This paper investigates the joint source-channel coding problem of sending a memoryless source over a memoryless degraded broadcast channel. An inner bound and an outer bound on the achievable distortion region are derived, which respectively generalize and unify several existing bounds. Moreover, when specialized to Gaussian source broadcast or binary source broadcast, the inner bound and outer bound could recover the best known inner bound and outer bound in the literature. Besides, the inner bound and outer bound are also extended to Wyner-Ziv source broadcast problem, i.e., source broadcast with degraded side information available at decoders. Some new bounds are obtained when specialized to Wyner-Ziv Gaussian case and Wyner-Ziv binary case.