Ryota Yamagata (JPN) sets before competing in the men's 4x100m relay heats during the London 2012 Olympic Games at Olympic Stadium. (John David Mercer-USA TODAY Sports)
The US Women's 4x100 relay team set a new world record on their way to capturing gold Friday, while the US Men's 4x400 team brought home a silver.
Women's 4x100m relay
Carmelita Jeter crossed the finish line pointing the baton at the clock showing a world record of 40.82 seconds Friday night as the United States won the women's Olympic 4x100-meter relay for the first time since 1996.
Tianna Madison, 200-meter champion Allyson Felix and Bianca Knight gave the U.S. a big lead heading into the anchor leg by Jeter, the 100 silver medalist.
Their time smashed the old record of 41.37 by East Germany in 1985.
Jamaica's Shelly-Ann Fraser-Pyce, Sherone Simpson, Veronica Campbell-Brown and Kerron Stewart finished second in a national record 41.41 and Ukraine was third in 42.04.
Men's 4x400m relay
Ramon Miller of the Bahamas chased down Angelo Taylor of the United States in the men's 4x400-meter final Friday night to win his country's first gold medal in a relay won by America at every Olympics since 1984.
Miller lifted the Bahamas to a time of 2:56.72, .33 seconds better than the U.S.
Trinidad and Tobago took third.
The South African team, anchored by double amputee "Blade Runner" Oscar Pistorius, fell behind well before Pistorius received the baton and finished last.
Taylor, a 400-meter hurdler, was thrust into the lineup after a flurry of injuries hit the Americans. Lashawn Merritt and Jeremy Wariner both pulled out before the preliminaries, where Manteo Mitchell ran the last 200 meters of the opening lap with a broken left fibula.
(The Associated Press contributed to this article.)