How does the liver's structure to modify the chemical composition of blood?

Erythrocytes have a short lifespan.
When coming to the end of their lifespan they are phagocytized by the liver.
This organ plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification.
Bile is stored in the gall bladder.

The bile flows in opposite direction inside the liver than
does the blood
http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/anatomy.html

The bile is secreted by the hepatocytes into the
canaliculi and flows into tube like structures, known as
ducts from the inside of the liver to the gallbladder to
be stored. When the bile is in the gallbladder, it is
concentrated and then released into the common
bile duct (when a hormone signals the gallbladder
to contract when bolis, food, enters the duodenum
[first part of the intestines].  The bile then is in
the common bile duct and flows to the intestines to
help emulsify fats so they can be digested and
absorbed.  

Erythropioetin is made mostly in the kidneys but is
also made in the liver to be transported to the bone
marrow to produce more red blood cells.  When the
red blood cells die off, then the heme part of the
red blood cells is used to make bilirubin.  Bilirubin
is a substance known as a pigment because it
colors other things.  (it is a greenish/brown).  The
liver takes this bilirubin and converts it into a soluble
form to become part of the bile.

The liver also is where metabolism takes place.
The foods are broken down into proteins, carbohydrates,
and fats.  This food is absorbed from the blood and
converted into glucose which is used as energy by
all the cells of the body.  The liver will store glucose
by converting it to glycogen until it is needed by the
cells and then it will be converted back into glucose.

The liver also makes certain proteins, such as
Albumin, which transports substances throughout
our body and is also the protein that hold fluids
in our blood vessels.

The liver can also store extra blood until it is needed.

It also removes toxins from the blood and converts
them into non toxic form that the body can dispose of.

The liver also makes clotting factors that help the blood
to clot.

The liver does so many things that effect the blood and
has over 500 plus functions that it is difficult to express
them all here.  

The blood comes to the liver through the hepatitic
artery and also the portal vein.  The blood is removed
from the liver through the hepatitic vein.

I hope this information has been of some help to you.