On the TV show "House," medical personnel don't wring out blood-soaked towels. On "Scrubs," they always find a good vein on the first try. And on "Grey's Anatomy," nobody tracks a bloody shoe around the white floors of the operating room.

But as a group of Sewickley Academy students -- and avid medical television fans -- learned yesterday while watching open-heart surgery at Allegheny General Hospital, real medicine is nothing like its many small-screen incarnations.

"It's so messy," said Mary Wingert, an 18-year-old senior who plans to study nursing next year at Case Western Reserve University. "They just throw the towels."

Twice a week for about a year, Allegheny General has allowed high school and even middle school students to watch open-heart surgeries from an observation room directly above the operating room.

The program is the brainchild of George Magovern Jr., chairman of the hospital's department of cardiovascular and thoracic surgery, and so far has drawn about 500 students from four Western Pennsylvania counties and West Virginia.

Yesterday morning, Dr. Magovern was doing a complicated procedure -- a double bypass and an aortic valve replacement on an 80-year-old man who couldn't accept blood transfusions because of his beliefs as a Jehovah's Witness. Observing the procedure were seven students in a Sewickley Academy anatomy and physiology elective class.

The students had just begun studying the heart in class and had a basic familiarity with valves, veins and arteries.

"We were talking about the valves yesterday and then we come here and they're replacing the valve," said Mary.

"It's a lot different than looking at a diagram," added senior Becca McCarthy.

And the students learned plenty that isn't in their textbooks. "I guess I just always imagined the heart as more fragile," said junior J.T. Ahearn, watching Dr. Magovern squeeze and shake the heart to remove excess air.

Like Mary, J.T. also hopes for a career in medicine. Watching the operation proceed, he and other students asked questions not just about the physiology, but about the physicians.

"Do you move up from anesthesiologist to surgeon?"

"How much experience do they have?"

Students watched the surgery proceed for more than three hours -- and even those who had their doubts going in were fairly transfixed.

Junior Tom Droney, for example, hopes for a career in business but took the anatomy class to learn more about the human body. In advance of the surgery, he was worried about how queasy he'd be in the presence of blood.

But as it progressed, it was really only the incisions in the patient's legs, where doctors extracted veins that would replace the heart's arteries, that bothered him.

"The thing that gets to me is the leg," he said. "It looks like a shark bite."

Generally, students expressed amazement at the intricacy of the operation, the number of people involved and the workings of the human body.

"The coolest part for me was seeing the heart beat," said Becca. "You don't really think you're ever going to see that."

Throughout the procedure, research assistant Pat Wolf guided the students through the nuts and bolts of the operation and answered their questions, with chief physician's assistant Giulia O'Keeffe coming in at one point to provide more detail.

When the operation was nearly over, Dr. Magovern made an appearance.

Students asked him questions such as why he used a bovine valve instead of an artificial valve (artificial valves require blood thinners), why he needed to cut into both legs (the vein in the first leg was too small to be effective) and what his hours are ("not bad -- about 12 hours a day").

"So many students in high school say 'Why bother with this? What's the practical application?'" he said. "Every time we've had students in, they've really enjoyed it. They can understand what a doctor actually does."