All connective tissues arise from the mesoderm, one of the three primary germ layers that form during embryonic development.

Here's a breakdown:

* Ectoderm: Forms the outer layer of the embryo and gives rise to skin, nervous system, and some glands.

* Mesoderm: Forms the middle layer and develops into muscles, bones, blood, cartilage, connective tissue, and other internal organs.

* Endoderm: Forms the inner layer and develops into the lining of the digestive system, respiratory system, and other internal organs.

So, while connective tissues are diverse (including blood, bone, cartilage, tendons, ligaments, and more), they all trace back to the mesoderm.