Sometimes, they are battle-hardened rebels with gaping wounds. Sometimes, they are children, peppered with shrapnel and screaming in pain.
Those who die are left on the sidewalk outside, to be claimed hours later by relatives.
An Associated Press team spent 24 hours at Dar al-Shifa hospital in Aleppo and witnessed the frantic work by overtaxed doctors and nurses to save those wounded in the battle for control of Syria's largest city.
The AP first visited the hospital last month and returned this week to get a fuller impression of how its staff is coping amid Syria's civil war. The routine is as simple as it is brutal: A barrage of shelling echoes over the city, and about 15 minutes later, the wounded flow in.
The medics work amid the wails of traumatized children, badly wounded men shouting Islam's declaration of faith in their final minutes, and rebel fighters holding RPGs mourning dead comrades, with tears streaming down their gunpowder-blackened cheeks.
Blood is everywhere. Orderlies mop it up as more wounded arrive. Amid the din of groans and cries for help, a worker spots a severed limb on the floor and tries to break the tension with some black humor.
"Anyone missing a foot?" he asks.
Once a private clinic owned by a businessman loyal to President Bashar Assad, Dar al-Shifa hospital has been taken over by volunteer doctors, nurses and aides united by their opposition to the regime and the need to give medical care to civilians and rebels.
The seven-story hospital stands only 400-500 meters (yards) from the front line in a neighborhood that is heavily shelled. Nearly three months into the rebel offensive in Aleppo, the facility has taken at least six direct hits, mostly affecting the upper stories; its staff uses the bottom three floors.
Most of the surrounding apartment blocks are badly damaged and deserted, with the only evidence of life being the fluttering of clothes on laundry lines or an occasional resident stepping onto a balcony to get a better cellphone signal.
Dar al-Shifa has only seven doctors, two of whom are trained for emergency duties, and two nurses. The atmosphere is a bizarre and somewhat unnerving mixture of urgency, nonchalance, resolve and anger.
The staff smokes freely in the corridors, watching TV during breaks in treating the waves of wounded. Dr. Osman al-Haj Osman even has moved his wife and two small children into the facility in order to be close to them.
Hospital officials say they see about 100-120 cases a day, of which 10 or 15 are children. Eighty percent of the cases are of civilians; the rest are mostly rebel fighters. In the 24-hour period that the AP was there on Wednesday and Thursday, the hospital's records showed nine dead and 107 wounded.
Because the hospital has no morgue, the dead are left on the sidewalk outside, where it is cooler. If the bodies are not identified and claimed within 12 hours, they are photographed and then buried. Residents who come to the hospital looking for missing relatives are shown the photos and - if they recognize a loved one - are given the choice of exhuming the remains for reburial elsewhere.
Osman, 30, spoke of the snap life-and-death decisions that he and others have to make when the hospital is flooded by casualties two or three times a day.
"I have to make a choice between a child with a 10 percent chance of survival and one with a 25 percent chance," he said.
"Our cruelest moments are when we get a child whose foot or part of his leg is only held by skin and we have to amputate," according to Osman, who said he was jailed and tortured by the Syrian regime twice since the start of the uprising in March 2011. "In the early days, we used to cry when we had a child with a severe injury, then recharge our psychological energy before we return to work.
"Now, there is just no time for that."
When AP journalists first arrived Wednesday afternoon, there were only a handful of patients being treated. Dr. Abu Rayan, who studied medicine in Moscow, stood in one corner chatting with two members of the hospital's pharmaceutical team. The doctor asked to be identified by his nickname for fear of retribution.
A man approached him, complaining of pain from shrapnel lodged in his right leg.
"Forget it, it will never come out," the 35-year-old doctor told him with a smile.
Nearby, Zakariya Khojah lay on a gurney, a tube draining a wound in his side. He had a lifeless stare fixed on the ceiling. Standing at his side was his 13-year-old son, Bashar.
"Papa, is there anything hurting you beside your chest?" the boy asked. The father replied with a slow shake of his head.
"I was walking just ahead of him when a bomb fell close to us," Bashar said. "He's all I got. My mother died three years ago."
The patient was later moved to a chair because the gurney was needed for someone else. Several hours later, he was brought outside to a pickup.
"I fear that my father may not get better," Bashar said before climbing in beside him.
Around 3:10 p.m., shortly after artillery blasts were heard nearby, a wave of wounded arrived. Frantic men screamed, "Emergency! Emergency!" as they carried the casualties inside.
In minutes, the small, three-bed intensive care unit was filled, and the overflow of patients had to be treated on the floor of the lobby.
"Where are you guys? Hurry up, please, guys!" yelled one of the escorts. Others shouted, "God is great!"
