Blood

Today I’m going to talk about: blood

I’ve divided my presentation into two parts:

First I’d like to talk about Blood and second I’ll present
characteristics of blood groups.

So, let’s start with blood

Blood, is a vital fluid found in humans and other animals that
provides important nourishment to all body organs and tissues and carries
away waste materials. Sometimes referred to as “the river of life,” blood
is pumped from the heart through a network of blood vessels collectively
known as the circulatory system.

An adult human has abbout 5 to 6 liters (1 to 2 gal) of blood, which is
roughly 7 to 8 percent of total body weight. Infants and children have
comparably lower volumes of blood, roughly proportionate to their smaller
size. The volume of blood in an individual fluctuates. During dehydration,
for example while running a marathon, blood volume decreases. Blood volume
increases in circumstances such as pregnancy, when the mother’s blood needs
to carry extra oxygen and nutrients to the baby.

Finally let’s consider: characteristics of blood group

1. Blood type A contains red blood cells that have a substance A on
their surface. This type of blood also contains an antibody directed
against substance B, found on the red cells of persons with blood type B.

2. Type B blood contains the reverse combination.

3. Serum of blood type AB contains neither antibody, bu

ut red cells in
this type of blood contain both A and B substances.

4. In type O blood, neither substance is present on the red cells, but
the individual is capable of forming antibodies directed against red cells
containing substance A or B.

If blood type A is transfused into a person with B type blood, anti-A
antibodies in the recipient will destroy the transfused A red cells.
Because O type blood has neither substance on its red cells, it can be
given successfully to almost any person. Persons with blood type AB have no
antibodies and can receive any of the four types of blood; thus blood types
O and AB are called universal donors and universal recipients,
respectively.

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