Drawing of a fixed human heart, including preserved cardiac vasculature.
Get any photo of a heart from an anatomical atlas or google and you will find images of the real thing. You can draw this yourself.
To begin I would suggest using an outline to copy the shape of the heart- which contains the coronary blood vessels and the major blood vessels going into and out of the heart.
Once you have a picture you can then alter it if that makes it easier using you phone setting to emphasise black and white.
You can also fiddle with the settings to increase brightness, contrast or any other settings that make the picture more appealing to you.
You can see that I have simply made outlines of the major structures. As with all accurate drawings it is essential everything is in place.
Notice its shape. Floppy at the top and firm at the apex.