Where does all our blood come from?

If you're wondering where blood comes from originally it happens around the 13-15th day during gestation. 

There are three layers to an embryo the ectoderm (the exoskeleton (e.g. skin)), mesoderm (organs), and endoderm (inner linning of organs). Blood develops within the mesoderm in what are termed blood islands.  

blood comes from your organs

ITS REPLACED  every 4 hours  from bone marrow if im not mistaken..  

if the blood  is so contaminated that   it cant be replaced you will die this is what happens with  severe carbon monoxide poisoning

my bet is the mineral iron. also, the bone marrow produces cells which travel through the porous heads of the large bones, these cells break-off and form red blood cells. 

they have heme or  hemoglobin, 

 the red blood cells which carry oxygen.  

the blood has many different cells and components.

Blood is manufactured by the body's hematopoietic cells.

Blood is mostly water that contains cells.  The water we drink, daily.  We get some from food too, of course.  The cells are made by conversion of food (like any cells).  The red blood cells are made in the marrow of the bones. Other stuff in the blood like hormones is made in other organs. Some of the stuff dissolved in the water comes from the stomach or intenstines (from what we eat) and other stuff is passed into the blood from the very many cells that are working for you as you live.  Gases enter and leave blood in the lungs, and the kidneys and liver do a lot of cleaning of dissolved stuff in the blood and help regulate the concentration of dissolved stuff in the blood (the water part of blood).

Blood is generated by the marrow in our bones.

Your blood is made in the spongy interior of the leg and arm bones, it exits through those tiny holes in it (look at a chicken leg bone next time, you'll see the holes).

Your body makes it.  Google "blood formation"

The red and white blood cells are continuously produced in the bone marrow.

Most of the proteins in blood are produced by the liver, while antibodies in blood are produced by a specific type of white blood cells. Other proteins in blood are produced by other cells in the body.

The liquid part of blood is ultimately water that you consume.