(ABC News)

There are no white doctor's coats that fit Mohammed Asaf.

At just 12-years-old, he's been working in Aleppo's busy and bloody Dar al-Shifa clinic for four months.

"In the beginning, when I saw blood, I would shiver and be frightened," he said. "But now, I see blood like water."

Inside the clinic, the wounded, many of them children, lie wherever there's space, some screaming out in pain. Mohammed's 11-year-old friend, Youssef Mohamed, works alongside him, tenderly caring for a rebel fighter.

Before the war, Aleppo had 5,000 medical workers. Today, that number has dwindled. Facilities rely on the help of kids like Mohammed and Youssef to care for the wounded in Syria's most populous city.

None of the children should be there, but two years of civil strife have left few innocents.

Outside the clinic, between bombardments, children play, jumping rope and shooting marbles, often just feet from spent shells.

Electricity, food and water are scarce. An Islamic charity whose contributors include the al Qaeda-linked group Jabhat al-Nusra has stepped in to fill the void and win hearts and minds. It distributes bread and clothes, and has also slaughtered goats, a rare luxury.

Inside the Dar al-Shifa clinic, Mohammed runs around getting supplies and caring for patients including a comatose little girl who is a victim of the day-in, day-out fighting in the streets and bombing from the air.

Three days after video of a smiling Youssef was filmed, he was brought into his own clinic, dead from shrapnel wounds.

Seventy thousand people have now died in this war. Even if children like Mohammed survive it, his childhood is lost forever.