Jenkins, the 83-times capped Blues and British & Irish Lions loose-head prop, has overcome a knee problem to replace Rhys Gill (Saracens) in the front row, with Gill missing out altogether, and Dragons back row forward Lydiate (ankle) returns to the flank vacated by Jones.
Osprey Jones, who makes his 60th international appearance on Sunday, is called into the second row in place of the suspended Bradley Davies (Blues).
One more change occurs on the bench, with uncapped Scarlets lock Lou Reed set to make his debut if required, but elsewhere Warren Gatland and his coaching team have said 'same again' to the team who gave them a winning start to the 2012 Championship in the tough opening fixture at the Aviva Stadium last Sunday.
"Gethin brings a wealth of experience to the team, which is the main reason we have brought him in for Rhys, who is unlucky to miss out with Paul James covering both sides of the scrum from the bench," said Wales head coach Gatland.
"Dan's return from injury is timely and Ryan's versatility allows us to cover for Bradley with minimum disruption, with Lou Reed also giving us an extra option from the bench.
"We cannot afford to underestimate Scotland, the amount of possession and territory they had against England last weekend meant that they should have won the game and they will come to the Millennium Stadium buoyed by that knowledge."
Wales assistant coach (backs) Rob Howley agrees that his side must have the right approach in order to achieve victory over Scotland this weekend.
"The standards we set in Dublin where high and we want to attain that level throughout the Six Nations," said Howley.
"We are playing particularly well at the moment, and it was a pleasing performance from the backs, we were accurate and took our opportunities well.
"The Six Nations is a magical championship and the one thing we all know is that if you don't front up in a Six Nations game you can get beaten.
"Scotland should have beaten England at the weekend, they will be obviously disappointed and they will want to go one better, which would obviously mean winning the game, so we must be ready for them."
WALES: Leigh Halfpenny; Alex Cuthbert, Jonathan Davies, Jamie Roberts, George North, Rhys Priestland, Mike Phillips; Gethin Jenkins, Huw Bennett, Adam Jones, Ryan Jones, Ian Evans, Dan Lydiate, Sam Warburton (C), Toby Faletau
REPLACEMENTS: Ken Owens, Paul James, Lou Reed, Andy Powell, Lloyd Williams, James Hook, Scott Williams