpected red blood cell antibodies that may cause problems in the recipient. Screening tests are also performed for evidence of donor infection with hepatitis viruses B and C, human immunodeficiency viruses (HIV) 1 and 2, human T-lymphotropic viruses (HTLV) I and II and syphilis.
Storage of blood: Each unit of whole blood is normally separated into several components. Red blood cells may be stored under refrigeration for a maximum of 42 days, or they may be frozen for up to 10 years. Red cells carry oxygen and are used to treat anemia. Platelets are important in the control of bleeding and are generally used in patients with leukemia and other forms of cancer. Platelets are stored at room temperature and may be kept for a maximum of five days. Fresh frozen plasma, used to control bleeding due to low levels of some clotting factors, is usually kept in the frozen state for up to one year. Cryoprecipitated AHF, which contains only a few specific clotting factors, is made from fresh frozen plasma and may be stored frozen for up to one year. Granulocytes are sometimes used to fight infections, although their efficacy is not well-established. They must be transfused within 24 hours of donation.
Functions of lymph system
The lymphatic system has three primary functions:
Fluid balance
The lymphatic system helps maintain fluid balance. It returns excess fluid and proteins from the tissues that cannot be returned through the blood vessels. The fluid is found in tissue spaces and cavities, in the tiny spaces surrounding cells, known as the interstitial spaces. These are reached by the smallest blood and lymph capillaries.
Around 90 percent of the plasma that reaches tissues from the arterial blood capillaries is returned by the venous capillaries and back along veins. The remaining 10 percent is drained back by the lymphatics.
Each day, around 2-3 liters is returned. This fluid includes proteins that are too large to be transported via the blood vessels. Loss of the lymphatic system would be fatal within a day. Without the lymphatic system draining excess fluid, our tissues would swell, blood volume would be lost and pressure would increase.
Absorption
Most of the fats absorbed from the gastrointestinal tract are taken up in a part of the gut membrane in the small intestine that is specially adapted by the lymphatic system.
The lymphatic system has tiny lacteals in this part of the intestine that form part of the villi. These finger-like protruding structures are produced by the tiny folds in the absorptive surface of the gut. Lacteals absorb fats and fat-soluble vitamins to form a milky white fluid called chyle.
This fluid contains lymph and emulsified fats, or free fatty acids. It delivers nutrients indirectly when it reaches the venous blood circulation. Blood capillaries take up other nutrients directly.
The immune system
The third function is to defend the body against unwanted organisms. Without it, we would die very soon from an infection.
Our bodies are constantly exposed to potentially hazardous micro-organisms, such as infections.
The body's first line of defense involves:
- physical barriers, such as the skin
- toxic barriers, such as the acidic contents of the stomach
- "friendly" bacteria in the body
However, pathogens often do succeed in entering the body despite these defenses. In this case, the lymphatic system enables our immune system to respond appropriately. If the immune system is not able to fight off these micro-organisms, or pathogens, they can be harmful and even fatal. A number of different immune cells and special molecules work together to fight off the unwanted pathogens.
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