Extracellular matrix (ECM) is present in all organs, though harvesting that matrix may not  always be feasible.  We routinely produce ECM from small intestine, urinary bladder, liver, and heart typically from porcine sources.  The cells of these organs are removed by either physical and/or chemical methods so that only the native ECM remains.  This ECM can then be used as a wet hydrated form, vacuum pressed into a multilaminate form, freeze dried (lyophilized) as a sheet form, milled into a particulate form and/or digested into a gel form.

Hydrated
ECM

Lyophilized
ECM

MANUAL removal of muscle layers from porcine urinary bladder