WASHINGTON — Defending his company under blistering criticism, the CEO of Goldman Sachs testily told skeptical senators Tuesday that customers who bought securities from the Wall Street giant in the run-up to a national financial crisis came looking for risk, “and that’s what they got.”

Lloyd C. Blankfein and other Goldman executives were lambasted by lawmakers for “unbridled greed” in an often-electric daylong showdown between Wall Street and Congress — with expletives frequently undeleted. Unrepentant, five present and two past Goldman officials unflinchingly stood by their conduct before a Senate investigatory panel and denied helping cause the near-meltdown of the financial system that turned into the worst recession since the Great Depression.

“Unfortunately, the housing market went south very quickly,” Blankfein said. “So people lost money in it.”

There was hour upon hour — nearly 11 hours in all, winding up just before 9 p. m. — of combative exchanges, occasional humor and long stretches of senators and Wall Street insiders speaking past one another. There was talk of ethical obligations versus financial transactions so complex that they all but defy explanation. And there were a half-dozen protesters dressed head to toe in prison stripes with Goldman officials’ names around their necks.

Senators from both parties verbally pounded the Goldman executives, accusing them of a financial version of rigged casino gambling that they said endangered the entire U. S. economy.

That drew a protest from Sen. John E. Ensign, R-Nev. In Las Vegas, he said, “people know the odds are against them. They play, anyway. On Wall Street, they manipulate the odds while you’re playing the game.”

Blankfein was the final witness in a daylong hearing on Goldman conduct that resulted in a Securities and Exchange Commission civil fraud lawsuit earlier this month against the firm and one of its traders.

Sen. Carl M. Levin, D-Mich., chairman of the subcommittee that conducted the hearing, cited a “fundamental conflict” in Goldman’s selling to clients home-loan securities that company e-mails showed its own employees had derided as “junk” and “crap” — and then betting against the same securities and not telling the buyers.

“They’re buying something from you, and you are betting against it. And you want people to trust you. I wouldn’t trust you,” Levin told Blankfein.

Blankfein denied such a conflict in a combative exchange. “We do hundreds of thousands, if not millions, of transactions a day, as a market-maker,” he said, noting that behind every transaction, there was a buyer and a seller, creating both winners and losers.

Goldman’s chief said the company didn’t bet against its clients — and can’t survive without their trust. He repeated the company’s assertion that it lost $1.2 billion in the residential mortgage meltdown in 2007 and 2008 that triggered the financial crisis and the recession. He also argued that Goldman wasn’t making an aggressive negative bet—or short—on the mortgage market’s slide.

Earlier, Levin said that financial industry lobbyists “fill the halls of Congress, hoping to weaken or kill legislation” to increase regulation. He accused Wall Street firms of selling securities they wouldn’t invest in themselves. That’s “unbridled greed in the absence of the cop on the beat to control it,” he said.

The Goldman witnesses strongly denied that the firm intentionally cashed in on the housing crash by crafting a strategy to bet against home-loan securities while misleading its own investors.

“I will defend myself in court against this false claim,” said Fabrice P. Tourre, a French-born 31-year-old Goldman trader who was the only individual named in the SEC lawsuit. “I deny — categorically — the SEC’s allegation.”

The SEC says Tourre marketed securities without telling buyers they had been chosen with help from a Goldman hedge fund client that was betting the investments would fail. The commission alleged that Tourre told investors that the hedge fund, Paulson & Co., actually bought into the investments. Tourre said he didn’t recall telling investors that.

Tourre said: “I am saddened and humbled by what happened in the market in 2007 and 2008, . . . but I believe my conduct was proper.”

In a brash January 2007 e-mail, Tourre had called himself “The fabulous Fab . . . standing in the middle of all these complex . . . exotic trades” that he had created “without necessarily understanding all of the implications of those monstrosities!!!”

Levin pressed Daniel L. Sparks, former head of Goldman’s mortgages department, on whether the company felt that it had a moral obligation to disclose to clients that it was making side bets against the same investments that it was selling to them.

Sparks said clients “should look at the assets themselves” that make up the mortgage-based securities they are buying. “Clients who did not want to participate in that deal did not,” he said of one particular transaction. Levin shot back: “I don’t think you want to answer. You’re not going to answer the question; it’s obvious.”

Sen. John McCain, R-Ariz., said that while there may not be proof that Goldman did anything illegal, “there’s no doubt their behavior was unethical and the people will render a judgment, as well as courts.”