Word quickly spread that the wounded, about 15 in all, had been standing in a bread line when a shell fell nearby.
A fighter carrying an RPG launcher on his shoulder walked over the wounded on the floor as he made his way to the narrow staircase leading to the X-ray room in the basement. A woman wearing the Muslim hijab and a blood-soaked black coat was on a gurney waiting for someone to attend to her. A man on the floor had a hole in his back the size of a tennis ball.
"May God curse Bashar Assad until he goes to his grave!" yelled a man in a loose gray robe. "He is a pig and son of a dog! May Allah curse his father, tanks and guns!"
The lobby was swiftly cleared of the wounded. Relatives took them away, either to their homes or to better-equipped hospitals in northern Aleppo province or in government-controlled areas of the city.
The respite did not last long. A series of blasts shortly after 4 p.m. brought a fresh wave of wounded, many of them children.
"Uncle, please take me to my mum at home," said one of them, a 9-year-old named Fatimah, pleading to a journalist.
Fatimah only had shrapnel wounds to her arms and lower torso, but she clearly was in shock. She had been shopping with three aunts and several cousins when a shell fell on the street nearby. One of her aunts died in the hospital.
"It's OK, sweetie. Just ask God to exact revenge on Bashar," a fighter told the girl, who wore her long brown hair in two ponytails.
She grimaced every time she looked at the other patients nearby. A man lying on the floor with a back injury repeatedly shouted, "There is no God but Allah, and Muhammad is his prophet."
Addressing the medic treating him, he said in a heart-wrenching voice: "May Allah have mercy on the eyes of your parents."
Next to him was a dying man who did not speak.
Next to Fatimah was a man whose right foot was hanging only by his skin. He held a cellphone in his right hand. As the staff walked past him to help others, he tugged at their coats.
"May Allah be with you," he said, pleading for assistance. The man eventually lost his foot and the staff bandaged his leg to stop the bleeding.
Rawyah and Bedour, two girls about 9 or 10, were screaming in pain as a doctor and two assistants attended to them. Lying on their backs, they kicked their legs in the air every time bits of shrapnel were removed from their bodies.
Undeterred by all the gore, Osman's two children, Omar and Rushd, wandered around the lobby the same way others their age would walk in a park.
"Don't worry about them. They've become used to this," he said. "As a family, we made a decision to live together. There is no such thing as a safe place. So, we live here and we die here. At least we will die while providing a service to our cause."
Rushd played with three screwdrivers, which she used to try and make a hole in a wall. She seemed totally oblivious to the cries of pain.
"The psychological pressure on us is tremendous," said Abu el-Baraa, a 23-year-old army medic who deserted his unit in July in rural Damascus and also asked to be identified by his nickname out of fear of retaliation. To avoid arrest, he walked for five days in the countryside and then obtained an ID card of an older brother that he used to get past army checkpoints on the road to Aleppo.
"This has been a miserable day par excellence," he said of Wednesday.
Around 9 p.m., guerrilla commander Sheikh Hussein and a band of armed fighters in camouflage fatigues stormed into the hospital carrying a wounded man named Ali Al-Sheikh, who died minutes later.
"Ali has been martyred, you guys," Hussein said, fighting back tears.
His men began weeping. One punched the metal door of an out-of-order elevator and another sat with his face buried in his hands.
Hussein, about 40, with an assault rifle slung across his shoulder, left the group and headed to one side of the hospital's lobby to offer a brief prayer for Ali. He did not use a prayer mat on the bloodstained floor.
Afterward, he tapped his comrades on the shoulder with his blood-soaked hands.
"Don't cry. Just say `thank you, God,' because he is now a martyr," he told them, his brown worry beads wrapped around the barrel of his rifle.
Al-Sheikh's body, wrapped in a sky blue sheet, was taken from the ICU and carried outside by the fighters who shouted, "There is no God but Allah."
Thursday morning was ushered in with an airstrike and intense shelling that sounded much closer than the previous day's attack.
There were more injured: a sniper victim who prayed loudly until he succumbed to his chest wound; a child no more than 10 who stared at his severed left foot lying in front of him; a man who begged for help and was told firmly by a medic: "Act as a believer and wait for your turn."
The overwhelmed staff asked those with superficial wounds to go home and come back later.
"My brother is dying!" cried a young man as he stood next to his wounded sibling. "For God's sake, people, come and help him!"
Dr. Abu Rayan was preparing to meet his wife and two children across town in a government-controlled area of Aleppo, using a fake ID to get him through checkpoints. But he delayed his departure to help out.
Then the power went off, and an overworked generator kicked in as the sound of shelling got louder.
"I don't know whether we will ever be able to lead normal lives again," Osman said. "Will we have dreams and ambitions like regular people, or have we been scarred forever?"