The Egyptians believed that the heart, rather than the brain, was the source of human wisdom, as well as emotions, memory, the soul and the personality itself.  Notions of physiology and disease were all connected in concept to the heart, and it was through the heart that God spoke, giving ancient Egyptians knowledge of God and God's will. For this reason it was considered the most important of the body's organs.  However, despite the ancient Egyptian's seemingly advanced medical and surgical knowledge, the heart's role in blood circulation was not precisely understood.

It was felt that from the heart, channels (metu) linked all parts of the body together.  These channels delivered not only blood, but also air, tears, saliva, mucus, sperm, nutriment and even bodily waste.  In fact, the only real function of the brain was thought to be to pass mucus to the nose, so it was one of the organs that were discarded during mummification.

Probably to some extent, this concept of channels may have had some symbolism with the Nile. Ancient Egyptians were thought to be in good health if the metu were clear and without blockage.  Disease was caused when a channel became blocked, much like an irrigation canal cannot deliver water if it is blocked.  

In the final judgment portrayed by the Book of the Dead, the heart of the deceased was shown being weighed against the feather of Ma'at, a symbol of universal truth, harmony and balance. Anubis was sometimes shown adjusting the balance of the scales slightly in favor of the deceased, to ensure it into the underworld.  The heart was thought to be given back to the deceased in the afterlife.

For this reason, the heart was one of the only organs not removed from the body during mummification.  Of course there was concern that the heart might testify against the deceased, so in order to prevent this, a heart scarab was often wrapped within the bandages.  The inscription on the scarab would most likely consist of Chapter 30 from the Book of the Dead:

O my heart which I had upon earth, do not rise up against me as a witness in the presence of the lord of things; do not speak against me concerning what I have done, do not bring up anything against me in the presence of the great god of the west..."

The heart amulets began taking the form of a vase with lug handles, perhaps symbolic of blood vessels, from the New Kingdom onward.  Chapter 29b of the Book of the Dead states that these should be made of seheret stone (cornelian), but they were often made from other materials.

So today, when we confront our lovers, we speak from the heart, and when we break up, it is our heart that is broken, in only another of many memories of our ancient Egyptian roots.