The Constituents of Blood•The average human has 4 – 6 dm³ of blood circulatingin his body.•The major constituents of blood can be separated bycentrifugation.The composition of human blood aftercentrifuge
•Blood consist of fluid called plasma which is made upof suspended blood cells and blood fragments.•Plasma makes up 55% of blood by volume. The other45% consists of red blood cells, white blood cells andplatelets.BloodPlasma Blood cells Blood fragmentsRed bloodcellsWhite bloodcells Platelets
Plasma•Plasma is the yellow liquid in our blood.•90% of plasma is water. The rest are dissolvedsubstances which include:•a. Nutrients such as glucose, amino acids and vitamins.•Proteins like antibodies, hormones, enzymes, albumins,fibrinogens.•Inorganic ions such as sodium, calcium, chlorides andphosphates.
Main Functions of Plasmaa. To transport nutrients to tissues.b. To remove waste products from tissuesc. To distribute hormones, enzymes, antibodies andother proteinsd. To distribute heat energy from the liver and musclesto all other parts of the body.
Red Blood Cells (Erythrocytes)•They are biconcave, disc – shaped cells withoutnucleus.•The red blood cells transport oxygen from the lungs toall parts of the body.•They contain a red pigment called haemoglobin whichcombines with oxygen molecules to formoxyhaemoglobin.
•They also carry carbon dioxide from body cells to ourlungs.•There are about 5, 000,000 red blood cells in eachcubic millimeter of blood.•Red blood cells are made in the bone marrow.•The lifespan of red blood cells is about 120 days.•When the red blood cells are worn out, they aredestroyed in the liver and spleen.
White Blood Cells(Leucocytes)•White blood cells are much larger than red blood cellsand they have a nucleus.•They are usually irregular in shape, colourless and donot contain haemoglobin .
•There are several types of white blood cells.•White blood cells are formed from bone marrow cells.•The lifespan of white blood cells depends on the typeof white blood cells. It varies from a few hours to afew months.•They play a vital role in the body’s defense againstdiseases. Some white blood cells produce antibodies torender bacteria inactive while other white blood cellsingest bacteria.•Unlike red blood cells. White blood cells can squeezethrough the walls of the blood capillaries into thespaces among the cells to destroy the bacteria.
Platelets (Thrombocytes)•Platelets are cell fragments produced by large cells in thebone narrow.•They appear as tiny oval – shaped structures withoutnucleus under a high – powered microscope.•There are between 250, 000 and 500, 000 platelets inevery cubic millimeter of blood.•They play an important role in blood clotting. When ablood vessel breaks, the platelets release clotting factors.
Blood Groups•There are many different systems by which blood isgrouped but the ABO system is the best known.•The ABO system classifies the human blood into mainfour groups called A, B, AB, and O.•During a blood transfusion, the donor’s blood must becompatible with the recipient’s blood.•When an incomplete type of blood is transfused, thered blood cells of the donated blood will clump together(agglutinate) and cause fatal blockages in the recipient’sblood vessels.
O A B ABOABABDonor’s bloodRecipient’sbloodCompatible Incompatible
•Blood group O can safely donate blood to anyone insmall quantities. People with group O are called universaldonors.•Blood group AB can safely receive blood from anyone.Group AB people are called universal recipients.Group Can donate to Can receive fromA A and AB A and OB B and AB B and OAB AB All groupsO All groups OBlood transfusion – donors and recipients
The importance of blood donations•By donating blood, one could have save lives ofothers.•Blood maybe needed for treatment of accident cases,cancer victims, haemophiliacs, surgery, gastrointestinalbleeding and in childbirth where a great loss of bloodoccurs.•The donated blood can be used either as unfilteredblood for one patient, or separated into components tohelp several patients.
Main uses of the components of donated bloodComponent Main usesPlasma Great loss of blood in surgery andchildbirthRed blood cells AnemiaPlatelets Bone marrow failure, leukemiaBlood proteins Burns
Storage and handling of donated blood•A donor normally gives about 400 cm³ of blood fromvein in his arm.•Blood should be collected under aseptic conditions intoa sterilised container containing anticoagulant solutionwhich prevents clotting.•The donated blood is tested for ABO group and thepresence of antibodies that maybe cause problems in arecipients.•Screening tests are performed for evidence of donorinfection and hepatitis, AIDS and other sexualtransmitted disease.
•The date of expiration should be written on the labelattached to the blood container.•The blood can be stored at 5 C for 10 days, or longerif glucose is added.•The blood maybe separated into several components.•Red blood cells can be stored under refrigeration for42 days, or they can be frozen for up to 10 years.•Platelets can be stored at room temperature for amaximum of 5 days.•Frozen plasma can be kept for up to 1 year.•Frozen plasma and red blood cells should be thawedin a water bath at temperature not exceeding 38 C.
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